New risk method to assess tree interaction with structures

Ground and structural responses to presence of trees can be detrimental if their probable interactions are not duly considered. For example, trees growing in swelling/shrinking clays can lead to damage of buildings that are in close proximity. Very often the problem is not identified until appreciable damage has occurred. Guidelines relating to acceptable distances of trees to buildings are available, but these usually require specialist knowledge of trees. Current practices concerning tree protection and the subject of assessing potential structural damage from trees are reviewed and shortcomings are identified. Following this, two new risk methods to assess likelihood of damage to structures are explained. One covers damage occurring from direct growth of tree roots and the other is associated with settlement/heave above shrink/swell clay. Both systems are intended to provide a basis for identifying situations where advice by tree specialists should be sought, ideally in advance of occurrence of damage. The former was tested by field surveys at several locations in and around London and the latter by well-documented case studies. Both demonstrated that the systems have broad applications. This led to the development of a set of recommendations, in the form of an index chart, for planting trees close to structures.