London clay – got that sinking feeling?
Property Problems | Purchasing a House | Selling Your House

The mention of London Clay can cause home buyers’ stomachs to sink. It’s the main culprit behind subsidence, which is something any surveyor should be checking for when they survey a property.

The problem:

Subsidence that causes cracking and structural damage.

Why it’s a problem:

Subsidence occurs when the ground beneath your home starts to sink, causing the property to move on its foundations. This can cause cracking and other structural damage. The three main causes of subsidence are the underlying soil, the age of the house, and the proximity of trees or shrubs.

Properties built on clay soils are vulnerable to subsidence because the soils are more likely to shrink when they are dry. Many London properties are built on London Clay, which is notorious for shrinking as it dries out. In addition, London houses built before 1965 tend to have shallow foundations and so are more prone to being affected by subsidence.

Trees planted close to properties suck moisture from the soil, especially during long spells of dry weather causing the soil to dry out which can affect the property. In contrast to this, if water continually escapes from a damaged drain or water pipe it can soften or wash away the soil beneath the foundations of a home which will also cause subsidence.

Although, the Association of British Insurers recommend that you contact your buildings insurer as soon as you think there may be a problem, Roy Ilott, spokesman for the Royal Institution of Chartered Surveyors disagrees and states”…If you are not sure about the cracks, it is best, in the first instance, to get hold of a building surveyor, who can give you some independent advice… In my experience, insurers are only going to remedy damage that has already been caused, and are not interested in carrying out preventive work.”*

What we recommend:

If you’re thinking of buying a home in London that was built before 1965, definitely get a surveyor to assess for subsidence. If you already own a London property, make sure subsidence doesn’t become a problem by checking drains and pipes regularly to ensure there are no blockages or leaks. Plant new trees a good distance from the property and prune them occasionally to reduce the amount of water they take up. If you suspect there’s a problem, contact your buildings insurer and an independent building surveyor.


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*From an article on the Independent.co.uk Friday 12 June 2015