RICS Issues Subsidence Advice

The Royal Institute of Chartered Surveyors (RICS) has issued advice to homeowners who fear that their homes may be at risk of subsidence.

It has also warned homeowners to watch out for the first signs of subsidence, which causes the most expensive home insurance claims.

Subsidence is caused by a combination of dry weather, shifting clay soils and tree movement. As the clay sub-soils dry out and crack, the ground sinks beneath the house, causing problems in the foundations and then when a hot spell breaks the rain causes the soil to expand. In hot temperatures trees will draw the moisture out of the ground, causing it to move. The expansion is rarely uniform throughout the soil and as a result the ground experiences ‘differential heave’, which can cause buildings to move and crack.

Signs that your property has been affected by subsidence include the appearance of diagonal cracks, wider at the top than at the bottom, near to windows and doors or other ‘weak’ parts.

Houses with shallow foundations, often built in the Victorian and Edwardian eras, are particularly at risk, although many built before 1965 have the same problem.

"We, like the home insurance companies, are expecting to see a rise in the incidence of subsidence," said a spokesman for the RICS.

"Finding the cracks and notifying your insurance company can be the easy part — rectifying the problem can be very complex, costly and disruptive to the household.”

"House owners should be prepared for delays as premature action can cause further problems and insurers will usually want to monitor walls for a season to assess a pattern."

How can you check for subsidence:

•    Check the type of soil on which your house is built. Clay soil is the biggest risk. Chalk and granite should not subside.
•    Make sure your surveyor investigates any potential underground mining works. Be especially careful in former mining areas or big tunnel digs.
•    Check foundation depths. Shallow foundations are at a greater risk of subsidence.
•    Look out for drainage leaks - fractured drains can either allow water to saturate the ground causing it to heave or can wash out the fine particles in the soil making the problem worse.

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