Indirect damage to buildings
The water content of shrinkable soils increases and decreases in relation to the natural seasonal changes. In winter, the shrinkable soil is wetter and increases in volume; in summer the reverse happens. These variations are called seasonal fluctuations.
These fluctuations can be modified or exaggerated by nearby trees and other vegetation, which can extract water from the surrounding soil, potentially increasing the shrinkage rate of the soil. Where the shrinkage is close to a building, it can cause a section of building foundation to drop further than an unaffected neighbouring section. The resulting damage is known as subsidence.
Building foundations can also lift through a process called heave, which again can result in building damage. Burst water pipes, drainage leaks, or the removal of a large area of vegetation, such as a tree, can be a cause.
Subsidence-related claims are costly and many insurance and mortgage companies now ask for an inspection and report of trees located close to buildings. Sadly, many trees are removed as a primary cause of building subsidence, when they're not. According to the London Tree Officers Association 70% of claims made against trees were unfounded.
Direct damage to buildings
Trees can cause direct damage to buildings and structures through direct contact with their roots, branches and stem. Large established buildings, such as houses, aren't normally affected; it's the smaller structures, such as walls, patios, sheds and garages, which are most at risk.
The damage would normally be caused by the annual increase in the girth of the root, branch or stem; as it increases in diameter it lifts or pushes the structure. The concrete foundations of most modern buildings are able to withstand such incremental growth, or to prevent root access altogether.
What to do if you notice damage to your property
You must first contact your insurers, who may ask for a report from a qualified structural engineer. If there are trees in the vicinity, it would be a good idea to contact an arboricultural consultant to carry out an assessment.
Evidence in support of any claim against Harrogate Borough Council should be sent to:
Finance Section, Harrogate Borough Council, PO Box 787, Harrogate HG1 9RW. If the tree is on the highway verge, it'll more than likely fall under the ownership of North Yorkshire County Council.
Page last updated 09/07/2018