Are you pouring footing and then slab ? Or slab and footing at once? Yes, either way full perimeter footing. Either way I would break it into two 24x48 sections with a piece of keyway. That slab will crack if you don't. Use re mat and not just fiber. Okay re mat and fiber, re mat only is fine, but not fiber only. A slab that rectangular is going to crack. Keyway is cheap and easy to install.
Aw it prolly won't crack... Ask them to put that in writing or put in that keyway.
I might would do a grade beam if doing two pours. Are you wet setting the ICF or leaving vertical rebar and spray foaming blocks to slab above grade ? Lots of energy loss at footer if above grade which defeats the purpose of ICF to begin with. I always poured inside the blocks, I mean set the blocks on below grade footing, popped chalk line and poured the slab. I have glued them to top of an existing slab when adding a safe room. You could be doing for storm resistance, but with garage doors, I think not. They'll blow out if a tornado is in the county somewhere. I was in a shop fixing to skedaddle out of there and a drum door blew out. So much for hurricane doors. But, it was a 14' drum door.
Yes pour a footer under doors too. Do not ever think of not doing it. I have three concrete finishing machines, bull floats, hand floats. Had two concrete pumps for years and built over a dozen ICF homes. Easily poured more concrete than any ten combined. Poured 175 yards a day many times. My a double s was on the line because I was the contractor. Hand finished slabs your size, even 40x60 on my knees with two 2'x4' pieces of plywood, yes I have. Contrary to popular belief, that is why I'm in my fifties and my knees are great. Friends are getting bionic knees, but not me. I can still lay floor or finish concrete all day on my knees. Dad is 75 and he can too. No knee or hip replacements in my bloodline ever.
I've built three story houses, 12/12 pitch roof, blocked the gables, all with ICF. I was the contractor, built the whole thing. One had a 5,000 square foot basement. Over 20 years, no problems at all that house was two stories above the basement.
