rubber membrane under exterior siding


Old 05-02-04, 02:07 PM
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rubber membrane under exterior siding

I have rain water infiltration to interior side of exterior wall sheathing (I see it in unfinished attic gable end). I plan to remove the exterior wood siding from the gable end wall down to 4-5 feet below the attic floor, apply rubber membrane (normally used on roof) to sheathing, and reinstall new wood siding. The wall below the attic floor is insulated with typical fiberglass batts with attached vapor barrier facing interior. Will the rubber membrane cause any moisture problems in upper portion of the insulated wall since there'll be insulation sandwiched between vapor barriers?
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Old 05-07-04, 05:35 AM
Join Date: Nov 2001
Location: USA
Posts: 1,873

The answer is yes, the proabability that a moisture problem will occur in this application is HIGH. In the above mentioned website, you want to read up on the section listed as "PERM RATINGS". It gives the rule concerning the vapor permability of materials applied after the vapor barrier, which is 5 to 1. The rubber membrane you intend to install clearly violates this rule.
Old 05-07-04, 09:48 AM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389

Take and check on the house wrap Tyvek I think thats what you want to use there . Should let air out but not let water in.


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