# PIB Roofing Membrane

> Single-ply membrane made from polyisobutylene, usually fleece-backed with a welding edge, long used in Germany and compatible with bitumen.

- URL: https://roof.wiki/pib-roofing-membrane/
- Topic: Low-Slope & Flat Roof Systems
- Also known as: polyisobutylene membrane; PIB sheet; Rhepanol
- Regions: Europe
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "PIB Roofing Membrane." roof.wiki. https://roof.wiki/pib-roofing-membrane/

## Key facts

- **Polymer:** Polyisobutylene
- **Oldest reported roof:** 1956, Germany
- **Typical backing:** Synthetic fleece
- **Bitumen compatible:** Yes, without separation layer
- **Typical width:** About 1.5 m (59 in)

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.

## Sources

1. Rhepanol hfk brochure — FDT FlachDach Technologie / Blauer Engel. https://produktinfo.blauer-engel.de/uploads/pdf_uploads/25837_DOS_FDT_Broschuere_Rhepanol-hfk_A4_ENG_WEB_en.pdf
2. Keeping out water since 1873 — Building. https://www.building.co.uk/focus/keeping-out-water-since-1873/3075040.article
3. Polyisobutylene — Wikipedia. https://en.wikipedia.org/wiki/Polyisobutylene