What this detail covers
- A typical window head build-up including lintel, cavity tray, and fire stopping.
- Maintaining membrane continuity and a managed drainage path.
Key steps
- Confirm lintel type (including any insulated lintel requirement) and cavity tray specification.
- Install cavity tray per manufacturer instructions and lap breather membrane over as required.
- Provide cavity fire stop material as specified and ensure internal lining boards meet the required FR rating.
Checks
- Cavity tray is installed with correct laps/ends to manage water.
- Fire stopping is continuous at the head.
- Window fixing zones and tolerances are maintained.
Common mistakes
- Missing cavity tray end dams/closures (water tracks into the wall).
- Cutting membranes after the fact and leaving unsealed laps.
Indicative only: always follow the engineer’s fixing schedule and the project drawings.