PMMA Liquid Roofing

PMMA (polymethyl methacrylate) liquid roofing is a cold-applied, solvent-free, two-component resin system. A peroxide catalyst is mixed in just before use, triggering rapid polymerisation on the roof. The resin is applied over a primed substrate, a needle-punched polyester fleece is embedded while it is wet, and more resin saturates the fleece to form a seamless, reinforced membrane.

Curing

The defining feature of PMMA is speed. Typical systems cure in about 30-40 minutes and remain fast even at temperatures near 0 C (32 F). Product data for one system lists it as rainproof after about 30 minutes, walkable after about 35 minutes and fully hardened after about 6 hours, allowing a small roof or a detail to be completed in a day.

Typical properties

One reinforced PMMA roofing system lists a thickness of about 2.3 mm (90 mil) with fleece, minimum elongation of 30%, and the ability to bridge cracks of about 2 mm (0.08 in). Reflective white top coats are available.

Uses

• flashing details on single-ply, bitumen and other roofs, including penetrations, upstands and drains
• small or hard-to-access flat roofs and gutters
• balconies, terraces, walkways, stairwells and parking decks, often with an integrated wearing surface
• inverted and buried roofs, where it can be covered by paving, tiles or growing media

Considerations

PMMA bonds to a wide range of substrates when correctly primed. Installers must mix the catalyst accurately and work within the short usable life of each mix, which one product lists as about 20 minutes.