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A better membrane

New designers 2003

One new roofing product launched at Dach und Wand was the TPE single-ply membrane.

A few years ago there were two common types of single-ply roofing membrane: the polyvinyl chloride (PVC) membrane, which relies upon plasticisers for long-term flexibility, and the ethylene propylene diene monomer (EPDM) rubber-type membrane, which remains flexible but cannot be heatwelded on site to form welded laps.

During the 1990s, several manufacturers developed the thermoplastic polyolefin (TPO) membrane, which offered flexibility without relying on plasticisers and could be heat-welded. However, experiences in North America showed that some membranes were difficult to weld on site. Laboratory testing showed that, for a given product, there is a minimum temperature at which the material can be welded and a maximum temperature beyond which the membrane starts to burn. This temperature range is known as the 'welding window' and some products have a narrow range, making it difficult for the tradesmen to get the welding equipment settings right for the speed of operation and air temperature.

The IKO Group has developed the next generation of single-ply membrane, the TPE membrane. It is understood that TPE is the collective term for a particular group of polyolefins with the basic properties of elastomers, but which can be processed as thermoplasts. The new SpectraRoof system is manufactured and distributed in the UK by Ruberoid.

A significant advantage of this material is that it is compatible with bitumen. This is of importance where a single-ply membrane is lapped over a bituminous vapour-control layer, and also for overlaying aged bituminous roofing. Ruberoid claims that the SpectraPlan TPE roofing membrane does not absorb moisture and is only affected to a very small degree by dirt pick-up. This means that it remains possible to carry out repairs or to add details such as new pipe penetrations throughout the life of the roof.

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