The Owners - Strata Plan No 7655 v The Owners - Strata Plan No 50081

The application

1. The applicants, pursuant to s 7 (Part 2) of the Trees (Disputes Between Neighbours) Act 2006 (NSW) ('the Trees Act'), have applied to the Court seeking orders that: the respondents remove at their expense the Liquidamber, the avocado and the privet; that the respondents poison then grind the stumps of the three trees; and that the respondents reimburse the applicants for the cost of all works necessary to rectify damage to the retaining wall after the applicants have completed those works.

Framework of Part 2 of the Trees Act

1. Part 2 of the Trees Act both enables and confines the Court's jurisdiction regarding damage or injury caused by trees. The Court must be satisfied of certain matters at s 10 of the Trees Act before making any orders. 10 Matters of which Court must be satisfied before making an order (1) The Court must not make an order under this Part unless it is satisfied: (a) that the applicant has made a reasonable effort to reach agreement with the owner of the land on which the tree is situated, and (b) if the requirement to give notice has not been waived, that the applicant has given notice of the application in accordance with section 8. (2) The Court must not make an order under this Part unless it is satisfied that the tree concerned: (a) has caused, is causing, or is likely in the near future to cause, damage to the applicant's property, or (b) is likely to cause injury to any person.
2. There is no question that the test at s 10(1) is met. The respondents dispute that their trees have damaged the retaining wall and therefore argue that s 10(2) prevents the Court making any orders.
3. If I find that the jurisdictional tests at s 10 are satisfied, I can make orders as described at s 9 of the Trees Act, after considering a range of matters set out at s 12. The orders sought by the applicants can be made, or I may make other orders as I see fit.

Expert evidence

1. At the hearing the Court was assisted by the evidence of: Guy Paroissien, arborist engaged by the applicants; Grahame Vile, engineer engaged by the applicants; and Marek Blaszczakiewicz, engineer engaged by the respondents. All three experts presented themselves as reliable and professional; they expressed their opinions honestly and without apparent bias. There have been no physical investigations undertaken, so inevitably much of their evidence falls into the sphere of opinion, but I found it to be reliable expert opinion, even where they disagreed with each other. Their views are summarised below, but were presented much more extensively at the onsite hearing.
2. Mr Paroissien described the Liquidamber as a large and healthy tree. He was of the view that displacement of the wall is due to the tree. In his opinion, the tree relies on the wall for support to some extent, so removing the wall would destabilise the tree. His opinion was that the tree needs to be removed for the damage to be rectified, but there is no need to remove the entire stump. Roots within 300 mm of the wall would need to be removed to allow rectification works.
3. Mr Paroissien was of the view that damage caused by other trees is relatively minor.
4. Mr Blaszczakiewicz has measured the retaining wall and compared it with requirements for a properly engineered retaining wall. He said the wall's design is only sufficient for a wall height of 800 mm, not the existing situation of 1100 mm of soil, with a large tree in close proximity. He expressed the view that this demonstrates that the wall is not supporting the tree. He stated that a typical retaining wall of this type has a life expectancy of around 50 years, so this 1960s wall has reached the end of its life. He pointed out that weepholes along the bottom of the wall were blocked with soil and debris, preventing proper drainage of subsurface water from behind the wall.
5. Mr Blaszczakiewicz was sure that a 7.5-metre section of wall near the tree needs rectification. He agreed generally with Mr Vile's cost estimate of such works.
6. Mr Blaszczakiewicz was of the view that a new retaining wall could be designed as either a drained or undrained wall. He said that although an undrained wall is possible, a drained wall would be preferable. An alternative design would allow for a replacement wall to be narrower with a geocomposite drainage sheet behind, leaving all soil and roots in situ. He conceded that this would leave up to 120 mm of soil supported at the top of the wall on the applicant's side of the boundary.
7. Mr Blaszczakiewicz saw no need to fix the southern section of wall near other trees. He measured only 65 mm displacement at the top of the wall there. Where there is no influence from trees there is up to 40 mm displacement at the top of the wall, so his opinion was that soil pressure alone was enough to displace the wall.
8. Mr Vile pointed out that weepholes along the bottom of the wall were not blocked but were only partially filled with some loose debris. Mr Vile thought the wall's construction was adequate for the site, considering that only minor displacement has occurred away from any trees.
9. Mr Vile was of the opinion that any alternative solutions to allow replacing the wall while retaining the tree and all of its roots were not really viable. He said proper drainage would be needed behind a new wall, requiring removal of soil and roots.
10. Mr Vile had costed the replacement of a 20-metre retaining wall at approximately $54,000. He expressed some agreement with Mr Blaszczakiewicz' suggestion that the 7.5-metre section of wall nearest the Liquidamber needed replacement.

