Siddiqui & Anor v Council of London Borough of Hillingdon

In claims alleging nuisance from tree-root encroachment, the claimant must prove on the balance of probabilities that the identified tree roots caused the damage. Desiccation is necessary for subsidence, whereas rehydration of previously desiccated soil may cause heave. Evidence of moisture at depth, historic vegetation, ground levels and the pattern of cracking may distinguish the two mechanisms.

Foreseeability is assessed by reference to what a reasonable landowner knew or ought to have known, including damage to neighbouring properties in the same development. Notice and an opportunity to abate are not universal conditions precedent to recovery. They matter where removal or management of the trees could have avoided or reduced the remedial works.

Two conjoined claims concerned structural damage to houses and a garage adjoining woodland owned by the Council. The claimants alleged that oak-tree roots had extracted moisture from London Clay, causing subsidence and requiring remedial works. The Council contended that the damage resulted from heave caused by rehydration of soil desiccated by vegetation present before construction.

The court also considered, in the alternative, reasonable foreseeability and whether the Council had been given a reasonable opportunity to abate any nuisance.

1. Disposition. Both claims were dismissed. The claimants failed to prove that Council-owned tree roots caused the claimed damage.
2. Causation and burden of proof. The burden remained on each claimant to prove, on the balance of probabilities, that tree-root action caused the relevant damage. The court applied the reasoning in The Popi M [1985] 2 All ER 712: the defendant was not required to prove an alternative cause, and uncertainty as to causation meant that the claimant failed.
3. House 9. The evidence supported heave rather than subsidence. Tree 39 and other vegetation had desiccated the soil before construction. The subsequent rehydration of that soil was consistent with heave. The Council’s oak roots could not realistically have regenerated beneath the 3.9-metre underpinning and caused the later damage. Garage 9 had suffered subsidence, but the evidence could not identify which vegetation caused it.
4. House 10. The damage was also caused by heave. The pre-existing trees, the evidence of raised ground and porch levels, and cracking wider at lower levels supported that conclusion. The expert evidence alleging subsidence from Council-owned trees was rejected.
5. Alternative issues. Applying the approach stated in Delaware Mansions Ltd. v Westminster City Council [2002] 1 AC 321, reasonable foreseeability depended on what the Council knew or ought to have known about neighbouring properties. Damage to House 9 would have made damage to House 10 foreseeable. However, notice and an opportunity to abate were not conditions precedent in every case. The claimant had to show that tree removal or management would have avoided or reduced the remedial works. That evidence was absent. The court also considered the guidance in L. E. Jones (Insurance Brokers) Ltd. v Portsmouth City Council [2002] EWCA Civ 1723 on reasonable opportunity to abate.