Expert advice on subsidence and heave from Craig Phillips
Craig Philips' Home Advice - Subsidence
One of the joys of owning your own house is knowing that you're secure, with the ground beneath your feet, and the roof above your head. But, what are you going to do when the ground beneath your feet starts to move on its own?
Sometimes the composition of soil beneath your house can change, especially if your house is built on sand, or clay. Leaking trains can wash away sub-soil, trees can suck moisture out of the ground, the ground water can wash out gaps in the soil - that's when you get subsidence.
Subsidence is mainly a problem in London and South-East. But with dry summers, more areas are getting affected by subsidence around the country - especially houses built before the 1950s, as they have shallow foundations.
The first and most obvious sign of any subsidence is cracks appearing in your wall. Small cracks are nothing to worry about, but you should regularly measure and monitor them, to see if there's any further movement, whether they're horizontal, or vertical, or even long-standing.
Now, on the opposite side of the wall, I've removed some of the render, so I can get a closer inspection of the crack. It's obvious some subsidence is happening here; the brickwork is starting to detach away from itself. Something needs to be done about this straight away; if if it was left unattended, it could weaken your house.
Now, if you think you've found evidence of subsidence in your home, the first thing you should do is call your home insurer. They will send out a surveyor to have a look. It might look like a major operation, but the fixes are often more simpler than they might seem.
Now, if you know your house is built on sand, or clay soil, or you live in an area that's affected by subsidence, there's a few things you can do to prevent it happening. It's often just a case of carefully pruning or removing some old trees, lining the drains to stop them leaking, or some minor structural work to support the building. Now, in some extreme cases of subsidence, the house may need underpinning to make the foundation sufficient, or the brickwork may need restraining with some steel lateral bars.
Of course, you don't only get problems when houses sink. It's quite rare, but you'll also get similar problems when your house starts to rise. "Heave" is what we call it when the ground under the house starts to rise. This is normally caused by having removed particularly thirsty trees, and having the soil swell up and the waterlogged as a result. Leaking drains can also over-wet soil, and lead to heave.
Once again, if you notice a large crack in your property, you should contact your home insurer straight away to address the problem, before it gets any worse. If left unchecked, heave can lead to real structural problems in your home. It can also lead to draft and damp, and all the problems that that brings.
Heave is sorted out in much of the same way, as it is caused by many of the same things, and again, is more common in houses built on sand or clay soil. Drains may be re-lined, and structural supports might need to be put in.
When you're planning the layout of your garden, try to avoid particular thirsty trees like oak, willow, poplar and elm. Now, if you are planning on having those trees, make sure you plant them far enough away from the house so the roots don't affect the foundations, because remember: those roots can grow up to two-and-a-half times the width of the branches of the trees.
So remember to keep those drains well-maintained, keep a close eye out for any cracks appearing, especially if your house was built before the 1950s. Stick to those simple, down-to-earth rules and you could save yourself a lot of trouble, right down to the earth.