Any suspicion of subsidence strikes fear into the heart of homeowners, and for good reason, as it can mean a substantial repair bill. As long as you don’t neglect the problem, it should be covered by your insurance policy but it’s important not to give the insurer any chance to refuse your claim.

Subsidence is when the building’s foundations slowly sink, and is most often caused by nearby trees and shrubs sucking moisture from the soil, leaking drains softening the ground, or old mine-workings or tunnels beneath the house.

Although subsidence can happen to any building, the biggest risk is for Victorian and Edwardian homes, which tend to have very shallow foundations. There’s also a particular risk if the house is built on clay-rich soil — which accounts for a good deal of the South-East.

Unless there’s a specific cause, such as a leaking drain or mine-workings, it usually starts with trees or shrubs sucking up the moisture from the soil. As the clay dries, a “shrink-swell” effect hardens and cracks it, and the foundations start to sink.

Subsidence is usually combined in your insurance policy with heave, a separate but related problem. This is caused by the ground becoming saturated, lifting up and sometimes sideways, and can result in symptoms similar to subsidence.

Identifying, Preventing and Fixing Subsidence

The most obvious signs of subsidence are:

  • Cracks appearing in brickwork and plaster, especially if they’re wider at the top.
  • Doors and windows sticking with no obvious reason.
  • Ripples in the wallpaper when there’s no sign of damp.

Cracks can also be caused by the house settling, especially if it’s new, but if they keep widening the chances are it’s subsidence. If you notice any of these issues, it’s important to inform your insurer at once.

It’s also advisable to have it looked at by a qualified surveyor. If there is subsidence, it may be possible to solve it by removing tree roots or repairing a leaking drain, but it’s likely your home will have to be underpinned, which involves adding extra support for your foundations. This should normally be covered by your insurance policy, but generally the minimum excess is £1,000 – often more in areas known to be prone to subsidence.

In addition, insurers often regard an underpinned house to be at greater risk, so you’ll face higher premiums. It makes sense, therefore, to prevent subsidence from happening and avoid having to make claim. Precautions to take include:

  • Before you buy a house, check the surveyor’s report for any signs of subsidence.
  • Don’t have trees or shrubs closer than 5-10 metres to the house.
  • Prune the branches of any trees regularly.
  • Make sure your pipes and drainage systems are well maintained, so they don’t leak into the ground.

When we ask questions about trees near your building, it is not – as many people think – so much about the risk of property damage if the tree falls over but of the risk of subsidence.