Low-Slope Roof

Built-Up Roof Systems

Built-up roof (BUR): a continuous, semi-flexible roof membrane, consisting of multiple plies of saturated felts, coated felts, fabrics or mats assembled in place with alternate layers of bitumen, and surfaced with mineral aggregate, bituminous materials, a liquid-applied coating or a granule-surfaced cap sheet.
Built Up roofs can have different surfaces to impact durability.
Smooth-surfaced roof: a roof membrane without mineral granule or aggregate surfacing.
Aggregate: Crushed stone, crushed slag, water-worn gravel any granular material.

Modified Bitumen Roof Systems

Modified bitumen: (1) a bitumen modified by including one or more polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.); (2) composite sheets consisting of a polymer modified bitumen often reinforced with various types of mats or films and sometimes surfaced with films, foils or mineral granules.
Styrene butadiene styrene copolymer (SBS): high molecular weight polymers that have both thermoset and thermoplastic properties, formed by the block copolymerization of styrene and butadiene monomers. These polymers are used as the modifying compound in SBS polymer modified asphalt roofing membranes to impart rubber-like qualities to the asphalt.
Modified bitumen roofs can have different surfaces to impact durability.
Smooth-surfaced roof: a roof membrane without mineral granule or aggregate surfacing.
Mineral-surfaced roofing: roofing materials whose surface or top layer consists of a granule-surfaced sheet.
Modified bitumen roofs can be installed in two ways.
Torch-applied: method used in the installation of polymer modified bitumen membranes characterized by using open flame propane torch equipment.
Heat welding: method of melting and fusing together the overlapping edges of separate sheets or sections of polymer modified bitumen, thermoplastics or some uncured thermoset roofing membranes by the application of heat (in the form of hot air or open flame) and pressure.

Single-ply Roofing Systems

Single-ply roofing: a roofing system in which the principal roof covering is a single layer flexible membrane often thermoset or thermoplastic membrane. Membranes are field applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers. They are often strengthened by the addition or incorporation of one or more reinforcing materials, including woven or nonwoven glass fibers, polyester mats or scrims, nylon, or polyethylene sheeting.
Single Ply roofing systems can be installed in several ways.
Ballast: a material, such as aggregate or precast concrete pavers, which employs its mass and the force of gravity to hold (or assist in holding) single-ply roof membranes in place.
Loose-laid membrane: a ballasted roofing membrane that is attached to the substrate only at the edges and penetrations through the roof.
Mechanically fastened membranes: generally used to describe membranes that have been attached at defined intervals to the substrate.
There are many types of single ply roof systems.
Polyvinyl chloride (PVC): a synthetic thermoplastic polymer prepared from vinylchloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers and other modifiers. Rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials.
Thermoplastic olefin membrane (TPO): a blend of polypropylene and ethylene-propylene polymers. Colorant, flame retardants, UV absorbers, and other proprietary substances which may be blended with the TPO to achieve the desired physical properties. The membrane may or may not be reinforced.
Ethylene interpolymers (EIP): a group of thermoplastic compounds generally based on PVC polymers from which certain single-ply roofing membranes can be formulated.
Ethylene propylene diene terpolymer (EPDM): designated nomenclature of ASTM for a terpolymer of ethylene, propylene and diene. EPDM material is a thermosetting synthetic elastomer.
Chlorinated polyethylene (CPE): a thermoplastic material, used for single-ply roof membranes, composed of high molecular weight polyethylene that has been chlorinated with a process that yields a flexible rubber-like material.
Chlorosulfonated polyethylene (CSPE or CSM): probably best known by the DuPont trade name Hypalon, a synthetic, rubber-like thermoset material, based on high molecular weight polyethylene with sulphonyl chloride, usually formulated to produce a self-vulcanizing membrane. Classified by ASTM Standard D 5019.