Subsidence results from the shrinkage or downward movement of the ground around the foundations of a building. As the ground moves, the foundations are in peril of failing and the building they support is at risk of potentially very serious damage.
On a brighter note, however, subsidence typically occurs over a fairly long period of time, before truly serious structural damage is caused. Therefore, the sooner the signs of any subsidence are spotted, the sooner remedial work may be undertaken and more serious damage averted.
As you might notice, however, these early signs are largely quite innocuous and might often be symptoms of nothing so serious as subsidence. So, just how may you spot subsidence and what steps might you take if you have any worries?
the first signs of subsidence are likely to be cracks in the walls – either on the inside, the outside or both of your house;
look out for new cracks that appear unexpectedly and are more than about 3 mm wide in either the interior plasterwork of the brickwork outside;
they typically run vertically or diagonally and are tapered, so that they are wider at the top than the bottom;
cracks may also appear around naturally weaker points in the construction, such as door and window frames;
as the cracks widen, you may find that windows and doors no longer open so easily, but stick or jam;
you might notice a crack or cracks in the exterior brickwork that tapers down to the ground, running through the damp proof course towards the foundations;
if you have an extension on your home, look out for cracks where the wall of the extension meets the main body of the house – the extension might be pulling away from the original structure as the ground beneath the two moves unevenly downwards;
all of these types of cracks are likely to appear unexpectedly, but are more likely to do so after a spell of particularly dry or prolonged dry weather – indeed, some of the cracks might seem to close again of their own accord as the seasons change, suggests a guidance note published by the Landmark Information Group;
still more difficult to spot may be a rippling or rucking of the wallpaper – where this is not caused by damp, but because of cracks appearing in the plasterwork beneath it.
But any of this type of cracking is in any case quite normal and evidence of a harmless settling of the ground, as a new house, in particular, beds down into its foundations. Settlement like this is quite different to subsidence – a distinction made both by surveyors and insurance companies.
The call to action
If any of these signs give cause for worry about subsidence, the first step is to contact your home insurer, to discuss any provision for subsidence insurance covered by your policy.
In appropriate cases, the insurer is likely to ask for a surveyor’s report, assessing the likely causes of the problems you have spotted and whether subsidence may be the root cause.
These investigations are likely to be quite complicated and may take careful monitoring over a period of some time – at least 12 months, for example, to determine the rate at which any cracks continue to widen. This is another reason, of course, why the sooner you raise the alert about any worries about subsidence, the better.
Further reading: Guide to subsidence and subsidence insurance