neighbours subsidence

[John Kefford]

I have just heard from my neighbours that their house is suffering from subsidence. The property will not need underpinning, instead metal will be used to strenghen the cracked area. The cause is not clear however tree roots and last summers heat wave are suspected. All vegitation has been cut back and drains have been checked. We live in an area of clay soil and this type of problem is not unusual. However it has caused me some worry as to what we should do next. Will it happen to our house? Should I tell my insurers? Will our neighbours subsidence effect our houses value? Should we move??

[dg]

Subsidence (i.e. the ground giving way) can be localised. But it is a specific cause which is often banded around as a general statement

Clay movement, tree roots, waterlogging, settlement, heave etc are all causes of movement with differing symptoms and cures.

If ground has subsided, then you have to be sure to treat the cause, and not just repair the damage. If tree roots are suspected, then you have to be careful as removing the tree can cause instability to the local soil, and so increase movement in foundations. Tree roots don't cause subsidence.

If you can, you should try and get a copy of the neighbours report - you can not rely on it for your house, but it should give an indication of the cause, and then you can decide if your property is likely to be affected.

But bear in mind that no surveyor can predict the future and it may well be impossible to say if your property will be affected too.

You have no need to tell your insurers, unless your property starts to be affected.

You may like to monitor the closest wall, but don't be unduly concerned. All movement is treatable and you are insured.

dg

[Michael McNeil]

I agreed up to here:

Trees abstract a huge amount of water daily and they can also return it in rainy and misty weather. Clay can rise without breaking as it is elastic, so water level changes under a clay layer can cause a lot of movement. Not irreversible though, so don?t panic.

I agree with the rest too. Say nothing to nobody.

[The Natural Philosopher]

They can lower the water table enough to cause severe shrnkage of clay slis.

Conversely, if you cut the tree down, the water table rises and you get heave.

This is QUITE different from roots physically pushing up the ground.

The best way to deal with a tree is to prune/lop/coppice it so it remains a constant size.

[John Laird]

M3 2. We had some unexpected settlement a few years ago after a very dry summer. It was put down to a leaking drain attracting tree roots. There was bone-dry shrinking clay just feet away from saturated clay. The drain was fixed and the tree cut down. Nothing moved after that.