This article covers advanced methods, materials, and considerations for parapet detailing for thermal, air, and moisture control in modern construction.
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Expanded Guidance
This article on Parapet Detailing for Thermal, Air, and Moisture Control includes key strategies for envelope continuity, product selection, code compliance, and typical failures to avoid. Systems are described with links to example products and performance tips based on field conditions.
🔍 Recommended Products
- Flashing Tape: 3M All Weather Flashing Tape
- Sealant / Liquid Flashing: Tremco ExoAir Liquid Flashing
- Thermal Insulation / Spacer: Rmax Polyiso Board
Best Practice Tips
- Ensure compatibility with adjacent layers and substrates
- Sequence flashing and weather barriers shingle-style
- Use mockups and field adhesion tests before bulk installation
- Coordinate across trades to maintain control layer continuity
Parapet Cap Flashing Integration
Parapets must include metal coping or cap flashing secured to blocking, lapped over base flashing. Extend membrane up and over the parapet wall, and install closure strips or sealant at fasteners. Incorporate thermal breaks to prevent heat loss at the parapet slab interface and include through-wall scuppers where required.
Thermal Bridging at Parapets
Parapets often interrupt the continuity of roof insulation, becoming major thermal bridges. To mitigate this, extend insulation over the parapet or install continuous rigid insulation on the exterior parapet face and top. Use thermal break materials beneath parapet blocking or coping channels to limit conductive heat flow.
Air Barrier Continuity
Extend the roof air barrier vertically up the back side of the parapet and over the top edge. Tie the air barrier into the wall air barrier below using compatible materials and sealants. Mechanical fasteners that penetrate the air barrier should be sealed with gaskets, tape, or membrane patches.
Moisture Management Strategies
Properly sloped parapet caps and flashing are critical to prevent ponding water. Flashing should project at least ¾” beyond the wall face and include drip edges. Parapets taller than 24″ may benefit from base-of-wall through-wall flashing to intercept driven rain and condensation.
Fire and Wind Resistance
Many jurisdictions require parapets to act as fire barriers. Use non-combustible materials and install fire-blocking insulation such as mineral wool at the parapet cavity. Secure coping against uplift forces with mechanical clips tested for wind resistance per ANSI/SPRI ES-1.
Integrated Coping and Cap Flashing
Use pre-formed metal coping systems with internal splice plates and foam closure gaskets. Stainless steel or Kynar-finished aluminum offers high durability. Ensure minimum 6″ overlap at joints and use compatible fasteners to avoid corrosion. Inspect for sealant failure and uplift gaps during annual maintenance.