The applicants' submissions

1. The applicants submit that three trees have damaged the wall: the Liquidamber and the two smaller trees that have been removed. They obtained advice that part of the wall near the Liquidamber is failing, is dangerous, and must be fixed. They say the Liquidamber needs to be removed to allow this. They say they cannot suffer the reduction in their driveway width that would result from an alternative solution to rectifying the retaining wall.
2. Although the two smaller trees have been removed, they argue that those trees also damaged the wall, including the southern section of wall that also requires rectification.
3. The applicants argue that the respondents should pay for tree removal and for 100% of the wall rectification costs, but also prepared 'short minutes of order' suggesting that the respondents reimburse them for 40% or 50% of the rectification costs. The applicants propose that they undertake all works on the wall, with some reimbursement of costs, and the respondents be responsible for removing the tree.
4. The applicants want orders to restrict the type of plants that the respondents might replant in the area near the wall.

The respondents' submissions

1. The respondents argue that the Liquidamber can and should be retained. The tree was a condition of consent for approval of their Development Application. They say their engineer has explained that tree removal is not required when rectifying the wall.
2. The wall dates from the 1960s. The respondents say that cracks in the wall were first noticed in 1997. They argue it is not fit for its purpose, being of insufficient structural strength to support more than one metre of soil and the associated hydrostatic pressure.
3. The respondents argue that the applicants have not undertaken proper investigation, and that the Court found in St Clair v Kilham [2018] NSWLEC 1071 that the level of satisfaction required at s 10(2) could not be reached without such investigation. They say the Court found in a very similar situation, in Price v Dougherty [2013] NSWLEC 1089, that damage to a retaining wall was due to the wall's age and other factors.
4. The respondents say the Court has no jurisdiction for any repairs beyond the 7.5-metre section nearest the Liquidamber. They don't want to alter the wall's location in any way that would put part of it on their property. Referring to Stanford v Hall [2012] NSWLEC 1217, they argue that if they must pay for any part of the wall's rectification, the standard for the replacement must be like-for-like, so that the applicants do not receive a better wall.
5. The respondents submit that if they are to pay for any rectification works, they will require more than 200 days for making financial arrangements. They say that, if rectification costs are to be apportioned, they should pay at most 11-13% of the costs.

The southern section of the wall

1. The two smaller trees have now been removed. They may have contributed to some displacement near the southern end of the wall, but this displacement is relatively minor and there is no evidence that it is dangerous. The two tree stumps are some distance from the wall and are no longer contributing to any damage. I see no need to make orders for that part of the wall or the remaining tree stumps.

The section of wall near the Liquidamber

1. I am satisfied on the evidence presented and on observations at the onsite hearing that the Liquidamber has damaged the brick retaining wall. Large surface roots of the tree can be seen growing against the retaining wall. Closest to the tree, where the roots are largest, the wall is most displaced, and significantly so.
2. In Price v Dougherty, Fakes C found at [18], [19]: 18 On the evidence before me, I cannot be satisfied to the level required by s 10(2) that the tree has caused the damage to the wall. The applicant was unable to demonstrate the nexus between the tree and the displacement of and damage to the wall. 19 Even if the tree had been shown to be a cause of the damage, thus engaging the Court's jurisdiction, as a matter of discretion after consideration of s 12(h)(i), no orders would be made for any compensation. Given the nature of the lean and the adjacent garden bed it appears that the displacement is most likely a function of the age and nature of the wall and gradual pressure from the trees and soil within the garden bed. Therefore, this element of the application is dismissed.
3. In St Clair v Kilham, at [25], I was not satisfied, on the balance of probabilities, that the rear section of a retaining wall had been damaged by trees.
4. Each situation that comes before the Court is a unique combination of factors: damage, causation, contributing factors and so on. The cause of damage to a wall was apparently less obvious in Price v Dougherty than it is here. In St Clair v Kilham, despite the absence of thorough investigation, I was satisfied on the balance of probabilities that the respondents' trees had damaged the front section of that wall, as I am here satisfied that the Liquidamber has damaged the wall.
5. The evidence of the engineers is that part of the wall must be replaced: a 7.5-metre section nearest the Liquidamber.
6. Mr Blaszczakiewicz gave evidence that a new thinner wall could replace the existing wall, reducing the level of encroachment into the applicant's property.
7. If this section of wall could be replaced without putting the tree at risk of failure, I would embrace this solution, but I cannot be satisfied of this. I am not convinced by Mr Blaszczakiewicz' reasoning with regard to the relationship between the wall and the tree. That the wall is not sufficiently engineered for the circumstances, to my mind, does not prevent the tree relying on it, to some extent, for structural support. I find Mr Paroissien's opinion more likely to reflect the situation here: the extent of the tree's structural roots growing against the wall has most likely established a structural relationship between the wall and the tree. The impact of removing the wall, even temporarily, is unknown, but the potential for damage or injury if the tree falls is in the range of serious to catastrophic.
8. Despite my best efforts, I see no alternative to ordering removal of the tree prior to replacing this section of the retaining wall.

