Division 7 - Thermal and Moisture Protection
     Section 07550 Protected Membrane Roofing (PMR)

image 4: Membrane roofing assembly.

This image shows all aspects of roofing procedures. The roofing system specified for this building is a PMR System (protected membrane roof). The protection comes in placing the built up roofing membrane directly on the roof slab and protecting it with insulation and gravel ballast. The protection is twofold. First the membrane assumes the constant temperature of the thermal mass of the roof slab which will not change considerably with the seasons. The insulation also provides a protective barrier against penetration by sharp objects and with its ballast of round gravel, a protection against UV light. The gravel ballast also holds down the insulation board and provides a general filter for straining larger particles prior to storm water entry into the roof drains. It also assists in snow melt as a thermal mass, which picks up solar radiation and stores it for re-radiation during the night.

Note the built up roof membrane below the insulation board. Counter flashing of vent pipes occurs on to this membrane. The roof drains have two flashing rings. One is directly clamped to the roofing membrane, while the other picks up the gravel filter fabric membrane above the insulation. A third extension of a strainer ring occurs in this roof drain to allow the water within the depth of gravel fill to directly enter into the roof drain. The roof drain is picking up water at two levels and has been specifically designed for the PMR System installed.

Division 7
Page 3 

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