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nibs · 05-06-16, 10:25 PM

Have a line on 4inch thick 2ft X 4ft high density blue styrofoam (probably roofmate) price is about $3 per pc ($12 per full sheet) Canadian or $9.60 us. Thirty cents US per sq ft.
It was used on a roof and covered both sides with hot tar.
I want to use it to insulate under a 2 inch floor slab with hydronic heat tubes.
The construct will be something like
water proof membrane,
1 or 2 inches of styrocrete,on grade, at about 1 cement 2 sand 6 or 8 ground up styrofoam by volume.
4 inches of tar covered styrofoam
piping and sand to just cover the pex heat pipe
2" normal cement possibly with mesh.
for a normal house hold floor.
My concern is with the tar, over the years it does not seem to have harmed the foam, but will the tar/oils be able to migrate upwards through the concrete?
Your thoughts would be appreciated.

05-06-16, 10:25 PM	#1
nibs Apprentice EcoRenovator Join Date: Jun 2010 Posts: 206 Thanks: 1 Thanked 18 Times in 17 Posts	Asphalt covered styrofoam Have a line on 4inch thick 2ft X 4ft high density blue styrofoam (probably roofmate) price is about $3 per pc ($12 per full sheet) Canadian or $9.60 us. Thirty cents US per sq ft. It was used on a roof and covered both sides with hot tar. I want to use it to insulate under a 2 inch floor slab with hydronic heat tubes. The construct will be something like water proof membrane, 1 or 2 inches of styrocrete,on grade, at about 1 cement 2 sand 6 or 8 ground up styrofoam by volume. 4 inches of tar covered styrofoam piping and sand to just cover the pex heat pipe 2" normal cement possibly with mesh. for a normal house hold floor. My concern is with the tar, over the years it does not seem to have harmed the foam, but will the tar/oils be able to migrate upwards through the concrete? Your thoughts would be appreciated.