Fill dirt!
 

I am wondering what kind of fill dirt do I need to get to support a 10x20 garage slab floor, I thinking sand because part of my yard holds water.

Ayuh,.... Sand is the least compactable soil out there,....

Crushed stone is Best,...
Compacted bank-run gravel is probably 2nd, so long as there ain't to much big bone,...

'ell,... Compacted clay makes a good base...

How much/ deep is the over-all fill,..??

I need about 6'' or 7''.

Then you'll wanta pull out any rocks at or over 1/2 that size...

Sand is compacted about 97% when it gets dumped from the truck. Its problem is it holds water, which is why crushed rock is good. Put heavy duty vapor barrier under the slab, over appropriate thickness of foam if you are heating the place, and compact your gravel in 4" lifts. 8" should suffice, but ask a local engineer/building department about that. Ensure good drainage away from the slab, and large overhangs on the structure; 3' is nice.

The dirt you need is Builder's Sand. Check with a local sand co. or concrete ready mix co. It's different than play sand for the kids sand box, concrete sand or that found at the beach. It can be of many different colors depending on the area it's from.

It's a compactable sand with the correct moisture content. You'll know when it's the right moisture for compacting by squeezing a hand full. It will form to your hand shape somewhat but break apart easily and compacts well with a vibrating plate compactor. The other choice is compacted chat. There's all kinds of info. on google.

The sand should be free of organic matter and there is an easy test for that. See pic. Forget the plastic. Water doesn't wick up through concrete like a sponge as some believe and is unnecessary. If you are in an area of termites don't forget to treat before filling.

Can you plant grass seeds in the builder sand?

Sure, but don't expect too much since it should be free of organic matter. It will need a vigorous feeding program and maintain a moisture content of around 30 percent by weight.

I thought 6 to 8 inches of compacted quarry process was good for this. No?

Its for supporting the foundation, but I would like to plant a lawn around the outbuilding once its finish.

CJ, grass will grow around your shop because there is dirt around your shop, sand won't stop the grass unless the sand is really thick, just spread it out.

I do disagree with not having a vapor barrier though, it is good to have that added protection incase water gets under the slab. Another thing I always did, because code called for it, we had to post hole down to solid ground every 4 feet on a grid to keep the slab from busting and sinking in the middle just in case the back fill settled away from the slab. You will need to cut the plastic at the post holes so the concrete will go into the holes.

Are you using wire in your slab?

I use I am going to use wire mesh and 6mil plastic.

according to a guy who teaches building science (this was posted on the greenbuildingadvisor.com site, but i don't have a linnk), concrete will wick water for about 5 kilometers up. NEVER install a slab without a good vapor barrier. P, EOS. See http://www.buildingscience.com/docum...flooring-probs

Ayuh,.... Not that I think a slab oughta be poured, Without a vapor barrier,....

But, ain't that 'bout 4, 1/2 Miles,..?? :eek:

For some reason I don't recall ever seeing bridge piers in water that were saturated to the top and covered with moss , lichen etc. from being wet. Place a piece of concrete or even a brick as used to veneer a house in a quarter inch of water and see if it is saturated completely through in 24 hours.