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Rainscreens and drainage planes

Building assemblies can get wet Building scientists assume that some rainwater leaks through the cladding or roofing and that water vapor migrates through insulated building assemblies, sometimes condensing within those cavities. These two phenomena both can dampen building assemblies. What are rainscreens? Builders often provide a 3/4-inch air space between siding and the water resistive barrier (WRB) as[…]Read more

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Air and Water Barriers

Old and new water barriers Once upon a time, builders stapled 15-pound asphalt felt to wall and roof structural sheathing as a water-resistive barrier (WRB). The 2012 International Residential Code (IRC) still specifies: “one layer of No. 15 felt… or other approved water-resistive barrier.” Most builders used perforated felt to allow water vapor to escape[…]Read more

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What is a Water-Resistive Barrier (WRB)?

Builders install a variety of products on the exterior of foundations, above-grade walls, and roofs as water-resistive barriers (WRBs), required by the International Residential Code (IRC). Water-resistive barriers are also called weather-resistant barriers, but the former term is now considered preferable. WRBs are buildings’ last and primary exterior water barrier. WRBs vary widely in their vapor[…]Read more