Subsidence signs: how to tell, and what to do next

When it is genuine, the order in which you act affects both the fix and who pays for it.

First signs of subsidence, in combination

• Diagonal cracking, wider at the top than the bottom, often stepped through mortar joints in brickwork, typically concentrated near doors, windows or where an extension meets the original house.
• Cracks visible inside and outside at the same position, appearing or growing after long dry spells.
• Doors and windows sticking as frames distort out of square.
• Rippling wallpaper or cracking at wall-ceiling junctions without a decorating explanation.
• Context: shrinkable clay soil, mature thirsty trees (oak, willow, poplar) near the building, leaking drains softening the ground, or a neighbourhood history of claims. No single sign is proof; the pattern is the evidence.

What do subsidence cracks look like?

A subsidence crack usually runs diagonally and is tapered (wider at one end, typically the top). It passes right through the wall, so it shows at the same place inside and out. Ordinary shrinkage and settlement cracks tend to be fine, vertical or horizontal, and stable.

Engineers grade a crack's width against the BRE damage categories: see BRE 251 and when to worry.

Internal signs of subsidence

• Cracks in plaster above door frames and at the corners of window openings, running diagonally.
• Doors that bind or swing open on their own, and windows that no longer close square.
• Gaps opening between skirting boards and the floor, or between the ceiling and the wall.
• Wallpaper creasing or tearing along a line where nothing has been decorated.

Signs of subsidence in the garden

Outside, look for the same story at ground level:

• a crack in the house that lines up with cracking in a path or patio;
• garden walls leaning or stepping;
• wide cracks opening in a clay lawn in a dry summer near a large tree.

Ground cracks on clay in a drought are common and not proof on their own. They matter when they sit beside cracking in the building.

How to check for subsidence

1. Photograph each crack with a ruler or coin beside it, and date the photo.
2. Mark the ends of the crack in pencil and note the date, so you can see whether it grows.
3. Check it again after a few weeks and after a change of season: a crack that moves is live, one that does not is usually old.
4. If it is growing, tapered or matched inside and out, stop measuring and make the calls below.

What it is not

Most cracking is not subsidence. New-build settlement, thermal and moisture movement, and lintel or plaster failures produce cracks too, usually vertical or horizontal, stable, and modest in width. The BRE damage categories put widths in context: below 5mm is usually cosmetic territory.

The right order of calls

1. Buildings insurer first, if you own and insure the property and the signs are credible. Subsidence is a standard buildings peril; the insurer appoints and funds the investigation and repair. Policy excesses for subsidence are typically higher than for other perils, commonly around £1,000, check your schedule.
2. Independent engineer's report where you want an assessment before involving the insurer, where you are buying the property, or where a claim is disputed: EMA Structures publishes £495 + VAT for an inspection with a full report covering signs of subsidence, read on 12 October 2026. Mid-purchase, this report is the difference between renegotiating and walking away.
3. Expect monitoring, not instant verdicts. Genuine investigations often monitor crack movement across seasons before prescribing. Underpinning is the last resort, not the default: many claims resolve with tree management or drain repairs.
4. Be sceptical of unsolicited diagnoses from anyone selling the remedy, the same conflict of interest that runs through building defects generally.

Selling or remortgaging a property with a subsidence history is manageable but disclosure-sensitive. Keep the engineer's reports, the completion certificates for any works and the insurer's claim records together; buyers' lenders will ask for them.