Decra TwoF Underlay

Advantages

BBA Certification Better Tensile Strength than traditional Bituminous 1F Protects property during & after construction Lightweight, easy to handle & install Easily Chalked marked Completely rotproof and long lasting  Tough & Durable Cost effective

Decra Roof Systems in partnership with it’s sister companies within the Icopal group, the world’s largest producer of roofing felts, is now able to offer from stock high performance underlay ideally suited for use with the Decra Roof System.

 

Product Information:

Suitable for use on all tiled roofs where insulation is provided at ceiling level and the roof is ventilated in accordance with BS5250.

Decra Two F underlay is manufactured from a low density polyethylene sheet material with a multifilament reinforcing grid and provides excellent tensile strength characteristics with high puncture and nail tear resistance. Decra Two F is compatible with most materials normally used within roof substructures and finishes. It may be cut and applied using techniques described in the current BS 5534: Part 1 (Slating and Tiling: including shingles). It is not suitable for use with solvent based timber treatments

 

Technical Data:

Recommended horizontal 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° +	100mm	75mm	100 - 150mm
NOTE 1. Any penetrations to the underlay should be suitably sealed to prevent water ingress. NOTE 2. Roofing underlay laps to valleys should comply with recommendation’s of BS 5534;  Part 1:1997 section 4.2.1.6

Performance & Properties

Nail Tear Resistance:	MD 93 N
	CD 113 N
Tensile Strength:	MD 248 N/50mm
	CD 393 N/50mm
Size and Coverage
Roll Length:	30m
Roll Width:	1.0m
Thickness:	0.15mm
Colour:	Black
Weight per Roll:	4.5 kg

 

                    
            
              

 

 

 

 

 

 

 

 

 

 

Installation

Decra Two F must be installed and fixed in accordance with the manufacturer’s instructions and the relevant recommendations of BS 5534-1: 2003 and BS 8000-6:1990. Installation can be carried out under all conditions normal to roofing work. Fixing instructions are enclosed with the roll.

As per all types of underlay, at eaves the underlay should terminate in line with the front edge of the fascia board and to comply with the recommendations of DTLR Robust Detailing, BRE Defects Action Sheet No9 and BRE Good Repair Guides an appropriate Decra Eaves Guard  must be installed underneath the breather membrane.