Berent v (1) Family Mosaic Housing (2) London Borough of Islington [03.07.12]

It is estimated that the value of recoveries by property insurers resulting in tree root subsidence cases is well in excess of £100 million with the majority of the monies recovered from local authorities, who are either self insured for the majority of the claims or entirely. In light of the Comprehensive Spending Review 2012 (carried out by HM Treasury), cash strapped local authorities would be very keen to reduce the size of recoveries by property insurers. Indeed, in most cases, local authorities have abandoned their policy of preserving street trees in favour of removal and replanting upon being presented with a potential claim for damage by third party property insurers.

The cost of failing to remove a tree resulting in sub-structure repairs (usually underpinning) can be 10 times the cost of superstructure repairs.

Two recent court decisions have re-visited liability for breach of duty, which has previously been a less contentious issue in light of strong decisions, which have largely gone in favour of the property insurers.

Domestic insurers seeking a recovery would normally expect an admission of liability from local authorities or commercial property insurers in circumstances where they can demonstrate:

  • The third party tree was within the recognised zone of influence
  • The soil (usually London clay) was desiccated
  • Live tree roots have been recovered from trial pits
  • Monitoring establishes cyclical movement consistent with tree root activity
  • There is no evidence of what precise steps the tree owner took to prevent or minimise the damage

There may be a debate about the extent of the damage and alternative contributing factors, but essentially the points above have been the key determining factors.

The issue of breach of duty had largely been conceded in cases prior to the determination of the case in Berent v Family Mosaic Housing: namely that the local authority with trees within a zone of influence located in soil capable of becoming desiccated, and therefore with capacity to damage third party property and who took no or no adequate steps to prevent or minimise the property damage.

Salient facts: Berent v Family Mosaic Housing

  1. The roots from two London plane trees allegedly caused damage to the Claimant’s property in 2003/2004
  2. Other potential causes of damage were considered, including a defective drainage system and vibration damage from railway tunnelling work
  3. The period of damage was reasonably short lived between September 2003 and Spring 2004
  4. Notice was given to the Defendant Local Authority in 2009
  5. The trees were removed in 2011
  6. The expert evidence was that pruning would not have prevented the damage

At first instance, the Court held that there was no proof that the Defendants could have appreciated the real risk of damage. The Court of Appeal’s judgment focused on liability for breach of duty and applied the well established test of: (i) to what extent could the consequence be reasonably foreseen (ii) to what extent action could be taken to eliminate the risk (iii) having consideration to the social desirability of that activity.

The test has further been refined and put as "…the general principle [is] that a person must be regarded as negligent if he does not take steps to eliminate a risk which he knows or ought to know is a real risk and not a mere possibility which would never influence the mind of a reasonable man" (the Wagon Mound (1967)).

Questions arising from that test are: how reasonable are these steps, how expensive will they be, and within what time scale could the party be expected to eliminate the risk, and how practicable are the steps necessary to eliminate the risk?

The decision

Arboricultural evidence from the Claimant was that the only remedy was to remove the trees. The Defendant Local Authority had to balance its obligations pursuant to the Town and County Planning Acts and the amenity value placed on trees. There had been no evidence of historical damage caused by the offending trees. The Local Authority had a prudent regime of tree management and there was no evidence that it should have had a different regime. The Claimant’s expert’s opinion was that all trees growing near the property would have to be removed and the Court found this a less attractive argument. Further, the Claimant’s experts were not able to identify the neighbourhood where damaged caused a particular area or "hotspot".

On balance the Court of Appeal found the steps necessary to prevent the risk of damage were disproportionate and contrary to the Local Authority’s obligations to preserve the amenity value of trees.

Consequences of the decision

Liability for breach of duty will no longer be largely conceded by local authorities. Provided they could demonstrate a reasonable tree maintenance policy backed by arboricultural expertise, the policy was implemented, and provided they have no reason to consider a particular tree or neighbourhood posed a higher than normal risk then potentially the claims could be defended.

Insurers and local authorities do not have to wait long to test the application of foreseeability following this decision. The High Court was at the same time preparing to hand down judgment in the case of Robbins v London Borough of Bexley [2012].

Salient facts: Robbins v London Borough of Bexley

  1. Evidence of damage to the Claimant’s property in 2003 and 2006.
  2. The Defendant’s poplar trees had been severely reduced, in all likelihood reducing the extent of movement to the Claimant’s property in 2006.
  3. There was a large disagreement about whether the Defendant’s tree was within a foreseeable zone of influence.
  4. Only one small root (less than 1mm in diameter) from the Defendant’s tree had been recovered from trial pits. It was largely accepted by the engineers that the property had been damaged by tree root activity.
  5. The Claimant’s arboricultural evidence was preferred on all the crucial issues.

The decision

The High Court held the Defendant Local Authority had not followed its own stated tree root policy and was liable for the damage that did occur. The decision was made in light of the evidence of earlier claims involving trees from Danson Park causing damage to neighbourhood properties (up to a distance of 35 metres), and the fact that the Court preferred the Claimant’s expert evidence that the roots were within the acceptable zone of influence capable of causing damage. The Local Authority had been aware of the potential risks of tree root damage to these properties since 1998, as they had been aware of the earlier claims and in fact settled some of them.

The judgment was reserved pending the appeal in Berent. Upon hearing submissions, the High Court made it clear that there were no special principles of law involved in tree roots cases in relation to the issues that arise in nuisance and negligence cases.

In Robbins, the High Court was satisfied the trees had posed a foreseeable risk since 1998, and the Local Authority could have taken reasonable steps to eliminate that risk.


Local authorities are likely to be more reluctant to concede the issue of liability. Insurers will need more evidence, which is likely to include:

  • Evidence of a reasonable tree management policy, its reasonableness and proof of implementation
  • History of claims and actions taken
  • More use of expert witnesses especially arboriculturists to comment on the tree maintenance programmes, zones of influence and alternative remedial action

The question of foreseeability between domestic householders, namely, whether a domestic householder is in a different category in law from any other reasonably prudent tree owner is currently being considered in the case of Khan v Kane and a decision in this crucial case is awaited.

Fifty shades of green may have become fifty shades lighter.

Peer reviewed by Daniel Crowley, Barrister, 2 Temple Gardens.