Fangyuan v Stockwell[2024] QDC 200

DISTRICT COURT OF QUEENSLAND

1. Introduction

1. [1]
   This case is about a retaining wall that has collapsed between two residential properties that back onto a common boundary at Wishart.  There is no dispute that it needs to be replaced.  The major issue in the proceedings is the cause/s for its failure.  It was erected in 2004 by the previous owner of the applicant’s property along the full length of the boundary between the two properties.  She did not purchase the property until a decade later and did not live in it between 2016 and 2021.
2. [2]
   Unfortunately, the parties have become entrenched in their positions as to the reasons for the failure of the wall.  The trial was originally listed for three days but the evidence ended up taking six days.  In my view, it was far more protracted than it needed to be, and the costs incurred are likely to be highly disproportionate to the very modest quantum involved. Further, the inaccuracy of the trial estimate provided by the parties meant that there were challenges in allocating additional hearing time that could be accommodated by the lawyers and the court. This matter was further complicated by the absence of pleadings.  
3. [3]
   A site inspection was undertaken on the first day of the trial.  Eight witnesses gave oral evidence, of which the parties were the only lay witnesses. 50 exhibits were tendered.  The parties provided very detailed written submissions and brief oral ones.

1. Respective cases

4. [4]
   These proceedings were commenced by the applicant (‘Ms Fan’) by way of an Originating Application filed on 10 July 2023.  The Points of Claim were filed on 24 January 2024.  It is alleged that the work undertaken by the respondents (‘the Stockwells’) on their adjoining property has materially contributed to the failure of the retaining wall, which has interfered with Ms Fan’s use and occupation of her property.   The claim is in the tort of nuisance.  The relief sought is the granting of an injunction requiring the Stockwells to demolish and remove the retaining wall and to replace it. 
5. [5]
   The Stockwells filed a Points of Defence and Cross-Application on 13 February 2024.  Their defence to Ms Fan’s claim is that the works undertaken by them on their property have not interfered with Ms Fan’s use and occupation of her land and if they have, such interference has not been substantial and unreasonable.  It is further asserted that Ms Fan has not established why damages would not be an adequate remedy.  
6. [6]
   The Cross-Application is articulated on three alternative bases, being nuisance, a breach of s 179 of the Property Law Act 1974 (Qld) (‘the PLA’) and negligence. 
7. [7]
   As to the claims in nuisance and for breach of s 179 of the PLA, it is alleged that:

   1. The Stockwells had a right to have their property supported by Ms Fan’s property.
   2. In about 2004, there were excavation works undertaken by the previous owner of Ms Fan’s property, which reduced the lateral support to the Stockwells’ property.
   3. The failure of the retaining wall has further reduced the lateral support to their property, which failure has been caused by the poor design of the retaining wall.
   4. The removal of the lateral support referred to in subparagraphs (ii) and (iii) above, is an actionable nuisance and a breach of Ms Fan’s obligations provided for in
      s 179 of the PLA. 
8. [8]
   As to the claim in negligence, it is alleged that:

3. (i)
   Since at least 2017, Ms Fan knew or ought to have known that there were risks:

3. (a)
   of the retaining wall becoming unstable or falling;

3. (b)
   of subsidence of the Stockwells’ land with consequential property damage;

3. (c)
   the Stockwells would not be able to use their land in the vicinity of the retaining wall; and

3. (d)
   to the safety of persons in the vicinity of the retaining wall.

3. (ii)
   Lateral support to their land has been unlawfully removed because of the excavation works, the reduction in support being provided by the retaining wall over time and the partial collapse of it; and

3. (iii)
   Ms Fan has failed to restore the lateral support to the Stockwells’ land.

9. [9]
   It is alleged that in relation to each of the three separate claims, Ms Fan has committed, adopted or continued the breaches.
10. [10]
    The following relief is claimed:

    1. An injunction requiring Ms Fan to demolish, remove and replace the retaining wall; or
    2. A declaration that the costs to demolish, remove and replace the retaining wall be borne by Ms Fan; or
    3. Unspecified damages in lieu of an injunction, including damages for loss of amenity.
11. [11]
    At a mention on 23 October 2024, the Stockwells were requested to properly particularise their claim for damages.  The Points of Defence and Cross-Application was amended, and damages were claimed in the following amounts:

    1. $63,256.60 to demolish, remove and replace the retaining wall;
    2. $6,700 to replace the timber paling fence;
    3. $9,400 to re-instate their garden; and
    4. $50,000 for loss of amenity.
12. [12]
    At a mention on 15 November 2024, counsel for Ms Fan made an oral application to amend the originating application to include an alternative claim for damages.  The application was opposed by the Stockwells.  The application was granted pursuant to
    r 658 of the Uniform Civil Procedure Rules 1999 (Qld), with reasons to be provided in this judgment.  The principal reason is because of the absence of any real prejudice to the Stockwells in that:

    1. The issue of damages had been previously raised on the first day of the hearing when counsel for Ms Fan made an oral application to make an amendment to include this relief.  It was said that the quantum of damages sought was $68,106.  This figure reflected the estimate in a quote provided by Brad Schaper, civil engineer to demolish, remove and replace the retaining wall with one comprised of galvanised posts and concrete sleepers.  Counsel for the Stockwells informed the court at that time that the application was not opposed.^[1] 
    2. This application to amend was on the almost identical basis to the abovementioned application.  The only difference is that the damages amount claimed has reduced from $68,106 to $61,006.  This is because the parties have agreed that this lower figure reflects the cost of removing and replacing the retaining wall in accordance with Mr Schaper’s quote.
    3. The damages claim is supported by Mr Shaper’s evidence, including his quote that was tendered as an exhibit.  No objection was taken by the Stockwells to this evidence.   The quantum of the quote is said to reflect the quantum required to abate the nuisance, being the removal and replacement of the retaining wall. 
    4. It was admitted by the Stockwells at the commencement of the trial that the retaining wall needed to be replaced with a concrete one.^[2]  Mr Schaper’s quote is for such a wall.
    5. The damages claim does not constitute relief for a new cause of action.  Rather it is an alternative to the injunction claimed in the originating application. 
    6. It is well established that damages may be awarded in lieu of an injunction where they are able to be ascertained and where they are adequate.

13. Credibility of the parties

13. [13]
    It is necessary at this point to address credibility issues as they inform some of the findings made below. 
14. [14]
    Significant time has passed since many of the events which form the relevant factual basis for the respective claims. Thus, it is not surprising that the parties may have had some difficulty in their evidence in recounting acts and conversations in detail. 
15. [15]
    I am conscious of the limitations of attempting to discern anything meaningful merely from the demeanour of a witness. It is but one of the considerations.  The others are the exhibits, the inherent consistency of their accounts, the consistency of their accounts with other witnesses and objective incontrovertible facts, and the inherent probabilities of the evidence in question. 
16. [16]
    This case is not one simply of a credit contest between the parties.  The Stockwells are the only witnesses on facts relevant to the construction of the retaining wall and work undertaken by them on their property on and around the retaining wall.  An assessment of their credit is vital to the ultimate determination of some of the issues.
17. [17]
    Generally, I did not find either of the Stockwells to be impressive witnesses.
    It was my distinct impression that they were unduly anxious to advance their claim by attempting to present their case in the most favourable light.
18. [18]
    As to Mrs Stockwell, she presented as defensive.  Some parts of her evidence were selective and unsatisfactory.  For example, she did not concede that a pomegranate tree had been planted near the retaining wall until confronted with photographic evidence of it in cross-examination. In my view, it is simply implausible that she had “forgotten all about it” until this time.  This is because the trees planted by the Stockwells proximate to the retaining wall has been a longstanding and ongoing dispute between the parties.  Mrs Stockwell’s failure to mention the pomegranate in evidence-in-chief seemed to be a deliberate attempt by her to downplay the number of trees that she and her husband had planted in the garden bed adjacent to the retaining wall.  This is in circumstances where she undoubtedly understood the ramifications for her and her husband which would potentially flow from the Court’s appreciation of the true extent of the work done by them along this boundary of their property.
19. [19]
    I also do not accept Mrs Stockwell’s evidence that she contacted Ms Fan in 2017, on the day after Ms Fan left the letter in her letter box.  It seems improbable to me that she did, despite her explanations for having specific recollections around this. There was no reason for her to have done this.  This is because at that time, the retaining wall was not adversely impacting on her property.  Further, as far as she was concerned, there was nothing to discuss as she was adamant that the retaining wall was entirely the responsibility of Ms Fan.  This mindset was on display once again in August 2020, when Mrs Stockwell again ignored a further attempt by Ms Fan to discuss this issue with her.  This is addressed further in paragraph 57 below.
20. [20]
    Further, I am in no way persuaded by Mrs Stockwell’s evidence regarding the enquiries she says she made about the desirability of having lilly pillies and mock oranges planted close to a retaining wall.  In particular, she said that when she purchased the trees from a nursery in 2009 she made these enquiries, and that further in 2020 she engaged the services of two arborists for the purposes of again seeking advice about these matters. 
    In my view, had she sought such advice, it would have featured in at least some of the communications to Ms Fan since 2017 (when the issue of the trees was first raised) and it does not.  Further, it seems inherently unlikely that arborists would be prepared to give the advice she contends they gave, in the absence of seeing the trees and their proximity to the retaining wall.  I make this observation in circumstances where the preponderance of the expert evidence establishes that lilly pillies are known to grow to a substantial size and have the potential to cause damage to retaining walls.  In my view, this is another example of an unsatisfactory aspect of Mrs Stockwell’s evidence intended to advance her claim.  
21. [21]
    As to Mr Stockwell, he was an equally unsatisfactory witness.  On some critical issues, he was at best reconstructing events, and on occasions even misrepresenting them. His evidence was at times evasive, in part contradictory, dissembled when it suited him, and some aspects were inconsistent with contemporaneous documents and were otherwise implausible.  I have been required to scrutinise his evidence with significant care.
22. [22]
    Mr Stockwell’s failure to be frank about the number of sleepers he added to the top of the retaining wall does him no credit.  He repeatedly maintained in evidence-in-chief his ‘story’ that only two sleepers had been added in response to direct questioning about it.  Then, when confronted with objective evidence to doubt this, he admitted to having placed three sleepers “in that area”. When confronted with further incontrovertible evidence, he was forced to concede that he had in fact added six sleepers. Not only was Mr Stockwell’s oral evidence replete with inconsistencies about this issue, it is also inconsistent with his instructions before the trial.^[3] These inconsistencies need to be considered in the context that Mr Stockwell has always known that Ms Fan has not been in a position to contradict his evidence on this point.
23. [23]
    Another example of Mr Stockwell having crafted a narrative around matters he perceived as necessary to make good his claim, relates to the number of cuts that he made into the vertical posts of the retaining wall to support the new sleepers that he added to it.  
    His evidence that it was his recollection that the vertical post shown in exhibit 41 was the only post he had cut into cannot be accepted. His explanation when confronted with photographic evidence was disingenuous. 
24. [24]
    A further attempt by Mr Stockwell to lessen the magnitude and significance of the work he did in the vicinity of the retaining wall relates to his evidence about the trees that were planted by him and his wife.  His evidence that an “oversight” explains his failure to mention the pomegranate and frangipani trees in his affidavit material is not believable. Further, his description of the trees that he had planted adjacent to the retaining wall as being of a “small to moderate size” at the times the retaining wall was observed to be failing cannot be accepted.  In addition, I am not persuaded by Mr Stockwell’s evidence that the two tree trunks shown in exhibit 34.1 are from two of the five lilly pillies that had been in the garden bed.  This is addressed in more detail in paragraph 50 below. Also, the size of the pomegranate branches, foliage and fruit depicted in exhibit 3 causes me to question Mr Stockwell’s evidence that it had only been planted there a couple of years earlier. 
25. [25]
    Additionally, for the reasons explained in paragraph 46 below, I am satisfied that the quantity of potting mix Mr Stockwell added to the backfill was much more than the “about 100 mil” that he spoke of in his evidence. 
26. [26]
    Ms Fan on the other hand, was a much more satisfactory witness. She impressed as a witness of reliability and honesty. She sought to answer questions directly and forthrightly. She was firm on the matters which she remembered and did not attempt to overstate any part of her evidence. She was quite prepared to say when she was asked about matters of which she had little knowledge.  She readily acknowledged when her recollection of some matters was incomplete.  Her evidence was plausible, consistent and lacked any signs of being concocted. 
27. [27]
    It is not surprising for example that Ms Fan could not recall whether the timber paling fence was removed on the first or second occasion that the builder from Barth Builders attended her property to make safe the area around the retaining wall.  This occurred more than three years prior to her giving evidence, with only weeks separating the two attendances.  It relates to a peripheral matter of no significance.  
28. [28]
    Ms Fan was cross-examined to the effect that she did not comply with her duty of disclosure in relation to a report from a surveyor and that there was something sinister about this.   I do not accept this.  She was clearly confused about the line of questioning in cross-examination.  The opinion from the surveyor was obtained prior to litigation being commenced, when Ms Fan was trying to put together the pieces of the puzzle.  Further, as she explained, she did not attach much weight to the fact that the retaining wall was found by a surveyor to be on her property. This was because it was her understanding that the wall needed to be constructed where it is in order to accommodate the presence of the manhole.^[4]     
29. [29]
    There was extensive cross-examination of Ms Fan to the effect that she attempted to influence the opinions expressed by the engineers, being Mr Wong and Mr Van de Hoef.   This was asserted to be in circumstances where Ms Fan:

