Should I install a poly moisture barrier before the rigid foam board against a basement wall?

DONandCATHY Crenna
Updated: Jan. 9, 2021

Hi There, I have just finished removing all of the damp, musty (and in a few places moldy) drywall, vapour barrier and fiberglass insulation from the basement of our home built in 1960 in Ontario in climate zone 5.  Outside the home I have jack-hammered and removed the concrete walkways that had cracked and settled on a slope towards the foudation wall. I installed window wells, added fill and re-graded the away from all foudation walls (concrete block) at +/- 10% slope.

Inside, I want to the best job I can, (without breaking up the concrete floor in the basement for an interior drainage system). So, I just want to check my understanding of the process before continuing much further. At present, I am considering moving as many as possible of the water, drainage and electrical lines that are in close contact with the block wall (to be relocated in a new stud wall later) to make room for the new insulation process.

From the block wall inwards I am considering the following sequence of materials:  6 mil Poly against the wall for moisture and radon protection, 2" rigid XPS foam board insulation held in place with the special plastic pegs (since the poly will not allow adhesive to affix it to the wall), blue sheathing tape on foam board joints, 2X4 stud wall 16" on-centre spacing, mineral wool batts, Smart barrier vapour retarder, mold resistant drywall, latex primer, and latex paint. 

I should also mention that I plan to use a subfloor product that I had purchased enough of, a while ago,  called "Tyroc" that is now not available. But it seems like a good product none-the- less.

Thanks for any input you may have. Don

Responses (3)

DONandCATHY Crenna
DONandCATHY Crenna 3 years ago
frank brex
frank brex 3 years ago

I have 2 inches of foam insulation that is glued on a concrete foundation how do I separate them ?