Cracks in walls

Cracks in your walls: harmless or subsidence?

Not every crack means your foundation is subsiding. Hairline cracks in plaster often come from shrinkage or temperature. But some cracks are a warning sign. This is how to tell the difference.

Report your cracks Subsidence survey

Crack in the wall of a house, measured with a crack gauge

Which cracks are a warning sign?

  • Stepped cracks in brickwork that follow the joints
  • Cracks wider than ± 2 mm
  • Cracks that keep growing or change after a summer or winter
  • Cracks above windows and doors, or diagonally from a corner
  • Together with doors or windows that stick, or floors that start to slope

Which cracks are usually harmless?

Fine hairline cracks in plaster or paint that do not grow often come from shrinkage of the material or from temperature changes. Keep an eye on them for a while.

How do you monitor a crack?

  • Fit a crack gauge, or draw a dated pencil line
  • Measure, for example, every three months
  • Take a photo each time with a ruler next to it
  • Note whether the crack widens in summer and closes in winter: that often points to shrinking clay

What is usually behind it?

A foundation that settles unevenly: one side goes down more than the other. Typical causes are drought in clay soil, a leaking sewer, trees close to the house and construction work nearby.

With serious damage, have a structural engineer assess the situation. Soiltek is a specialist contractor: we record, measure, propose a technique and carry out the repair, in consultation with your engineer.

What can we do?

Deep Lift

Expanding resin strengthens the ground under the foundation, without digging.

Slab Lift

Sunken concrete floors back to level.

Frequently asked questions

From what width is a crack dangerous?

Stepped cracks, cracks wider than ± 2 mm and cracks that keep growing often point to subsidence. Hairline cracks in plaster are usually harmless.

Should I fill a crack?

Not before you know where it comes from. A filled crack comes back as long as the cause remains, and you can no longer see whether it grows.

Who pays for the repair?

That depends on the cause and your policy. A subsidence survey report helps you in the discussion with your insurer.

Not sure?

Send us a few photos of the cracks and the surroundings of your house. We will look, with no obligation, at what may be going on.

Report your cracks

Read also: Subsiding house · Causes of subsidence · Buying a house with cracks · Cracks after a dry summer · Cracks from shrinking clay: from survey to repair · Trees next to your house on clay