existing founds suitable?

Just doing a bit of exploratory research for my sister.

She wants to build a first storey extension over her existing single storey addition.
Only after a general opinion at this stage but do you think that a three course corbled foundation, would be suitable to take a timber framed extension above.
The current founds are built onto a sand/gravely soil with solid 9" walls above the current extension has a pitched welsh slate roof and this will be retained above, but could be changed to artificials to save a bit of weight only after ageneral opinion at this stage to give her some idea of costs as if necessary the whole thing could be taken down.

Cheers
Gareth

I don't think the type of existing foundation matters, but the depth will be more relevant.

Are these as deep as existing foundations which are supporting a second story?

In any case, building control may want at least 1m, and possibly more if the ground is not firm - or even piles.

Although a timber fame will be light, it will still get wind and other live loads which will have to be transfered to firm ground

Really, you've got to plan for the worst case, and if this makes the project unaffordable, then some proper investigation and contact with the BCO is needed to see what will be required and if this makes the project feasible

If they are sat in good stuff and an SE is willing to underwrite them as such, then notwithstanding that they don't comply with current design standards, they will be acceptable.

Tsk Woodster, you won't need 1m deep in sands.

Other things to think about are adequacy of existing lintels, but, with a ply-clad timber-framed structure, it's unlikely to present much of a problem.

Shytalkz said:

Tsk Woodster, you won't need 1m deep in sands.

Click to expand...

I know that, master.

I did say that the BCO may want 1m deep.

Cheers boys good point about the founds on the rest of the house, will get the brother-in-law to dig another test hole on the main part of the house. I suspect that they will be the same as the addition is original to the house.
house is actually 3 storey and has been stood up for 100years so hopefully founds will be suitable.

lintels etc wont be a problem as the existing windows are being replaced and the existing roff will be coming off in its entirety.

You have pretty much confirmed what I already thought was just trying to save a few quid on structural calcs if possible. i can pretty much spec the build part of the extension to satisfy BC, the only thing I was unsure of was the suitability of the founds.
Among the usual BC drongos we have a couple of decent ones here in Oxford who won't insist on unnessecary works or clacs if they are happy. I have one of them signing off a loft for me next week so will have a word in his shell like then and if needs be will speak with a SE.

Cheers for the help

Gareth