Fluid applied air/moisture barriers are effective and economical means of controlling moisture in wall assemblies. Moisture control assists in preventing mold growth in wall assemblies. Fluid applied air/moisture barriers also offer performance advantages over building wraps and traditional asphalt- impregnated felt or paper moisture barriers. They can be used in all types of wall construction over wood, gypsum and cement-based sheathings. They can also be used over prepared concrete and concrete masonry units. They generally consist of three components (Figures 1a and 1b on page 204):

1. A spray- or trowel-appliedjoint treatment for filling sheathing joints, spotting fasteners, and protection of rough openings, corners and other changes of plane in sheathed wall construction.
2. Areinforcing mesh or tape used in conjunction with the joint treatment to reinforce sheathing joints, corners, and changes of plane, and for repair of minor cracks in concrete or concrete masonry wall construction.
3. Awaterproof coating applied by spray, roller or brush to prepared sheathing, concrete or concrete masonry wall surfaces.

When properly applied to sound supporting construction, these components function together as an air barrier and seamless moisture barrier in the wall assembly. Some of the advantages of a fluid applied air/moisture barrier include:

Effectively blocks air leakage Increases occupant comfort Reduces energy costs by reducing heating and cooling loads Reduces risk of condensation caused by air leaks through the wall construction Seamless moisture barrier no tears, holes, or lap joints that can compromise performance in service reduces risk of installation errors Protects sheathing and rough openings from weather damage during and after construction minimizes risk of weather damage to sheathing and associated repair or replacement costs Simple installation procedures No special tools or skills required; reduces labor costs Durable Does not tear or lose its effectiveness with exposure to weather during construction or while in service Structural/fully adhered Rigid and stable under air pressure loads, does not tear or blow off the wall with wind Distinct colors Facilitates job site inspection and quality control Water based Safe to use, easy clean-up, VOC-compliant Provides opportunity for pressure equalized or pressure moderated wall design Minimizes risk of rain water penetration through wall assembly Doubles as air barrier and moisture barrier in wall assembly Efficient use of materials