§ Lord Beaumont of Whitleyasked Her Majesty's Government:
Whether they intend to fund or commission any research into the causes of building subsidence and the role played by tree roots.
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§ The Parliamentary Under-Secretary of State, Department of the Environment, Transport and the Regions (Baroness Hayman)The Department of the Environment, Transport and the Regions intends to commission later this year a project to prepare a practical handbook that draws together existing knowledge on tree roots and their interaction with soil, man-made structures and objects. In addition, a proposal is being formulated for a project to assess the effect of pruning on the water uptake of trees and the consequential abstraction of water from the soil.
§ Lord Beaumont of Whitleyasked Her Majesty's Government:
Whether they possess any data on the effects of tree roots on buildings and their relationship with subsidence and, if so, whether they will publish it.
§ Baroness HaymanInformation about the incidence of tree species implicated in subsidence damage was included inTree Roots and Buildings published in 1981 by Dr. Cutler and Dr. Richardson. Their work was based on the Kew Tree Root Survey (1971–79). Much of the survey data on the tree root systems was obtained from investigations carried out during the assessment of alleged subsidence damage. The text was republished in 1989 to take account of additional information or data about the structure of root systems.
The National House Building Council and the then Department of Environment commissioned research between 1979–1985 and 1989–1994 to quantify the seasonal and long-term changes of soil drying and moisture deficit in the vicinity of trees on clay soils. The results of this work have been published in technical journals, and are to be published in the proceedings of the conference Arboricultural Practice: Present and Future, held in 1995.
The Building Research Establishment, through research commissioned by the Department of the Environment, Transport and the Regions, has over recent years investigated the effect of trees on ground movements and building foundations. Current work, funded up to 1998, is primarily concerned with the determination of ground movement prior to and following the removal of trees (a possible solution to subsidence damage known to be caused by trees) at locations close to and remote from trees. The results of this work, to date, have been published in conference papers, and in the journal of the Institution of Structural Engineers. BRE also established a database, under contract from the Department of the Environment, Transport and the Regions, to log subsidence damage and factors relevant to each case. The data have not been analysed for publication.
All this work has informed the development of various British Standards, and codes of practice—most notably NHBC Standards Chapter 4.2, which deals with the construction of foundations close to trees.