[2025] UKUT 053 (LC)

Mr Neill submitted that the claimant could not establish on the balance of probabilities that the movement to either the extension or the garage occurred as a result of the roots from T1. It was important to note that two different structures were in issue, with different sets of foundations at different depths. The claimant’s case essentially turned on the identification of two sets of juvenile oak tree roots, present in a borehole, at a depth of less than 2.0m. The claimant was asking the Tribunal to draw inferences from the pattern of measured movements at the property that it was attributable not just to root-based subsidence but to T1.

It was the authority’s case, based on the views of Mr Freeman, that movement of the extension was caused not by root-induced tree subsidence but by drainage failure. Unnaturally high moisture content was found in BH1 at depths of 0.9m and 1.5m, for which the only plausible explanation was water escaping from drainage. Drainage failure is likely to have caused sub-surface erosion and therefore the settlement identified within the extension. Whilst the damaged drain discovered in 2015 was repaired, there were other drains subsequently identified on the property (during the underpinning works) that could also have contributed to water escape.

Whether the results of the investigations made in June 2015 were consistent with root-induced subsidence relates to the question of desiccation, which is a sign of root-induced subsidence. It was now agreed that there was no desiccation in the subsoil.

Whilst it was common ground that there was some downward movement to the extension, it was the authority’s case that this was progressive, not cyclic and not indicative of root-induced shrinkage. It was common ground that the movement to the garage displayed a seasonal pattern indicative of tree root desiccation, but no borehole was dug behind the garage to ascertain the extent and depth of any roots, and whether they were attributable to T1, so the burden of proof could not be met.

T1 was growing at a considerable distance from both the garage and the extension and it was Mr Pryce’s view that the roots observed were beyond the maximum published tree to damage distances. Such roots as were found in BH1 were unlikely to be capable of extracting sufficient amounts of moisture to cause significant subsidence. And there was no evidence whether the root samples belonged to T1 or its neighbour T2.

The claimant’s case was not that T1 caused any shrinkage in 2014 which gave rise to the damage to the property, but that from 2015 to 2017 the net downward movement was caused by T1’s root system continuing to extract water even after 2015 when the drain was repaired. The authority submitted that it was unlikely a mature oak tree would behave in this way and the roots found were more likely to be ‘outliers’ attributable to the broken drain.

The authority’s case was that T1 was neither the ‘natural and probable’ cause of the subsidence that occurred, nor did it pose a real risk that subsidence might occur in the future. But even if it had had some influence on the degree of movement identified to the two structures the claimant had not established on the balance of probabilities that it was the ‘effective and substantial’ cause.