    1. engaged Mr Wong personally even though she had solicitors acting for her;
    2. was at her property and provided background information to Mr Wong and Mr Van de Hoef when they carried out their respective inspections of the retaining wall;
    3. requested to be present at her property when Mr Wong and Mr Van de Hoef participated in the joint conclave at her property; and
    4. offered to drive Mr Wong to her solicitor’s office in February 2024.
30. [30]
    I was unpersuaded by this line of cross-examination.  It assumes a level of calculation on the part of Ms Fan that is inconsistent with my impression of her.  She personally approached Mr Wong after he was recommended by a parent whom she knew at the school where her children attended.  I am persuaded by her evidence that she had not previously been involved with any litigation and did not know that she had to go through a solicitor to engage Mr Wong.  Further, there is nothing odd about Ms Fan having provided the experts with some background information when they were present on her property for the purposes of carrying out their inspections.  Her explanation for having requested to be present for the joint conclave on her property was also logical and believable. In addition, her offer to drive Mr Wong to her solicitors for the purposes of him signing his affidavit is also most likely explicable by her naivety about such matters, rather than there having been some improper motive.  In short, it is my view that none of these actions on the part of Ms Fan were of such a nature as to invite suspicion or to create any real doubts about her credibility.  
31. [31]
    While I have endeavoured to resolve conflicts on issues which appear significant, I do not think it is essential to resolve all conflicts in the evidence.  Where I state something as a fact below, I accept the evidence that supports that fact.

32. The two properties

32. [32]
    The Stockwells live on the higher of the two properties at 5 Mayfair Close, Wishart. It is on the side of a hill with a gradual slope across their land down to and across Craig Street. They purchased their property in approximately early 2002. It was a vacant block. 
    Their home was built over about a six-month period commencing in April 2003. They moved into it in October 2003. 
33. [33]
    Ms Fan’s block is at 38 Craig Street, Wishart.  It was vacant at the time the Stockwells moved into their property.  It is also on a moderately sloping block.  The northern boundary of Ms Fan’s property adjoins the rear of the Stockwells’ property. 
34. [34]
    Mr Stockwell arrived home one day in late 2003 or early 2004 to see that the previous owner of Ms Fan’s property had excavated the land as shown in exhibit 30.  He said that after the excavation, he noticed that much of his land adjacent to the boundary subsided.  
35. [35]
    Over the next six or so months, the previous owner of Ms Fan’s property built a free-standing two-storey home.  It faces west towards Craig Street.  

32. Construction of the retaining wall

36. [36]
    Around mid to late 2004, the previous owner of Ms Fan’s property constructed some walls around the northern, southern and western boundaries of the property, including the retaining wall. There was backfill placed behind the retaining wall on the Stockwells’ side. The previous owner has not given evidence. 
37. [37]
    The retaining wall has apparently been constructed 500 millimetres within the boundary of Ms Fan’s property.  A stormwater drain covered by a manhole is towards the western end of the retaining wall.  It is on the Stockwells’ side of the retaining wall and is relatively close to it.  
38. [38]
    Australian Standard AS 4678-2002 applied to the design and construction of the retaining wall (‘the Australian Standard’). It is not known whether the then owner of Ms Fan’s property complied with the requirements and recommendations contained therein, although it seems unlikely. 
39. [39]
    It is agreed between the parties that the retaining wall (as originally constructed) is approximately 13 metres in length.  It is comprised of timber horizontal sleepers and vertical posts that are 190 millimetres wide and 70 millimetres thick at 1.1 to 1.2 metre centres.  The height varies along its length and is between 1.6 and 2.4 metres, with the highest section in the north-eastern corner of Ms Fan’s property.  Geotextile mesh was placed behind the timber sleepers and a gravel drainage layer was put in behind the wall.  Much remains unknown about the retaining wall and its construction. There is no evidence for example about the intended design life of it, its construction details, whether piped drains were installed underground, the ground water conditions in the vicinity of it, the foundation bearing capacity, or the foundation embankment strength parameters. 
40. [40]
    Relevant building regulations apparently required retaining walls with a height of more than one metre to be approved.  It is agreed between the parties that no approval was obtained.
41. [41]
    It was Mr Stockwell’s evidence that since mid-2022, he has seen water pooling on about five occasions on Ms Fan’s property in front of the retaining wall.  These were said to have occurred after rain events.  I am not persuaded that this evidence enables any conclusions to be drawn about the nature or extent of any subsurface drainage installed when the retaining wall was constructed.  As Mr Wong explained, further information would be required, including the time taken for the pooled water to drain away.  Another relevant factor would be the volume of the rain that had fallen.   

32. Work undertaken on the Stockwells’ property 

42. [42]
    It is not in dispute that after the construction of the retaining wall, in around early 2005 the Stockwells added some sleepers to it and constructed a timber paling fence on top of it.  For the purposes of these reasons, I will refer to the combination of the retaining wall, the added sleepers and the timber paling fence as the ‘high wall’.  Cosmetic sheeting was placed by the previous owner of Ms Fan’s property along the entire length of the high wall, as seen from her property.^[5]
43. [43]
    The Stockwells also did some other work in the vicinity of the retaining wall on their side.  This included adding potting mix as backfill, creating a garden bed, planting trees, installing a water feature and constructing two decks. One of the decks is over the manhole for the stormwater drain (‘the small deck’).  The other deck is larger and at the opposite end of the retaining wall towards the north-eastern corner of it (‘the large deck’).  The Stockwells have also built a much smaller retaining wall close to the water feature.   I will address each of these in turn. 

32. Additional sleepers and timber paling fence

44. [44]
    As discussed in paragraph 22 above, I am satisfied that in approximately late 2004, Mr Stockwell added six timber sleepers to the top of the retaining wall.  They were not attached in any way but were placed on top of it.^[6]  They were each 2.4 metres long and 200 millimetres high.  This added weight on the retaining wall was over a length of 4.8 metres and to a height of 600 millimetres.  As Mrs Stockwell explained, the sleepers were kept in place by potting mix piled up against them.  Exhibit 11 shows the three timber sleepers immediately next to the small deck.  The other three sleepers were immediately next to those, and were positioned in front of the roots of the tree shown in the photograph.   The location of these additional sleepers along the retaining wall is also marked on the diagram in exhibit 18.3.
45. [45]
    After these six sleepers had been added, Mr Stockwell constructed a timber paling fence on top of the retaining wall along the whole length of it.  It was at two different heights, being approximately 1.5 and 1.6 metres.^[7]      

32. Extra soil, garden bed and trees

46. [46]
    By the time that Mr Stockwell had finished placing the additional six sleepers on top of the retaining wall, there had been some subsidence of the backfill that had been placed there by the previous owner of Ms Fan’s property.  Mr Stockwell replaced this with potting mix from Bunnings.  He then added further potting mix to this backfill.  As explained in paragraph 25 above, I do not accept that the potting mix added was to a depth of approximately 100 millimetres.  In my view, it is likely to have been at least 400 millimetres and probably closer to 500 millimetres (‘the extra soil’). This is in circumstances where the added sleepers increased the height of the retaining wall by 600 millimetres, and it was Mr Stockwell’s evidence that only half to one sleeper remained exposed after he had added the extra soil.    
47. [47]
    For the initial 12 or so months, lawn was laid over the backfill in the area immediately in front of the high wall from the Stockwells’ side. In approximately late 2005, some of the lawn was replaced with a garden bed, which was approximately nine metres long and a metre wide.  Initially, the garden bed was planted with tropical plants, such as yellow torch gingers. These remained there for the next four or so years.
48. [48]
    In approximately 2009, the tropical plants in the garden bed were removed and it was re-planted.  I am satisfied the trees that the Stockwells planted at this time were at least five lilly pillies, two mock oranges, a frangipani, and a pomegranate (‘the trees’).  Exhibit 3 shows that by 2017 the trees were very well established, were providing a continuous hedge along the entire length of the garden bed and were significantly overhanging the high wall.  I accept Ms Fan’s evidence that this was the general appearance of the trees once they had become established.
49. [49]
    Mr Stockwell would irregularly prune the trees from his side of the high wall, cutting back branches within his reach.  Mrs Stockwell explained that they had been reluctant to prune the trees during the five-year period that Ms Fan’s property was tenanted, as they did not want the cuttings falling into Ms Fan’s yard.  I accept Mrs Stockwell’s evidence that the pruning was done every couple of years when the trees were getting “untidy”. 
50. [50]
    It was the Stockwells’ evidence that they have only removed four trees from the garden bed.  Mr Stockwell said that three of these are the lilly pillies shown in exhibits 34.1 and 34.2, which he said he removed in mid-2021. There are two reasons why I am not persuaded that the two trees shown in exhibit 34.1 are two of the five lilly pillies that had been in the garden bed.  First, the trunk sizes of the trees shown in exhibit 34.1 are markedly smaller than the trunk size of the lilly pilly which remains in the garden bed, as shown in exhibit 34.3.^[8]  Such a significant size differential in the trunks would seem unlikely for trees of the same type, planted at the same time and in the same garden bed.  Second, it seems highly improbable that lilly pillies that had been growing in the garden for more than a decade would have such small trunks as shown in exhibit 34.1. This is particularly so, given the very established nature of the trees by 2017.^[9]  Of course, they continued growing for a further four or so years before they were removed. 
51. [51]
    Mr Stockwell said he thought the pomegranate was removed from the garden bed in late 2017 or early 2018.  I am not persuaded by this because when Mrs Stockwell was cross-examined about a text that Ms Fan sent her on 1 September 2020, it was her evidence that none of the trees had been removed at this time.  Further, there is little difference between the density of the trees overhanging the high wall in 2017 (as shown in exhibit 3) and in approximately 2020 (as shown in exhibit 4). It seems likely that the pomegranate was removed from the garden bed sometime between September 2020 and May 2021 (when Barth Building undertook the make-safe work).

