DOT Underpinning & subsidence repairs
Underpinning strengthens a building’s foundations by taking them deeper or onto firmer ground. It’s a serious job, and it’s also one that’s sometimes sold when it isn’t needed. This page explains how to tell whether you need it, what the process looks like, and who pays.
Planning & Building Regs rules last checked October 2026Not every crack means underpinning
Fine cracks in new plaster
Hairline cracks in plaster, especially in a newer house or a new extension, are usually shrinkage as it dries out. Fill, repaint and keep an eye on them.
Cracks that open and close
Cracks that get wider in summer and close in winter point to clay soil drying out, often near trees. The answer may be dealing with the tree or the drainage, not the foundations.
Diagonal cracks that keep growing
Wider diagonal cracks near doors and windows, doors that start sticking, or a wall that’s visibly moving. Get a structural engineer out before anything else.
This is general guidance, not a diagnosis. Our signs of a structural problem page goes into more detail.
Why foundations move
Clay soil shrinking
Clay shrinks as it dries in hot summers and swells again when it’s wet. Much of the Midlands sits on Mercia Mudstone and clay. The British Geological Survey identifies shrinking and swelling clay as a main cause of ground movement under houses.
Trees & vegetation
Tree roots pull water out of clay soil, making it shrink. Removing or heavily pruning a big tree can also make the ground swell.
So “cut the tree down” isn’t automatically the fix. Get advice first.
Leaking drains
A broken drain can wash away or soften the ground under a foundation. The insurers’ trade body (ABI) lists drainage problems as a cause of subsidence and recommends keeping gutters and pipes leak-free.
A drain survey is often one of the first checks.
Old mine workings
In former coalfield areas like parts of Stoke and Nottinghamshire, old shallow workings can cause movement. The ABI includes mining among the causes of subsidence.
A coal mining report will show whether there are known workings near your house.
From the first crack to the completion certificate
Tell your insurer
If you suspect subsidence, contact your buildings insurer before you start any work. Subsidence is often an insured risk, and insurers usually want to manage the investigation themselves.
Monitor & investigate
Cracks are often monitored over months to see if the movement is ongoing. Trial pits, soil tests and a drain survey find the cause.
Fix the cause
Repairing the drains or managing the tree may stop the movement on its own. Underpinning is for when the foundations themselves aren’t up to the job.
Engineer’s design
A structural engineer picks the method: traditional mass concrete, beam-and-base, or mini-piled. The choice depends on how deep good ground is and how much access there is.
Notices & approvals
Underpinning always needs Building Regulations approval. If it’s near or under a party wall, your neighbours need notice under the Party Wall Act.
Build in sections
Mass concrete underpinning is dug and poured in short sections, never all at once, so the house is always supported. Building Control then inspects the work and signs it off.
Sources: LABC: underpinning · Gov.uk: Party Wall Act · ABI: subsidence
What it costs
Underpinning starts from around £6,000
The final cost depends on how much of the building needs it, how deep firm ground is, which method the engineer specifies, and access.
If it’s an insured subsidence claim, the insurer usually appoints the contractors and sets the scope. Check your policy for the subsidence excess.
For non-insured work, such as building a new extension next to an older, shallower foundation, we price it from the engineer’s design.
Common questions
Is underpinning covered by home insurance?
Subsidence is a common insured risk on buildings policies, but every policy is different and most have a higher excess for subsidence. Speak to your insurer before you commission any work, because they may want to run the investigation.
Can I stay in my home while it’s underpinned?
Usually, yes. Most underpinning is dug from outside. Internal work is more disruptive, and the engineer will tell you what to expect.
Will underpinning affect selling my house?
Buyers and their surveyors will ask about it. Keep the engineer’s report, the Building Regulations completion certificate and any guarantee. Properly documented underpinning reassures a buyer much more than unexplained cracks do.
Does underpinning need planning permission?
Usually not, but it always needs Building Regulations approval.
Useful next reads
Worried about cracks?
Tell us what you’re seeing. We’ll give you an honest view on whether it needs an engineer, and we won’t sell you underpinning you don’t need.
Underpinning near you
Based in Uttoxeter, working across Staffordshire, Derbyshire and the Midlands. Find local planning advice for your area.