The Forestry Forum

 I need to pour a concrete slab for my new/used owb the question is can I get a way with 12in of gravel under the slab  for a free floating slab    the gravel will be on top of the original ground I just don't want it to crack all to pieces at some point I will raise the floor to the same level as the owb slab

What's the original ground composed of? If its sod or other organic material, I'd scrape it off first and go from there.

I dug down about a foot and I had some pea gravel,all small stones,I laid that into the hole and than I welded a bunch of old steel together,to keep the cement together and made a wooden frame,that I coated with used motor oil so the cement would not stick to it. Heatmor dealer suggested I build a steel frame around the back side where the pipe go into the ground. I guess that part breaks. My sticks out of the ground about 8 inches. Probably have 14-16 inches of cement??? Makes augering out the ashes much easier and I put a bucket under the auger. Been there since '07 and all is fine so far.

original ground ..yes should compact the gravel

I will depend a lot on what the original ground is.  I would suggest removing the top layer a with all the organic and then try for 18 inches.  be sure the insulation extends beyond the foundation not just underneath it.

Also if you pour the concrete you will likely be building failure.  Keep it stiff and place the concrete instead.  It is an engineer thing.