32. The other work

52. [52]
    The Stockwells added two decks at either end of the garden bed adjacent to the retaining wall. The small deck covers the manhole adjacent to the north-western end of the retaining wall^[10].  It was constructed by Mr Stockwell within weeks of the retaining wall having been completed.  The large deck is adjacent to the retaining wall at the other end. It was built in two stages, with the first stage in 2005.  It was extended in approximately 2009.  It has been contended on behalf of Ms Fan that the decks were physically attached to the retaining wall.   I have been unable to resolve whether this is correct and have proceeded on the basis that each of them at least partly abutted the retaining wall, but were not physically attached to it.  
53. [53]
    A water feature was also built by Mr Stockwell in approximately 2007 or 2008.^[11]  It is approximately 2.5 metres long and has a water depth of about 300 millimetres.  The edge of the water feature is positioned approximately 1.2 metres from the original position of the retaining wall and is towards the middle of the backyard.  It is made of cement and tiles.  Waterproofing paint was applied to the shell of it.  No drainage was constructed around it.  Its position is such that if it were to overflow or leak, it could potentially drain downhill towards the retaining wall.  Counsel for Ms Fan made much of the green algae on some of the tiles of the water feature that can be seen in photographs of it.^[12]  I am not persuaded that the presence of the algae can be explained by the overflow of water from the water feature.  This is in circumstances where I am satisfied that this was an infrequent occurrence. It seems more probable that the green algae has been caused by water frequently being deposited there when sprayed from the fountain in windy conditions.
54. [54]
    There is a much smaller additional retaining wall comprised of two sleepers close to the water feature. I am satisfied that this was put there after Ms Fan started to notice problems with the high wall, as discussed below.  The sleepers had been moved from a garden edge in the front yard.  

32. Ms Fan purchases her property

55. [55]
    Ms Fan purchased her property in approximately May 2014.  At this time, the high wall was covered with the cosmetic sheeting installed by the previous owner. This meant that Ms Fan was unable to see the retaining wall or the timber paling fence that had been installed by Mr Stockwell, although she could see the trees from the Stockwells’ property overhanging the high wall. She lived at the property with her mother and two children for approximately two years, prior to renting it out in 2016. Tenants remained living there for the next five or so years.  Over this time, Ms Fan would carry out three monthly inspections.  She and her family returned to live at the property in 2021 and have remained living there.  
56. [56]
    At some point in 2017, Ms Fan noticed that there was a crack in the cosmetic sheeting of the high wall.  She also noticed that branches, foliage, and pomegranate fruits from the Stockwells’ trees were overhanging it and causing it to tilt towards her property.
    The extent of this is depicted in exhibit 3.^[13]
57. [57]
    Ms Fan did not know the Stockwells.  She tried to contact them by leaving a letter in their letter box.  I do not accept Mrs Stockwell’s evidence that the letter was handwritten.  I prefer Ms Fan’s evidence that it was typed and that a copy of it is exhibit 2.   It referred to Ms Fan having recently undertaken an inspection of her property.  It was noted that the Stockwells’ trees were overhanging the high wall.  She expressed a concern that these trees may have been impacting on the high wall as she had observed a “noticeable tilt” in it.  Ms Fan attached a photo that she had taken depicting her concerns.^[14]  As explained in paragraph 19 above, I accept Ms Fan’s recollection that neither of the Stockwells contacted her in response to this letter.
58. [58]
    In approximately 2019, Ms Fan was present at her property for another inspection and noticed that the crack in the cosmetic sheeting over the high wall was getting bigger and that the wall was starting to lean further towards the roof of her residence. She also said that the Stockwells’ trees were overhanging it to the extent that they were covering the gutter of her roof.  She was becoming concerned that the high wall was at a point where it was presenting as a safety risk. 
59. [59]
    On 7 August 2020, Ms Fan forwarded Mrs Stockwell a text requesting her email address, as Ms Fan was wanting to send her an email regarding the retaining wall.   Mrs Stockwell did not meaningfully engage with Ms Fan. Instead on 12 August 2020, she sent a text to Ms Fan wanting to know how Ms Fan had obtained her mobile number.   Later that day, Mrs Stockwell forwarded another text to Ms Fan making it clear that she would not be responding to further texts from Ms Fan. A further request was made for
    Mrs Stockwell’s email address and Ms Fan forwarded another photo showing the overhanging trees and the tilt to the high wall.  
60. [60]
    It seems that there was subsequently a conversation between Ms Fan and Mrs Stockwell.  This is because it was referred to in a further text that Ms Fan forwarded to Mrs Stockwell on 30 August 2020. Ms Fan again expressed her concerns about the ongoing encroachment of the trees over the high wall, the crack in the cosmetic sheeting and the “big tilt” to the high wall.  She said that such was the situation that she was worried the high wall would collapse.  She requested the Stockwells to remove the trees and invited them to come onto her property to inspect the high wall.   In cross-examination, Ms Fan explained that at this time her primary concern was the impact to her property if the high wall was to fail.   
61. [61]
    In a text dated 1 September 2020, Mrs Stockwell responded that they had no intention of removing the trees and that they were being cut back “every few years when they get untidy”.   Consistent with this, none of the trees were removed at this time.  Ms Fan was left in no doubt that the Stockwells were not prepared to accept any responsibility for the failure of the retaining wall.  Two reasons were proffered for this.  First, that it belonged to Ms Fan in circumstances where it was required because of the excavation works undertaken by the previous owner of Ms Fan’s property.  Second, prior to the retaining wall being constructed, the previous owner of Ms Fan’s property had not sought the Stockwells’ input about the decision to construct it with timber.  
62. [62]
    By text message on 2 September 2020, Mrs Stockwell forwarded a photo of their paling fence to the Ms Fan noting that it was straight.^[15]     
63. [63]
    It was the evidence of Ms Fan that the crack in the retaining wall continued to get bigger and the lean on it towards her property became more significant.   She said that she was becoming greatly concerned about the safety of it. 
64. [64]
    By early April 2021, the failure of the retaining wall was starting to impact on the Stockwells.  From this point, they began to communicate with Ms Fan more proactively about the issue, although they continued to refuse to contemplate the prospect that anything they had done to their property may have contributed to its failure.  Consistent with this, on 6 April 2021 Mrs Stockwell forwarded a text to Ms Fan requesting her to “please have someone investigate your retaining wall as it is collapsing”.  Ms Fan responded that she had commenced renovations at her property and she was checking if a building engineer could come and urgently inspect it.  Ms Fan said that her plan at this stage was to have a builder remove the cosmetic sheeting to expose what was behind it.  
65. [65]
    In the following weeks, the cosmetic sheeting was removed from the high wall.  The tilt was now to such an extent that the top of the timber fence was resting on the gutter of Ms Fan’s house. The photographs in exhibit 6 depict the exposed retaining wall and timber paling fence.^[16]  The was the first time that Ms Fan had seen the two decks and the tree roots close to the retaining wall.   She could now appreciate that its failure also posed a risk to the Stockwells’ property, because of the subsidence in the ground level near it. 
66. [66]
    The high wall was inspected by an engineer and on 4 May 2021, Ms Fan again requested Mrs Stockwell to provide her email address so that the engineer’s report could be forwarded to her.  Mrs Stockwell provided this.  On the following day, Ms Fan sent
    Mrs Stockwell an email raising the urgent need to rectify the situation.   She referred to the overloaded soil and the Stockwells’ overgrown trees pushing the high wall, as factors contributing to its collapse.  She said that she had arranged for a building engineer to assess the compliance of the structure and design.  She attempted to informally negotiate a resolution, where they both equally contributed to the cost of replacing the retaining wall.  She offered to obtain two quotations for such work to be undertaken and suggested that the Stockwells may also wish to obtain their own quotation. 
67. [67]
    On 7 May 2021, Ms Fan permitted Mr Stockwell to come on to her property to inspect the retaining wall.^[17] Three days later, Ms Fan enquired about how Mr Stockwell’s inspection had gone and told Mrs Stockwell that a soil report was being obtained.^[18] 
    The Stockwells responded to this enquiry on 12 May 2021, by informing Ms Fan that they were obtaining a report from an engineer, pending which they would respond to her suggestion that the costs of replacing the wall be shared.   They enquired whether Ms Fan had considered any short term supports for the wall to mitigate further failure.   Two days later, Ms Fan responded and reiterated that she thought the Stockwells’ overgrown trees had contributed to the damage to the high wall.  She told them that she was concerned about the instability in the retaining wall, particularly given that her family were about to move back into the property.   
68. [68]
    In late May 2021, Ms Fan’s insurer engaged Barth Building to inspect the retaining wall and to make it safe (‘the make-safe works’) and a report was prepared.^[19]  The paling fence was removed from the top of the retaining wall.  Timber props were added to the lower side of the retaining wall on Ms Fan’s property and attached to star pickets to stop further leaning of the wall.  For safety, temporary fencing and a barrier mesh were placed on each of the properties in the vicinity of the retaining wall.^[20]  I do not accept as was suggested to Ms Fan that the trees depicted in the Barth Building report photographs represent the entirety of the trees that the Stockwells had planted along the retaining wall since 2009.  This contradicts Mr Stockwell’s evidence. Further, as explained in paragraph 51 above, I think it probable that at least the pomegranate tree had been removed by this time.  Further, it is worth observing that I accept Ms Fan’s evidence that she returned home one day around this time and observed that there were trees from the Stockwells’ property on the ground.  Barth Building returned on 16 June 2021. On that occasion, the timber props were replaced with steel ones.^[21]   
69. [69]
    From the middle of 2021, both parties commenced seeking out expert opinions as to the cause for the collapse and the appropriate design features to rebuild it.  They had each retained lawyers by May 2022.  There were ongoing communications about the respective positions of the parties regarding the reasons for the failure of the retaining wall.^[22]  Ms Fan explained that there were two reasons why she did not go ahead and fix the retaining wall.  The first was that she believed that the backfill the Stockwells had placed behind the retaining wall and the trees they had planted near it had contributed to its failure. She also did not have the financial means to fund a rebuild of it in circumstances where the insurance claim she had made in respect of it had been refused. 
70. [70]
    Ms Fan’s evidence was that in approximately February 2022, the northern end of the retaining wall collapsed after a significant rain event.  Late that month, she forwarded the Stockwells a text to say that the supporting posts had moved and she was very worried that the wall would collapse.^[23]
71. [71]
    By a letter dated 18 May 2022, Ms Fan’s then solicitors forwarded a letter to the Stockwells enclosing a stormwater map, an engineering report and a quote to repair the retaining wall.   It was stated that the Stockwells’ works on their property was the primary reason for the failure of the retaining wall.  A proposal was put forward for the Stockwells to contribute 60 percent to the cost of replacing it.  This proposal was not accepted. ^[24]   
72. [72]
    Ms Fan’s evidence was that over the six months prior to the trial commencing, the retaining wall had continued to deteriorate.  She explained that the part of it in front of the large deck has further collapsed and that it has also collapsed around the middle of the length of it.  
73. [73]
    There is no doubt that the retaining wall in its current state is substantially impacting on the ability of both parties to use and enjoy the backyards of their respective properties.    

