Singleply roofing systems

Single-ply roofing systems, consist of a continuous membrane usually between 1 and 3 mm thick, covering any form of flat or pitched roof (Fig. 6.6). As waterproofing is reliant on the single membrane, a high quality of workmanship is required and this is normally provided by the specialist installer. In refurbishment work where the substrate may be rough, a polyester fleece may be used to prevent mechanical damage to the membrane from below. Life expectancies are typically quoted as 25 years. The wide range of membrane materials used may generally be categorised into thermoplastic, elastomeric and modified bitumen products. In many cases the single-layer membrane is itself a laminate, incorporating either glass fibre or polyester to improve strength and fatigue resistance or dimensional stability respectively. Both thermoplastic and elas-tomeric products are resistant to ageing under the severe conditions of exposure on roofs. Fixings offered by the proprietary systems include fully bonded, partially bonded, mechanically fixed and loose laid with either ballast or concrete slabs. Joints are lapped and either heat or solvent welded, usually with THF (tetrahydrofuran). A final seal of the plastic in solvent may be applied to the joint edge after the lap joint has been checked for leaks. Most manufacturers provide a range of purpose-made accessories such as preformed corners, rainwater outlet sleeves and fixings for lightning protection.

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