What is Subsidence?
Subsidence is the downwards movement of the ground beneath the foundations of a building. This loss of support causes subsequent damage to the property.
There are many evident signs of subsidence in a property, most notably cracks in the walls, ceilings or masonry and the expansion of existing cracks. If you notice cracks in the property you are purchasing, get in touch with a London Chartered Surveyor for advice.
Common causes of subsidence are:
- Shrinking soil
- Vibrations in the ground
- Previous mining activity in the area.
The depth of the foundations and the proximity to trees and drainage systems will affect the possibility of a property being affected by subsidence.
Houses with foundations less than two metres deep are more likely to have problems with subsidence. Building regulation changes in 1976 stated that a building must be constructed to safeguard against damage by the swelling or shrinking of subsoil. If you are purchasing a property in London built before this time, it is important that you find a Chartered Surveyor to provide a house survey in advance of exchanging contracts.
For more information about subsidence and how it can be treated, see our article, ‘Subsidence Cracks – what to do if you think you have subsidence’.
Subsidence and London
Subsidence is a common problem for home owners in London due to its construction on London clay; one in 50 houses in London and the South East has suffered from subsidence.
Clay soils are particularly vulnerable to shrinking, and London clay, which most of the Greater London housing stock is built on, is the most shrinkable soil type as it is highly susceptible to changes in volume depending on its moisture content. London has the highest shrink-swell clay hazard in the country and, therefore, movement of the ground beneath buildings in London can be common and will cause signs of subsidence in properties.
Previous research has indicated that the south east of London is the location that has the most problems with subsidence. There are, however, many additional areas across London that suffer from subsidence caused by clay shrinkage, including the NW, N and W postcode areas in London.
Although property type is not a common issue that influences subsidence, Victorian and Edwardian properties are the most affected, as they have shallow foundations. Large parts of North London have properties built in the Victorian and Edwardian eras, so, if you are planning to buy a home in the north of London, be aware of any cracks when viewing property.
With many areas in London prone to subsidence, whatever type of property you are buying and wherever you are in the capital you should make sure you get a surveyor who has local experience, as they will be aware of where properties are most susceptible and how evidence of subsidence manifests.
The investigation of subsidence will be included in the environmental search conducted by your conveyancing solicitor, where they will check the risk of subsidence, whether the property has previously been treated for subsidence and if there have been any subsidence claims in the past. When assessing the risk of subsidence, your solicitor will take into account the local London area, so it is important to select a conveyancer with experience conducting property transactions in your area.
Your conveyancing solicitor will need to obtain the necessary legal documentation and information to confirm that any subsidence repair works were conducted in keeping with the specifications of works required and had been approved by the Local Council Building Control.
Whether you decide that a HomeBuyer Report or a Building Survey is more appropriate for your new London home, your Chartered Surveyor will investigate and seek to identify any evidence of subsidence, such as cracks and misalignments. Your survey report will inform you of the nature, pattern and severity of the movement, and whether the movement is dormant or active and progressive.
Although older properties are more prone to subsidence, make sure to get a house survey whatever age your new house will be. Newly built properties can suffer from issues with settlement, which is when the weight of the property causes the ground to move. The damage settlement can cause is similar to the signs of subsidence.
If you have any concerns about subsidence or settlement in the property you are purchasing, be sure to discuss this with your surveyor as they will be able to modify their survey to suit your needs.
Your Chartered Surveyor should also advise you on the probable cause of the subsidence and the best course of treatment should signs of subsidence be evident in your London property.
For more information about house surveys when buying a house, take a look at our article, ‘how to get a house survey’.