What subsidence actually is
Subsidence is the downward movement of the ground beneath a building, which can crack walls and distort the structure. Common causes include shrinkable clay soils that swell and contract with moisture, tree roots drawing water from the ground, leaking drains washing away soil, and historic mining or made-up ground.
It's distinct from 'settlement', the small, even movement most new buildings experience. Subsidence is uneven movement, and it's the unevenness — not the existence of a crack — that matters.
The warning signs
Telltale signs include diagonal cracks wider than about 3mm (often wider at the top), especially near doors and windows or where an extension meets the original building; doors and windows that stick or won't close; and rippling wallpaper at wall-ceiling joints. Cracks that are vertical, hairline and stable are usually nothing to worry about.
Many homes show old, stabilised movement that was dealt with years ago. The key questions are whether movement is ongoing, what caused it, and whether it was properly remedied — which a structural survey can assess.
How it affects mortgages and insurance
Lenders rely on the valuation and survey; clear evidence of ongoing subsidence can lead to a retention, conditions, or a declined mortgage until the cause is investigated and remedied. Underpinning (strengthening foundations) is the most serious fix and is expensive.
Insurance is often the bigger long-term issue. A property with a history of subsidence can be harder and pricier to insure, and the existing insurer may need to continue cover or pass it on. Always confirm that buildings insurance is available and affordable before you commit.
How to check ground risk before you offer
Ask the seller directly (the property information form covers structural movement and insurance claims), look for the signs on a viewing, and note nearby trees and any extensions. During conveyancing, the environmental search and — in former coalfields — a coal-mining search assess ground-stability risk.
Screening the environmental and mining context before you offer helps you avoid sinking survey fees into a property with a known ground problem. A TrueBrick report surfaces the environmental and planning context for the address, so you go into a survey already aware of the risks worth probing.
Frequently asked questions
Should I walk away from a house with subsidence?
Not necessarily. Historic, remedied movement that's now stable is common and often insurable. Ongoing subsidence is more serious. Get a structural engineer's view and confirm insurance is available before deciding.
Will subsidence stop me getting a mortgage?
It can. Lenders may require investigation or remediation, or decline until the cause is resolved. Evidence that the issue is historic and that insurance is in place helps the case.
How do I check for mining or ground risk?
An environmental search is standard in conveyancing, and a coal-mining search is added in former coalfields. A pre-offer report can flag the environmental context so you know whether to probe further.