Matters at s 12

1. I have considered the matters at s 12 of the Trees Act. This large mature shade tree is of extremely high value in the landscape, enhanced by its heritage setting. Unfortunately, a reasonable solution for its retention is unavailable.
2. Neither party's actions have directly caused the damage. The respondents have maintained for many years a large tree that is of value not only to them but to their neighbours and the surrounding environment. The applicants have taken steps to deal with their damaged retaining wall, following advice that it has become dangerous.
3. The evidence is that the wall is on the applicant's property, with its back edge running along the common boundary (at least at ground level). For all intents and purposes it acts as a boundary retaining wall.
4. The situation here differs from Stanford v Hall, where I contemplated at [42] the gain or loss that might fall to the applicant should a new wall be of superior or inferior quality compared to the wall being replaced. Here, as I found above, the wall acts as a retaining wall along the common boundary, benefiting both parties. Were it not for damage caused by the respondents' tree, the retaining wall might have remained functional for many more years. The wall must be fit for purpose, regardless of the standard of the existing wall. The fairest conclusion I can find, therefore, is that costs of repairing the wall shall be shared equally by the parties. As all works will primarily affect the applicants, the applicants shall organise, and initially pay for, the works. As pleaded by the respondents, and consented to by the applicants, the period for reimbursement shall be 12 months. If the applicants want to fix the remainder of the wall at the same time that is a matter for them.
5. Replacement of the wall is to be carried out in accordance with the recommendations in the report of Mr David Willows, Alliance Geotechnical, dated 20/01/2017.
6. The respondents shall bear the costs of tree removal.
7. The presence of gardens near boundary retaining walls is not particularly unusual and there is nothing to suggest that the respondents would be foolhardy or vindictive with any future plantings on their land. I see no need for orders restricting the respondents' future plantings on their land.

Orders

1. As a result of the foregoing, the Court orders that: 1. The application is upheld. 2. Within 90 days of the date of these orders the respondents are to engage and pay for a suitably qualified and experienced arborist (minimum AQF level 3) with all appropriate insurances to remove the Liquidamber to ground level. The works are to be done in accordance with the NSW Code of Practice for the Amenity Tree Industry. 3. The respondents are to give the applicants 2 weeks' notice of the works in (2). 4. The applicants are to provide all access required for the works in (2) during reasonable hours of the day. 5. Within 30 days of the date of these orders the applicants and the respondents are each to obtain three quotes from each of the following: 1. a structural engineer; 2. a geotechnical engineer; and 3. a building contractor to carry out the services and works listed in section 6 (Recommendations), other than 6.1 and 6.4, in the report of the engineer Mr David Willows, Alliance Geotechnical, dated 20/01/2017, for the 7.5-metre section of wall nearest the tree, as follows: 1. 6.2 Engineering design drawings and specification for the replacement retaining wall be prepared by an experienced structural engineer, following the comments and principles described in this report. 2. 6.3 The structural engineering drawings be reviewed by an experienced geotechnical engineer, to confirm that the design drawings are consistent with the geotechnical advice contained in this report. 3. 6.5 During construction, site inspections be carried out by an experienced geotechnical engineer, to observe the exposed soil and rock materials, temporary support measures and drainage systems, verify the foundation materials for the retaining wall footings and advise on other geotechnical items. 1. Within 45 days of the date of these orders the parties are to swap quotes and choose the cheapest of each of the three categories of quotes, unless they agree on others. 2. Within 6 months of the date of these orders the applicants are to arrange and pay for the design and construction of the 7.5-metre section of wall according to the quotes from order (5). 3. Within 2 weeks of completion of the works, the applicants are to give the respondents copies of receipted invoices for the completed consultation and works as quoted in (5). 4. Within 12 months of the date of these orders the respondents are to pay the applicants 50% of the total of the invoices in (8). 5. Liberty to relist on 7 days' notice for the purpose of working out these orders.

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D Galwey Acting Commissioner of the Court

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DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated. Decision last updated: 09 May 2018