[2025] UKUT 053 (LC)

The property is a detached, traditionally constructed two-storey house, with attic rooms under a hipped roof, built in the early part of the 20^th century. It has a two-storey extension to the rear right hand side (looking from the front) and a single storey garage/workshop abutting the rear righthand corner of the house. The rear garden of the property backs on to grounds belonging to Bush Hill Park Golf Club (“the Golf Club”) in which is a row of trees protected by a Tree Preservation Order confirmed on 20 May 1958 (“the TPO”). The row includes, close to the boundary of the property, two oak trees which have been referred to as T1 and T2. T1, the subject of these proceedings, is agreed to be 28m high. It is 29.15m from the garage and 31.65m from the extension. T2 is also 28m high. It is 33.1m from the garage and 35.4m from the extension. There are two cypress trees in the rear garden, one 8.0m high on the right hand boundary with No 96 and one 4.5m high on the left hand boundary with No 100.

Mr and Mrs Mackinnon moved to the property in 1975 and were the insured owners in January 2014 when they noticed internal cracking in the kitchen and external cracking at the junction of the rear boiler room (in the extension) and main house. The damage worsened during the summer of 2014 and was reported to the claimant in December 2014.

The claimant instructed loss adjusters Crawford Specialist Property Services UK (“Crawford”) to investigate and prepare a technical report. Crawford issued a report (“the Crawford Technical Report”) to the claimant on 11 March 2015. It described, inter alia, 2mm internal cracks in the bathroom and kitchen, a 7mm diagonal tapering crack to the rear right hand side of the extension at first floor and a 6mm vertical tapering separation of the garage junction to the main house. The pattern and nature of the cracking was described as indicative of an episode of subsidence apparently caused by clay shrinkage. T1 was identified as a possible cause of root induced shrinkage. The subsidence ought therefore to have been reversible, by rehydration of clay soils in the winter months causing the cracks to close, provided the cause of the movement was dealt with. The report recommended further investigations, involving trial pit(s) to determine the depth and type of footings, boreholes to determine the nature of the subsoil and influence of any roots, and monitoring to establish the rate and pattern of movement. A specialist arboriculture report would also be necessary.

Crawford instructed CET Structures Ltd (“CET”) to carry out ground investigations. CET visited the property on 1 June 2015 and in the course of their investigations dug a trial pit and sank two boreholes. The block plan below is extracted from their site investigation factual report and shows the relationship of the house, the extension and the garage, together with the location of the trial pit and borehole 1 (TPBH1) on the rear right corner of the extension. As notes on the plan show, the site slopes down from rear to front and from left to right looking from the road frontage. Borehole 2 (BH2) was sunk at the front of the house as a control. The findings of the site investigation (“the CET report”) were supplied to Crawford, including an analysis of root samples dated 4 June 2015 and laboratory test results dated 10 June 2015.

On 19 June 2015 Crawford issued an addendum technical report (“the Crawford Addendum report”) to the claimant setting out the findings of the CET investigations. It concluded with a recommendation that T1 should be removed, confirming that they were satisfied there would be no adverse risk of heave to the property in doing so. The CET survey of drains at the rear of the property had identified the need for repair to drains around the extension, but drainage was not believed to be a factor in causing the structural movement. The drains were subsequently repaired in September/October 2015.

Crawford next instructed MWA Arboriculture (“MWA”) to provide a report for the purpose of assessing the potential role of vegetation in respect of subsidence damage. MWA carried out a site visit and reported to Crawford on 20 July 2015. The report concluded:

“Based on the technical reports currently available, engineering opinion and our own site assessment we conclude the damage is consistent with shrinkage of the clay subsoil related to moisture abstraction by vegetation. Having considered the available information, it is our opinion that on the balance of probabilities T1 will be the principal cause of any damage due to clay shrinkage subsidence. If an arboricultural solution is to be implemented to mitigate the current damage and allow the soils beneath the property to recover to a position such that an effective repair solution can be implemented we recommend that T1 is removed. We have given consideration to pruning as a means of mitigating the vegetative influence, however in this case, we do not consider pruning offers a viable long term solution.”

On 28 July 2015 Crawford instructed Knight Associates to commence level monitoring. Monitors were installed at 12 points around the rear of the house, the extension and the garage. A total of 11 readings were taken from the date of installation through to 18 January 2018.

On 26 August 2015 MWA made the first application to the authority for removal of T1. It was accompanied by the four reports produced between March 2015 and July 2015, that is: the Crawford Technical Report, the CET report, the Crawford Addendum Report and the MWA report. These reports, which I will refer to as “the 2015 reports”, were the basis of the claimant’s case in each of their three applications to the authority for consent to fell T1. The application stated briefly the reason for applying to have the tree removed:

“The neighbouring property 98 Old Park Ridings is suffering movement/damage identified by engineers as being due to clay shrinkage subsidence and the above tree has been recommended for removal to restore stability. Due to the size and proximity of the tree to the property , pruning does not offer a viable alternative solution in this case. Oak roots have been recovered from below the foundations in a plastic clay soil of high plasticity/volume change potential which from the soil test results were found to be desiccated.”

