Subsidence is a term used when the ground supporting a building moves downwards and the building responds to that movement. It is an important structural concern, but visible cracking alone does not prove that a property has subsidence.
Why can London properties be affected?
Ground conditions vary across London. Shrinkable clay soils can be sensitive to changes in moisture, while trees and vegetation can influence moisture conditions near foundations. Leaking drains and other sources of water can also affect local ground conditions.
Possible warning signs
- Stepped or diagonal cracking in masonry.
- Cracks that change noticeably over time.
- Distortion around doors and windows.
- Sloping or uneven floors.
- Separation around extensions or structural junctions.
- Repeated cracking after cosmetic repairs.
Other causes can look similar
Settlement, thermal movement, moisture-related defects, roof movement, inadequate support, alterations and localised masonry defects can produce cracking that may initially be mistaken for subsidence. This is why diagnosis should consider the complete pattern of evidence.
How is suspected subsidence investigated?
- Detailed visual structural inspection.
- Review of crack location and pattern.
- Assessment of nearby trees and vegetation.
- Drainage investigation where appropriate.
- Trial pits to establish foundation depth where necessary.
- Soil investigation where ground conditions require confirmation.
- Crack monitoring where the key question is whether movement is continuing.
Why monitoring may be recommended
An inspection provides a snapshot. Monitoring can provide evidence about changes over time when the engineer needs to determine whether movement is active or historic. The appropriate duration and method depend on the property and the defect.
What should a homeowner do?
Avoid simply filling and repainting significant cracks before the cause has been considered. Keep records of previous repairs, insurance claims, drainage works, tree works and any previous structural reports. This history can be valuable to the engineer and insurer.
Buying a property with a history of subsidence
A history of subsidence does not by itself establish the current condition of a property. The relevant questions are what caused the movement, whether it has stabilised, what remedial work was completed, and what evidence is available today.
Laytoe Structures provides structural inspections, subsidence assessments and crack monitoring for residential properties across London, with reports tailored to the specific structural concern and the requirements of the client, lender or insurer.
If you would like an engineer to look at your property, see our structural inspection service in London. Inspections start from £420* with a written quotation before we visit, or call 020 3983 5057.