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Putting in a concrete front porch

I am putting in an 8' x 10' porch that is 21 inches above the dirt around it. The minimum concrete delivery around here is 6 yards. Instead of putting in dirt for fill, I was thinking of just getting the six yards, which would just about raise an 8' x 9' surface 21 inches. As opposed to pouring a slab 21" thick, I want to dig a trenches on either side of the porch & throw the dirt from the trenches where the porch is. The trenches would extend below the frost line. All the concrete would be about 8" thick, with rebar 1' on center.

Does this make sense? I was also thinking about covering the surface with 1/2" thick granite tiles 12" square & putting them down with thinset. As long as I seal it, would this work?

Re: Putting in a concrete front porch

I would definitely not pour a 21" thick slab. Pouring concrete that thick has a whole list of technical issues that are above this board, shrinkage, thermal, etc. Your best bet is to either pour some frost walls or pier footings, raise the grade with fill and then pour your slab. Good luck.

Re: Putting in a concrete front porch

What about pouring the frost walls and the slab at the same time? Will that work? Thanks.

Re: Putting in a concrete front porch

A 21 inch slab is definitely a no go. Before I offer more help could you tell us exactly what part of the country you live in? There are alternatives that you might consider but climate issues must be dealt with first.

Re: Putting in a concrete front porch

Do you know how heavy a 21" slab would weigh? Neither do I. Concrete porches are usually built in two stages. First the footing or foundation (sometimes two stages) and then a slab on top, overhanging the side walls. Stone or gravel fills the void.

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