The evidence provided by Ms Davidson shows that the authority’s Tree Officer, Mr Downing, was responsible for reporting and making a recommendation for each of the three applications. It is therefore helpful to review the full sequence of applications, with the reasons for refusal in each case, to understand the context for third refusal with which this case is concerned. Mr Dowding made a site inspection on 1 October 2015 and then wrote a concise analysis of the 2015 reports. In his report Mr Downing noted the lack of any level monitoring or crack monitoring, which was a required submission where a tree was alleged to be the cause of subsidence building damage. Without it a progressive and cyclical pattern of building movement related to vegetative subsidence could not be demonstrated. He went on to say:

“Nevertheless, the submitted evidence does not show on the balance of probabilities that the tree in question is a significant material cause in subsidence damage to the property. Live tree roots have not been found and desiccation of soil is not shown in the upper soil horizons where live tree roots would be expected to be found. The soil is only shown to be desiccated at significant depth where it only appears ancient relic tree roots have been found. The tree is approximately 30m distant to the property damage. It is unlikely that the tree has rooted this far and more likely that prior to development of the residential buildings the whole area was forested and this is the explanation for any roots found.”

In recommending refusal Mr Downing noted that no other reasonable alternative solutions had been presented by the applicant, although it appeared that a root barrier installed across the garden could be achievable to prevent tree root encroachment and any potential damage to the property. A refusal notice was issued on 15 October 2015.

Level monitoring over the next 12 months demonstrated continuing movement at the property. MWA made a second application for consent to fell T1 on 5 October 2016, supported by the 2015 reports together with the results of level monitoring between 28 July 2015 and 22 September 2016. This application contained extended reasons as set out below, with information underlined which has subsequently been agreed by the parties to be wrong and misleading:

“Investigations into the damage have been conducted and the following information/evidence obtained:

1.

Engineering opinion is that damage is due to clay shrinkage subsidence.

2.

Foundations extend to 900mm bearing on to clay.

3.

Site investigations and soil test results have confirmed a plastic clay subsoil of high volume change potential (NHBC Classification) susceptible to undergoing volumetric change in relation to changes in soil moisture.

4.

Suction values indicate severe to very severe desiccation in BH1 (BRE Digest 412) located to the rear of the property and closest to the offending tree.

5.

Live oak roots have been recovered from below foundation depth in TP/BH1 & depth of 5600mm below ground level.

6.

The observed desiccation is coincident with recorded root activity.

7.

Desiccation is at depths beyond ambient soil drying effects and entirely consistent with the soil drying effects of significant vegetation.

8.

Level monitoring for the period 28.07.15 to 22.09.16 clearly shows a cyclical pattern of movement indicative of the effects of the offending tree on soil moisture and volumes to the rear of the property. The uplift phase of the building can only be attributable to an expanding clay soil from a desiccated sate due to the soil drying effects of the oak.

9.

Drains can be discounted as a causal factor given the recorded desiccation and by reference to the level monitoring data.

Established evidential and legal tests pertinent to subsidence damage claims have been met and the evidence confirms there can be no other cause of the movement and associated damage at the rear of the property other than the indirect influence of the subject tree.

Removal offers the only predictable arboricultural solution in abating the influence of T1. Pruning does not constitute a viable long term alternative solution in restoring stability to the property.

In the event the tree is retained, underpinning is very likely to be required at significant cost.”

Before issuing a notice of refusal on 6 December 2016 Mr Downing produced a lengthy report which included an acknowledgement that:

“Some (not all) evidence of damage to the rear of the extension and the garage appears to be conducive with seasonal movement of foundations. However, the level monitoring results do not appear to be clear, being that the initial summer (2015) monitored was extremely wet and although a downward trend of foundation movement is shown in the latter part of 2016, the monitoring is ceased and foundation recovery is not shown, I would suggest without a further period of level monitoring, there is uncertainty as to whether seasonal movement of foundations is adequately demonstrated although it may be likely that seasonal movement has occurred.”

