Term: Water Resistant Barrier

A sheet, spray- or trowel-applied membrane or material layer that prevents the passage of liquid water even after long or continuous exposure to moisture.

Source: RR-1101: Evaluation of Cladding and Water-Resistive Barrier Performance in Hot-Humid Climates Using a Real-Weather, Real-Time Test Facility; RR-1010: Innovative Passive Ventilation Water-Resistive Barriers—How Do They Work?; Info-301: Drainage Plane/Water Resistive Barrier