PIB Roofing Membrane

PIB (polyisobutylene) roofing membranes are synthetic single-ply sheets based on polyisobutylene, a rubbery polymer of isobutene. PIB is one of the oldest polymeric roofing materials still in use and is associated especially with Germany and central Europe.

History

PIB roofing membranes have been made in Germany for many decades; one manufacturer reports single-ply products on the market since the 1930s and a reference roof installed in 1956 that remains watertight. One German manufacturer has supplied the UK market since the mid-1970s, and a trade report put PIB at about a third of that company's market segment.

Construction

Typical PIB sheets are laminated to a synthetic fleece on the underside, which protects the membrane from the substrate, keeps it dimensionally stable and provides a bonding surface for adhesives. Products commonly have a prefabricated welding edge along one side, and seams are joined by hot-air welding. Sheets are commonly about 1.5 m (59 in) wide.

Properties

• Bitumen compatibility: unlike EPDM and many PVC sheets, PIB can be laid directly onto existing bituminous roofs without a separation layer, which suits refurbishment.
• Flexibility: usable across a wide temperature range.
• Composition: a trade report states that only about a quarter of one manufacturer's material comes from oil-derived sources, the rest being mineral.
• Approvals: products are tested for hail resistance (EN 13583) and root resistance (FLL), allowing use under green roofs.

Installation

The fleece backing allows PIB sheets to be bonded to substrates with adhesive, and the bitumen compatibility makes them a common choice for overlaying old bituminous roofs. Manufacturers' system instructions govern attachment and detailing.