The Greater London Authority - Tree and Woodland Framework for London, seeks to conserve, manage and enhance the urban tree resource, supported by the London Boroughs. However, the Town and Country Planning Act, makes planning authorities liable for the cost of structural damage to property if they refuse permission to fell trees that are shown to be causing structural damage. This is a major liability and burden in costs and resources to both insurers and London Boroughs.

Street trees frequently damage infrastructure, roads, pavements and property. These conflicts pose a dilemma because of the undoubted amenity and environmental value of trees. Without a sustainable solution to this problem, increasing with climate change, there will be a crisis for London trees and increasing council and insurance liability.

EnviroScience have devised a method that protects both buildings and infrastructure from tree induced subsidence, and protects trees thought to be causing damage, from unnecessary felling.

The method (patent pending) enables rooting away from vulnerable structures. The design reduces clay shrinkage especially in the area of building foundations, while managing safe root growth away from structures, thereby enabling the tree to be conserved. There is also a benefit to tree health, reducing stress and disease risk, both increasing with climate change.

There are a range of adaptations to the method for differing needs of garden and street trees. Roots are also safely managed by a new design of barrier designed to control pavement lifting and finally by enabling precision root pruning near structures without excavation.

Tree root mapping using specialist ground penetrating radar, enables highly cost effective project planning, management, root protection and management, aeration design and precision root pruning, without excavation.

The proposed method has been discussed with the Building Research Establishment (BRE) who have encouraged trialing the technique. The Greater London Assembly - London Tree and Woodland Framework (LTWF) have expressed support for the proposal, with representatives from Forestry Commission, English Nature, Corporation of London (Epping Forest Conservators), Royal Parks etc. The insurance sector have shown interest. The method has been presented to the London tree Officers Association (LTOA) and London Boroughs.

The London Boroughs have both tree liability and affected property, as well as a political interest to find a sustainable solution to this economic and environmental problem. Insurers have an interest to minimise liability and defuse conflict and delay. With scientific validation and publication of a successful trial, insurers and the Boroughs will be in a position to apply this to their own liabilities and also propose this sustainable solution when faced with TPO and street trees thought to be causing subsidence. There are versions of the method adapted to manage street tree and garden tree subsidence.

In essence the method addresses both the needs of the tree and the building. Cost maybe as low as 5% of underpinning cost. At this low cost, risk is low with potentially high returns. Thus the method should relieve a very large liability and cost burden on both Councils and insurers, while enabling the tree induced subsidence problem to be addressed proactively, beneficially and sustainably, in support of GLA and the London Borough's urban trees policies.

Projects can be planned to suit the client. EnviroScience would survey, design and manage the project in close co-operation with the Senior Arboricultural Officer, insurers, Building Control and Highways representatives. Ground work/tree work can either be by Council direct labour/contractor or contracted to EnviroScience.

Costs can often be minimised by incorporating in maintenance and existing works.

A controlled trial for publication is proposed. It is preferred to validate the method by repeatability, with more than one tree/building and it would be advantageous to trial both street and garden trees, thus ideally at least 6 trees/buildings. These would have ideally already been surveyed for seasonal movement over at least a year. However if not, monitoring could commence with the project. The detail of the trial would be agreed between parties. EnviroScience welcome expressions of interest from potential partners.

The method is subject to a patent application. EnviroScience are pleased to describe the method to clients in detail, subject to signing a simple Patent Office secrecy agreement. Please contact

Dr Richard Stow BSc ING PhD
Environmental Scientist and Engineer

EnviroScience
6 Roydhouse
Shelley
Huddersfield
HD8 8LR