On this garage slab project (see “Garage slab quote” thread), I’m getting everything lined up, checked availability of pink 2″rigid insulation at Menards, guy tells me I need to use 250…not 150 under a garage slab, even with 4000 psi concrete and rebar. Is Code in Rochester, but they don’t stock it, has to be special ordered. No problem except it would be a week and a half before I get it…might not fit in with contractor’s schedule.
Of course the good old boys down in Fillmore County always use 2″ 150 under garage slabs.
So you kind fellows that have recently done garage slabs with insulation underneath…is it critical that I use the 250 rated stuff? Is there some reasoning behind this or is it just code conspirancy?
Fear of course is that someday I’ll reno a tractor in there, the concrete has cracked or even if I saw in joints, a whole section will compress into the foam. Doesn’t seem likely, but if it DID happen would be a pain in the a**.
Replies
The key factor you are worried about is compressive strength of the foam. I would call DOW at 800-441-4DOW. The will probably need to know the weight per square foot of you slab and intended load etc. but in any case should have a good handle on the relative difference of the two densities. Good Luck
Chip