Rebuilding our pre-fab concrete garage with something a little more habitable (office & utility, for now!).

Single storey timber ladder frame, clad in feather edge. under 30m sq. shallow pitch roof with single ply covering.

We are on heavy clay subsoil.

The old concrete slab is going this weekend. I hope!

Undecided on foundation type. And whether to just put a 1m deep strip foundation in, so in the future we could go 2 storeys up?

It is not subject to regs, but I would like it to comply to future proof it.

I am right in thinking a raft would be more expensive to construct than simple strip foundations?

Thank you.

Just remember you’ll need full building control evidence for the foundations if you wish to go up with the second lift retrospectively   

That’ll need photographic evidence and measurements recorded.
Possibly get them signed off as if for a 2-storey extension first as last is the safest route.

Strip founds are quick and simple, and for what you’re looking to achieve I’d prob stick with KISS philosophy here, more so to attract a simpler builder, if you’re not DIY’ing the whole thing.

Raft is better, but you’ll need a structural engineer report before doing anything to check what options work; you may find only a raft will work here/with current soil conditions/being on made-up ground, for eg. 

43 minutes ago, Nickfromwales said:

KISS philosophy

Fixing  structural reinforcement is a skill, and most builders don't have it. So choose cost or bodge. Plus the SE assessment and design.

Strip footings are easy and is prob just 1m deep.

On 24/10/2024 at 18:47, Nickfromwales said:

Just remember you’ll need full building control evidence for the foundations if you wish to go up with the second lift retrospectively   

That’ll need photographic evidence and measurements recorded.
Possibly get them signed off as if for a 2-storey extension first as last is the safest route.

Strip founds are quick and simple, and for what you’re looking to achieve I’d prob stick with KISS philosophy here, more so to attract a simpler builder, if you’re not DIY’ing the whole thing.

Raft is better, but you’ll need a structural engineer report before doing anything to check what options work; you may find only a raft will work here/with current soil conditions/being on made-up ground, for eg. 

I know a friendly building control officer. So I may just give him a call & get regs as I build , probably be cheaper in the long run too.

Yes, footings on the clay round these parts is normally 1m deep.

The slab has gone, a foot thick in places! glad I had a man with machine + breaker. Still been here next spring otherwise!