PolyFoam XPS Polyfoam Slimline Membrane - 100m x 1.5m

• Improves the thermal performance of inverted and green roofs
• Waterproof and water vapour permeable
• Enables thinner insulation and less ballast to be used

Polyfoam Slimline Zero Membrane is a separating and water flow reducing layer (WFRL) designed for use in low moisture impact inverted and green roof systems. Its water-resistant properties significantly reduce water flow through the roof construction, helping to maintain the thermal efficiency of the insulation by minimising rainwater cooling effects.

By incorporating Polyfoam Slimline Zero Membrane, inverted and green roof systems can be made lighter, as less ballast is needed. This reduction in ballast is achieved through improved drainage above the insulation layer, which also reduces the risk of flotation.

What is its role in an inverted roof assembly?

• Placed above the insulation but below ballast or paving, it acts to slow rainwater flow, reducing “cooling” effects on insulation.
• Serves as a separating layer / filter to stop fines and debris migrating into the waterproofing system.

Limitations & considerations

• The membrane is water-resistant but vapour-permeable; it is not a vapour control layer (VCL).
• UV exposure: not designed for permanent exposure; should be covered / ballast applied promptly.
• Joints should be correctly aligned and sloped; poorly aligned laps may permit water ingress or bypass.
• Must be protected from mechanical damage in later construction phases.