Most property owners' insurance policies will include the risk of subsidence but, except when we have a sustained dry - or even wet - period, this is not something that many people think about.

Yet spotting an issue - and taking positive action - early can save you money, as well as your insurance company, because there is usually a significant excess that you have to pay.

There are a number of potential causes of subsidence, not just old underground mine workings, collapsing drains and the more obvious factors. For example, clay soil is particularly likely to cause subsidence because it shrinks and swells according to its moisture content. In periods of exceptionally dry weather this can become very prevalent. It has been estimated that as much as 75% of subsidence claims relate to properties built on clay soil.

What may not be so readily thought of is that trees and shrubs can extract moisture from deep within the soil and cause shrinkage, if roots have to extend in search of scarce water. On the other hand, removing mature trees can cause previously dry soil to swell up, resulting in its expansion, which can lead to what is called 'heave'.

Another common cause of subsidence can be leaking drains - something that an owner occupier might spot easily, but a tenant may be less likely to care about. It is likely that 20% of subsidence claims are caused by drains leaking into sandy soil types, resulting in soil erosion beneath a building's foundations.