What is subsidence?
Subsidence is the downward movement of a surface, causing the ground beneath the foundations of a building to become unstable.
Common reasons for subsidence are:
- The shrinking of soil beneath a property
- Previous mining activity on the site
- Ground vibrations
Soil shrinkage can be caused by a number of factors, such as water leaking into the soil under the property, as this can wash away the soil from the foundations. This is most common in soils with a high sand or gravel content.
Clay soils are also particularly vulnerable to shrinking, and as the soil shrinks, it pulls the foundations which may result in structural movement. Clay soil shrinkage can also occur following a dry spell of weather.
Tree roots surrounding a property can significantly influence the likelihood of subsidence occurring as they can cause the shrinkage or reduction of the soil beneath the foundations by extracting water. Tree roots removing moisture from the soil is the most common reason for subsidence in properties.
Evidence of subsidence
There are many visible signs, on both the inside and outside of a property, which suggest the existence of subsidence.
The usual indications of subsidence are:
- Cracks in the walls, ceilings and outside brickwork
- Expanding of existing cracks
- Cracks appearing after a long phase of dry weather
- Rippling of wallpaper that isn’t caused by damp
- Sticking of doors and windows suggesting doorframes or windowframes have changed shape
It is essential to seek advice as soon as you notice signs of subsidence, as the sooner it is identified and diagnosed the easier it will be to rectify. Solving subsidence can be a lengthy process, with many cases having to be monitored for up to 12 months, making it even more important to get help as soon as possible.
If you see any signs of subsidence in your house, or the house you are intending to buy, get in touch with a Building Surveyor for expert assistance.
The most common treatments for subsidence include:
- Pruning or removal of trees and bushes
- Repair work to damaged drains and pipes
- Underpinning the foundations
Although it is a treatment commonly associated with subsidence, underpinning the foundations to increase their depth and prevent further movement is a costly and lengthy process and thus is only recommended as a last resort.
The most appropriate treatment option will largely depend on the cause of the subsidence. For example, if plants and trees are to blame then the pruning or removal of them should resolve the problem. If you have this kind of subsidence then your surveyor will inspect the plants and trees surrounding the property and should be able to recommend a specialist that can advise whether the plant ought to be pruned or completed removed.
Similarly, if the subsidence is caused by soil being washed away by water leaking from drains, repair work to the damaged pipework may stabilise the building enough.
Whilst subsidence can seem scary, it's important to remember that subsidence is usually successfully treated, and, if considered reasonable by your insurance company, the costs for identifying and treating it may be covered by your buildings insurance – so be sure to contact a professional if you are concerned about subsidence in your property.
If the property you are intending to purchase has been repaired for subsidence in the past, your conveyancer should attain the necessary documentation to verify that the repairs were conducted to the standards set out by the Building Research Establishment.
There are two main documents required should the property have a history of subsidence.
- A formal Completion Certificate, which is issued by the council if underpinning had been carried out.
- A Certificate of Structural Adequacy, which is produced by Building Surveyor if the repairs were undertaken as an insurance claim.
Both the formal Completion Certificate and Certificate of Structural Adequacy should be available from the owner of the property, so if your surveyor reports of any previous subsidence repair work make sure your conveyancing solicitor obtains the relevant documentation.
If you are buying a property you suspect may have subsidence both the HomeBuyer Report and the Building Survey will give an indication of whether there is a risk of subsidence in the property. The valuation survey conducted by your lender will not identify if the property is at risk of subsidence, so it is vital that you commission an independent surveyor to inspect the property.
It is always important to get a house survey on any property you intend to buy, as it will ensure that the biggest purchase you’re likely to make is in a safe living condition. By comparing quotes from surveyors you can get a house survey at a cost-effective price.
If you have any concerns about subsidence in your home, be sure to contact a Building surveyor and they will be able to tell you if there is subsidence and what the probable cause of it is.
Updated August 2020