garage floor

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Gary, I don't know what your experience level with concrete is, I've done about 4000 square feet of flatwork, probably more than most diy'ers, but thats about it.

I know the books say 4" is fine, but as an amatuer I use, and therefore recommend to other amatuers, a thicker slab. My base prep may not be perfect. I am not as adept as a pro at placing and consolidating the mix as it floods out of the truck. The mesh nevers stay in place. I believe the drivers, seeing you're not a pro, add more water to help out (weaker mix). This is all okay with me, but because I realize I end up with a weaker slab, I bolster my odds against cracking with a thicker slab. It only a little more $ for the extra concrete. In this case, its 3.1 yards per inch of thickness.

As far as expansion joints, what I would do is break it up into 6 parts, 13x14. Build form work for this grid pattern. Pour alternating blocks. Do three blocks on day one. Thats 10 yards of mix (full truck, sometimes a break on delivery fee). Pull down forms. Nail your expansion joint material into the slab edges. Next pour day, fill in the alternating grids.

I know a pro would would just dump it all and float it out, but if Im going to get the floor reasonably uniform, I like to screed it, and I could get a beeter finish if I only had to do 500 sf a day. Just my 2 cents. Good Luck.