Groundwork & Foundations Question

Can i build off a reinforced concrete slab for a double garage

I am about to build a double garage, it requires no planning or regs, as long as i stay within 30sq mtrs and under 2.5 high, I have already checked with my local council
It will be built in the same place as the garage i just removed which was asbestos.
It will be bigger as the original one was single, I was thinking of a slab 4" floor and 8"-10" around the edge to support the blockwork, would this be ok?

Thank you for you help everybody The only reason i would like to make it as easy as i could is because the access is not good.
But i have somebody coming to dip out a put in full foundations next tuesday.
Thanks again

7 Answers

Best Answer

The foundations of the new structure would depend on load weight (brick, block timber etc), and ground sub-strata (clay or sand etc)/ best speak to Council Building Control
about this who can advise on the locality. Also the ground bearing slab (WHICH SHOULD BE REINFORCED) is best built 'suspended' (supported) off the outer brick walls which have been built off an appropriately designed footing.Cracking problems have been experienced in the past, NHBC report, with unsupprted slabs laid directly onto poor ground (even when laid on vibro-compacted hardcore) which is subject to movement, but alright if compact virgin sand is the sub strata situation for the slab.

Answered 26th Apr 2011

SEL Building-Development-Electrical Services

Member since 23 May 2010

I would not really recommend doing so, if you was going to go ahead and start that amount of work you should just put proper foundations in, Just incase you deside to build on top of the garage at a later date.

It would really depend on the ground the slab was sat on.

Answered 26th Apr 2011

P W building services

Member since 23 Jul 2010

yes houes ar built on 8"

Answered 26th Apr 2011


Member since 10 Dec 2008

The only sure way is to excavate down and put some new foundations in.
You are putting quite a bit more weight on that slab.
Your suggestion of thickening the edge wont work, as to create a raft foundation with deeper edges, you have to incorparate steel mesh x 2 layers in main slab, tied into, made on site steel cages in the outer edge.
This is normally calculated and designed, your 8/10 inches are not going to be enough.
Although you say you dont need planning etc, do it properly.

Answered 27th Apr 2011


Member since 29 Oct 2008

if you want it to last dig footings ,and do it right

Answered 26th Apr 2011


Member since 7 Jun 2008

yes thats fine , as long as the extra 8,10 inch is to the same depth as original slab.

Answered 26th Apr 2011


Member since 8 Nov 2010


Answered 27th Apr 2011

Michael Murphy Builder

Member since 26 Nov 2009

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