concrete pad thickness and what under it?

[gotrocks]

I just scanned the other replys in a hurry and did not see any mention of a vapor barrier.
I would certainly reccommend that you put one down, 6 mil poly would be better than nothing.
I wish I had put some conduit in my slab so I could have elec in the middle of my shop. Also wish I had put in a 4 inch under slab for a shop vac to collect sawdust. But if you never plan to do woodwork in the area that would not be of any benefit.
Is my .02 up? Good luck with the project.

PS I like my tin roof.

 

[Slamfire]

Lack of conduit under the floor is the reason they put joists in the ceiling. /forums/images/graemlins/smirk.gif

 

[Slippy]

My thought is keep the high end and and to the low end. That will put your shed floor higher than all the ground around allowing for water, especially that which rolls off the roof to drain away from the shed. You did not say, but usually shed that size don't have gutters. I have used a product that is a left over from curshed rock. It is real fine and packs as hard as a rock. I put it under my pole barn and it is the only concrete around my house that has not cracked.

 

[fractal]

I just finished a similar project. Had a metal shed that came with the house that the former owner had put on top of a wooden frame floor. Wood had rotted out and a family of skunks moved in. Went in one day to get the mower out and it was stuck. Pulled a little harder till I saw this little black tail with white stripe under the wheel at which time I stopped pulling and started running. It crawled out from under the mower and moved into the flooring. Seems it had set up a nest in the grass collection bag..

So, moved the shed, got rid of the wooden floor and poured concrete. It is at the base of a hill so I had a similar problem to you.

First of all, I used 2x4's for my framing. This leaves a 3 1/2 inch thick pad (silly dimensioned lumber ... 2x4's aren't 2 by 4 ..). I leveled the ground with the tractor with a very slight (1 in 10) slope back to front by digging down in the high area and filling the low area. I compacted the dirt with the loader, added a yard of pea gravel, packed with yard roller and 10x10 inch tamper, added a half a yard of sand, packed with yard roller and 10x10 inch tamper, framed it with 2x4's, layed out the rebar and poured the concrete. As to why the mix of fill? I figured I needed a yard and a half for base and had the sand left over from an earlier project..

Just moved the shed back last week. Project took about 6 months since I gave the base time to settle (yeah, that's a good excuse /forums/images/graemlins/smile.gif )

I dug into the hill slightly so the top of the pad was just above the slope of the hill. Unfortunately this leaves the front of the shed 3 inches above grade and me needing to build a ramp. I am now using a piece of plywood with some scrap lumber under it to roll the mower and other implements into the shed.

If I were to do it again, I would dig down until the front of the pad was maybe 1-2 inches (instead of 3-4) above grade and build a curb on the high side to run the water around the shed. One person suggested it and I thought I would try my way. His way would have been better.

So, to answer your topic ... 3 1/2 inches thick should be fine for a tool shed and is what you get with 2x4 framing. I have been told that gravel is better than sand for the base.