What Is a Mechanically Attached WRB?
A mechanically attached weather resistant barrier is a building membrane that is fastened to the exterior sheathing using cap nails, staples, or screws rather than an adhesive backing. These systems have been the industry standard for decades and remain a cost-effective solution for commercial and multi-family projects where budget is a primary constraint.
Exteriors Design LLC installs mechanically attached WRBs across Portland, OR and the Pacific Northwest. While these systems require more careful detailing around penetrations than self-adhesive alternatives, our experienced installation crews ensure every mechanically attached WRB performs at the level your project demands.
How Mechanically Attached WRB Installation Works
Mechanically attached WRBs are installed in horizontal courses starting at the base of the wall, with each subsequent course overlapping the one below by a minimum of 6 inches. Vertical seams are lapped a minimum of 12 inches. All fasteners are cap nails or cap staples with large-diameter heads that minimize membrane puncture damage. Seams, penetrations, and transitions to window and door openings are sealed with compatible flashing tapes to create a continuous drainage plane.
Critical to performance is the correct sequencing of the WRB with windows, doors, and other penetrations. Our crews are trained in the "perfect wall" sequencing approach that ensures water that does penetrate the cladding is directed out of the assembly at the drainage plane level.
Benefits of Mechanically Attached WRBs
- Lower material cost: Mechanically attached WRBs cost significantly less per square foot than self-adhesive alternatives
- Fast installation: Experienced crews can install mechanically attached WRB faster than adhesive systems on straightforward buildings
- Proven track record: Products like Commercial Tyvek have 40+ years of documented performance data
- Wide manufacturer support: Available from DuPont, Fortifiber, Vaproshield, and other major manufacturers with strong technical support networks
- Code compliance: Meets all Oregon and Washington state building code requirements for weather resistant barriers
Ideal Applications
Mechanically attached WRBs are well-suited for budget-sensitive multi-family projects, Type V wood-frame construction, renovation projects where self-adhesive compatibility with existing substrates is uncertain, and projects with simple geometries and fewer penetrations where detailing risks are minimized.
When specified alongside a quality cladding system and detailed correctly at all transitions, mechanically attached WRBs perform reliably in Pacific Northwest conditions. The key is experienced installation — the WRB is only as good as its sequencing and flashing details.
Request a WRB Estimate
Exteriors Design LLC installs Commercial Weather Smart, Commercial Tyvek, Revealshield IT, and Vaproshield IT on commercial projects throughout Portland, OR. Call us at (503) 914-0200 or submit a project inquiry online.