Hot of my recent problem with water, I would like to seek advice and to how
much of problem it may have caused.
We have had a leaking water pipe under the garage for a while and there is a
significant amount of standing water there. The garage is integral to the
house (albeit an extension) and has a couple of bedrooms over it. The water
all seeped away and with leak being constant, I guess the water must have
found a level and the rest flowed off under the foundations.
Realistically, how significant is this likely to be to the foundations? Is
this a case of getting a surveyer in to advise?
Mike - this very much depends on the type of soil and for how long the water was
running. The water could soften clay or wash away sand, or in gravel or chalk
it might have very little effect. But even if you know the soil type, nobody
can say for certain what effect the water may have had - the only way to find
out is to dig a trial hole to expose the soil at the bottom of the foundation.
But is it really worth doing this? My feeling is that if the water had caused
any foundation problems they would probably have shown up by now.
So my advice is only get in a Building Surveyor or Structural Engineer if you
see any cracking to walls or ceilings, wrinkly wallpaper or jamming
Hi Mike. This is a classic cause of subsidence for houses built on
clay soil. However I dont see what you can do about it after the
event, other than cross your fingers. If there is no structural house
damage, I dont see a need to engage a surveyor. If all is well, it
probably will stay that way.
Is it? No. It isn't. My old house when demolished had a lake under it,
on clay soil..
The biggest danger is shrinkage when it dries out, not any damage from
getting or staying wet.
Soil is wet. Foundations are designed - or rather have developed over
years - to cope with it.
All the leak has done is raised the local water table a bit. Now its gne
back down to where it was.
If you didn't get heave (soil expansion to crack foundtaions) when it
was wet, its unlikely you will get subsidence (soil shrinkage due to
being dry). In this respect raised floors (which it sounds like you
have, although I can't actually envisage a garage with a raised WOODEN
floor...) are an advantage. There is an air gap to ansorb expansion
without actually lifting the floor!
The right advice is as abocve. Do nothing. If any signs of cracking
show, then yes, you may need to underpin locally on the advice ofd a
structural engineeer, but I would say you have 95% chance or better that
nothing needs to be done now, or ever.
What sort of quantities were you talking about when you said "a leak"?
If it was a continual small quantity it would have made no difference
Look at how much rain falls in an heavy shower. And trees pour it back
up by the ton every day -and the ground is at ease with all that.
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Clay is unlike other types of soil in that it creeps under weight when
it gets wet. Ask any surveyor.
Presumably your house was built with foundations sufficient for the
wet conditions. Most arent.
It wasn't. It had at best 8" deep brick plinth laid on the clay :-)
The chimney area was totally un injectable, and soaked up water like a
sponge, as did the spine wall attached to it.
The whole house was too rotten to be worth renovating, so we pulled it
down and built a new one. #
HOWEVER even those completely ridiculous foundations were, in fact,
adequate for an old timber framed house. Might have had problems tho if
we had attempted to soldve the damp problem by e.g. digging a french
drain around the house and lowering the water table. My giess is that
part of the house would have sunk a couple of inches.
New house has up to 2.8m deep concrete foundations :-)
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