What this detail covers
- A typical window cill build-up and finish strategy.
- Ensuring DPC continuity under the cill and across the cavity.
Key steps
- Confirm the cill type (fabricated to suit cavity) and the required cavity width.
- Install DPC continuously under cills and across the cavity as shown.
- Maintain breather membrane continuity and install cavity fire stop material as specified.
Checks
- DPC is continuous and correctly lapped/drained.
- Cill supports and fixings do not puncture critical moisture layers without the specified detailing.
Common mistakes
- DPC discontinuity at cill ends leading to moisture ingress.
- Insufficient cavity clearance/drainage path.
Indicative only: always follow the engineer’s fixing schedule and the project drawings.