Does Permeability Matter in a Housewrap?

The more quickly a wall dries, the better. By Steve Easley I often get questions regarding the permeability of building wraps. Permeability is the ability of any material to allow water vapor to pass through it. The 2006 International Residential Code requires a weather-resistive barrier or WRB, behind all cladding systems. This code change is long overdue. Builders in recent years have been plagued with water intrusion and mold-related problems. These problems stem primarily from untrained field forces not installing weather-resistive barriers and flashing properly. In addition, there is widespread lack of attention to moisture management detailing in general. Because of this, builders are spending a great deal in unnecessary callback costs. The concept of weather-resistive barriers is certainly not a new one. For years builders used building paper over walls with diagonal 1x4 or 1x6 skip sheathing. This system had 1-in. continuous gaps that required secondary protection. It was and ...  more