Outbuilding foundation depth in ballast type soil

17 Jan 2015
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United Kingdom
We plan to build a large outbuilding which will be for a shed / storage come gym of approx 7x5m. Out soil type, fortunately is stoney ballast as evidenced by the fact that our rear house extension was dug at about 1.2m and easily passed building regs despite some large trees some 3m away.

Would I be right in thinking that for the outbuilding (brick build with solid floor) foundations we could get away with 0.5m to 0.6m to reduce our cost? I think I recall our building inspector saying that because of the favourable soil conditions he may have passed the foundations of the extension at 0.6m. The only reason we went to 1.2m was because it seemed to be the standard depth that builders go to without wanting to wait for a building inspector.
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Highly likely that if your recent inspection revealed good (unchanging) ground, at that depth, then yes you should be ok with a shallower footing. As long as ground conditions are similar, of course.
You are still required to have a minimum thickness of concrete though.
Why not go down just 0.4m and save a further 33%?

As long as the money you save is not less than the money it will cost to remedy future movement.

I'd probably look save money on the laminate and light switches instead of foundations.

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