32. Relevant legal principles

32. Nuisance

74. [74]
    The tort of nuisance is concerned with a continuing situation or condition, rather than an isolated or rare event. Relevant to this case, an adjoining neighbour is said to have committed a private nuisance when they are held to be responsible for:

    1. an act or omission causing physical injury to a neighbour’s land and/or structures on it, or
    2. an act or omission substantially interfering with the use or enjoyment of a neighbour’s land, where in the light of all the surrounding circumstances the interference is held to be unreasonable.^[25] 
75. [75]
    The onus lies on the neighbour contending the nuisance to prove the elements of the cause of action. If the nuisance complained of consists of substantial physical injury to land or structures on it, the fact of that injury or damage need only be proved, and the onus shifts to the adjoining neighbour to show the reasonableness of any precautions that have been taken. 
76. [76]
    Fault of some kind is almost always necessary.  It must be reasonably foreseeable that there is a risk of damage if the adjoining neighbour’s use of their land which constitutes the nuisance is continued.^[26] 
77. [77]
    As to whether an interference is unreasonable, the test is objective.^[27] It is a question of whether what has been done is reasonable from the perspective of both parties.  In cases of nuisance by interference with a neighbour’s use and enjoyment of their property, the court considers all the circumstances in determining whether the interference is unreasonable.  If the adjoining neighbour has taken precautions against interference, this is but one of the considerations to be taken into account.^[28] If there has been material or substantial physical damage to property, this will normally be sufficient to establish that an interference is unreasonable.^[29]
78. [78]
    In determining whether an interference with the enjoyment of land is substantial, injury to health need not be proved.^[30] Further, the damage itself need not be substantial. 
    Rather, it needs to be established that the activities constituting the nuisance interfere, to a greater extent than is reasonable, with the neighbour's use of their land.^[31] 
    An interference will be substantial where the use of the adjoining neighbour’s land is rendered hazardous by a threat of damage which is foreseeably likely to result from that dangerous state of affairs.  
79. [79]
    Not only does liability attach to an adjoining neighbour for creating a nuisance, but it can also attach where the nuisance is continued or adopted, or where the adjoining neighbour negligently fails to remedy or abate it.  A nuisance is continued where, with actual or constructive knowledge of the existence of it and the possibility of danger occurring in consequence of it, there is a failure within a reasonable time to take measures to remedy it.^[32]
80. [80]
    Regard is to be had to a variety of factors, including the nature and extent of the harm or interference and whether all reasonable precautions were taken to minimise any harm or interference.  It is necessary to consider the practicality of preventing or minimising the happening of any damage and the nature of the measures required, including their difficulty, their length, their cost and the time available for the preventative action to be taken.^[33]  The financial circumstances of the adjoining neighbour are also relevant.^[34] 
81. [81]
    It is well established that while trees or their roots are not per se a nuisance, they will become actionable where encroaching roots cause physical damage to structures standing on the neighbour’s land, including retaining walls.  This is irrespective of whether the roots have penetrated the neighbour’s land.^[35]  Further, if some activity causes water to come onto the neighbour’s land, including along the ground, this can be actionable as a nuisance.  An example of where this might occur is where a structure has been built on the higher property, increasing the flow of water onto the lower property.   In addition, I accept the submission by counsel for the Stockwells that a structure like a retaining wall, which was not a nuisance when it was constructed, can become a nuisance.  
82. [82]
    Factual causation is central to the question of whether there has been a substantial and unreasonable interference with a neighbour’s use and enjoyment of their property. 
    This is to be determined by applying common sense to the facts of the case.^[36]  The act or omission must have materially contributed to the damage suffered, which may be the case even if other factors have played a significant role.^[37] Scientific proof is not required.^[38] 

83. S 179 of the PLA

83. [83]
    At common law an owner of land is entitled to have their land in its natural state supported by adjoining land.   A neighbour who withdraws support is liable in nuisance if it creates subsidence which causes actual damage.^[39]  It is a nuisance to which strict liability attaches, meaning that proof of fault is unnecessary. 
84. [84]
    It is well established that a neighbour cannot be made liable for the subsidence of adjoining land resulting from the withdrawal of natural support by an act (such as excavation) of a predecessor in title.^[40]  The reason for this is that there is no continuing duty running with the land to supply artificial support for the natural support which has been taken away by the act of a previous owner.  This is because the duty is not a positive one to support the adjoining land, but rather a negative one not to interfere with the natural support possessed by that land.  The person who originally made the excavation or otherwise withdrew the support is the one that breaks this negative duty, and that person is and remains responsible for the consequences of the act, whenever those consequences occur.^[41]
85. [85]
    The effect of s 179 of the PLA is two-fold. In terms of the right to support of land, it codifies the abovementioned common law rules, without adding to them.  In addition, it extends these common law rules to any building, structure or erection placed on that land, so that the obligation not to withdraw support applies not only to unimproved land.
86. [86]
    There are a few observations to be made about this legislative provision.  First, the essence of an action under this section is physical damage that is usually consequential upon an isolated unintentional event, rather than on ongoing situation.  Second, it does not seem to extend to a reduction in support that is not a complete withdrawal of support. Third, an omission to act, including failing to take action to prevent a loss of support from occurring, does not seem to fall within the scope of this section.  Fourth, retaining walls located on boundaries (including those that collapse leading to the subsidence of land) are not covered by this section. This is because the retaining wall is located on the boundary and the obligation not to withdraw support relates to actions on one property which withdraws support from any other land or building.

83. Negligence

87. [87]
    The tort of negligence is separate and distinct from the tort of nuisance.   The relationship between occupiers of neighbouring properties is a familiar category where the common law imposes a duty of care on each neighbour in relation to the other neighbour. 
88. [88]
    The general proposition is that liability in negligence depends upon proof of fault through the negligent infliction of harm.  It does not depend on the prevention of harm.^[42]  It follows that an adjoining neighbour is not required to guard against all risks of harm or to safeguard their neighbour completely from all perils.^[43]  Rather, the duty is to take reasonable care to avoid exposing the neighbour to unnecessary risks of harm.
89. [89]
    For a neighbour to succeed, it must show that the adjoining neighbour unreasonably failed to take measures reasonably open in the circumstances which would have protected them from harm. 
90. [90]
    The statutory framework provided for in the Civil Liability Act 2003 (Qld) (‘the CLA’) must also be considered.  Pursuant to s 9(1) of the CLA, an adjoining neighbour does not breach a duty to take precautions against a risk of harm to a neighbour unless the risk was foreseeable, not insignificant and in circumstances where a reasonable person in the position of the adjoining neighbour would have taken the precautions.  The effect of this legislative provision is to direct the court’s attention to the level of risk that needed to be guarded against, when considering whether an adjoining neighbour has breached its duty of care.  It requires an objective enquiry.
91. [91]
    In assessing whether a risk of injury is foreseeable, it is not necessary for the precise harm to have been foreseeable, provided the harm is of the same kind or type as that which was reasonably foreseeable.  It is also not necessary for the precise sequence of events by which the harm came about to have been foreseeable. It is sufficient if a consequence of the same general character as that which followed the negligence, was reasonably foreseeable.
92. [92]
    Pursuant to s 9(2) of the CLA, in determining whether a reasonable person would have taken precautions against a risk of injury, the considerations include the probability that the harm would occur if care were not taken, the likely seriousness of the harm and the burden of taking precautions to avoid the risk of harm. These factors reflect the common law’s approach as explained by Mason J in Wyong Shire Council v Shirt.^[44]
93. [93]
    A court must identify what a reasonable person would have done, rather than using hindsight to identify what would have avoided the harm.  A finding of negligence does not inevitably flow from a failure to eliminate a risk of harm that was reasonably foreseeable and preventable. The fact that a risk of injury could have been avoided by doing something in a different way, does not of itself give rise to or affect liability for the way in which the thing was done.^[45]

83. Remedies

94. [94]
    The prima facie remedy to which a successful applicant is entitled in claims for nuisance, negligence and a breach of s 179 of the PLA, is an injunction.^[46] However, it is discretionary and the facts of each case must be considered.  Damages may be awarded in lieu of an injunction where they are able to be ascertained and where they are adequate.^[47]  Once damage has been established, there is an entitlement to damages for any resulting loss which is a natural and foreseeable consequence of the wrongful act of the respondent.
95. [95]
    The measure of damages recoverable for the commission of a tort is those that are compensatory.  Their function is to put the successful applicant in the same position as if their rights had been respected as far as the award of a sum of money can do.^[48] 
    This usually gives rise to two competing measures of loss, either the repair or replacement costs involved or the ‘diminution in value’ measure.  The courts will usually apply the ‘test of reasonableness’ involving a consideration as to what in the particular circumstances would most reasonably give effect to the compensation principle.^[49] 
    This involves a consideration of the reasonableness of the applicant’s desire for replacement. Relevant to this is a determination of the advantages to the applicant of replacement and the extra cost to the respondent in having to pay damages for replacement rather than for the diminution in the value.   If the fair measure of damages is replacement, “the wrongdoer has no-one but himself to blame”.^[50]
96. [96]
    The issue of ‘betterment’ can arise in tort claims for replacement or repair costs.  
    The questions to be determined are whether betterment exists and if so, whether an account for it should be allowed.
97. [97]
    If a party placed in a difficult situation by reason of a breach of duty owed to them has acted reasonably in the adoption of remedial measures, they will not be disentitled to recover the cost of such measures merely because the party in breach can suggest that other measures less costly might have been taken, or because the party incidentally derives some greater benefit over and above mere indemnification.^[51] 
98. [98]
    Before a finding of betterment can be made premised upon a successful applicant being overcompensated, the court must be satisfied that:

