Underlay

Quick Links

Selection of Underlays
What is the best roofing underlay for your roofing project ,

For best Quality and performance
Decra 300 High Performance Underlay
For economy
Decra TwoF Economy Underlay

Breather Membranes

Decra 700 High Performance Breather Membrane

Roofing underlay is required and should comply with the recommendations of BS5534: 2003: Code of Practice for Slating and Tiling, BS 8000-6: 1990 Workmanship on Building Sites, and BS 5250: 2002: Code of Practice for Control of Condensation in Buildings.

 

 

 

 

 

Unsupported (roofing underlays draped over rafters or counterbattens):

 

Underlay should comply with BS 747 2000 Type 1F or 5U
 
NOTE: Although 1F & 5U may be used with Decra roof systems, Decra roof systems recommends selection of an appropriate Decra underlay, which offer the best value with regard to performance and specification.

Fully supported (roofing underlays laid directly to boarding or sarking): Underlay should comply with the recommendations of BS 5534: 2003: Code of Practice for Slating and Tiling. It should also be vapour transmission tested in accordance with BS 3177.

 

Decra underlays

High performance underlays and breather membranes for use with the Decra Roofing system are available from Decra, and can be ordered with Decra Roof Tiles. These underlays have been selected by Decra because they offer the best value with regard to performance and specification when used with Decra roof systems. Underlays supplied by Decra also offer a one-stop roofing solution, maintaining the quality of the total roof envelope and consequently reducing risk for the roof client.

Decra's range of underlays and membranes

Recommended laps for underlay

Pitch 

Minimum headlap   Minimum sidelap
Not fully supported  Fully supported 
.
10° to 12° 300mm 200mm 100 - 150mm
12.5° to 14° 225mm 150mm 100 - 150mm
15° to 34° 150mm 100mm 100 - 150mm
35° and above 100mm 75mm 100 - 150mm

 

 

 

 

 

 



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.

 

Contact

Let Decra offer you expert advice and information at every stage of your project.

For technical advice and assistance.

01293 545058

Or for local advice
technical advice and support