Dow 2" 150 or 250?


Old 05-23-03, 05:27 AM
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Dow 2" 150 or 250?

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 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**.
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Old 05-23-03, 10:35 AM
Join Date: Oct 2001
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I'm baaa-aaack

Spoke to a structural engineer and that's just fine to use Foamular 150. If I look at it realistically, Foamular 150 has a compressive strength of 15 psi which translates into 2160 psf. We very typically get soil bearing pressures of 2000 psf for our commercial buildings, so the 150 could actually be better than the soil you are laying it on! If you do get a crack, the #4 bars will hold it together.

Having said that, if the 250 is code do you really have a choice?

Old 05-23-03, 01:17 PM
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That's kind of what I thought. Consensus seems to be that I can get away with 150. BTW, I live in a county where the code doesn't apply.
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