June 2004

Due to the hot weather last year, tens of thousands of homes shifted and cracked with subsidence claims rising from 32,000 in 2002 to 54,000. With the summer season approaching, what do you need to know about subsidence?

Subsidence usually happens when: either houses are built on clay soils and due to drought the clay contracts; or on sandy soils when water leaks in from, for example, a broken drainpipe, it can wash away the soil from the foundations.

Key signs that indicate subsidence are:

• New or expanding cracks in the plasterwork
• New or expanding cracks in the 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 and can't find a reason for them, get specialist help as soon as possible. If it is subsidence, the sooner it is diagnosed the better.

It's important to remember that subsidence can usually be rectified. Check with your insurance broker 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 from a chartered surveyor.

Establishing whether there is a problem and rectifying it, can take a long time, often up to two years. You should only be concerned if cracks appear suddenly and are more than 3mm wide. In most cases you might have to monitor cracks and measure them for up to a year.

What can be done to rectify the problem?

Tree roots
Consumer champion ‘Which’ estimates that about 70% for all subsidence cases are due to tree roots sucking moisture out of the soil. Is some cases the best solution may be to remove the trees, but this can spoil the view and could potentially detract as much as 20% from the value of the property. In other cases, removing the trees may add to the problem, so make sure you seek specialist advice before acting.

Pipework
Where soil is being washed away because of leaking drains or water pipes, these should be repaired as soon as possible. This will normally be sufficient to stop the problem.

Underpinning
Underpinning the foundations usually prevents further movement. It's a lengthy, costly and disruptive procedure that can cost anywhere between £5,000 and £50,000 or more. It should only be used a last resort, where no other options are available.