[tops911]

If you do a 40" foundation you'll need 1/2" rebar in the wall and footing. You'll need to rent some forms to pour the wall. What I get from my father (who did this work over 20 some years) is to use a key type joint and keep the slab 10'x10' and you should have no problems with cracking. There is a metal key joint made to use in slabs, you could pour the entire slab at one time but you'll need to use the metal key joint and trowel flush with the joint. A couple of other things to consider is the slab going to sit on the foundation or is the slab going to be inside the foundation walls. If the slab is inside the foundation the floor can have a slope twards the garage door for drainage. You dont need much something like 1" per 10'. A draw back is you'll have a ledge that sticks up an inch or so. Normaly the foundation walls are 8" thick. So you'd about a 4" ledge that would not be even with the floor. I used to do this kind of work 17 years ago, But now I shoot howitzers. Cement work is hard on the knees, artillery is hard on the ears.