Recommendations for a Low Slope 2 Pitch Roof

BUR

• Alternating layers of felt saturated with bitumen are called BUR (built-up roofing) systems, also called tar and gravel roofs. The bitumen waterproofing is made of asphalt, derived either from petroleum or coal tar. Up to four plies, each 36 inches wide, are applied in a crisscross fashion. These layers are topped with hot asphalt, gravel or other coatings. They are sometimes covered with a sheet of bitumen, combined with polymer plastics.

Single-Ply Membranes

• Commonly named for their chemical acronyms, single-ply membranes are manufactured sheets that are glued to low slope roofs. There are two types of single-ply membranes: thermoset materials cannot be softened after they are heated while thermoplastic membranes can be softened. EPDM rubber (Ethylene Propylene Diene Monomer), a thermoset, is the most widely used covering for roofs as low as 2:12. Panels of black or white EPDM, 7-1/2 to 50 feet wide, are glued together. EPDM is competitively priced and easy to apply. The two most commonly used thermoplastics applied to roofs as low as 2:12 are PVC (Poly Vinyl Chloride) and TPO (Thermo Plastic Olefin). PVC sheets 6 to 12 feet wide and 45 to 90 mils thick come in a range of colors, usually gray or white. PVC panels have a long history of dependability. TPO is newer on the market than PVC and less expensive. TPO sheets, usually 40 to 100 mils in thickness, are typically black or white and contain UV absorbers and flame retardants.

Modified Bitumen

• Rolls of reinforced fabrics saturated with bitumen-containing polymers are called modified bitumen. They have been applied to flat roofs in the U.S. since the 1970s. SBS polymer-modified bitumen (Styrene Butadiene Strene) is applied to cold adhesives or hot asphalt although some varieties are self-adhesive. Rolls of APP polymer-modified bitumen (Atactic Poly Propylene) are applied by heat and should not be applied directly to wood.

Spray Polyurethane Foam

• A pump pushes measured amounts of isocynate and polyol, the ingredients of a base layer, through two hoses to a spray gun that mixes them into sprays. A top layer of rubber-like plastic is sprayed onto the base layer or applied by hand or with power rollers. The top layer can also be a fabric saturated with a thermoset, including acrylic, butyl rubber, silicone, polyurethane or other plastics. The top layer protects the surface from ultraviolet rays and makes it fire resistant.