Workshop extension.

[Stav242]

Hi all, just joined the forum to seek some advise and knowledge on my new smallish project.

 

Have a 3x4m single storey extension to an existing workshop. It's a lean-to against the main house.. so planning class it as attached and hence an extension... Even thought the lean to is not linked structurally. 

House and workshop are both 1860ish solid stone. Workshop is 18" thick solid stone walls and concrete slab floor. 

Have planning approved to extend by the 3x4m with same external materials.

 

I'm at the stage of starting ground works to dig out foundations.. there is not a lot as it's only 2 wall - about 5m. Ground is a bit of top soil then seems to be some large rocks (too heavy for me to move by hand) about 30cm down. It's bedrock in the local area.

 

I was under the impression that foundations for this wont need to be very deep (50cm)- but do I need to remove these huge rocks - to then replace with concrete foundations?

 

How do I work out the width of the foundations?

 

Any suggested type of foundations... Strip or trench fill?

[nod]

300 doesn’t sound deep enough 

If you dig the foundations down 600 x 600 and request a visit from your local building control 

They will tell you there and then if you are deep enough