Installing windows in commercial wall systems requires careful sequencing of pans, flashings, tapes, and sealants. This article outlines the best-practice layer order to maintain waterproofing and airtightness.
Overview
Improper sequencing of window installation layers can compromise air and water tightness. Proper execution requires understanding the order of water-shedding and airtight elements and ensuring product compatibility. This includes sill pans, pre-stripped flashings, air barrier returns, and sealants.
Best-Practice Layering Sequence
- Install rigid or flexible sill pan with slope to drain
- Apply corner boots and primered tape at sill
- Install window into prepared opening
- Backer rod and sealant around window frame perimeter
- Apply jamb and head flashing tapes in shingle fashion
- Tie WRB or air barrier to head flashing and jamb returns
🔍 Quick Picks
- Flexible Sill Pan Kit: SureSill Sloped Sill Pan Kit
- Liquid Flashing for Rough Openings: Tremco ExoAir Liquid Flashing
- High-Adhesion Flashing Tape: 3M All Weather Flashing Tape
QA/QC Tips
Mockups should be completed for complex systems. Conduct field adhesion tests for tapes and sealants. Observe sequencing during installation to avoid reverse laps. Verify drainage through sill pans and test via spray rack as part of ASTM E1105.
Conclusion
Waterproof and air-seal your windows by carefully sequencing installation layers. Use compatible systems and adhere to tested methods to avoid callbacks and performance failures.
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