    1. there has been an improvement in the reinstated property beyond ‘new replacing old’^[52];
    2. the superior replacement must confer a benefit upon the successful party which is not merely speculative^[53]; and
    3. the benefit accruing to the successful party is both realisable and quantifiable in monetary terms.^[54]
99. [99]
    Chapter 2 Part 2 of the Civil Liability Act 2003 (Qld) (‘the CLA’) provides for proportionate liability.  In particular, pursuant to s 28(1)(a) of the CLA, an apportionable claim is “a claim for economic loss or damage to property in an action for damages arsing from a breach of a duty of care”.  The primary operative provision of Part 2 is s 30(1), which removes joint and several liability of a “concurrent wrongdoer”, namely “who is 1 or 2 or more persons whose acts or omissions caused, independently of each other, the loss or damage that is the subject of the claim”.  The parties have not referred to any Queensland case which has decided whether these provisions of the CLA can apply to a claim in private nuisance. 
100. [100]
     Relevantly, each of the equivalent provisions to s 28(1)(a) of the CLA in New South Wales, Victoria, Western Australia and Tasmania are identical to each other and provide that an apportionable claim is “a claim for economic loss or damage to property in an action for damages (whether in contract, tort or otherwise) arising from a failure to take reasonable care, but not including any claim arising out of personal injury”.
101. [101]
     It is contended by the Stockwells that the proportionate liability provisions in the CLA do not apply to any claim in nuisance.  It is submitted that there are two principal reasons for this.  First, the Queensland regime is said not to apply to as broad a range of cases as the equivalent provisions in the other States. Second, the Stockwells rely on the Tasmanian Supreme Court decision in Prestage v Barrett^[55]where the proportionate liability provisions in the Tasmania legislation were held not to apply to such a claim.  This was because it was found that it is the cause of action that must arise from the failure to take reasonable care and not the particular loss, and the tort of private nuisance does not need to arise from the failure to take reasonable care. 
102. [102]
     I am not persuaded to accept the reasoning adopted in Prestage as determinative of the issue in this case.  This is because, as discussed below, there is considerable support at the appellate level in Victoria, New South Wales and Western Australia for an approach to proportionate liability that looks to how a claim is framed, and to the findings of the court, rather than being limited to whether a lack of reasonable care is an element of the cause of action.  
103. [103]
     In Reinhold v NSW Lotteries Corporation (No 2)^[56],Barrett J found that the nature or quality of a claim for the purposes of the proportionate liability provisions could not be determined without taking into account the court’s decision on the claim, and that it will be the findings ultimately made that determine whether the provisions are satisfied. 
     This was followed in the Victorian Court of Appeal in Godfrey Spowers (Victoria) Pty Ltd v Lincoln Scott Australia Pty Ltd^[57].
104. [104]
     Perpetual Trustee Company Ltd v CTC Group Pty Ltd (No 2)^[58] is a New South Wales Court of Appeal case where the defendant was found liable in damages for breaching its obligations of care under a mortgage origination deed.   While it was not necessary to decide whether the claim was an apportionable one under the New South Wales legislation, Macfarlan JA considered it.  However, this was in circumstances where his reasoning was obiter and based on the assumption that the plaintiff was entitled to succeed on at least one cause of action that did not require it to prove that the defendant failed to exercise reasonable care.  Based on that assumption, Macfarlan JA said that had it been necessary to decide, that he would have found in favour of the plaintiff that the proportionate liability provisions did not apply. This is because it was necessary that the failure to take reasonable care is an element of the cause of action upon which the plaintiff succeeds.  However, it is important to note that Macfarlan JA did not consider nor found to be wrong the abovementioned Victorian appellate decision of Godfrey Spowers.  Further, Meagher JA and Barrett JA did not endorse his Honour’s views.  Meagher JA preferred not to express any view on this reasoning.  Barrett JA did not agree with the reasons of Macfarlan JA.  He expressed the view that the nature or quality of a claim for the purposes of proportionate liability provisions could not be determined without taking into account the Court’s decision on the claim, and that it will be the findings ultimately made that determine whether the provisions apply.
105. [105]
     The question of apportionable claims was again considered by the New South Wales Court of Appeal in Rahme v Benjamin & Khoury Pty Ltd ^[59].  The principal judgment was delivered by Macfarlan JA and his Honour endorsed his abovementioned approach in Perpetual.  In Rahme, the solicitors were found to owe fiduciary duties to the client, and were found to have breached those duties by acting in circumstances where the interests of the client conflicted with the financial interests of the solicitors, who stood to gain considerably by the plaintiff entering into the relevant agreement.  His Honour found that for a defence of proportionate liability to be available, it was necessary that the absence of reasonable care was an element of the cause of action upon which the plaintiff succeeded.  However, it is of note that in that case the successful cause of action was based upon the solicitors acting when they had a conflict of interest.  It did not involve any finding that the solicitors acted without reasonable care.  Further, there was again no consideration of the approach adopted in Reinhold or Godfrey. 
106. [106]
     This issue was also considered by the Victorian Court of Appeal in Tanah Merah Vic Pty Ltd v Owners Corp No 1 of PS613436.^[60]  The Court held that it was no longer appropriate to follow the reasoning of Barrett JA in Reinhold, in part because it was considered that Barrett JA had qualified his position in Perpetual. Further, it was observed that Godfrey was “merely obiter dicta”.  It was held that the correct approach was as set out by Macfarlan JA in Perpetual that the “terms in which a claim is framed … are an essential determinant of whether the claim can be said to arise from a failure to take reasonable care.
107. [107]
     In Prestage, Estcourt J followed the approaches of Macfarlan JA in Perpetual and Rahme and the Victorian Court of Appeal in Tanah Merah. 
108. [108]
     On the same day that Prestage was delivered, the West Australian Court of Appeal delivered its decision in Herridge Parties v Electricity Networks Corporation t/as Western Power.[61] It analysed the equivalent provision in Western Australia and considered the approach in Rahne (and thereby Taneh Merah and Prestage) to be wrong although it did not need to decline to follow it.   It was held that the claims in nuisance advanced by the plaintiffs (and found to be established on the evidence) did arise from a failure to take reasonable care within the meaning of the definition of ‘apportionable claim’ in the Western Australian legislation. This was on the basis that proving an unreasonable interference for the purposes of the law of nuisance, required the plaintiffs to prove a failure to take reasonable care and was therefore considered a civil proceeding for the recovery of damages arising from a failure to take reasonable care. It was further held that a reference to a ‘cause of action’ is generally to the fact or combination of facts which give rise to the right to sue.
109. [109]
     In the recent New South Wales Court of Appeal decision of Gerard Toltz Pty Ltd  v City Garden Australia Pty Ltd (in liq)(No 2)^[62] Stern JA and Basten AJA, in very considered obiter dicta statements, endorsed the reasoning in Herridge. Basten AJA was doubtful about the conclusion in Taneh Merah to the effect that in Perpetual Barrett JA had qualified his position as articulated in Reihnold.  Stern JA agreed and determined that a claim which is upheld on the basis that there was a failure to take reasonable care will constitute an apportionable claim irrespective of the pleaded cause of action.  
110. [110]
     Consistent with the approaches referred to in Herridge and Gerard Tolz, in determining whether the proportionate liability provisions of the CLA apply, I am persuaded to look at the facts which give rise to the cause of action, rather than the description of the form of the action.  
111. [111]
     Further, I am not persuaded by the Stockwells’ submission that the Queensland regime is to be interpreted more narrowly than the equivalent provisions in the other States as referred to above.  This is said to be because s 28(1)(a) of the CLA employs the words “arising from a breach of duty of care”, while the provisions in the other States employ the words “arising from a failure to take reasonable care”.  This submission is inconsistent with the explanatory notes to the amending legislation, which explain that the amendments were intended to provide national consistency.^[63]  Further, in my view the difference in the language used in s 28(1)(a) of the CLA and the equivalent provisions in the other States, is not critical.   It seems that where fault in the context of nuisance is premised on a breach of duty of care which allowed the nuisance to arise, and this neglect amounts to a failure to take reasonable care, it is an apportionable claim to which the CLA applies.
112. [112]
     The effect of s 31 of the CLA is that where there are concurrent wrongdoers, the liability of each is limited to an amount reflecting the proportion of the damage or loss claimed which the court considers just, having regard to the extent of each wrongdoer’s responsibility for the damage or loss. 
113. [113]
     Pursuant to s 30(4) of the CLA, the proportionate liability provisions apply even if a concurrent wrongdoer is not a party to the proceedings.
114. [114]
     The onus is on the party relying on the proportionate liability provisions to prove the limitation of their liability on this basis.^[64]  It involves a consideration of the facts that have been proved which allow the Court to be satisfied that another person is a concurrent wrongdoer and then allocate the proportionate liability which is just and equitable in the circumstances.  The court has a wide discretion in making the apportionment.^[65] 
115. [115]
     The Court is required to make findings about the whole conduct of each concurrent wrongdoer.  It includes a comparative examination of the degree of departure from the standard of care of the reasonable person, as regards the causative conduct of each of the concurrent wrongdoers and the relative importance of their acts in causing the loss suffered by the applicant.^[66]    
116. [116]
     Damages are also recoverable for the annoyance, inconvenience and discomfort caused by an interference with the use and enjoyment of land which does not cause material physical damage or pecuniary loss.^[67]  It covers a wide range of tangible and intangible considerations which are not capable of reasoned articulation.^[68]  It is difficult to quantify such damages and they cannot be assessed with any kind of mathematical precision. Relevant considerations include those set out in paragraph 44 of the Stockwells’ submissions. 

