Drainable housewraps, also known as enhanced WRBs (Water-Resistive Barriers), provide a textured or channeled surface that allows incidental water to drain from behind cladding. This article explains how to select, install, and inspect WRBs for optimal moisture management and air barrier continuity.
Benefits of Drainable WRBs
- Promote vertical drainage behind cladding systems
- Reduce trapped moisture and risk of mold or material decay
- Improve drying potential in mixed or humid climates
- Comply with ASTM E2273 drainage testing standards
Installation Best Practices
- Install housewrap with textured/drainage surface facing outward
- Shingle lap all seams 6 inches horizontally, 12 inches vertically
- Use cap fasteners, not staples, to prevent tearing
- Seal all penetrations and transitions using compatible flashing tape or sealants
Integration with Windows and Cladding
- Wrap into window rough openings and tape corners using flexible flashing
- Drainage must continue uninterrupted at window heads and sills
- Lap cladding starter strips and bottom edge over WRB termination
- Use weep screeds or air gaps for ventilated cladding systems
QA and Field Testing
- Visually inspect lap direction and penetration sealing
- Perform water spray tests at windows and cladding terminations
- Use blower door and smoke pencil to identify air leaks at WRB seams
- Confirm drainage material is not compressed or blocked by fasteners or insulation
Photographic documentation of each wall plane after WRB installation is recommended before cladding is applied.
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