Hello there! I am getting ready to build a 10×12 ft kitchen extension on my home. Above it will be a second story bedroom. My architect is telling me I have to use a trenched footing. The hole house is slab on grade, no crawlspace, no basement. Why cant I just dig down to below the frost line with an 8″ wide footing and flare out the bottom. This way I can pour the slab monolithically. Wouldnt this accomplish the same thing? To do it his way I will need to excavate more than I want to, and there is very limited space. There are also concerns I have for not wanting a back hoe in there (tearing up my entire lawn, breaking the sewer line etc.) What do you think? How do you pour the slab if you have to set up forms etc?
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Ask the architect why not. We can't guess at all the possible circumstances and his thinking. Then let us know what he says.
DG/Builder
I think the footing size is the issue, not whether its dug by hand or machine. "Trenched" just refers to the fact that the footing is formed by a sub-grade trench.
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edited to add: Forms are necessary regardless. Monolithic pour is OK - we do it all the time here in So. Cal. Just tie the footing rebar into the w.w.m. or slab rebar, if any.
Edited 2/3/2006 12:35 pm by Huck
I just poured a monolithic slab on grade (about 11" above finished grade, to match an existing house slab) like you want to do, 16' X 24'. It worked fine, and satisfied local code and the inspector, but here near Atlanta we don't have to go so deep, or use foam underneath. It does use more gravel, because it kind of ramps down into the footing "trench", but I love only having one 'crete truck delivery.
Once you get the gravel placed, the 6-mil plastic under the slab part gets pinned down and keeps gravel from slumping into the trench. Fill the trench first all around, then fill your slab area.
I have an idea where you use rebar stakes and Hardiplank to define the inner edge of the footing, to minimize the concrete use - I didn't do that here, but I think it could work . . .
Forrest