Mark P Posted November 21, 2009 Report Share Posted November 21, 2009 House is maybe 50 years old, wood panel exterior siding, 2x4 framed exterior walls. A new shower surround is being installed against an exterior wall. Fiberglass batt insulation will be installed in the wall cavity with kraft paper facing the inside of the house and the new surround placed over that. Should a 4mil plastic barrier be placed over the studs behind the shower? Quote Link to comment Share on other sites More sharing options...
hausdok Posted November 21, 2009 Report Share Posted November 21, 2009 What kind of surround are you talking about? Tiled or pre-fab fiberglass? One piece or 3 to 5 piece? Regardless, I'd probably use a barrier and then a layer of cement backer board OT - OF!!! M. Quote Link to comment Share on other sites More sharing options...
Mark P Posted November 21, 2009 Author Report Share Posted November 21, 2009 It would be a pre-fab fiberglass. I don't know how many pieces. The question came up with some people I know who are refabing a house. One of them saw on HGTV that a plastic barrier is needed between the shower and outside wall or else there would be a mold problem. There has been some discussion and some think the plastic would cause more of a problem, some think the kraft paper would be fine. Why would you use a cement backer board? Quote Link to comment Share on other sites More sharing options...
hausdok Posted November 21, 2009 Report Share Posted November 21, 2009 It'll absorb vapor diffision and release it slowly. Otherwise, you might end up with rivulets on the plastic barrier. With no way to drain that 4 mil into the shower pan you wouldn't want that. Did you consider closed-cell foam with a barrier for that exterior wall? Fiberglass doesn't provide the most consistent wall you know. OT - OF!!! M. Quote Link to comment Share on other sites More sharing options...
Scottpat Posted November 21, 2009 Report Share Posted November 21, 2009 Take a look at this document, I think it will answer your question. I just used some of the information for a home I'm doing phase inspections on. http://www.buildingscience.com/document ... mendations Quote Link to comment Share on other sites More sharing options...
kurt Posted November 21, 2009 Report Share Posted November 21, 2009 I'd never use the polyethylene sheet for reasons Mike said. I'm somewhat confused why anyone thinks they want or need a sheet there; isn't the plastic shower wall a vapor barrier? Honestly, this is something I really don't know. I never see plastic shower surrounds; maybe a dozen my entire career. All I see is tile surrounds, and that's another story. Quote Link to comment Share on other sites More sharing options...
ghentjr Posted November 21, 2009 Report Share Posted November 21, 2009 House is maybe 50 years old, wood panel exterior siding, 2x4 framed exterior walls. A new shower surround is being installed against an exterior wall. Fiberglass batt insulation will be installed in the wall cavity with kraft paper facing the inside of the house and the new surround placed over that. Should a 4mil plastic barrier be placed over the studs behind the shower? Either green sheetrock or cement board should be over the studs, plastic not needed. Most of the plastic (fiberglass) surrounds have no body and they need to be against a solid surface. Think of an adult slipping and bumping one without support and popping one of the interlocking seams. P.S. I hope the water supply is on the interior wall and not the exterior. Quote Link to comment Share on other sites More sharing options...
Mark P Posted November 23, 2009 Author Report Share Posted November 23, 2009 Thanks Everyone. Quote Link to comment Share on other sites More sharing options...
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