The ever changing weather conditions and the increase in hot dry summers and comparatively dry winters in recent years has seen an increase in subsidence in buildings and properties.
Subsidence is the downward movement of the ground supporting the building. Damage occurs because the movement is often uneven, causing cracks in walls, floors and ceilings. The main cause of subsidence in the UK is the shrinkage in dry weather of clay soils which expand and contract with changes in their moisture content. The escape of water from leaking or damaged drains below the ground can also cause subsidence.
Subsidence damage to buildings is generally distinctive in appearance, cracks in walls usually having the following features:
- Noticeable from both inside and outside the property
- Reaching below the damp proof course, this is often results in doors and windows sticking, reflecting the distortion of the building.
Much less common but causing damage of a similar nature are:
- “Heave” is the upward movement of the ground supporting the building.
- “Landslip” which is the movement of a mass of ground down an incline or slope trying to find a natural level.
Buildings and properties can suffer minor cracking as a result of a number of causes:
- Consolidation settlement of soil due to the weight of the building. This normally occurs early in the life of a building
- Temperature changes of the building superstructure causing expansion and contraction
- Drying and shrinkage of building materials: cracks arising are generally uniform in width and narrow (hairline to 3mm) and can be dealt with cosmetically by decoration or minor maintenance work.
Common Causes – Tree Types
Research indicates that the majority of subsidence issues in buildings and properties involve trees to some degree. Trees that have fine root structures longer than other species, such as poplars, willows, elms and oaks are the most likely to cause problems.
For example: A safe distance for an Oak tree is 30m from the building.
What actions can you take to help?
If you should reside in a clay soil area there are a number of simple actions you can do to protect your property and alleviate long-term problems:
- Do not plant trees or large shrubs close to the house, garage or outbuildings.
- Trees which are older than the structure but within the safe distance can be managed by a programme of pollarding or crown thinning carried out to control the amount of foliage produced, which will in turn reduce the amount of water it requires.
- Trees which are older than the structure should not be removed as this could cause uplift of the ground and heave
- Never remove or in any way alter a tree on which there is a preservation order, without the appropriate consent.
- If in doubt obtain specialist advice from a tree surgeon or similar professional. (Initially the cost involved will normally have to be borne by the policyholder and will only be reimbursed by the insurer if a claim is met.)
- The tree may be within a neighbouring garden or in the street. If you are worried about the potential subsidence problems that a neighbour’s tree could cause, discuss it amicably and try to persuade him or her to take an appropriate action. Only if your neighbour is uncooperative, or the tree is the property of the local authority, write a letter expressing your concern and keep a copy for future reference.
For more information contact Emma Patrick, Private Clients Manager on 01625 547754 or email@example.com