Few words in a surveyor’s report land as heavily as “underpinning”. It sounds expensive, disruptive and permanent, and the temptation is to start pricing up the fix straight away.
UK subsidence-related insurance claims reached £153 million in the first half of 2025 alone, so it can be a devastating issue for homeowners.
Before you compare methods, you need to know one thing: what is actually moving your house? Get that wrong and even the most expensive underpinning can fail, because you have treated the symptom and left the cause in the ground.
First, confirm it really is subsidence
Not every crack means subsidence. New builds settle for a year or two. Plaster cracks with the seasons. Thermal movement opens and closes joints. Genuine subsidence, the downward movement of the ground beneath your foundation, usually shows as diagonal cracks that are wider at the top, often near windows and doors, and that keep growing.
The only reliable way to know is a proper diagnosis: a structural engineer’s assessment, usually with trial holes to expose the foundations and soil, and frequently a drain survey. That investigation is not a formality. It tells you the cause, and the cause decides the cure.
What are the causes of subsidence
Property subsidence almost always traces back to one of a handful of causes, which are heavily influenced by the local ground conditions. Here are some of the main reasons why subsidence occurs:
- Clay shrinkage. Clay shrinks in dry summers and swells in wet winters. Shallow foundations sitting in that active zone move with it.
- Trees. Roots draw moisture from clay, drying and shrinking it. A thirsty tree in a hot summer sits behind a large share of subsidence claims.
- Leaking drains. Escaping water washes fine particles out of the soil, creating voids the foundation drops into.
- Made ground. Poorly compacted fill on former industrial or infill sites settles unevenly under load.
- Inadequate original foundations. Older properties often sit on shallow footings that were never designed for today’s conditions.
The five underpinning options, compared
| Method | How it works | Best suited to | Disruption | Relative cost |
|---|---|---|---|---|
| Mass concrete | Excavate in bays beneath the footing, fill with concrete | Severe, deep subsidence and heavy loads on accessible sites | High: excavation, long timescales | Labour-intensive, rises with depth |
| Beam and base | A reinforced concrete beam spreads load onto concrete bases | Uneven loads where continuous mass concrete is impractical | High to moderate | Moderate to high |
| Mini-piled | Small-diameter piles augered or driven to deep stable strata, tied with needle beams | Deep competent strata, restricted access, high loads, made ground | Moderate: specialist rig, generates spoil | Higher per pile |
| Resin injection | Expanding structural resin compacts the soil and re-levels | Shallow to moderate subsidence needing a quick, clean repair | Low: often completed in a day | Lower, depends on extent |
| Screw pile | Helical piles installed with low vibration, load transferred via brackets or needle beams | Restricted access, near trees, made ground, low-vibration sites | Low to moderate: minimal spoil | Mid-range |
Insurance, building control and resale
You will also need to think about some other factors to ensure you comply with building regulations and the property value isn’t harmed for any future resale.
Insurance. Where subsidence is covered and a claim has been made, the insurer’s appointed engineer often specifies the method. Insurers increasingly accept resin injection and piled solutions as alternatives to traditional underpinning, provided the design is properly engineered and supervised.
Building control. Underpinning is notifiable structural work. It requires building control approval and sign-off, and that certification also protects you subsequently.
Resale. An underpinned property must be disclosed on sale and can affect both insurability and mortgage lending. Proper engineering and complete certification are what reassure a prospective buyer and their lender, so retain every document.
Screw pile underpinning
For many properties, screw pile underpinning is the least disruptive method that still founds on stable ground. Installation is low-vibration and generates minimal spoil. The system suits restricted-access sites that a large rig cannot reach. Load is transferred through brackets or needle beams onto piles bearing in competent strata below the active clay, and the structure can often be returned to service quickly.
It is not universally applicable. Where movement is severe, loads are very high, or ground conditions genuinely require mass concrete, we will advise for an alternate underpinning method.
Require Underpinning? Recommended next steps
If you have been advised that you need underpinning:
- Obtain an independent structural engineer’s assessment before committing to any method.
- Require the cause to be identified, not simply the movement measured.
- If a drain is implicated, have it repaired and the movement monitored first.
- Ask which methods suit your cause, access and loading, and why.
- Retain every report and certificate for resale.
Concerned about movement at your property in the South East of England and considering screw pile underpinning? Contact Preformed Substructures. We will help establish the cause, and whether a low-disruption screw pile underpinning solution is appropriate, before any excavation begins.
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