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    

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.

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