My thoughts are not to let anybody pour anything bigger than about 10x10 without grooving it for stress relief. The Amish dude who poured my dad's 40x24' garage did it in one piece and refused to notch it. Also didn't order air entrainment or fiber reinforcement or use reinforcing mesh. Also didn't slope it right, so the low spot was slightly east of center, when the low spot should have been at the doors on the west wall. So, within a few months, he had cracked concrete, and every time we get a driving rain there are puddles in the garage.

You might be able to pour 10x22 without making the joints/grooves, especially if it's fiber reinforced or they embed steel road mesh in it.

I helped a friend do a driveway pour about 11x40, maybe 20 years ago. The slab is still in good shape, but it's an average thickness of about 6", has road mesh in the middle of it, and was poured on a compressed sand base. Still, I'm impressed that it never cracked, considering the week or three it spends under water every spring. We made one frame about an inch lower than the other, leveled it off with a 2x6, went out to lunch, and then broomed it with a coarse push broom. Tied ropes to the broom head and handle, you'd pull the rope on the handle to broom a rough surface onto the concrete, then the other guy would haul it back to his side in the air, and then broom another 18" swath from low side to high side, repeat until entire surface is roughened.

Absolutely, positively, under pain of death, do not pour concrete over grass.
Hopefully there are zero contractors who would do that. Most contractors in MI will order a truckload of sand, tamp it down, and pour on top of that.



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