Modified Bituminous Membrane Roofing

Use this CSI 3 part SimpleSpecs™ master specification to specify rigid roof insulation, modified bituminous roofing membrane, and related flashings.

Roofing is composed of multiple plies of roofing membrane that are applied using hot asphalt or cold adhesive, or by torch application. The top ply has mineral granules or aluminum foil to provide physical protection and prevent ultraviolet degradation.

Roofing membranes are either SBS (styrene butadiene styrene) or APP (atactic polypropylene) modified bitumen with an integral reinforcing mesh. They are often installed over a cover board to provide protection against hail and foot traffic and for enhanced fire protection.

The ability of a roof to withstand high winds and resulting wind uplift is directly affected by the roof systems construction and attachment. Organizations such as Factory Mutual (FM) and Underwriters Laboratories (UL) rate roof systems for wind resistance. While FM is an insurer and therefore places requirements on more than just the insulation attachment, their ratings can be used as a guide for the roofing system.

Roof insulation is available in many forms, the most common of which are included in this section.

The R-value of any insulation that uses a blowing agent, in this case polyisocyanurate and extruded polystyrene, decreases after the insulation is manufactured. Consequently, the R-value for this type of insulation is rated by LTTR – Long Term Thermal Resistance, typically measured 5 years after manufacture.

For assistance in selecting and detailing modified bituminous membrane roofing refer to the National Roofing Contractors Association (NRCA) Roofing Manual: Membrane Roof Systems, available from NRCA at www.nrca.net.

Related SimpleSpecs™ master specifications:

07 51 13 – Built-Up Asphalt Roofing 

07 52 00 – Modified Bituminous Membrane Roofing

07 54 00 – Thermoplastic Membrane Roofing

07 56 00 – Fluid-Applied Roofing

07 65 00 – Flexible Flashings

07 72 00 – Roof Accessories 

07 72 23 – Roof Vents

07 72 33 – Roof Hatches

07 72 36 – Smoke Vents