Additional Vapor Barrier Plastic if Using Foam Board

[duwem]

Saw a video on U tube where before pouring concrete they put down plastic sheet, taped the joints with that red insulation tape, then put 4x8' foam board on top of that with no tape at the joints, then the in floor heat pipes.

Is this common, or do most just tape the joints of the foam?

 

[Randy in Maine]

As long as the foam fits pretty well there is no need to tape the foam joints.

 

[duwem]

That's with plastic under it, or just foam itself?

 

[rburke65]

I'm thinking you want the plastic....vapor barrier.....under the insulation.

 

[Chris705]

What you saw on You-Tube is what I did in my garage....belt and suspenders approach. For me I liked the fact that the insulation board protected the VB underneath it. I didn't want the concrete guys to mess up the tape on lots of seams verses only a few taped seams on the plastic. Also felt for the low cost of plastic it was something worth doing if I ever wanted to proceed with a floor finish in the future that might be moisture sensitive. I believe there are many differing opinions on doing it a certain way.....

 

[Gooch]

It's a vapor barrier not an air barrier, don't waste your time taping the seams. the concrete is your air barrier. just overlap the seams a couple feet and call it good.