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Two layers of WRB’s installed on wall. What are the potential problems?

jlafferty | Posted in General Questions on

I have recently been hired by a homeowner for interior finishes on a project in climate zone 4.  The GC installed a modular addition and is doing some renovations to the existing house.  Over the last few weeks I have been tracking progress of the exterior renovations and improvements.  The siding was stripped off and a perforated house wrap was installed.   All of the windows have been replaced with Renewal by Andersen and the windows were properly taped to the WRB.  The siding crew, upon realized that the original Celotex fiberboard wall sheathing (that is now under the perforated house wrap) was insufficient to support the new vinyl siding, installed 1/2″ OSB on top of the Celotex and perforated house wrap and then covered this with Tyvek.  The Tyvek cannot be taped to the window flanges as the window trim has already been installed.  The Tyvek is just pinned under the J-Channel for the vinyl siding. 

I can see the potential for water entering around the Tyvek that is unsealed around all of the windows.

Is this a recipe for disaster with 1/2″ OSB sandwiched in between two WRBs?

What happens when two WRBs are installed in this manner?  Is moisture build up going to be an issue?

Thank you in advance for your feedback.

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  1. Expert Member


    I'd be more worried by two other things, rather than that there are two layers of WRB: The potential for bulk water intrusion you describe being possible because of the poor detailing of the outer WRB, and that they used one of those garbage perforated WRBs, the inventor of which should be shot in front of the children.

    Two layers of a high-perm WRB like Tyvek detailed properly would cause no problems. Anything sandwiched by them could dry easily. But those perforated WRBs rely on all the little holes for their permeability, and I'm not sure how much moisture can actually dry towards the interior through them - especially if as you say the outer layer may let a lot in.

    Bet you are happy you are only involved in the interior trim.

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