We looked at a new house today which is built on a hill. At the front, there is a built in garage at ground level, with steps up to the door at the side. The ground at the side and the back is at "1st floor" level.

The garage only extends 2/3 of the way back in the house, which made me think. How hard would it be to have the back dug out? And as the garage is not the full width, the side as well? It's easy enough for builders to put in RSJs and cut doorways into the walls. Is it feasible to dig out a store room and a tool room in the space around the garage?

Should be easy, as long as you can sign very large cheques !

Big consideration would be foundations and floor structure.

Next consideration will be damp-proofing. There should be some there already (hopefully) that you would have to break into, then you've have to link it up with the new proofing. Not trivial.

The new house we have just got has that and the back wall is 4ft thick to hold the wall and house up. If it only goes that far back I suspect it was not the owners thinking let's have a smaller garage but more let's not have the house collapse

Get the plans and technical drawings and the calulations the back wall will have a lot of lateral pressure from the outside

The house was built around 1970, so will be of fairly modern construction. There is a thick mortar line between the top of the garage and the ground floor, which I suspect is the DPC. There's no sign of damp in the garage front to back or top to bottom, though it may be that all the walls are against voids (and next doors garage).

So I guess the worst case is that the new spaces might need to be tanked, at a cost of several thousand.

Here's an odd alternative. Would it be cheaper to dig new footings about half a metre in from the existing and build a new, separate wall and floor with a separate DPC?

quote:

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Originally posted by jossey
The new house we have just got has that and the back wall is 4ft thick to hold the wall and house up. If it only goes that far back I suspect it was not the owners thinking let's have a smaller garage but more let's not have the house collapse

Get the plans and technical drawings and the calulations the back wall will have a lot of lateral pressure from the outside

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I,m in the process of doing this, about to go away but will post up pics on my return.
Dug out under house going back into hill. went as far as the base of the original foundations. new strip foundation with a new skin wall within the old one.
Must go now..

During excavation.
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[URL=http://s1180.photobucket.com/user/southernkitcarclub/media/Kentons/IMG_0258%20Small.jpg.html]
As of today


[Edited on 2/11/15 by kenton]

Cool! I take it the original depth was where the block work changes.

Yes, about halfway up you can see the damp course.

Is this the new SKCC clubhouse ?

looks great, and wish I had a void under my house like that !!

steve m

There was a documentary not so long ago about people doing just this in London... Causing chaos for everyone else around them due to the heavy machinery required.

In some cases they were going 2 storeys down... an interesting feat when most of them were mid terraces! Some pretty nasty horror stories too.. I guess its easier in London as its all gravel/sand.. If you live on solid granite it might be harder!