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NAHB Paper Looks at ‘Rain Screens’ for Wall Claddings
In response to industry concerns over the threat of water intrusion and insufficient drainage to the durability and usability of residential construction, the NAHB Building Product Issues Committee has recently published “Improving Drainage and Drying Features in Certain Conditions: Rain Screen Designs for Absorptive Claddings.”
The multi-year effort enlisted the participation of builders, consultants and product manufacturers.
Examining the problem of moisture intrusion, the NAHB paper takes a conservative look at current and developing design and construction methods that can help limit moisture in exterior walls to an acceptable level.
The document offers some guidelines for designing and constructing a building enclosure with a “rain screen” that uses “absorptive” or “reservoir”-type exterior claddings — including Portland cement plaster (stucco) and manufactured stone veneer — over wood frame wall construction with wood-based sheathing.
As a supplement to existing manufacturer recommendations and industry standards, the guidelines are designed to help builders more effectively use these claddings in a manner that provides a moisture-resistant, durable building enclosure.
A “rain screen” approach resists rain penetration in three ways:
- The exterior cladding layer sheds most water at its outer surface.
- Anticipating that some water will go behind the outer surface, it intercepts that moisture with a dedicated airspace/capillary break.
- This space is vented to the outside to not only provide drainage but to encourage drying as well.
The document contains several drawings illustrating how drainage and drying can be achieved behind absorptive claddings using a variety of readily available materials, and it includes information on the manufacturers of drainage products.
“The process of continually improving the quality of new home construction and remodeling is of paramount interest to NAHB in service to its members,” said Finley Perry, a Massachusetts residential general contractor and 2008 chair of the committee. “The Building Product Issues Committee is proud to offer this latest tool to our more than 200,000 members to benefit America’s home buyers.”
To downloand the paper, NAHB members can click here.
For more information, e-mail David Jaffe at NAHB, or call him at 800-368-5242 x8317.
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