Parapets are one of the most vulnerable locations in the building envelope. This article outlines critical detailing steps for maintaining control layer continuity across parapets and roof-wall transitions, ensuring thermal efficiency, water resistance, and long-term durability.
Typical Parapet Failures
- Gaps or cracks between roof membrane and parapet wall
- Insufficient insulation on the exterior face or top of parapet
- Inadequate coping installation allowing wind-driven water intrusion
- Thermal bridging at structural steel or CMU transitions
Control Layer Coordination
Detail all four control layers (air, vapor, water, and thermal) across the wall, roof, and parapet junction. Extend the roof membrane continuously up and over the parapet, terminating beneath coping or cap flashing. Exterior insulation should wrap continuously from wall to parapet face and cap. Membranes should be sealed using flashing tape or fluid-applied systems at all changes in plane.
Coping and Cap Flashing
- Use pre-manufactured metal coping with internal cleats and continuous cleat anchoring
- Sloped coping tops to drain water toward the roof side
- Seal coping joints using double butyl tape or continuous gaskets
- Where coping is not used, install through-wall flashing and counterflashing with reglet seal
Field Quality Control
- Check membrane transitions from wall WRB to roof membrane behind parapet
- Ensure continuous exterior insulation on parapet face and top
- Inspect coping anchor fasteners and joint sealant compression
- Photograph parapet interior and cap prior to cladding installation
Field mockups and infrared thermography can be used to verify thermal continuity across parapets.
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