Managing moisture in the wall cavity—particularly incorporating methods for
draining bulk water—continues to be a growing concern for the industry.
Requiring or specifying a drainage space between the water-resistive
barrier and the exterior wall covering has quickly become part of this
moisture management strategy. Now, recent changes to the International
Building Code and International Residential Code are bringing new
drainage requirements to a larger portion of the country, meaning
builders and contractors may need to rethink how they approach building
envelope design going forward.
Water-resistive
barriers are an intervening layer installed behind exterior wall
coverings to resist moisture and provide protection to underlying
components. Common types of WRB materials include roll goods, such as
flexible sheets (ASTM E 2556 Type 1 or 2) and asphalt-saturated organic
felt (ASTM D 226 Type 1 No. 15 felt), specialized sheathings comprised
of foam plastic, wood or gypsum-based products, fluid-, liquid-, or
roller-applied materials and self-adhered membranes.