Advice and guides
Signs of subsidence to look for in your home
Find out what a crack in your wall might mean, when to worry about wall cracks, and what happens next. This advice covers homes across Hampshire, from chalk downland to soft coastal ground.
Reading the cracks in a Hampshire home
Most houses settle after they are built. In older Hampshire homes, especially those on chalk around Andover or clay near Fareham, hairline cracks often appear where walls meet ceilings or above door frames. These usually stay thin and do not grow.
A serious crack or settlement behaves differently. It tends to run diagonally through brickwork, widening as it goes. A diagonal crack in brickwork meaning movement is often visible where one side sits higher than the other. If you can fit a two-pound coin into the gap, the wall has moved enough to need attention.
Knowing when to worry about wall cracks comes down to measuring them over time. A crack that stays the same width for years is likely old settlement. One that opens wider each month suggests the ground beneath the foundations is still shifting. Homes in Southampton and Portsmouth, built on reclaimed ground, show this pattern more often than those on solid chalk.
Sticking doors and sloping floors
Doors that suddenly jam or windows that refuse to close fully can point to movement in the frame. When a sticking doors sloping floor house appears together, the structure may be distorting because one part of the foundation has dropped lower than the rest.
This does not always mean subsidence. Swollen timber in humid weather causes doors to stick, and old floorboards sag with age. But if the problem appeared recently, affects several doors at once, and lines up with new cracks in nearby walls, the cause is more likely structural.
Floors that slope visibly, where a marble rolls to one corner without being pushed, suggest uneven support underneath. In areas like Totton and Hythe, where soft silts and estuary gravels lie under many homes, the ground compresses unevenly. A specialist surveyor uses levels and laser equipment to measure exactly how much the floor has dropped and whether the movement is ongoing.
First steps when you suspect movement
The first steps suspected subsidence demands are simple and worth doing before calling anyone. Take clear photographs of every crack, inside and out. Place a ruler or coin next to each one so the width is visible in the picture. Write the date on a piece of paper in the shot.
Check the same cracks again in four weeks. Photograph them from the same angle. If they have grown, you now have proof of active movement rather than an old scar. Keep these records together, as any chartered building surveyor or structural engineer will ask to see them.
Avoid filling the cracks with polyfilla at this stage. Filling them hides evidence of how fast they are opening and makes it harder for a surveyor to read the pattern. Leave them exposed until a chartered building surveyor or structural engineer has looked at them. This applies whether your home is a flint cottage in Winchester or a newer build in Basingstoke.
Who to contact first in Hampshire
If the cracks are growing or the floor slope is obvious, the next step is arranging a survey. Your buildings insurer should be contacted early, since most policies cover the cost of investigating subsidence. The insurer will usually appoint a loss adjuster and may recommend a structural engineer.
You can also seek independent advice. A specialist structural surveyor will visit the home, examine the cracks, check drainage, look at nearby trees and assess the soil type. On that first visit, the surveyor takes measurements, sketches the crack patterns and may install small glass tell-tales across the worst gaps to monitor future movement.
In Hampshire, the ground varies sharply within short distances. A surveyor familiar with the county understands why homes in Fleet behave differently from those in Gosport, and why made ground near Lymington needs different investigation than chalk slopes in Petersfield. That local knowledge shapes what they look for first.
What does subsidence actually look like at home?
Subsidence shows itself through changes in the building fabric. The ground beneath the foundations moves, and the walls follow. Here is what you might notice around your home.
- 1
Diagonal cracks in walls
Cracks running at an angle through brick or plaster, often wider at the top. They may indicate one section of the wall dropping away from another.
- 2
Doors and windows jamming
Frames distort when walls move. A door that closed easily last month but now scrapes the frame can signal shifting foundations below.
- 3
Gaps around window frames
Visible daylight between the frame and the wall means the opening has changed shape. This often accompanies cracking in the surrounding brickwork.
- 4
Sloping floors
A floor that visibly tilts, or where objects roll to one side, suggests uneven support beneath. This develops slowly and worsens over months.
Questions homeowners in Hampshire ask
- How wide should a crack be to worry?
- Hairline cracks under one millimetre are common in older houses. Once a crack exceeds three millimetres, or grows noticeably over weeks, it warrants professional assessment.
- Will insurance cover the inspection?
- Most buildings insurance policies cover the cost of investigating subsidence. Contact your insurer early so they can appoint a loss adjuster to oversee the process.
- How quickly must I act?
- If a crack appeared last week and is already widening, arrange a survey promptly. Slow, stable cracks can wait; active movement needs timely assessment.
- What happens on the first visit?
- A specialist surveyor examines the cracks, checks drains and trees, measures floor levels and may fit monitoring points to track further movement over coming weeks.
- Should I photograph the cracks?
- Yes. Take dated photos with a ruler beside each crack. This gives the surveyor a record of how the damage has progressed before their visit.
Tell us about the cracks in your home
Send details of what you have noticed. An adviser will review your description and explain what kind of survey or repair might apply. There is no obligation to proceed.
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