Foundations suitable for building 2nd storey?

[DarrenSL]

Hi.

We currently have a single storey extension to the side of our house and would like to add another storey (+pitched roof). Looking at the original plans from when the extension was built (30yrs ago) the foundations are 700mm wide x 23mm deep and lie 0.75m below ground level (to reg d3 if that means anything?).

The ground around the house is level and solid, about 2 ft of dense clay then hard 'cinders' (needs a pick to break). There is also a row of conifers approx 8m away.

My question is ... do you think the foundations may be strong enough or is this project a non starter?

Thanks.

 

[plstering]

UNDER PINING

 

[^woody^]

Normally, the foundations for a single story are OK for a double storey

 

[freddiemercurystwin]

Probably by their description although you never know until you expose them, phone up Building Control (not Planning) and explain, hopefully an inspector will be prepared to have a look (at no charge), you'll have to dig down to expose them but if they look ok he'll give you the thumbs up. If he is happy, ask for it in writing then you can fill in the hole and worry about the rest. This is a pretty common route to take so they're used to doing this.

 

[geraint]

UNDER PINING

is that for your old dog or are you pining for something else....

 

[DarrenSL]

Thanks for the quick response guys. It's good to see the forum is still so active.

Underpinning is a show stopper for me (not least cos the extensions along the boundary and my grumpy neighbour is likely to object strongly!). I will follow Freddy's advice and see what they say

 

[RonnyRaygun]

700mm wide x 23mm deep

Not going to be much good for anything at that depth...

Seriously though, 700mm is plenty wide enough for two storeys. As long as the footings are in good condition you shouldn't have any problems.

They'd probably need to be deeper if starting from scratch but shouldn't stop you putting another storey on top.

 

[theoldun]

deleted

 

[RonnyRaygun]

Mine too

 

[theoldun]

[quote="DarrenSL

the foundations are 700mm wide x 23mm deep and lie 0.75m below ground level (to reg d3 if that means anything?).

700 wide I understand. 750 below ground I understand, but what is the 23mm????
oldun

 

[RonnyRaygun]

I think he means a 700mm wide by 230mm deep strip footing, founded 750mm below ground

 

[DarrenSL]

Oops sorry yes I do. 230mm deep.

 

[DarrenSL]

Well, I spoke to building control regarding the foundations. They didn't need to come out to inspect the foundations as they had the original records from 1980. Unfortunately the raft foundations are for single storey only so underpinning (or moving house) is the only option.

We really like the house and area so really didnt want to move so ... what sort of cost are we looking at for underpinning c.10m of foundations? Was thinking about £5k maybe less.

Bigger problem for me is neighbour relations. The underpinning work would mean digging up her patio as the extension is right on the boundary. In fact the foundations actually cross the boundary (permission was given at the time).

If we choose to go ahead with the work, can she prevent access? Or, am I less likely to receive planning permission if she objects strongly?

 

[joe-90]

Why don't you demolish the whole thing and start again. You'll have to declare the underpinning when you sell and for some daft reason it lowers the value.

 

[chappers]

your neighbour can object all they like but ultimately wont be able to prevent you carrying out the work. There is however a pretty involved process to go through if he does put up resistance.
Check up on the party wall act