Guide
Signs of subsidence and what to do first
By Structural Repairs UK · Updated 2026-11-09
Subsidence is the downward movement of the ground beneath a building’s foundations, and its typical signs are new diagonal cracks near doors and windows, sticking doors and cracks that widen after dry weather. The first steps are to photograph and measure the cracks, check for leaking drains, tell your insurer, and leave nearby trees alone until you have advice.
What is subsidence?
Subsidence is when the ground under a building’s foundations moves downward, taking part of the building with it. In the UK the most common cause is clay soil shrinking as it dries, often because tree roots draw out moisture in late summer. Leaking drains are the other usual cause, as water softens the ground or washes fine material away. Less often, old mine workings or poorly compacted ground are to blame. Heave, where the ground swells upward, is a related but different problem.
What are the signs of subsidence?
The classic sign of subsidence is a new crack, wider than a hairline, that runs diagonally from the corner of a window or door and is wider at one end. It usually shows on both the inside and outside of the wall. Movement is often seasonal, so cracks may open in late summer and partly close in winter. Other signs tend to develop alongside the cracks, and several together are more telling than any one alone.
- Diagonal or stepped cracks wider than about 3 mm
- Cracks wider at the top or bottom than the middle
- Doors and windows that start to stick
- Wallpaper creasing or tearing at wall and ceiling junctions
- Gaps opening between skirting boards and floors
- A bay or extension pulling away from the house
What should I do first if I think it’s subsidence?
Start a record before anything else. Photograph every crack inside and out with a ruler or crack gauge in shot, note the date and width, and mark each end with a pencil line. Check again every few weeks and note any doors that stick and when they started. Keep everything in one folder or phone album. Do not fill, stitch or decorate over the cracks yet. A clear record helps an engineer find the cause and helps your insurer assess a claim.
Why should I check my drains?
Leaking drains are one of the commonest causes of subsidence, so checking them early is worthwhile. Warning signs include gullies that overflow, damp patches near a crack, a sewer smell or signs of rats. A CCTV drain survey, which sends a camera through the pipes, is a common first check, at a guide price of about £150 to £350 inc VAT, varying by region and access. If you have already told your insurer, ask before booking one, as they may arrange it as part of the claim.
When should I tell my insurer?
Tell your insurer as soon as you suspect subsidence, and in any case before permanent repairs start. Most buildings policies cover subsidence subject to their terms, and the subsidence excess is commonly about £1,000, so check your schedule. The insurer usually appoints a loss adjuster, who may bring in an engineer to investigate. Telling them early does not commit you to a claim, but repairing first can make one harder. Cover is never automatic, so read your policy wording.
Should I cut down a tree near my house?
No, do not fell or heavily prune a tree near your house until you have advice. On clay soil, removing a large tree can let the ground swell back as it rewets, which is called heave and can lift and crack a building. The tree may also be protected by a tree preservation order or a conservation area, so check with your council first. If there is a claim, the engineer and insurer will usually decide whether a tree is involved and what should happen.
Will I need underpinning?
In most cases, no. Most subsidence claims are fixed without underpinning: the cause is dealt with, for example by repairing drains or managing a tree, the building is monitored until it stops moving, and the cracks are then stitched and made good. Underpinning is used only where the foundations need strengthening. A typical repair once the cause is dealt with is a guide £2,500 to £12,000 inc VAT, varying by region and access and confirmed in writing after a survey.
Questions about this guide
Is subsidence covered by home insurance?
Subsidence is usually covered by buildings insurance, subject to the policy terms and excess. The subsidence excess is commonly about £1,000, higher than for most other claims. Policies often exclude settlement of new buildings, poor workmanship and damage that started before cover began. Read your policy wording, and tell your insurer before permanent repairs start.
How quickly does subsidence get worse?
Subsidence usually develops slowly, over months or seasons rather than days. Clay movement tends to follow the weather, with cracks opening in late summer and partly closing in winter, while a leaking drain can cause steadier movement. Sudden, rapid cracking is unusual. If it happens, keep people away from the affected area and get the building inspected promptly.
Can an old house still suffer subsidence?
Yes, old houses can suffer subsidence, and shallow foundations on clay make many older homes more vulnerable. A house that has stood for a century can still move after a very dry summer, a new leak in an old drain, or a nearby tree growing larger. Age alone does not prove a house has finished moving.