Expanding on his previous analysis, Mr Downing referred to the leaking drains noted in the CET report as a likely reason for the high moisture content of the soil sample taken from under foundations at BH1. He also commented that a quantitative assessment of heave should be undertaken to support the statement in the Crawford Addendum Report that there was no adverse heave risk to the property, which was contrary to a statement in the earlier Crawford Technical Report that a soil risk analysis had suggested a potential heave risk. His conclusion included the following paragraph:

“Without a quantitative soil heave assessment I am unable to determine this application adequately informed. A simple qualitative assessment, together with the data from the soil investigations appears to suggest that the buildings were built on a clay soil with a deep-seated moisture deficit without the appropriate precautions to prevent seasonal movement as a result of any vegetation. Removal of the tree is unlikely to be an effective means to stabilize the foundations and in fact is likely to be more damaging causing soil heave as the soil re-hydrates. The Local Authority cannot authorize the removal of the tree given that further damage is potentially likely to the property as a result of the trees removal.”

A third application for consent to fell T1 (“the 2017 application”) was made by MWA on 8 November 2017, enclosing the 2015 documents together with level monitoring results from 28 July 2015 through to 17 May 2017 (a further reading on 23 November 2017 was made available before the Tree Officer reported) and a heave calculation. The reasons provided in the application form were identical to those listed above from the 2016 application, with the addition of a further paragraph dealing with the risk of heave:

“The previous refusal notice (Ref: 16/04564/TPO) refers to a deep-seated persistent moisture deficit and removal of the tree may result in further damage to the property. There is no evidence of a deep-seated persistent moisture deficit provided by the council. A heave calculation has been undertaken (attached) and engineering opinion is that the level of predicted heave is concluded to be acceptable. This allows the council to make an informed decision in relation to heave.”

Again it was stated that: “In the event the tree is retained, underpinning is very likely to be required at significant cost and insurers reserve the right to recover these costs in the event consent for removal is refused.”

The application was assessed by Mr Dowding, who noted that the level monitoring did not appear to show the seasonal summer shrinkage and winter recovery associated with root related moisture extraction. His report included comments made by the authority’s structural engineer. In particular these challenged the interpretation of CET data which had concluded that the subsoil was desiccated and introduced the idea that a previous equilibrium had been compromised by the planting of new trees closer to the property within the garden. The conclusion was that the most probable cause of damage to the property was the softening of foundation stratum due to leaking drains. Consent was refused on 2 February 2018 (“the third refusal”) for three reasons:

“1.

The Council does not consider that the grounds specified by the applicant/agent (i.e. damage to property) sufficient reason to justify the proposed removal of a tree of significantly high amenity and bio-diversity value that makes a positive contribution to the amenity of the locality and wider environs.

2.

The Council does not consider that it has been adequately demonstrated that the tree is a material cause in structural damage to the property in question.

3.

No reasonable alternative solutions to the alleged structural damage have been adequately considered or instigated, such as the installation of a root barrier.

Informative: The tree is significantly older than the property and the applicant is hereby advised that the removal of this tree may lead to heave which can cause damage to property.”

The claimant then instructed Crawford to provide an engineering solution to the problem. Crawford, in their Specification Request Document for the claimant dated 1 March 2018 stated: “Roots noted to a depth of 5.6m bgl in the site investigation so a piled solution will be required on this occasion.” They sought arboricultural advice and reported to the claimant on 11 April 2018 that installation of a root barrier would not be possible due to the lack of access to the rear for an excavator, and because it would need to extend into neighbouring properties whose owners may not give consent. On 17 April 2018 the claimant notified the authority that it intended to seek reimbursement of the cost of underpinning necessitated by the third refusal.

Crawford sought tenders for remedial repair works to the property, to include the underpinning solution, and appointed Optera to carry them out. Works were carried out to the property between September 2018 and June 2019. During the course of piling works to the garage a land drain was encountered 1.2m below ground level which ran parallel with the back of the garage and was on the line of piles. This was excavated, removed and diverted around the piles with the existing clayware pipe replaced, but there is no evidence that it was damaged or leaking. The footing in the garage was found to vary in depth with a 1.0m deep footing on the right-hand side and a 100mm footing on the left-hand side.

The total cost of works was £220,596.41, including professional fees and VAT. It was agreed that repairs to the property would have been required even if consent to fell had been given and therefore that only the costs of underpinning should be the subject of a claim. The expert engineers were directed to provide, after the hearing, a joint statement showing their respective positions on the apportionment of the total cost between repairs and underpinning, and between the garage and the extension. For the claimant Mr Allen apportioned £126,581.53 to underpinning, of which 67.5% was attributed to the garage and 32.5% to the extension, with £16,899.22 on top for professional fees giving a total of £143,480.75. For the authority Mr Freeman apportioned £88,453.91 to underpinning, of which 68% was attributed to the garage and 32% to the extension, with £10,759.08 on top for professional fees giving a total of £99,212.98.

The claimant sent a letter of claim to the authority on 3 August 2020, confirming a total outlay of £253,548.39 with quantum of claim to be clarified in due course. A response, denying liability, was made on behalf of the authority on 27 January 2021. The claimant made a reference to the Tribunal on 31 January 2024.