117. The experts

117. [117]
     The experts called were two arborists, being Mr Herlihy and Mr Martinelli and three engineers, being Mr Wong, Mr Van de Hoef and Mr Schaper.
118. [118]
     Mr Herlihy inspected the trees on the Stockwells’ property in the garden bed adjacent to the retaining wall at the request of Ms Fan on 22 August 2023.  Mr Martinelli’s inspection occurred at the request of the solicitors for the Stockwells approximately six months later.  They have provided reports dated 23 August 2023 and 2 February 2024 respectively. 
119. [119]
     While Mr Martinelli has a higher certificate qualification than Mr Herlihy and has more experience in writing expert reports, I am satisfied that they are both suitably qualified and experienced to provide expert opinions on issues relating to the trees.  Further, I am not persuaded by the cross-examination of Mr Herlihy to the effect that his opinions were somehow improperly influenced by the circumstances in which Ms Fan came to engage him.  I accept Mr Herlihy’s evidence that Ms Fan did not seek to suggest to him that the trees had contributed to the collapse of the retaining wall.
120. [120]
     Mr Wong inspected the retaining wall at the request of Ms Fan on 21 January 2023.
     Mr Van de Hoef’s inspection was at the request of the Stockwells and occurred on 14 August 2023.  Their reports are dated January 2023 and 17 August 2023 respectively.  They provided a joint expert report dated 25 August 2023. Mr Wong provided a subsequent report dated 8 September 2023 and Mr Van de Hoef provided responses to further questions in a letter dated 12 February 2024.
121. [121]
     Despite some cross-examination to the contrary, I have no hesitation in accepting that Mr Wong is appropriately experienced to provide expert assistance to the court about the potential causes for the failure of the retaining wall.    
122. [122]
     There was extensive cross-examination of Mr Wong about the circumstances in which he came to be involved in this matter.   While he has significant experience as an engineer, this is the first time he has been involved in litigation as an expert witness.  He had no previous experience in conducting inspections, writing reports, or being involved in the process of providing a joint expert report.  His naivety about such matters was reflected in his approach to them. For example, Mr Wong attended the inspection with his business partner, who is also a civil and structural engineer.  While they clearly discussed the issues surrounding the failure of the retaining wall, I am satisfied that the opinions in
     Mr Wong’s reports are his.  Further, I accept that at the time of providing his initial report, Mr Wong was not familiar with the code of conduct for experts.  I also accept
     Mr Wong’s explanations as to why the joint expert report did not accurately reflect all his opinions and it needs to be considered in this context.  I am also not persuaded by the line of cross-examination suggesting that Mr Wong has advocated for Ms Fan or otherwise conducted himself other than professionally in providing independent expert assistance to the court. 
123. [123]
     On 5 February 2024, the solicitors for the Stockwells requested Mr Van de Hoef provide a supplementary report addressing some matters relating to the excavation works undertaken by the previous owner of Ms Fan’s property.  Mr Van de Hoef responded to these further questions in a response dated 12 February 2024.^[69]  The Stockwells rely on these responses to submit that the uncontested evidence is that the excavation works resulted in a reduction in lateral support to their property.  I do not accept that the evidence can be used in this way.  The reason for this is that at a mention on 23 October 2024, the issue of the excavation works was addressed and senior counsel for the Stockwells informed the court that the relevance of these works was limited to it being a background fact to establish that the retaining wall was constructed for the benefit of
     Ms Fan’s property and not theirs. Given this characterisation of the relevance of the excavation works, it is not surprising that neither Mr Wong nor Mr Van de Hoef were questioned about this issue when they gave evidence on 5 November 2024.
124. [124]
     It is contended on behalf of the Stockwells that one of the reasons the Court ought not to find that any of the work undertaken by them contributed to the collapse of the retaining wall is because of the absence of necessary scientific calculations.  I am not persuaded by this.  There is a dearth of information as to the construction of the retaining wall and the physical conditions in the vicinity of it.  The same can be said about other matters, such as the weight of the backfill, the trees and the decks.  This has the consequence that the lateral forces that may have been applied to the wall from the various sources are not susceptible to precise mathematical calculation by the engineers. Another piece of information that is not known is the amount of pressure the retaining wall could withstand.   In addition, it is relevant that none of the experts inspected the retaining wall prior to its failure when everything remained in situ, thereby further reducing the likely reliability of many of the calculations that could potentially be undertaken.  In these circumstances, the Court must do the best it can on the evidence to make a judgment and assessment of such relevant matters by reference to the standard and burden of proof, including the party who bears the onus with respect to the issue under consideration.
125. [125]
     Mr Schaper’s evidence was limited to the estimated costs of demolishing and removing the existing retaining wall, building a new concrete one, and replacing the timber paling fence and the Stockwells’ garden bed.  He inspected the retaining wall on 23 February 2024 and his quote is dated 29 February 2024.

117. Ms Fan’s claim in nuisance

126. [126]
     The question for determination is whether the abovementioned works undertaken by the Stockwells on their property, have individually or in combination, substantially and unreasonably interfered with Ms Fan’s use and enjoyment of her land.   Ms Fan claims that they have in circumstances where they have materially contributed to the failure of the retaining wall.
127. [127]
     Ms Fan said that her concerns regarding the state of the retaining wall have affected her mentally and that she struggles to sleep when it rains.  She has no access to her backyard.  Further, her hot water system has been leaking and the presence of the steel posts installed by Barth Building means that it has not been possible to get access to the system to replace it”.^[70]  I accept this evidence.
128. [128]
     It is submitted on behalf of the Stockwells that the retaining wall has reached the end of its design life.  This submission is based on Mr Van de Hoef’s opinion that as of August last year when he inspected it, that it was approaching the end of its design life.  I am not persuaded by this. Mr Van de Hoef’s opinion was in part informed by the fact that the sleepers and vertical posts are timber.   However, Mr Wong explained that the timber is hardwood which would usually last for up to 25 years.  I prefer Mr Wong’s evidence on this point.  Further, it seems probable that the retaining wall had started to fail up to nine years prior to Mr Van de Hoef’s inspection.  This is because according to Mr Van de Hoef, as far back as 2014, aerial photos showed forward movement of the retaining wall.  Further, by 2017 the cosmetic sheeting of the high wall had begun to crack.    
129. [129]
     The expert evidence establishes that there are two potential causes for the failure of the retaining wall.  The first is the deterioration of the bases of at least some of the posts.
     The other is the excessive lateral forces placed on it by at least some of the work undertaken by the Stockwells on their property.   I have addressed these in turn below.
130. [130]
     As to the deterioration in the bases of at least some of the vertical posts, it is common ground between the experts that this is a contributing factor to the failure of the retaining wall.  I accept Mr Van de Hoef’s opinion that this deterioration led to a reduced section and bending capacity of these posts.  This ultimately led to them being unable to resist the significant lateral forces being applied by the extra soil, trees and large deck to the retaining wall, as discussed in paragraphs 135, 140, 141, and 149-151 below.
131. [131]
     It seems likely that the deterioration to these post bases is explicable by the way the previous owner of Ms Fan’s property designed and then constructed the retaining wall.  In particular, the bases ended up being housed in a cavity in circumstances where they were below ground level, with the sleepers on the soil side of them and the cosmetic sheeting on the open side of it.   This created a situation where the bases of the posts were probably subjected to wet soil conditions over extended periods, thereby causing their decay.  At the mention on 23 October 2024, counsel for Ms Fan conceded that the design of the retaining wall had contributed to its failure.  
132. [132]
     It has not been established by Ms Fan that any of the work undertaken by the Stockwells on their property has contributed to the deteriorated state of the vertical post bases. 
     In particular, it is unlikely that if water has been flowing over the top of the retaining wall, that a source of it (in any material sense) has been the water feature. 
133. [133]
     Having said this, because of the decayed posts, there was insufficient resistance to withstand the six sleepers added by Mr Stockwell to the top of the retaining wall.  It is in this sense that the additional sleepers contributed to the collapse of it.  It is of note, that the “bending failure” referred to in the Stockwells’ submission, was to an area of the retaining wall close to where the additional sleepers had been placed. 
134. [134]
     The evidence establishes that the vertical posts did not comply with the standard design from a 2004 Timber Queensland publication.    In the joint expert report, Mr Van de Hoef clarified this by saying that the applicable calculations showed that they were “a little” undersized.  This is in circumstances where he explained in his initial report that such a deviation from a standard design did not necessarily have the consequence that it could be considered to have been a cause of the failure of the retaining wall.  This is because retaining walls are not designed to be at the point of collapse when they are subjected to working design loads.  I have been left in the position of being unable to conclude whether this design feature of the retaining wall contributed to its failure.
135. [135]
     Turning to the lateral forces placed on the retaining wall, I do not accept the Stockwells’ submission that Ms Fan’s case about the associated pressures and the failure of the retaining wall rests on a “bald assertion”.  Mr Wong and Mr Van de Hoef agree that at least some of the work undertaken by the Stockwells had this effect.  The issue in dispute relates to the extent to which this has occurred.  Mr Van de Hoef described it as having been “small”.  It is my view that it has been more significant.  As to what has contributed to these lateral forces, I am satisfied that it is a combination of:

     1. the weight of the extra soil and the trees;
     2. the tree roots touching and close to the retaining wall; and
     3. the weight of the large deck. 
136. [136]
     In explaining the reasons for these findings, a useful starting point is a consideration of the Australian Standard.  Relevantly, it differentiates between dead loads and live loads and provides that the definitions of them need to be considered in conjunction with those provided in AS1170.    
137. [137]
     It was explained by Mr Wong that live loads refer to the transient or moving loads that structures experience due to human occupancy, furniture, vehicles and other temporary factors.   He further explained that in contrast, dead loads are those that remain relatively constant over time and include the weight of the structure itself.  The Australian Standard expressly provides that backfill is a dead load.^[71]  It was Mr Wong’s evidence that the additional sleepers added to the retaining wall and the large deck are also dead loads. 
     He also explained that while some trees can be live loads, that the trees on this retaining wall are better characterised as dead loads.  I accept this evidence.
138. [138]
     The Australian Standard relevantly provides that a retaining wall should be designed to accommodate pressures from live loads up to 5kPa.  The position is different for dead loads.  Once a retaining wall has been constructed, it is recommended that it is not subjected to any additional pressures from dead loads. This is because of the known potential adverse impacts that dead loads can have on the stability and performance of such structures.  
139. [139]
     Despite the abovementioned recommendation, here there are three dead loads that for many years were likely exerting pressures against the retaining wall.  I think there is a real likelihood that the extra soil deposited by the Stockwells was sufficient on its own to have applied sufficient lateral pressure to the retaining wall to have materially contributed to its failure.  Even if I am wrong about this, I consider it probable that the lateral pressure from the extra soil, together with the pressures applied by the trees and the large deck had this consequence.   The reasons for this are discussed below.
140. [140]
     Accepting that the extra soil was added to a depth of at least 400 millimetres and well over half the length of the wall, it is conceded in the Stockwells’ submissions that this is a substantial quantity.  It has been there for a long period of time.  I accept Mr Wong’s evidence, that the pressure on the retaining wall from it is likely to have exceeded the
     5 kPa referred to in the Australian Standard for live loads.  If the recommendations had been followed, it should not have been added at all.   Of note, Mr Van de Hoef’s assumption that only 300 millimetres of extra soil was added over 4.8 metres is not established on the evidence.  In addition, I am not convinced that the level of the extra soil in August 2023 is a reliable indicator of the level it was at in the years prior to the failure of the wall.  I reject the submission that it is “pure speculation” to conclude that the extra soil has had a role to play in the failure of the retaining wall.  
141. [141]
     As to the weight of the trees and their roots, I am persuaded that they are likely to have applied additional lateral pressures to the retaining wall.   In making this finding I am mindful that Mr Martinelli concluded in his report that while trees can damage retaining walls, the Stockwells trees have not damaged this retaining wall.  The reasons for this were said to be the insufficient sizes of the trees and their root masses. 
142. [142]
     Three assumptions have been made by Mr Martinelli in his report that were not borne out in the evidence.  The first of these is that the trees in the garden bed had been regularly pruned.  In his opinion, this is significant because it would have limited the root growth.  However, the trees were not regularly pruned as explained in paragraph 49 above.  Further, Mr Martinelli accepted in cross-examination that even if trees are regularly pruned, the roots of them will continue to grow in search of nutrients to support their regeneration. 
143. [143]
     A second assumption made by Mr Martinelli is that the height of the trees would have been approximately three metres.  However, after Mr Martinelli was shown photographs of the trees, he accepted that they were higher than this and that they were “significant”. 
144. [144]
     Mr Martinelli also assumed in his report that the root balls of lilly pillies and mock oranges tend to be relatively small.  However, in cross-examination he accepted that the root ball of one of the trees remaining in the garden bed (as shown in exhibit 10.5) did not fit this description.
145. [145]
     Further, it seems likely that the opinions contained in Mr Martinelli’s report were expressed without being aware that approximately half of the trees had been removed from the garden bed by the time he carried out his inspection.  Relevantly, his report expressly states that his opinions were based on the vegetation that was present at the time of his inspection. I am also satisfied that of the trees that remained in the garden bed, that they had been somewhat neglected compared to the state of them prior to the failure of the retaining wall and the make-safe work.  Indeed, Mr Stockwell referred to one of the lilly pillies having died.
146. [146]
     Mr Van de Hoef has expressed the following opinions about the trees which I am not persuaded by, as they are contrary to the opinions of both arborists:

