Recommended foundation depths in shrinkable clays
On 18 January, Mr G. A. H. Trollope expressed the opinion that the minimum foundation depths in shrinkable clays on sites without trees, as recommended by the Building Research Establishment, were inadequate in that it was not reasonable to ignore the long-term likelihood of trouble from trees introduced within the presumed lifetime of the building concerned. Richard Driscoll (of the Geotechnics Division at BRE) considers the extent to which it would be feasible to adopt recommendations that would satisfy Mr Trollope’s criteria:
Mr Trollope expresses concern about BRE continuing to find 0.9m-deep foundations for lowrise buildings acceptable on clay sites without trees. He suggests that trees are normally planted after site development and, therefore, that foundations should be designed to take account of ‘very likely future events’ and, in particular, of clay subsidence.