Digging down for house extension?

D

DaveD

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I'm considering a house extension to the rear of our house. We have a garden that slopes down away from the house and was wondering if theres any reason not to dig down and drop the floor level of the extension by a couple of feet. Essentially end up with a split level room. This would be preferable to going straight out level with existing floors and then stepping down to the garden level.

Are there any reasons this would not be possible in a normal 3 bed semi?
 
No reason, but some things to be aware of, and you will defo need an engineer to sign off on it......

Dig down beside your foundation is not a problem. How deep depends on the soil type, and the fall in your garden. If for example, your new firm ground, on which you'll put your new foundation is below that of your house, talk to him about the need to underpin your existing foundation and/or connecting it to the new one. (basically drilled, re-bar chemically bonded in, projecting into the new one.......)

It's not difficult, but you do need to do at least a trial dig down against your house to see ground conditions.

Personally, I like split level !
 
galwaytt said:
No reason, but some things to be aware of, and you will defo need an engineer to sign off on it......

Dig down beside your foundation is not a problem. How deep depends on the soil type, and the fall in your garden. If for example, your new firm ground, on which you'll put your new foundation is below that of your house, talk to him about the need to underpin your existing foundation and/or connecting it to the new one. (basically drilled, re-bar chemically bonded in, projecting into the new one.......)

It's not difficult, but you do need to do at least a trial dig down against your house to see ground conditions.

Personally, I like split level !
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Thanks galwaytt, didn't think it should be a problem but not being experienced in this area I though it wise to ask before even talking to banks about money, must now get on to some recommended builders and get them to have a look.

D
 
Hi Galwaytt saw this post and was wondering about building an extra floor under the house ie. the whole footprint of the house,i saw a company in England who dig out new spaces under the house ,do you know if there are any builders specialising in this in Ireland ?PLANNING ISSUES ? THANKS
 
Crumbs, that's a biggie............technically, I suppose, it would be possible.....but, and it's an enormous but, at what cost? I could easily see it costing as much as the house itself........I'm finishing a new build, greenfield site, with a 42m sq basement. Cost of groundworks and formwork for that one room alone came to 40k......+ VAT.

Planning ? Yes, you'll need planning. If in an urban area, it won't be as much of an issue to get, but in a rural one there could be all sorts of ramifications.....septic tank/treatment plant/percolation capacity, etc. Ratio of house size to site size.......
 
Someone did this near me recently, knocked house down, dug down for a basement and rebuilt house on top, pm me if you want more details of where the house is if you want to call in and ask them who did it for them.
 
galwaytt said:
If in an urban area, it won't be as much of an issue to get,
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quite the opposite i would say, think of undermining your neighbours houses, in an urban area.

a good rule of thumb, be as far away from your neighbour as you intend going down.
 
setemupjoe said:
Hi Galwaytt saw this post and was wondering about building an extra floor under the house ie. the whole footprint of the house,i saw a company in England who dig out new spaces under the house ,do you know if there are any builders specialising in this in Ireland ?PLANNING ISSUES ? THANKS
Click to expand...

Check out May's edition of "Living etc." mag., where this is mentioned as an option. Cost is put at £250-£300 per sq. ft. One company mentioned is http://www.tlbc.co.uk/main.htm

I'd be surprised if there were similar specialists here, where basements are quite rare. They're quite common in UK inner cities, and hence there's experience of them to draw on. Either way, it's bound to be an expensive option.
 
NiallA said:
quite the opposite i would say, think of undermining your neighbours houses, in an urban area.

a good rule of thumb, be as far away from your neighbour as you intend going down.
Click to expand...

no, actually. Local authorities now have an expressed desire to increase density, and vertically is the only way it'll work, due to land prices.

There is absolutely no issue with digging down beside your neighbours, you are not undermining them by going down. Now, if the people doing it don't do it properly............hey, that's a whole other ball of wax.

The only other question that comes to mind is, is the house a semi-D ? Now that would complicate matters probably.........
 
thanks guys some good info there i'll look into it more
 
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