In central florida.

What should one think is the maximum depth of a monolithic slab footer?

Thanks

 

Are you talking about the minimum thickness for a slab or how far the slab should be below grade? Thickened edge, flat slab or post tensioned?

I suggest you find out from your local building official since you will have to do it right to get a permit. The depth/thickness could vary with the type of building.

Dick

 

You are not dealing with frost in your location, so you are asking about thickening the sides of your slab and biting into the existing ground. Unless you are pouring on un-even ground, because that would be considered a monolithic retaining wall that is poured with the slab and I make all my slab and combo retaining walls 6” thick with #5 Re-bars all around, many as high as two feet. I also dig post holes below the frost line in each corner and one in-between on all four sides, depends on length.

What I think you need to know is this, widen the edges all around at a with of 6” and bite into the ground about 4”. Use #4 or #5 rebar all around the perimeter, than pour the slab and (Edge Trench) (Grade Beam) all at once.

Add the Re-bar after your pour and strike-off, than push them down into the concrete about two inches with a hand float or a shovel… than bull float the slab.

 

Is this new construction or existing?

Dick

 

This is an addition.

The reason I'm asking is the depth of the footer our engineer specified was 18" below the 4" slab for a total of 22" with two #5 rebar.

From what someone else has told me, this seems a bit excessive and since the central florida ground is mostly sand, cave-in at those depths is likely.

The other issue is that it joins an existing home, and he's having us put #5 rebar drilled into the existing footer every six feet. All this is fine, but the existing footer is more shallow than the 22" he's requiring on the drawing.

I worry about if a rain comes before the slab is poured, could it undermine the existing home's footer.

Thought I'd get some good opinions before I start complaining about the depth of the footer.

Have a permit, so we'll have to get approval before we change it, but am willing and just want it to be right and proper.

Thanks for the responses.

 

That sounds about right to me for the depth, but I would use 4-#5 bars caged in the perimeter beam. 6' OC for stubbing in rebar sounds very light. I would do it every 2 foot OC.