     1. It is usually only palm trees or other trees with similarly dense root systems, that can exert sufficient pressure on a retaining wall to significantly contribute to the failure of it.  
     2. For trees of the type that were planted to adversely impact a retaining wall, there would need to be approximately 250 of them planted 100 millimetres apart.
     3. The trees in the garden bed had “relatively sparse tree root systems”.    
147. [147]
     In cross-examination, criticism was levelled at Mr Herlihy for not having ascertained the precise species of lilly pillies that had been planted in the garden bed.  In my view, their particular species is of marginal relevance. As Mr Herlihy explained, all the species (apart from the dwarf ones), can grow to approximately the same height, being about
     15 metres.  Also, I accept Mr Herlihy’s evidence that lily pillies have not been specifically cultivated for ornamental screening in high-density residential areas. 
148. [148]
     Further, I accept Mr Wong’s evidence that because of the known impact of tree roots on retaining walls, it is prudent to plant them at least 25 feet from a retaining wall.  
149. [149]
     The size, age and number of trees in the garden bed^[72] has led me to conclude that it is probable that the weight of them has contributed to the exertion of lateral pressure on the retaining wall.  I am equally persuaded about the impact of their roots on the retaining wall for the following reasons:

     1. Tree roots, including those of established lilly pillies, can cause retaining walls to lean or even collapse by exerting force against them, or growing under them and causing upheaval to them as the roots expand.  
     2. Even though the garden bed was a somewhat confined area for the size and nature of the established trees, the roots of them would have continued to grow relatively unabated in search of nutrients. 
     3. Of the trees that have remained, at least some of them have large root balls proximate to the retaining wall and/or touching it.   This is confirmed by some of the photographs and the observations of Mr Wong at the time of his inspection.^[73]   It seems likely that at least some of the trees that have been removed from the garden bed would have had similarly large root balls, either touching the retaining wall or close to it.   
     4. Both arborists concurred that the roots shown in exhibit 10 are sufficient to have exerted at least some pressure on the retaining wall. 
150. [150]
     As to the large deck, I am persuaded that this structure too has exerted lateral pressure on the retaining wall.  While I accept Mr Van de Hoef’s evidence that it probably did not account for much additional force on its own, its significance arises when it is added to the lateral pressures arising from the extra soil and trees, as discussed above.
151. [151]
     For the abovementioned reasons, I am satisfied that the combination of the dead loads of the extra soil, the trees and the large deck have adversely impacted on the stability and performance of the retaining wall.  This is by magnifying the lateral pressure acting on it.  This has increased its deflection and overall movement and has materially contributed to it being pushed forward and failing. I consider it is probable that in the absence of these lateral pressures, the retaining wall was unlikely to have failed. I reject the Stockwells’ submission that the defective state of the retaining wall was such that it needed to be replaced, even absent any tortious conduct on their part.
152. [152]
     It is well-known that significant loads in the vicinity of a retaining wall can place undue pressure on it, as can the roots from large established trees. Without advice, the Stockwells placed the retaining wall under such stress by adding the extra soil, the trees and the large deck.  Further, as to the trees, they are of such a kind that they grow vigorously and can have dense and invasive roots. They grew as anticipated, with branches overhanging the high wall and the roots growing to a significant size, with some of them touching or close to the retaining wall.  Material damage has resulted to the retaining wall.  This has interfered with Ms Fan’s use and occupation of her land and such interference has been significant and unreasonable. The Stockwells are liable in nuisance.  
153. [153]
     Also, it has been approximately seven years since Ms Fan first raised her concern about the impact of the trees on the retaining wall, and this was after the high wall had begun to tilt towards her property. This concern was largely ignored by the Stockwells. 
     Her attempts to again engage with the Stockwells a few years later (after the crack in the retaining wall had become larger), fell on deaf ears.  While the Stockwells did start to engage with Ms Fan more meaningfully in approximately April 2021, this was after the retaining wall started impacting on them.  They continued to refuse to contemplate their potential contribution to its failure and have even tried to conceal the true extent of the work that they did.  The pro-active steps that the Stockwells have taken to remedy the situation have been effectively limited to the removal of a few of the trees from the garden bed and the six sleepers from the top of the retaining wall.  This could not be considered reasonable in the circumstances.
154. [154]
     Given these findings, it is probably unnecessary to decide whether the small deck and the water feature have also resulted in additional lateral pressures against the retaining wall.   To the extent that findings are required, it is my view that their respective contributions, whether they are considered individually or in combination, are relatively minor and have not materially contributed to the collapse of the retaining wall. 
155. [155]
     In arriving at this conclusion, I am mindful that the small deck is considerably smaller than the large deck.   I accept Mr Van de Hoef’s evidence that it is a relatively light weight structure and therefore would not have been imposing significant surcharge loadings on the soils near the retaining wall. 
156. [156]
     As to the water feature, the evidence raises for consideration two different ways that it potentially applied lateral pressure to the retaining wall.  These are by virtue of:

     1. the weight of the structure itself; and
     2. the water coming over the edge of the water feature or being sprayed from it and flowing into the soil, adding to the lateral pressures that the soil was already exerting on the retaining wall.
157. [157]
     With respect to the weight of the water feature, while I accept Mr Wong’s evidence that its location is such that it is in the “zone of impact”, I am not persuaded that it is sufficiently close to the retaining wall to have exerted much if any lateral pressure on it.  I accept Mr Van de Hoef’s evidence in this regard.
158. [158]
     I am not persuaded that any significant volume of water from the water feature found its way to the soil in front of the retaining wall.   As explained in paragraph 53 above, it seems unlikely that water was frequently flowing over the edge of the water feature.  Further, there was a flat paved and stoned path separating the water feature from the soil.  

159. The Stockwells’ claim in negligence

159. [159]
     As to the Stockwells’ claim in negligence, it is alleged that:

3. (i)
   Since at least 2017, Ms Fan knew or ought to have known that there were risks:

3. (a)
   of the retaining wall becoming unstable or falling;

3. (b)
   of subsidence of the Stockwell’s land with consequential property damage;

3. (c)
   the Stockwells would not be able to use their land in the vicinity of the retaining wall; and

3. (d)
   to the safety of persons in the vicinity of the retaining wall.

3. (ii)
   Lateral support to their land has been unlawfully removed as a result of the excavation works, the reduction in support being provided by the retaining wall over time and the partial collapse of it.

3. (iii)
   Ms Fan has failed to restore the lateral support to the Stockwells’ land. 

160. [160]
     At the mention on 23 October 2024, senior counsel for the Stockwells articulated in the following way the measures that it is alleged it was incumbent on Ms Fan to have taken from 2017:

“She should have engaged an engineer to identify the cause of the lean of the wall. She should have engaged a qualified engineer to design some means by which the lean in the wall could be stopped. And if it could not be stopped, to design and install a replacement wall which would ensure that lateral support to the respondent’s property would not ultimately be removed.”^[74]

161. [161]
     The evidence does not establish that Ms Fan was aware that the retaining wall was at risk of collapsing from 2017. Her concerns around this time centred on the Stockwells’ overgrown trees putting sufficient pressure on the timber paling fence, causing it to tilt and thereby crack the cosmetic sheeting on her side of the fence.  It was in this context that she requested the Stockwells to prune their trees.^[75]
162. [162]
     Ms Fan’s property was tenanted at the time, and she was only visiting it intermittently, in the context of inspections. It is perhaps not surprising that it was not until approximately 2019 that she noticed that the crack in the cosmetic sheeting was getting bigger.  At this point, the trees had become so overgrown that their branches and foliage were covering the gutter of her roof.  In short, her concerns at this point were not about potential damage to the Stockwells’ property on account of the retaining wall. 
     Rather, she was worried that the tilt in the high wall had become so marked that it was going to pose a safety risk to her family when they moved back into the property. 
     These concerns were again raised by Ms Fan in her communications with Mrs Stockwell commencing in August 2020.
163. [163]
     In my view it was not until approximately early April 2021, that Ms Fan became aware that the retaining wall was failing.  She could not see the retaining wall at this time but was informed of this fact by Mrs Stockwell in a text dated 6 April 2021. I reject the submission of the Stockwells that there is no evidence that Ms Fan took any (much less any reasonable) steps to address it.  Contrary to this submission, over the following six or so weeks, Ms Fan:

     1. immediately responded to Mrs Stockwell’s text to the effect that she would be arranging for a building engineer to urgently inspect it;
     2. arranged for the cosmetic cladding to be removed, so that the retaining wall and the timber paling fence were exposed;
     3. had an engineer carry out an inspection and prepare a report and provided a copy of the report to the Stockwells;
     4. agreed to Mr Stockwell coming onto her property to carry out an inspection;
     5. informed Mrs Stockwell that she had obtained a soil report that she would provide to them;
     6. enquired about the prospect of making an insurance claim and suggested to the Stockwells that they also explore this option, given that it was her understanding that the retaining wall and timber paling fence had been mainly damaged by the extra soil and trees;
     7. informed the Stockwells in various communications in early to mid-May 2021 that she was contacting builders to see if a temporary support solution could be implemented;
     8. sought the cooperation of the Stockwells in suggesting to them that she considered the best solution would be for them both to agree to the retaining wall being rebuilt;
     9. offered to obtain two quotations for the rebuilding of the retaining wall; and 
     10. arranged for Barth Building to do the make-safe works on the retaining wall in late May 2021.
164. [164]
     Ms Fan had Barth Building re-attend her property on 16 June 2021 to finalise the
     make-safe works required.
165. [165]
     I am satisfied that the taking of reasonable measures did not require Ms Fan to carry out the extensive works involved in demolishing and removing the existing retaining wall and replacing it.  This is particularly so in circumstances where:

     1. it has been reasonable for Ms Fan to seek the assistance of experts in understanding the cause of the collapse of the retaining wall, given that she was not involved with the construction of it, and the Stockwells have undertaken work in the vicinity of it;
     2. Ms Fan reasonably explored the option of an insurance claim (which has been rejected);  
     3. Ms Fan has been willing to contribute financially to the replacement of it on the basis that the Stockwells also contribute, where there are expert opinions to the effect that the Stockwells have contributed to its failure;
     4. I accept Ms Fan’s evidence that she has not had the financial means to fully fund the costs of replacing the retaining wall; and
     5. by correspondence dated 3 March 2023, the Stockwells’ lawyer informed Ms Fan that the Stockwells did not give her permission to access their land and that any attempted access would be treated as a trespass.^[76]
166. [166]
     For the abovementioned reasons, the Stockwells’ claim in negligence fails.

