TREE RELATED SUBSIDENCE OF LOW RISE BUILDINGS AND THE MANAGEMENT OPTIONS

Abstract

Summary Trees have long been known to cause damage to man-made structures. Damage may be a result of growth leading to disruption or displacement of structures. Alternatively, damage can be caused as trees distribute biomechanical stress as a result of wind loading. Failure of trees or parts of trees can cause direct damage as they impact property. Trees can cause differential damage to low rise buildings as a result of their ability to abstract water from soils through transpiration leading to changes in soil volume, in particular of clay soils, as water content within the clay fraction is reduced. All of these modes of damage can lead to financial loss to the owners of the trees, third parties and dimunition in the value of buildings, and thus to the insurance carriers. This paper attempts to provide a review of the evidence associated with the particular problems with subsidence of low rise buildings when caused or perceived to have been caused by volume change of clay soils as trees abstract water. A literature review is presented and the key findings discussed. This provides the basis for consideration of a theoretical ‘Model Tree’. An assessment of modern technical solutions to the problems is also given