Recommended Headlaps and Sidelaps
Head laps and side laps to roofing underlays should comply with the recommendations of BS5534: 2014: Code of Practice for Slating and Tiling and BS 8000-6: 2013 Workmanship on Building Sites.
| Head Laps (recommended minimum) |
| Pitch |
Unsupported |
Fully Supported |
Vertical |
| 12.5° to 14° |
225mm |
150mm |
100mm |
| 15° to 34° |
150mm |
150mm |
100mm |
| 35° + |
100mm |
75mm |
100mm |
| Detail Laps (recommended minimum) |
| Pitch |
Unsupported |
Fully Supported |
Vertical |
| Side lap |
100mm |
100mm |
100mm |
| Verge |
25 - 50mm |
25 - 50mm |
25 - 50mm |
| Hips |
150mm |
150mm |
- |
| Valleys |
300mm |
300mm |
- |
| Eaves |
|
25mm |
25mm |
| Ridges |
as table above |
|
|
NOTES:
1. Any penetrations to the underlay should be suitably sealed to prevent water ingress.
2. Underlay laps to valleys should comply with recommendations of BS 5534.