Klober’s Permo® extreme test success

Klober‘s Permo® extreme RS SK2 roofing underlay has recently undergone rigorous testing at the BRE’s Garston laboratories to determine whether it can withstand the UK’s weather without support boards. Without the need for support boards, roofing contractors can save a significant amount of both time and money.

Made from robust polyethersulphone fleece, Permo® extreme RS SK2 is a tear-resistant underlay that allows vapour to escape whilst keeping rainwater out, designed for use on low pitched roofs. It can be used at 12.5o or more for profile tiles, 15 o for slates and 22.5 o for plain tiles. 

In the BRE tests, Permo® extreme RS SK2 was laid at 12.50 with no slates or tiles on top of it and a 10-to-15mm deep drape – or sag – between rafters, in line with the latest update to BS 5534, the code of practice for slating and tiling for pitched roofs and vertical cladding. The underlay was fastened to the rafters with tacks and 50mm Butylon tape fixed down the rafters to seal around any nail penetrations. Battens were installed with fixing nails through the Butylon tape and the next layer of Permo Extreme RS SK2 laid with a 100mm headlap so adhesive strips meet.

The first test was a rain deluge test designed to create one-in-fifty-year conditions. The second combined wind, driving rain and suction from underneath, with all three elements increasing every five minutes over a 55-minute period, again mimicking one-in-fifty-year conditions.

The Permo® extreme RS SK2 was tested at over 110 Pascals. Graham Copson, Klober’s Technical Manager comments on the testing: “Most interlocking tiles start to leak at between 25 and 30 Pascals, so it performs far better than interlocking tiles.”

Klober Ltd
Unit 6F,
East Midlands Distribution Centre
Short Lane
Castle Donington
Derbyshire
DE74 2HA

Tel: 01332 813050

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