Practical Law

The recent cases of Denness v East Hampshire District Council and Robbins v London Borough of Bexley have shed further light where property damage is alleged to have been caused by the roots of adjacent trees.

Both property and tree owners will be affected by these decisions as the long-held view that liability is always established merely by the proximity of trees to buildings built on shrinkable soils may well be confined to history.

Denness v East Hampshire DC

This judgment confirmed the risk-based approach taken in Berent v Family Mosaic Housing and London Borough of Islington. It also provides a stark illustration of the perils in failing to call appropriate expert evidence to deal with the risks of tree root damage. It should provide further relief to local authorities when facing such claims.

This was a typical tree root claim, where the claimants alleged that nearby beech trees belonging to the local authority had caused damage to their house. The single joint engineering expert supported their case. There was no other expert evidence.

The judgment

The court adopted the reasoning in Berent and held that the correct issues to be determined were:

• Causation.
• The extent of any risk of damage, and the chances that anything untoward would happen.
• What damage was foreseeable if the risk became a reality?
• Was it practical to prevent or minimise the damage?
• If it was practicable, how simple or difficult were the measures that could be taken?
• How lengthy was the work that would be involved, and what was the possible cost of such works?
• Was there sufficient time for preventive action to have been taken, by persons acting reasonably in relation to the known risk, between the time when it became known or should have been realised by the defendant and at the time when the damage occurred?

On the facts the court disagreed with the opinion of the single engineer on causation. It found that the claimants had failed to adduce any evidence as to what preventative measures could or should have been taken.

Practical impact of Denness

This case further confirms that tree roots claims are not strict liability, as has often been thought in the past. Liability will turn on the risks involved, and the steps that could have been taken to reduce that risk. Just because trees are close to buildings on clay shrinkable soils does not mean that liability follows. Each case must be the subject of a careful risk analysis by relevant experts. Where the risk is low, and there is no history or other damage, then taking no steps may well prove to be reasonable.

The case also demonstrates the peril in failing to adduce the relevant expert – in this case an arboricultural expert – to deal with the risk. Without such an expert, a claimant will fail to discharge the burden of proof.

Robbins v LB Bexley

In Robbins v London Borough of Bexley, there was a history of damage caused by other trees adjacent to the implicated tree. The case was determined in favour of the claimant and highlights the importance of having a full record of works previously carried out. Significantly, it also confirms the importance of studies which show that ordinary pruning may not be effective to prevent ongoing damage by trees.

This claim was more unusual because the damage to the claimant’s property was caused by poplar trees at the extremes of their recognised zone of influence, some 30 metres. The court found that such damage was reasonably foreseeable to this particular defendant because there was a history of adjoining poplar trees causing damage in the past.

Significantly, the judge referred to the BRE report, Controlling water use of trees to alleviate subsidence risk (the Hortlink study). This study found that unless the crown of trees was reduced by 70-90%, then there would be little affect in moisture uptake:

“In my judgment the results of this study have important implications for the prevention of damage by tree roots. Prior to the study it appears to have been the received wisdom that any significant pruning of trees would reduce the moisture taken up by the roots, with the result that a regular cycle of pruning could reduce the risk of subsidence. The Hortlink study shows that such a general assumption is not well founded. Unless the extent of the pruning is very severe, that is over 70% of crown reduction by volume, the effects will not be significant. Further, even such extensive reduction may not have an effect for more than two seasons.” (Paragraph 81, judgment.)

This study may be of huge importance in tree root claims. The received wisdom is that the local authority should have reduced the branch lengths by some 25%, and a failure to do so was the negligent cause of damage. Now, following the Hortlink study, it can be argued that even if this was done, the damage would still have occurred. Defendants will therefore have a potential argument on causation, thus providing a complete defence to these claims.

In Robbins, the claimant only succeeded because the defendant had pruned to much greater than 25%. It was held that the defendant should always have done this, therefore preventing the damage.

In light of the Hortlink study, the only way to actually prevent damage may be to remove the trees completely. This argument was rejected at first instance in Berent as being undesirable as it would lead to a wholesale removal of similar trees whether or not they had actually caused damage in the past.

Practical impact of Berent, Robbins and Denness 

When bringing or defending tree roots claims, advisors should ensure their respective arboricultural experts are aware of the research that pruning may have no affect. Since tree owners cannot be expected to remove all trees before damage, they may well be able to argue that any negligence (if proven) would not have made any difference.

The converse is that once damage has been notified, there may be little that the tree owner can do but remove the tree or, via their insurers, pay for underpinning if the tree is to remain. Advisors should therefore be alive to potential disputes between tree owners, who understandably may want to keep their trees, and insurers whose commercial interest will be in their removal.

Both property and tree owners will be affected by the decisions in Berent, Robbins and Denness. Advisors will need to consider at an early stage the evidence that will be needed to bring or defeat claims. The long-held view that liability is always established merely by the proximity of trees to building built on shrinkable soils may well be confined to history.

Muhammed appeared for the defendants in Berent, Robbins and Denness.