A protected membrane roof places the waterproofing layer directly on the structural deck, covered by extruded polystyrene insulation and a top layer of ballast, pavers, or a green roof system. This inverted design protects the membrane from ultraviolet degradation, extreme temperature swings, and mechanical damage. It requires a robust structural deck to support the heavy ballast.
We're installing a protected membrane roof on the hospital addition, so the pavers will go down right over the rigid foam.
Because the membrane stays at a relatively constant temperature beneath the insulation, it experiences far less thermal expansion and contraction than conventional roofs.
Also heard as
- inverted roof assembly
- IRMA roof
Related terms
PMR
A roofing assembly where the rigid insulation is placed above the waterproofing layer.
Plaza deck
A waterproofed structural slab over occupied space, topped with pavers, soil, planters or a wearing slab.
Single-ply roof
A roofing system that relies on a single layer of flexible synthetic membrane to provide waterproofing.