Subsidence – the downward movement of the ground beneath a building’s foundations – is one of the biggest worries for anyone buying a home. Left unchecked it can cause serious structural damage, yet many suspected “subsidence” cracks turn out to be harmless. This guide covers the signs to look for, how to tell active movement from historic movement, and what to do if you’re concerned.
The main signs of subsidence — at a glance
- ✓ New or widening cracks, often diagonal and wider at the top
- ✓ Cracks around doors and windows, where walls are weakest
- ✓ Doors or windows that suddenly stick or won’t close properly
- ✓ Sloping or uneven floors
- ✓ Rippling or tearing wallpaper that isn’t caused by damp
What is subsidence?
Subsidence is the gradual sinking or downward settling of a building’s foundations, usually caused by changes in the ground beneath it. As the foundations move, the structure above is put under stress – which can show up as anything from fine cracks to serious structural instability.
It’s a common issue across the UK, particularly in areas with clay soil, which shrinks and swells as its moisture content changes. But it can happen anywhere, and any type of property can be affected – from Victorian terraces to modern new-builds.
Signs of subsidence to look for
The clearest warning sign is cracking that follows a particular pattern. Subsidence cracks are typically diagonal, wider at the top than the bottom, thicker than a 10p coin, and often appear where the structure is weakest – around windows and doors, and where an extension meets the main house.
Alongside cracking, watch for doors and windows that stick or no longer close cleanly, floors that feel uneven or sloping, and wallpaper that ripples or tears at the joints. Individually these can each have an innocent explanation – but together, and combined with new cracking, they point towards movement.
Important: not every crack means subsidence. Hairline cracks are extremely common and usually harmless – caused by normal settlement, temperature changes or drying plaster. It’s the width, pattern and location that matter, which is exactly what a surveyor is trained to read.
Active or historic subsidence?
A key question is whether movement is active (still happening) or historic (occurred in the past and since stabilised). Active subsidence tends to show new or expanding cracks, and doors or windows that have recently started to stick. Historic subsidence often leaves older, filled-in cracks that haven’t changed in size or shape for years. Telling the two apart usually needs monitoring or a professional assessment.
What to do if you suspect subsidence
If you’re buying and spot any of these signs, the first step is a thorough building survey by a qualified surveyor. They’ll assess whether subsidence is a genuine concern and, if so, whether it’s active or historic.
Where active subsidence is found, the next step is identifying the cause – which can involve a soil investigation or drainage survey. Treatment ranges from simple fixes, such as removing nearby vegetation or repairing leaking drains, through to underpinning (strengthening the foundations) in more serious cases. With the right advice, subsidence doesn’t have to be a deal-breaker – it just has to be understood before you commit.
Worried a property might have subsidence?
Don’t guess. A RICS building survey tells you whether movement is active, historic or nothing to worry about – before you commit to buying.
Get your instant quote →or speak to a surveyor on 0330 043 4650
Disclaimer: This article is provided for general educational purposes only and is based on industry research, professional knowledge and experience. It does not relate to any specific property and should not be relied upon when making a purchasing decision. Prospective purchasers should always commission an independent RICS-regulated surveyor to conduct a full inspection and provide a report on the actual condition of any property of interest.