The concrete contractors that have bothered to call me back (2 out of 9!) have given me wildly different estimates, and slightly different specs for the job. The estimates I'm going to settle by trying to get one or two more, but I wanted to ask about the specs.
The slab is butted against the house foundation, 23' deep, 20' wide. The expensive contractor spec'd a 6" thick slab, #4 rebar plus wire mesh. The cheaper estimate said "rebar plus mesh" but didn't spec a thickness, just 4000 PSI. Given how many yards he said I'd need (6-6.5), he seems to be pouring a 4" thick slab. Is that sufficient in northern New England? He will put an expansion joint in the middle.
I don't know a lot about concrete structures, and want it to last. What kind of questions should I be asking?
I also got some quotes for asphalt paving, just as a backup. Any particular reason to like one over the other? I tend to prefer concrete slightly for the durability.