The Best Flat Roof Coating Materials

Single-Ply Roofing

• The most common flat roofing on the market, single-ply roofing comes in panels from .45 to .95 inch thick and 6 to 12 feet wide that are glued to the roof or attached by barbed plates and corrosion resistant fasteners. Panels of black ethylene propylene diene monomer (EPDM) rubber held together by adhesives are competitively priced, easy to apply and are the most popular single-ply roofing on the market. Panels of more expensive polyvinyl chloride (PVC), usually gray or white, are welded together chemically or by heat. Panels of black or white thermoplastic olefin (TPO) are laminates of polypropylene and ethylene propylene polymers with seams welded by hot air. TPO panels are newer on the market than PVC and are cheaper.

Built-Up Roofs

• You apply layers of paper saturated with asphalt on top of one another in cross-crossed fashion for a BUR covering. Because a BUR roof absorbs heat, you have to top it with a reflective coating, usually gravel or a special sheet. Add a new layer of saturated paper every 10 years. You need to completely tear off and replaced a BUR after 10 to 30 years. The cost of buying and installing a BUR is generally low compared with other flat-roof coverings, but they are difficult to inspect and maintain.

Spray-On Roofing

• You spray insulation onto a roof then cover it with urethane or acrylic and top that with a thin layer of sand or tiny crushed stones. The sand or stones protect the acrylic or urethane from ultraviolet rays. Spray foam roofing materials are easy to apply and repair with caulking, but you have to reapply them every 10 years.

Paint-On Protection

• You paint reflective white liquids called cool roof coatings on roofs to extend their life and protect them from weathering, ultraviolet radiation and damage caused by heat and cold that makes them expand and contract. You ordinarily apply them on older EPDM roofs and smooth roofs made of modified asphalt that are covered with dirt and debris that is difficult to clean. The Lawrence Berkeley National Laboratory found that cool roof coatings lose about 20 percent of their reflective ability over time, most of it in the first year.