House Wrap

Published on January 29th, 2013 | by Henri

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Avoiding moisture problems caused by house wraps

Q.    You recently commented on moisture problems caused by Tyvek. This has me all concerned about our 150-year-old vertical plank-and-beam house, which we had re-sided about 10 years ago with cedar clapboards and Tyvek underneath. Rot on those supporting 3-inch thick planks would be the end of the house.

From the exterior, all appears well. We painted the clapboards and I don’t believe that I have repainted since. The west side of the house especially looks great. The clapboards aren’t moldy, appear sound; the paint looks as good as new. Should I peel some off and take a look? That would mean removing Tyvek as well.

A.    Tyvek or any other housewrap was a good choice for a plank house as it provides an air barrier – an important feature for energy efficiency. (Housewraps are not necessary with plywood or OSB sheathing properly installed, as the sheathing provides an adequate air barrier; I prefer, from experience, to use asphalt-impregnated felt paper.)

But the use of housewraps is not subject to the problems I mentioned in the column you are referring to if the siding is isolated from the housewrap by installation over either furring strips or Benjamin Obdyke Home Slicker or equivalent. This provides a drainage plane and air circulation behind the siding.

I certainly would not suggest that you rip the clapboards and the Tyvek off to see if there is a problem behind them. If you back-primed the clapboards you are less likely to have a problem, but if not I suggest that you keep the clapboards painted and all joints between different materials (siding and trim) caulked to reduce the penetration of wind-driven water. Do not use silicone caulking; it will peel off in a short time and can actually lead water into the joints it is meant to protect. Use polyurethane caulking, which you can get in masonry and construction supply houses.

Hopefully, any moisture that may have been driven through the Tyvek and wet the planks may work itself out and evaporate to the inside of the house.

Do not apply wood siding directly over housewrap.

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