Subsidence is the downward movement of your house’s foundations. This can be caused by a number of factors.
For example, clay soils shrink and swell depending on their moisture content, so can be affected by a long, dry spell. Trees and shrubs draw the water from the soil, causing it to shrink. This is a particular problem in extended hot weather, as the parched plants push their roots under or through foundations in search of water.
Also, leaking drains can soften or wash away the ground beneath the house, particularly if the soil has a high sand or gravel content.
Keep an eye out for subsidence
Although cracks are often thought to be a clear sign of subsidence, you shouldn’t panic at the first sight of one. It’s not uncommon to find fine cracks in the plastered walls of new properties (as the building settles under its own weight) and changes in temperature can cause minor cracks where walls and ceilings meet.
If visible cracks appear suddenly in a particular area of the house, they'll need further investigation. Subsidence might also be a problem if diagonal cracks appear in both the plaster inside and the brickwork outside, especially if they widen out at the top.
Other things to look out for are doors and windows that stick (due to the distortion of the building), rippling wallpaper that isn’t caused by damp, and cracks at the join of an extension and the main building – meaning it’s probably pulling away from the house.
Is it time to call in the experts?
If you suspect your property may be affected by subsidence and you have buildings insurance, call your insurer to find out more. Depending on your policy, you may be visited by an assessor who will check the extent of the damage.
You’ll probably need to call on various experts, such as a structural engineer or tree expert to assess the cause of the problem.
This measuring and monitoring could go on for some time, with investigations being carried out to discover how the cracks develop, the type of soil the house is on, the depth and condition of the foundations and drains, and what part tree roots have to play (if any).
What should you do next?
How to solve the problem depends on what’s causing it. Trees may need to be pruned or removed, or drains and brickwork repaired. The most extensive work involves underpinning the property while the foundations are strengthened.
There are steps you can take to try and avoid such problems occurring. Check drains, pipes and gutters for blockages, splits and leaks. Prune shrubs and trees regularly, and plant any new ones well away from your house.
But the most important thing you shouldn't do when you notice potential subsidence is to ignore it.