Undertaking building surveys in London means that you are almost certainly going to come across the ever present and constant that is the London Clay.
London Clays fluctuate greatly in their water retention and desiccation properties. In simple terms, they expand in the winter by virtue of holding moisture and contract or shrink in the summer when there is less rain and vegetation affects greater take up of moisture. This does not make them a particularly good sub-ground matter on which to build.
Many a subsidence report will site London Clays as the cause. However, the building surveyor will know that it is often a combination of factors and not just the London Clay sub-soil, this being a contributory factor, but other factors that lead to subsidence and are reported in building surveys will be at play, these are commonly:
- Blocked drains.
- Proximate vegetation.
- Often inadequate footings or foundations, especially in Victorian properties.
- Adjacent building works.
Subsidence is one of the key factors that our building surveyors look for in building surveys and is often a substantial worry for buyers, quite correctly. However, although London Clays are often cited by London building surveyors and insurance companies as the cause of subsidence, as the above list shows, they are a contributing factor but there will almost certainly be at least one or more of the above contributing factors.
Thus the building surveyor must be fully aware of all possibilities and fully follow the trail in order to correctly diagnose the cause of any cracking and subsidence found during a building survey.
As experienced London building surveyors, we are keenly aware of all possible risk factors and the risk of subsidence is foremost in the mind when undertaking a building survey. We also undertake specific defect report analysis of subsidence matters for insurance companies and for owners of property whom are worried about cracking.
Building owners should look for cracking that opens up wider in the summer months or appears in the summer months and for cracking that has a 45 degree trajectory, often at corners and first floors.
RES Property Surveyors are also Expert Witness surveyors, undertaking diminution in value claims relating to subsidence and we are thus keenly aware of the issues subsidence can cause in terms of reduction in Market Value and diminution in value to properties. Our Expert Witness surveyors would be on hand to assist in any such cases.