When to Coat a Flat Roof

Coating and Maintenance

• Regular inspections and repairs help control the need for coating. Coating, though, is part of regular maintenance and, far from waiting until just before the roof fails, should take place whenever signs of fading, drying or minor cracking begin. Depending on the type of roof and climate, the timetable for coating can begin from immediately to five years after the roof is installed. Repeat coatings can take place every five years or more to substantially extend the life of the roof.

Built-Up Roofs

• For years, roofing consisted of layers of felt sandwiched between layers of bitumen, consisting of asphalt and gravel that provided a water-resistant seal. Today, combinations of varied percentages of coal tar, asphalt and cement cover bases of felt, fiberglass or “organic” materials including cotton and recycled paper. These composition roofs, called BURs, last from 15 to 25 years, depending on composition and climate. They need one year to cure and may be coated thereafter every 5 to 10 years. Silver paint has been used for many years; elastomeric coating is a newer synthetic that coats and waterproofs for up to 10 years and can double the life of the roof.

Membranes

• If a little elastomeric coating is good, a roof-covering membrane of it is better. Ethylene propylene diene monomer (EPDM), and polyvinyl chloride (PVC) sheets 25 to 40 feet wide make a roof waterproof for 10 to 12 years. Other materials may be described as thermoplastic, thermoset or spray applied urethane foam systems. Coating these black “rubber roofs” is a necessity for energy conservation. It does not follow, however, that if a little is good, a lot is better. Too many coatings can become heavy, crack and compromise the underlying roof. Always consult a professional in the trade regarding materials and timing.

Metal Roofs

• Copper and tin roofs are among the most maintenance-free and long lived roofs. Today’s copper and stainless steel roofs may look great for decades. Older galvanized “tin” roofs require a coating of paint immediately after installation and periodically thereafter. Inspect the roof annually in spring or fall for fading and wear from heat or hail.