Subsidence is a problem that develops when changes under ground cause foundations to shift and stop supporting the walls as they should.

Subsidence is one of the most costly problems that can befall your property, but it is usually one that is covered by your buildings insurance policy, though there is generally an excess level of £1,000. If the subsidence is caused by water escaping from the drainage system then the excess level can be as low as £50. However, it is worth checking the small print to see what your excess levels are and if other buildings such as garden walls are covered. Even in the scenario of a home's value being irrevocably damaged a cash settlement can be made to reduce the mortgage in the first instance and retain the cash balance thereafter.

There are many reasons for a house to suffer subsidence. Some of the most common are:

• Clay soil under a home shrinking in the summer when dry and expands when wet causing the foundations to move. This in turn upsets the structure of the house and can cause the walls and plastering to crack.
• Past mining in the area, such as the tin mining in Cornwall.
• Extracting water from the ground for some commercial activity.
• Other human activities, such as tunnelling for drains as in Newcastle building the Metro underground tube system.
• Building property on landfill sites - aside from the potential health hazard, this is one of the main reasons why it is not normal to find homes built on them.

The tell-tale signs of subsidence are usually cracks or bulges in the walls or floors of a building.