What this detail covers
- A typical window jamb/reveal build-up in a cavity wall situation.
- Fire protection board selection (FR30/FR60) and cavity fire stopping.
Key steps
- Confirm cavity width, wall tie positions, and fire-stop requirements with the designer/spec.
- Maintain breather membrane continuity to the external skin of the panel as designed.
- Install cavity fire stop material as specified and ensure jamb lining boards are correct (FR rating per spec).
Checks
- Cavity fire stop is continuous at the jamb.
- Membranes and tapes are lapped/closed correctly before access is lost.
- Jamb build-up allows the correct window frame position and fixings.
Common mistakes
- Missing/partial cavity fire stop at reveals.
- Membrane laps reversed, allowing moisture tracking.
Indicative only: always follow the engineer’s fixing schedule and the project drawings.