Made from spun bonded polypropylene, this Spirtech 400 2S is a four-layer, vapour-permeable underlay designed for pitched roofs. Boasting exceptional strength, durability and hassle-free installation, it offers an innovative solution from Redland as a heavy-duty underlay featu... Read More
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Made from spun bonded polypropylene, this Spirtech 400 2S is a four-layer, vapour-permeable underlay designed for pitched roofs. Boasting exceptional strength, durability and hassle-free installation, it offers an innovative solution from Redland as a heavy-duty underlay featuring a unique adhesive system. This system brings horizontal laps together, creating an impervious membrane that persistently resists wind uplift.
This Spirtech 400 2S underlay is perfect for both warm and hybrid roof systems, where wind penetration could compromise roof insulation performance at rafter levels, as well as traditional cold roofs. It effectively counters wind uplift forces, ensuring reduced wind loading on roof tiles. It benefits from comprehensive coverage under Redland's 15-year SpecMaster guarantee when integrated into a SpecMaster project.
To establish an airtight membrane, the vertical side laps of this Spirtech 400 2S demand sealing with Redland's DivoTape or other compatible Redland underlay accessories. DivoTape, a UV-resistant PE foil with mesh reinforcement, delivers airtight sealing for laps and junctions. It's effortlessly stretchable and tearable by hand, measuring 60mm wide and 25m long.
For complying with BS 5534:2014 underlay requirements and achieving robust wind uplift resistance across the UK, there's no necessity to bond or seal the vertical side laps (only horizontal ones) if the vertical laps align with rafters or counter battens. However, if they don't, sealing or bonding is recommended for a wind-tight membrane. For roof pitches from 12.5° to 14.5°, you will require a 225mm to 150mm headlap, a headlap of 150mm to 100mm for 15° to 34.5° pitches and a 100mm to 74mm headlap for 35° pitches and above.
Question:
I think my roofer may have installed one strip of felt upside down. Battens are installed but not the tiles yet. Could this be a problem? Thanks
Answer:
The strip upside down will be letting vapour into the roof instead of away from the roof as its meant too
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