Arboricultural Consultant

P.G. Biddle

Dr P.G. Biddle, O.B.E., M.A., D.Phil., F.Arbor.A.
Registered Consultant of the Arboricultural Association
Honorary Fellow, Insitute of Chartered Foresters

Review - Jim Keyes

J.D. Keyes Registered Arboricultural Consultant

Review in Arboricultural Journal Vol. 22, (4), 1998.

The publication of Tree Root Damage to Buildings represents a tremendous step forward in arboricultural literature. In two beautifully produced volumes, Dr P G Biddle sets out to provide a comprehensive analysis of how the interaction of trees, soils and water can cause foundation movement to buildings. This impressive work combines his scholarship, research findings and conclusions derived from many years of intense hands-on involvement in the subject. Since it is written to be widely accessible, it does not presume that a reader will have any particular prior specialist knowledge in arboriculture, soil science or structural engineering. However anyone approaching it with a serious interest in the subject will gain and be challenged by the experience.

Unlike many prefaces, that in Volume 1 is essential reading and should not be missed. Here the imaginative format is introduced. Colour background is used to both highlight essential points and to indicate the source of information on which tables and graphs are based (throughout the work Biddle scrupulously acknowledges other sources of information). The main text of Volume 1 divides into twenty subject chapters. Each concludes with a concise summary of its content and is followed by a case history from Biddle's files. The case histories do not necessarily link with the preceding chapter, rather, they reflect the author's evolving approach over the past twenty years and his concern for proper investigation.

Volume 2 illustrates the accumulated results of three projects to determine patterns of soil drying in the proximity of trees on clay soils. The projects were commissioned by Milton Keynes Development Corporation (MKDC), the National House Building Council (NHBC) and the Department of the Environment (DoE), now the Department for the Environment, Transport and the Regions (DETR). This volume essentially gives context to the text of Volume 1.

The early chapters of Volume 1 'Causes, Diagnosis and Remedy' provide succinct explanations of tree and root physiology, soil structures and behaviour, soil moisture deficits and possible interactions between trees and buildings. Chapter 8 looks closely at climatic influences and the way in which the factors which control evaporation can be modelled from meteorological data. The brief discussion that follows on climatic change and global warming may well depress all of us with a responsibility for trees.

Reading chapter 9, arboriculturalists will probably begin to sharpen their pencils. It deals with the comparative effects of different species and of individual trees and groups. Biddle sets out his assessment of the knowledge to date, his opinions and also, his tentative views. No two arboriculturalists are likely to agree with each other on all aspects of this question, so it should provoke discussion and hopefully, further thought and research.

After skilfully presenting other forms of damage by tree root action, in Chapter 10 Biddle moves on to the strategy and methods of proper investigation where trees are likely or alleged to be responsible for damaging building movement. These chapters - 11-16 inclusive - demand the closest attention. In my experience, the systematic approach and application of the recommended techniques would save many expensive and regrettable errors. The following Chapter discusses remedial action after damage has occurred and clearly explains where tree management could and could not, provide an acceptable remedy.

Chapter 18 examines in detail the prediction and prevention of damage by trees and the implications of subsidence risk assessment. Essential and occasionally provocative reading for all arboriculturalists. The summary of this chapter is particularly effective. An examination of the legal framework follows and this includes a commentary on the important judgements relating to 'foreseeability' and the 'scope of duty'.

Biddle concludes with well thought through suggestions for a revised role for all the professions who are involved with or have a responsibility for, trees and buildings. A brave chapter with which to conclude, since I suspect that not all of his suggestions will be welcomed.

Tree Root Damage to Buildings should prove an indispensable companion to all engaged in the management of trees on cohesive soils and in the investigation of tree root induced movement damage to buildings. I have no doubt that it will be widely quoted, have many extracts copies for proofs of evidence and of course be criticised. The latter must be expected, since the author has challenged some existing dogma. However, and as he says in his preface, he is always interested in hearing from anyone wishing to correct technical inaccuracies. I did not note any, and while I hold some differing views, I am most certainly not going to air them when reviewing a work of this excellence and breadth.