Householders told that trees must be removed because of subsidence should insist that insurance companies provide proper evidence that the tree is to blame, the Dulwich Society's open meeting on trees and subsidence was told in September.
Over 100 people attended the meeting, organised by the Wildlife and Trees committees at the Old Library, Dulwich College, and heard criticisms from several experts that some insurers fail to obtain adequate evidence and often insist on trees and shrubs being removed as the cheapest, quickest and easiest solution.
The meeting was organised because of rising concern about the dangers posed to Dulwich's tree heritage from subsidence claims. It heard from four specialists in law, insurance, ecology and arboriculture as well as from representatives of the Dulwich Estate and Southwark Council and was chaired by His Honour Michael Rich QC, the society's president. The society plans to publish a record of the debate and also hopes to publish longer accounts in the Newsletter. The first of these, by Jim Smith, former chair of the London Tree Officers' Association's executive and London trees and woodlands framework manager for the Forestry Commission, is scheduled to appear in the next issue.
Mr. Smith told the conference he had spent two years helping to write the Institution of Structural Engineers' report Subsidence of low rise buildings, published in 2000, which involved the collaboration of the entire industry, from engineers and insurers to local authority tree officers, and remained the nationally recognised authority on resolving subsidence problems.
Unfortunately, he added, "many insurers' loss adjusters and arboricultural consultants do not actually follow the recommendations in that report. Frequently, they don't adopt a forensic approach in investigations. They fail to eliminate other potential causes of movement before identifying the tree as the potential cause."
Mr. Smith criticised what he called "loss adjusters' complacency in almost always assuming that the tree is the cause of the problem. My experience is that they commission limited tests to fit this hypothesis rather than to establish the real mechanism at work."
He said the Building Research Establishment had analysed the tests routinely used by insurance companies to establish the desiccation, or drying-out, of soils
and concluded that none of them was satisfactory. "By using tests that are less reliable and less accurate and then taking calculations off those, you're building into that process a margin of error that we, as tree officers, find unacceptable."
The Institute of Structural Engineers, the Building Research Establishment and the newly revised London Tree Officers' Association document A Risk Limitation Strategy for Tree Root Claims all advised using a set of tests appropriate to the soil type to eliminate other causes prior to establishing the tree as the cause of the movement, he added,. These test results required cross correlation with each other and with tests on ground conditions and the presence of leaking drains to create an accurate picture of the mechanism at work.
"Only by approaching this matter forensically and with due diligence can it be resolved to all parties' satisfaction. To date this has not been happening - indeed in many cases loss adjusters have actually withheld key test information, specifically, we believe, because they know it weakens their case."
Other highlights, quotations and points from the meeting include:
David Nicholson-Lord, Wildlife and Trees Committees