How Do I Know If My House Has Subsidence?

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Quick answer

You know your house may have subsidence when you see diagonal cracks wider than about 3mm near doors and windows that show on both the inside and outside of the same wall and keep widening over time — often with sticking doors and sloping floors. But you cannot confirm it yourself: the diagnosis depends on whether the cracks are actively moving. Screen the ground for the address (is it on shrink-swell clay or in a coalfield?), then have a RICS surveyor or structural engineer monitor the movement and classify it. Confirmation almost always needs a period of monitoring.

A step-by-step check

StepWhat to do
1. Look for diagnostic cracksCheck walls near doors and windows for diagonal cracks wider than about 3mm that appear on both the inside and outside of the same wall. These openings are the weakest points and where subsidence cracks usually show first.
2. Test whether the cracks are movingPhotograph and date each crack, or bridge it with a paper tell-tale. Cracks that widen over weeks or months indicate active movement; stable cracks that have not changed for years are usually cosmetic.
3. Check doors, windows and floorsNote any doors or windows that have started to stick or drop out of square, rippling wallpaper, and floors that slope or skirting that has pulled away — secondary signs that support (or weaken) a subsidence read.
4. Screen the ground for the addressReview available ground-hazard and mining records, noting their map scale. A low regional class or no returned record cannot diagnose cracks or rule out building movement. Discuss signs with a surveyor.
5. Get a professional assessmentA RICS Level 2 or Level 3 survey, or a structural engineer's report, classifies the damage against BRE Digest 251 and advises whether monitoring is needed. This is the step that confirms or rules out subsidence.

Why can't I confirm subsidence on my own?

Subsidence is diagnosed by movement over time, not by a single crack. A structural engineer or RICS surveyor rules out other causes — thermal cracking, wall-tie failure, lintel problems and heave (ground swelling upward, often after a tree is removed) — and monitors the cracks, sometimes across a full seasonal cycle because shrink-swell clay moves with the weather. Insurers and lenders act on that professional assessment, classified against the BRE Digest 251 damage scale, not on a homeowner's judgement.

“If you are worried that your property may be suffering from subsidence, contact your buildings insurer, who will be able to arrange for the damage to be assessed.”
— Association of British Insurers, subsidence guidance

How do I check the ground for the address?

Available ground-hazard maps describe susceptibility at their stated scale. The BGS GeoSure 5 km grid is regional context, and a coalfield screen does not provide a building-specific mining search. Low or missing map readings cannot establish the cause of a crack or rule out movement in a building.

What if I'm buying rather than already own the house?

Request the seller's information and any investigation, repair and insurance documents. Give signs of movement to a surveyor and agree an appropriate inspection or specialist investigation. Ask your conveyancer about the relevant searches and check actual insurance terms before committing.

Start with the ground

Use the free ground screen as regional context for questions. The £24.99 Complete report brings available ground, flood, crime, energy and sale records together. It does not supply a property's insurance claims history, diagnose subsidence or clear a building. Spatial checks use the postcode location and missing sources stay gaps.

Run the ground-stability checkSee a sample report

Still not sure it's subsidence? Check what the ground under that address is doing.

The £24.99 Complete report collects available public records and explains their source limits. Spatial checks use the postcode location. It does not diagnose movement, provide past insurance claims or replace a survey and specialist investigation.

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£24.99 one-off · no subscription · Human-checked and emailed to you. See a sample report · Review report options and coverage

Frequently asked questions

Look for the diagnostic pattern first: diagonal cracks wider than about 3mm near doors and windows, visible on both the inside and outside of the same wall, that are getting wider over time. Add sticking doors, rippling wallpaper and sloping floors as supporting signs. Then screen the ground — is the address on shrink-swell clay or in a coalfield? Finally, confirm with a RICS survey or structural engineer, who will monitor the cracks and classify them against the BRE Digest 251 scale. No single sign proves subsidence; it is the combination plus professional confirmation that does.
You can gather strong evidence yourself — measuring crack width, tracking whether cracks are widening, and checking whether the ground is high-risk clay or former mining. But you cannot confirm subsidence without a professional. A RICS surveyor or structural engineer monitors movement over time and rules out other causes such as thermal cracking, wall-tie failure or heave. Lenders and insurers act on the professional assessment, not a homeowner's judgement.
Because the diagnosis depends on whether cracks are moving, confirming active subsidence usually involves a period of monitoring — often several months and sometimes across a full seasonal cycle, since shrink-swell clay moves with the weather. An initial survey can flag the likelihood quickly, but insurers typically require monitoring data before accepting a claim and agreeing remediation.
No. Subsidence is downward ground movement, often from clay shrinking in dry weather. Heave is the opposite — the ground swelling and pushing the foundations up, for example after a large tree is removed and the clay rehydrates. Settlement is the small, one-off downward movement of a new building or extension as the ground compresses under its weight, and is normally harmless. A structural engineer distinguishes between them, because the fix differs.
Ask for the seller's information and any past investigation, repair and insurance documents. Agree the appropriate survey and any specialist investigation with a surveyor. Discuss property-specific searches with your conveyancer and obtain insurance terms for the actual home.

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Sources

HouseCheckup provides area-level ground screening, not a structural diagnosis. Only a RICS survey or structural engineer can confirm subsidence at a specific property.