Subsidence usually happens when houses are built on clay soils, and either the water table drops due to a long, dry spell or water is sucked out of the soil by trees and shrubs. As the clay contracts it pulls the foundations, triggering deflection which may cause structural damage to buildings. Different types of clay shrink and swell at different rates. There could be movement in the ground beneath your home if you find:
- New or expanding cracks in plasterwork
- New or expanding cracks in outside brickwork
- Doors or windows sticking for no particular reason
- Rippling wallpaper that isn’t caused by damp
If you spot any of these problems, have trees on or around your property and can’t find a reason for them, Peter Scott can provide specialist advice and assistance. If it is subsidence, the sooner it is diagnosed the better and it’s important to remember that subsidence can usually be rectified.
Check that your buildings insurance covers subsidence. Most insurers will aim to be as helpful as possible in dealing with any claim. They will recommend that you get specialist advice. A chartered surveyor will be able to work out whether or not there is subsidence and what the likely cause is. If diagnosis is not straightforward, they may recommend you bring in a structural engineer combined with an arboricultural consultant to give specialist advice.
Establishing whether or not there is a problem often takes a long time as seasonal monitoring has to be undertaken. There is rarely any cause for real concern unless cracks appear suddenly and are more than 3mm wide. In most cases the first signs of a problem are visible cracks in a particular area of the house and these will need to be measured and monitored, perhaps for as long as 12 months. Solving subsidence can be a lengthy process which can take up to two years.
Taking a few simple precautions can help reduce the risk of structural damage. Trees and shrubs planted too close to a property are a common cause of problems. The attached table indicates the suitable planting distances of various trees from houses, garages or outbuildings. You should also consider the proximity of trees to underground drains and buildings including any belonging to neighbours. Ensure that trees and shrubs are pruned regularly. Expert advice should be sought from an arboricultural consultant to make sure they are pruned correctly. Regular general maintenance checks should be carried out around a property.