160. The Stockwells’ claims in nuisance and s 179 of the PLA

167. [167]
     As to the claims in nuisance and for breach of s 179 of the PLA, it is alleged that:

     1. the Stockwells had a right to have their property supported by Ms Fan’s property;
     2. in about 2004, there were excavation works undertaken by the previous owner of Ms Fan’s property, which reduced the lateral support to the Stockwells’ property.
     3. the failure of the retaining wall has further reduced the lateral support to their property, which failure has been caused by the poor design of the retaining wall; and
     4. the removal of the lateral support referred to in subparagraphs (ii) and (iii) above is an actionable nuisance and a breach of Ms Fan’s obligations provided for in s 179 of the PLA. 
168. [168]
     I am not persuaded by the Stockwells’ contention that Ms Fan is liable for the removal of lateral support consequential upon the excavation works undertaken in 2004, or strictly liable for a further reduction in lateral support because of the failure of the retaining wall.  There are several reasons for this. 
169. [169]
     First, the principle as articulated in paragraph 27(a) of the Stockwells’ submissions that a landowner is obliged not to remove support to an adjoining neighbour’s land does not advance this contention.  
170. [170]
     Second, according to the Stockwells the excavation work undertaken in approximately 2004 was extensive, involved the entirety of Ms Fan’s property, was to a depth of about 10 feet, and created a significant fall between the boundary of the Stockwells’ property and the void created by the excavation. To the extent to which the Stockwells rely on the excavation work undertaken by the previous owner of Ms Fan’s property, as set out above the law is well settled that Ms Fan cannot be made liable for this.
171. [171]
     Third, I do not consider that the Queensland Civil and Administrative Tribunal decision in McMah v Burgess^[77] assists the Stockwells’ argument. I reject the Stockwells’ submission that this decision is authority for the proposition that while Ms Fan was not involved with the excavation, that she somehow “inherited the obligation” under s 179 of the PLA to ensure that the Stockwells’ land remained supported.   The applicable legal principles as articulated by the High Court in Torette (and referred to in paragraph 84 above) are well settled.  Further, while I accept that an adjoining neighbour can be liable in nuisance (and negligence) where they are aware of a condition on land (such as the removal of support) which puts the neighbour’s land at risk, it is outside the scope of s 179 of the PLA.  This scenario is not a nuisance to which strict liability attaches and proof of fault is necessary.  As was explained by the adjudicating member, in such a situation the adjoining neighbour is required to take such steps as is reasonable in all the circumstances to prevent or minimise the risk of damage to the neighbour’s property. 
172. [172]
     Fourth, counsel for the Stockwells rely on one of my previous decisions to support the submission that Ms Fan can be liable under s 179 of the PLA for a withdrawal of support based on a failure to act.   I am not persuaded by this.  Turner v Kubiak^[78] is a very different case, involving a species of nuisance for which strict liability does not attach.   I have not been referred to any relevant authority or any analysis of the statutory provision that would support the contended proposition.  In my view, the Stockwells’ claim in this regard cannot succeed to the extent that it relies on an omission by Ms Fan to take action to prevent a loss of support from occurring.  
173. [173]
     Fifth, the Stockwells seek to make Ms Fan liable for damage consequential on an ongoing state of affairs which has reduced support.  However, for an adjoining neighbour to be liable in nuisance for withdrawal of support under s 179 of the PLA, the neighbour needs to have created the subsidence by a complete withdrawal of support and usually by an isolated unintentional event (such as an excavation). 
174. [174]
     Sixth, while the evidence establishes that the precise location of the retaining wall places it on Ms Fan’s side of the boundary, for all intents and purposes, it is a retaining wall on the boundary.  It seems that the Stockwells treated it as such in circumstances where they built the timber paling fence on top of it. As explained in paragraph 86 above, a failure of a retaining wall leading to subsidence of land is outside the scope of s 179 of the PLA, (although it may give rise to another cause of action such as nuisance or negligence to which strict liability does not attach).
175. [175]
     Finally, it is noted that the Stockwells’ submissions refer to a document titled the Filling and Excavation Code.  It is not an exhibit before the Court.  Further and in any event, it is irrelevant to a determination of any potential breach by Ms Fan of s 179 of the PLA.  
176. [176]
     Given that each of the Stockwells’ claims in nuisance, a breach of s 179 of the PLA and negligence have failed, they are not entitled to any of the relief sought in their
     Cross-Application.  
177. [177]
     For completeness, even if the Stockwells had succeeded with their Cross-Application, I would not have made any allowance for their loss of amenity claim because: 

3. (i)
   For the reasons detailed above, the work the Stockwells have undertaken on their property has materially contributed to the collapse of the retaining wall; and

3. (ii)
   The position of the Stockwells has always been that they hold no responsibility for the failure of the retaining wall and they have stood firm on this, as evidenced by:

3. (a)
   Their refusal:

3. (1)
   to engage with Ms Fan when she raised with them concerns about the retaining wall, initially in 2017 and then again in 2019 and 2020; and

3. (2)
   to attempt to move towards a solution in response to the email dated 18 May 2022 from Ms Fan’s then solicitors offering to resolve the dispute on the basis that the Stockwells contribute 60 percent of a quote for replacing the retaining wall (to reflect the contribution to the damage of the retaining wall by the works undertaken by the Stockwells on their property).

3. (b)
   Mrs Stockwell’s evidence (corroborated by Mr Stockwell) that:

3. (1)
   Ms Fan has always been willing to negotiate with them; and

3. (2)
   up until the commencement of the hearing, the attitude of her and her husband to the litigation had been that they would not contribute to the costs involved in replacing the retaining wall until ordered to do so by a court.

160. Relief

178. [178]
     While the prima facie remedy to which Ms Fan is entitled is an injunction, in my view it is appropriate to make an award of damages in lieu of this.  This is in circumstances where the loss is capable of being estimated in monetary terms and I consider damages are adequate.  
179. [179]
     The only witness to give evidence about the estimated costs of demolishing, removing and rebuilding the retaining wall is Mr Schaper.  The quote he provided incorporates the costs of demolishing the failed one, obtaining geotechnical and survey reports, replacing it with an engineered concrete sleeper retaining wall and installing a timber paling fence on top of it.  The parties agree that the cost of this work totals $61,006.
180. [180]
     The Stockwells contend that this is not the appropriate measure of damages.  Rather it is said that any award of damages ought to be based on the diminution in value of the retaining wall.  However, I accept that it is reasonable for Ms Fan to claim the costs associated with replacing the retaining wall and it is the Stockwells who bear the evidentiary onus in relation to the unreasonableness of this.^[79]  The evidence does not establish (as the Stockwells suggest) that the retaining wall had little or no value and that it needed to be replaced absent any tortious conduct by them.  The circumstances of this case are such that in my view, a fair measure of the damages are the costs of replacing the retaining wall. 
181. [181]
     It is further submitted that there should be a reduction of the damages to which Ms Fan is entitled in respect of the replacement of the retaining wall.  It is said that to allow damages without such a reduction does not place Ms Fan in the same position as if the Stockwells’ tort had not occurred. This is because it is contended that she will be overcompensated where the materials and design for the replacement one mean that it will be more durable or more strongly built and offer a longer design life than the retaining wall that is to be replaced.
182. [182]
     These submissions face two difficulties. First, in oral submissions it was contended on behalf of the Stockwells that the retaining wall could be replaced with a timber one.  However, this is without substance given that it was admitted between the parties at the commencement of the trial that any new retaining wall should be made of concrete.^[80]  Second, the Stockwells have not adduced any evidence by which the Court could assess the betterment for which they contend. There was no evidence as to the financial advantage accruing to Ms Fan by virtue of this supposedly superior retaining wall. 
     This includes for example evidence of the cost of replacing the retaining wall with a timber (or other) one which does not have the superior qualities and extended life of the one on which Mr Shaper’s quote is based.  I decline to make any reduction in the damages otherwise payable by the Stockwells on account of betterment.
183. [183]
     Ms Fan having established that the Stockwells caused the damage and the amount of damages for which they should be responsible, it is then necessary to determine whether the damages should be reduced because the Stockwells are a concurrent wrongdoer pursuant to s 31 of the CLA.  In my view the damages should be reduced.
184. [184]
     This is because for Ms Fan to have established her claim against the Stockwells in nuisance, she was required to prove a breach of duty of care by them in the context of them having failed to take reasonable care.  As is clear from my reasons above, I am satisfied Ms Fan has discharged her onus in this regard in circumstances where there has been a negligent failure by the Stockwells in the ways described in paragraphs 152 and 153 above. The unreasonable and substantial interference found to constitute the private nuisance is consequential upon the absence of such care. In these circumstances the claim in nuisance has arisen from a breach of duty of care as provided for in s 28(1)(a) of the CLA.   This has the result that it is an apportionable claim to which s 31 of the CLA applies.  
185. [185]
     I am also satisfied, for the reasons detailed in paragraph 131 above, that the evidence supports the inference that the previous owner of Ms Fan’s property failed to take reasonable care in the construction of the retaining wall, with the bases of the vertical posts housed in a cavity and therefore exposed to wet soil conditions over extended periods, thereby causing their decay.  They are concurrent wrongdoers for the purposes of the CLA.   
186. [186]
     In my view, the degree to which they have each departed from the standard of care and the relative importance of their acts in causing the retaining wall to fail are indistinguishable. In all the circumstances, I apportion 50% responsibility to the Stockwells. 

160. Conclusion

187. [187]
     I direct that any submissions in respect of the form of the orders and costs (not to be longer than five pages) or alternatively a proposed draft order if the parties are agreed, be filed within seven days.