Every penetration in a wall WRB (water-resistive barrier) is a potential path for air and moisture intrusion. This article outlines tested methods and products to seal WRB penetrations for pipes, conduits, fasteners, and structural elements.
Types of Penetrations
- Small penetrations (fasteners, screws, ties)
- Medium penetrations (conduits, pipes, HVAC sleeves)
- Large penetrations (beams, ducts, equipment mounts)
Each requires a different sealing approach based on movement potential, substrate compatibility, and long-term durability.
Sealing Strategies
- Use flexible flashing tape with primer around small static penetrations
- Install pre-molded gaskets or split collars for dynamic conduits and pipes
- Backwrap WRB membrane around larger openings and seal with fluid-applied flashing
- Use sealant-compatible fasteners or pre-installed grommets for furring and cladding supports
Testing and Inspection
Inspect WRB penetrations at sheathing, furring, and cladding stages. Look for unsealed or reversed laps. Conduct water spray testing on large mechanical and equipment penetrations. Verify that sealants are compatible with WRB type (e.g., self-adhered, liquid-applied, or sheet systems) and do not degrade with UV or weather exposure before cladding is installed.
Common Errors to Avoid
- Overdriven screws that tear the WRB
- Using incompatible sealants (e.g., asphalt-based on silicone WRBs)
- Failure to account for movement in pipe/conduit transitions
- No back damming or pre-wrapping around large openings
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