Use this 3-part SimpleSpecs to specify weather barriers for exterior walls behind masonry veneer, metal panels, or siding.
This specification includes the following types of barriers; however, other types may be added as required:
- Sheet barriers
- Rubberized sheet barriers
- Fluid-applied barriers
Barriers serve as a barrier against water infiltration, air infiltration, and moisture vapor transmission through exterior wall assemblies.
Barriers must be applied to a solid substrate. Even a sheet type cannot span between framing members, since wind loading could cause it to deflect and the seams to open.
A vapor retarder is generally defined as a material having a moisture vapor transmission rate less than 1 perm when tested to ASTM E96.
Careful consideration of numerous factors is required to prevent condensation from occurring within roof, wall, and floor assemblies. Climatic conditions including mean summer and winter temperatures and average relative humidity, both indoor and outdoor, can have a huge effect on moisture vapor movement. In addition, the location of the weather barrier within the assembly is critical.
In order to be effective, the barrier must be continuous, with joints sealed and the weather barriers sealed around all penetrations and at the perimeter.