what to do with an insulated slab over the winter – GreenBuildingAdvisor

I’ve given up on getting any structure up on my workshop slab, so now I need to decide what, if anything I should do to protect it over the winter. I’m in zone 5, close to zone 6. The slab is 36×50, 6″ deep with 12″ thickened edge. There’s R22 of insulation underneath, and R33 of insulation on the edge. Eventually there will be skirt insulation around it, but I have to grade a slope around the slab first. The concrete is 32MPa, 4-5% air entrained. 

My primary concern is frost heaving, so getting the skirt insulation done is certainly a good idea, but is a lot of work. My house actually has no skirt insulation, just 12″ of insulation on the slab edge, and it’s been fine for 7 winters. So I’m wondering if I can get away with leaving the area around the slab uninsulated for one winter. 

The secondary concern is freeze-thaw cycling on the top of the slab. I think the air entrainment will help with this. Should I even worry about it at all? If the risk is only surface level, aesthetic damage then I’ll just take my chances. I’m planning on putting a floor coating on it, and filling in some areas of spalling and whatnot won’t be the end of the world. The only mitigation method I can think of is buying more foam insulation to cover it, which would cost me about $1000, and I’d have no use for it afterwards. I looked into straw bales, but that’s more expensive than foam. Should I cover it with plastic, to keep it dry? I could put an ice rink on the plastic.