The evolving landscape of foreseeability in tree root subsidence cases
Recent decisions have provided further clarification in establishing liability for damage arising from the effects of tree roots on properties.
Recent court decisions have provided further clarification in establishing liability for damage arising from the effects of tree roots on properties. The question of reasonable foreseeability in such cases was considered and clarified by the decision of Berent v Family Mosaic Housing and the London Borough of Islington  EWCA Civ 961 and has made it plain what the applicable test of foreseeability should be. In addition, the decision has helpfully steered the law of tree root nuisance away from what appeared to be a developing trend of quasi strict liability for such tree root damage.
Prior to Berent, the case law had arguably started to evolve to the point where a position of strict liability was in danger of emerging, especially in particular locations and in respect of local authority liability. It appeared to be the case that the dangers posed to properties by large trees on clay subsoils were so widely acknowledged and publicised that the hurdle of foreseeability was easily overcome by claimants, making liability a foregone conclusion following evidence of damage.
The law in relation to claims alleging damage from tree roots previously centred on the House of Lords decision in Delaware Mansions Ltd v Westminster City Council 1 AC 321. This decision repeated the historical rule of law that encroachment by roots is a nuisance for which damages will lie if damage to property is caused. However, the Judgment in Delawarewas not inconsistent with the subsequent steer towards a position of strict liability.
The case of Berent has further addressed the issue of liability and seemingly added some pragmatism and realism to the issue. The Court of Appeal considered that there had to be a ‘real risk’ that the relevant trees were causing damage, not just a theoretical risk. In assessing the risk, the social utility of the activity causing the risk is to be considered and therefore the public amenity of trees is considered a relevant factor.
Assessing the foreseeability of the risk means assessing what practical measures could have been taken to abate the risk. In Berent, it was concluded that, in the absence of information identifying a particular tree as posing a particular risk, it was not proportionate to expect the local authority to fell all of the trees in a risk area.
The subsequent case of Khan and Khan v (1) London Borough of Harrow and (2) Mrs H Kane  EWHC 2697 (TCC) provides an interesting analysis of the reasonable residential homeowner’s level of knowledge in respect of tree root damage and the point at which this translates into reasonable foreseeability. Mrs Kane, the second Defendant, was found liable for damage caused to the Claimant property by a Lawson Cypress hedge on her property.
The court accepted that Mrs Kane had no actual knowledge of the damage her trees were causing to the Claimant property. Therefore, constructive knowledge was the central issue in the case.
The court stated that only an objective test of knowledge was needed, that of a ‘reasonably prudent landowner’. It was argued by the Claimant that the Defendant had the requisite level of knowledge (leading to reasonable foreseeability) because of the media attention recently given to the issue of tree root subsidence in clay subsoil. Whilst the court agreed that homeowners may now have a base level of knowledge on the subject area, it concluded that without further notice of a specific risk, it was understandable that homeowners would not take any action.
This follows the reasoning in Berent. The Defendant must have some evidence of a particular heightened risk, before an obligation exists to take action to abate.
The two implicated trees in Khan were an Oak tree and a Lawson Cypress hedge. The court found that the size of the Lawson Cypress and its proximity to the Claimant property would cause a reasonably prudent landowner to appreciate that there was a real risk of damage to neighbouring property. The court did not find this to be the case in respect of Mrs Kane’s Oak tree.
Khan therefore applies what might be viewed as a “common sense” approach to foreseeability for homeowners.
Although it is not explicitly stated in his Judgment, perhaps Mr Justice Ramsey in Khan also had in mind the comments made in Berent on amenity. The much maligned Lawson Cypress was perhaps never going to successfully defend its existence on the ground of amenity, being the source of dispute between neighbours nationwide due to its popularity as a hedging tree along property borders, combined with its propensity for rapid growth and excessive eventual height.
The rules for establishing liability in tree root nuisance cases have therefore been distilled by these cases.
Berent shows us that foreseeability depends upon the extent of the risk the tree poses as weighed up against the reasonable practical steps that can be taken to alleviate the risk. The social amenity provided by the tree or trees in question will form part of the balancing exercise.
However, it is also the case, following Khan, that a common sense approach needs to be applied to tree management. Parties do not need the benefit of expert opinion, it seems, to appreciate that a large tree or shrub in very close proximity to a neighbouring property should be carefully managed and maintained.
For further information about the issues raised in this article please contact Johanna Smallman on 0161 233 7475 or at email@example.com or George White on 0161 214 0650 or at firstname.lastname@example.org.