Do you know the difference between subsidence and settlement?

Do you know the difference between subsidence and settlement?

As a homeowner, the sight of cracking in the walls of your home can be a great worry. Cracking can be a sign of subsidence, which in turn can equal costly structural work, difficulties buying home insurance and issues when you want to sell.

But surely not all cracks spell major remedial work? Well, in short the answer is no they don’t. Cracking in walls does not always mean that you have a subsidence problem; it could be due to other less serious causes.

The difference between subsidence and settlement

Firstly, it’s good to understand the difference between subsidence and settlement. Settlement usually occurs in new or relatively new buildings. It is caused by the ground compacting beneath the building – some movement occurs as the ground adjusts to accommodate the new load. Also, adjustments can occur as different construction materials settle down with different shrinkage rates.

The builders responsible for the construction of a new property may be contracted to return in a few months to make good any settlement cracks that have appeared since the build.

In older buildings, like my flat, thin cracks can appear with the changing seasons (i.e. changing temperature and changing moisture content), as the materials of the property expand and contract. Most hairline plaster cracks are in fact harmless.

The RICS (Royal Institute of Chartered Surveyors) website states:

Generally it can be considered that hairline cracks which appear on an annual basis are not structurally significant, but cracks which increase in width gradually over a period of time should be investigated. When they become between 16-25mm, they are classified as severe under the BRE Digest 251 (classification of visible damage to walls). 

Structural movement occurs all the time and is usually so small in scale that it passes unnoticed. However, when this movement and distortion threatens the future safety of the building – action will probably need to be taken sooner rather than later.

Cracking can, in some cases, be a sign of a more serious problem in the form of subsidence. This is the vertical downward movement of a building foundation caused by the loss of support of the site beneath the foundations. Clay soils, trees and shrubs close to the property or leaking drains are all possible causes. For more information, check out our blog post: how to spot signs of subsidence.

If you are concerned about cracking in the walls of your property, it’s probably best to consult a qualified, registered surveyor. By seeking expert advice, you’ll either put your mind at rest or catch a problem early before it escalates.

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Published 24 February 2011