Slab base

[nate379]

Ground prep for a slab, is it necessary to dig out a hole and backfill with gravel?

Under the 1-2" of road base (#1 minus) I put down it is fill dirt, which is a mix of dirt and large/small rocks. Maybe a little bit of clay mixed in, but we don't have too much of that around here. Soil is fairly gravelly. There is a HUGE gravel pit about 1 mile down the road from me to give you an idea.

I see pics on here where the guys darn near pour the slab right on the grass! I'm just looking for a pro or semi-pro's $0.02.

 

[rodnok1]

Two things to worry about fill under slab, is it compacted and does it absorb water and expand/contract. I have seen people scrape off sod and compact soil and pour slabs for patios all the time. I compacted base soil, put 4 inches of #5, vapor barrier and 2 inches sand/clay mix and compacted alot during. I have heavy clay and fairly high water table though.