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edwena_gw

Do I have a double moisture barrier problem?

edwena
16 years ago

I am ready to start installing the Kerdi. While rereading my notes, instructions, etc. I suddenly realized that I may have a double moisture barrier problem.

The tub-surround shower alcove has 1 exterior wall, shares 1 wall with another room, and the third wall is a partition in the bathroom.

The tub is in and all the plumbing is completed. The Durock is installed.

These are the layers on the exterior wall of this 1911 house. 1. Cedar shingles. 2. Old tar sheeting of some kind. The places where I have removed a couple of exterior wall shingles this black stuff has been crumbly, however, until bothered it is probably doing the job. 3. Next is Owens Corning Pink insulation with the paper covering. Paper looks like a sandwich with a thin tar covering. Paper covering is toward the inside of the house. 4. Durock. 5. Kerdi after I install it.

Layers on wall shared with another room. 1. Wallpaper. 2. Lathe and plaster. 3. Same pink insulation with paper next to other room - insulation side toward bathroom. 4. Durock. 5. Kerdi after I install it.

There are no braces in the space between the studs. I put up a few supports but they don't totally obstruct the stud space. There are two niches, however, there is about 1" between the back of the niche and the adjoining wall because of the way the plaster was keyed. Generally, the insulation runs the full length of the chase, down to the floor behind the tub.

There is a low plumbing access door on the bathroom partition. I haven't built this door yet, so I could put a vent in the bottom part of it. Might allow more moisture into the joist spaces than it would let out. I have built and will tile the tub skirt so I could put a vent here also. But same question, would this let moisture out from the stud spaces, or allow more in from the steam in the bathroom? We have put a fan in this bathroom and there is also a window.

Thanks in advance for the help. I am going to hold off on the Kerdi until this issue is solved.

Edwena

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