Residential Covered Porch with Slab-on-Ground Details

[azogr]

Hi all, I am looking for input on the best detail to use for a covered porch foundation. We will be using a slab on grade which will sit on a ledge in the existing concrete wall at the house side. At the outside I was originally planning to use a strip footing with block wall and over pour the slab. Is this the most economical detail or would something like a turned down slab be better? Our frost depth is 36" and there will be about 12" of reveal above grade. What is typically done in this situation? I am also concerned about the best way to anchor the posts and slab for uplift. Thanks in advance.

 

[oldestguy]

Not addressing the uplift (maybe use the slab's weight)consider replacing current soil with a clean granular compacted fill to 3 or 4 feet, extended out 4 feet at bottom. Thus, no or minimal frost heave. Less than 5% P-200 is best, but even 10% P-200 is quite frost heave resistant. Even with a wall and footing, any frost susceptible soil under the slab is not good. Another alternative is place the slab on 3 inches of closed cell Styrofoam, but it must be extended out 4 feet to keep soil below the slab from freezing.

Edit: Of course that soil under the porch area is sufficiently firm for any option not using replacement with complicated fill, right? If not improve it or replace.