Inverted Roof Membrane Assembly (IRMA) concrete roof, insulated externally with a moisture resistant high compressive strength DCT GA300 XPS insulation that serves to protect the membrane from UV exposure and maintains the roof slab at a stable indoor temperature. The insulation is weighted down by a stone ballast loaded above a water resistant ProctorGeo IRMA geotextile to manage rainwater above the insulation layer.

DCT GA 300 is a closed cell high compressive strength, low moisture absorption extruded polystyrene (XPS) general application board for insulating roofs, walls and floors in commercial and residential applications 

ProctorGeo IRMA is a water resistant and vapour permeable spunbonded polyolefin non-woven geotextile for use as a separating layer in ballasted or paved Inverted Roof Membrane Assembly (IRMA) flat roofs.