Damp, mould and structural
Subsidence: the signs, the causes and what to do
Subsidence is the downward movement of the ground beneath a building, which can crack walls as the structure moves unevenly. Common causes include clay soils shrinking in dry weather, nearby trees drawing water from the ground, and leaking drains washing soil away. Most homes never suffer it, but suspected subsidence needs a professional assessment.
- Also known as
- ground movement, foundation movement
- Easily confused with
- normal settlement of a new build, thermal or seasonal cracking, heave (the opposite: ground rising)
- How serious
- High: concerns the building structure, so always get it assessed
- Typical cost
- Usually no cost for DIY control
How to identify subsidence
The classic sign is diagonal cracking that is wider at the top than the bottom, often near windows and doors where the structure is weakest, and typically wider than about 3mm.
Other signs include doors and windows sticking as frames distort, cracks visible both inside and outside in the same place, and rippling wallpaper at wall joints. Cracks that appear suddenly or keep widening are more concerning than fine, stable hairline cracks.
Subsidence is often linked to a trigger: a recent very dry summer on clay soil, a large tree close to the house, or a drainage leak softening or washing away the ground.
How serious is it?
High: concerns the building structure, so always get it assessed
Subsidence is the most serious problem in this cluster because it concerns the ground supporting the building, so it should always be assessed by a professional rather than self-diagnosed.
That said, not all cracks mean subsidence. New buildings settle, and seasonal temperature changes open and close fine cracks harmlessly. The pattern, width and whether a crack is still moving matter more than its presence alone.
How to fix it yourself
- Do not attempt structural DIY. The useful first steps are observation and recording, not repair.
- Photograph each crack with a ruler or coin for scale and date the photos, so movement over weeks can be judged.
- Note any obvious triggers: large trees close to the house, a recent very dry spell, or signs of a drainage leak nearby.
- Check and clear drains and gutters, since leaking drains are a common subsidence cause and fixing a leak may halt movement.
- Avoid filling cracks until the cause is understood, because cosmetic filling hides ongoing movement.
When to call a professional
- You see diagonal cracks wider than about 3mm, cracks that pass through inside and outside walls in the same place, or cracks that keep widening.
- Doors and windows have started to stick and the frames look out of square.
Who to call
- A structural engineer or a Royal Institution of Chartered Surveyors (RICS) member for an independent assessment of the cause and seriousness.
- A drainage specialist if a leaking drain is suspected as the trigger.
Frequently asked questions
How do I know if cracks are subsidence or just settlement?
Settlement is normal in new buildings and usually leaves fine, stable cracks. Subsidence tends to cause diagonal cracks wider than about 3mm, often near openings, that pass through inside and outside walls and may keep widening. If cracks are growing or doors are sticking, get a professional assessment.
What causes subsidence?
Common UK causes are clay soils shrinking in dry weather, trees and large shrubs drawing water from the ground near foundations, and leaking drains washing away or softening the soil. Identifying which trigger applies is the surveyor or engineer first task, because the fix depends on the cause.
Should I be worried about cracks in my walls?
Most cracks are cosmetic. Be cautious about diagonal cracks wider than around 3mm, cracks visible on both sides of a wall, sudden new cracks, or sticking doors and windows. These warrant a structural engineer or RICS surveyor. Fine, stable hairline cracks are usually nothing to worry about.
Sources
Editor, HomesAndHedge
Oliver leads HomesAndHedge's editorial coverage of home and garden problems. He researches and writes the plain-English explainers on pests, invasive plants, damp and mould, drainage and wildlife, drawing on guidance from bodies such as the Property Care Association, the RHS and the NHS, and is clear about when a job needs a qualified professional.
Last reviewed: 8 June 2026