Roofing felt vs. poly

I am in the process of renovating my bathroom. I am at the stage where I am now hanging roofing felt onto the studs as a vapor barrier. After further research, however, it seems that poly may be the way to go, as the felt may be more of a retarder, not a barrier. I only have one sheet of roofing felt up so far, so its definately not too late to tear it off and go with 6 mil poly.

Should I replace the roofing felt with poly? Thoughts? Thanks a lot!

To me both are fine, your choice.

Thanks.

Either one will work in that method, but that method is a very poor way to make a moisture barrier and does nothing to waterproof the walls.

The best way to install a moisture barrier and at the same time waterproof the walls is to apply a surface membrane such a Kerdi. If you'd like a slightly cheaper (?) way you can apply 3-4 coats of a liquid membrane such as Redguard or Hydroban instead. The liquids work OK for tub enclosures. The Kerdi method, I think is better as a complete shower system.

Jaz

I guess im a little confused. Are you proposing that I put Kerdi on the studs, then go over the Kerdi with my CBU?

This is in a standard 3-wall tub/shower. I was under the impression that 6 mil poly behind the CBU, plus my 8x16 tiles set in high quality thinset would be more than enough to prevent water from making it to the wall cavity.

I ripped out old ceramic on CBU and there was never any water damage or even a suspicion of moisture behind the CBU.

I'm just tryingto clearly understand for my particular application. Thanks again!

Kerdi is a surface membrane, you install it over the wallboard or CBU and tile direct over it. That is the whole benefit of surface membranes, they prevent the substrate from getting wet.

The paper and plastic will act as a vapor barrier if installed correctly. The CBU, tiles and grout will not stop vapor and the installation will not be waterproof. A surface membrane, when installed correctly makes the job waterproof and watertight. It's just a better way to go, but it is not critical on a tub enclosure installation.

Jaz

Got it. Thanks very much for your help.

Tub Surround?

DensShield and Redgard the seams and screw heads.

DensShield and Redgard the seams and screw heads.