Homeowners can choose among different kinds of flat roofs.

All types cost $250 to $350 per “square” (100 square feet). Flat roofs usually come with a 10-year warranty but the roofs can last 25 years if properly installed and maintained.

Modified Bitumen
A single-ply rolled roof similar to an ice-and-water shield but impregnated with a mineral-based wear surface. Torch-down systems involve heating the adhesive as the material is unrolled. Newer peel-and-stick systems are safer and easier.

Its light-colored mineral surface reflects heat and cuts energy bills. Its price is in the middle of the pack.

Built-Up Roof (BUR)
The traditional hot-tar-and-gravel roof is built from three or more plies of waterproof material alternated with hot tar and ballasted by a layer of smooth river stone. Once made of tar paper, these types of roofs gradually are using more advanced materials such as fiberglass membranes.

Gravel is an excellent fire retardant. Attractive for windows and decks that overlook the roof. It’s the cheapest of the four roof varieties.

Rubber Membrane
EPDM (short for ethylene propylene diene monomer) is a true rubber. The durable material resembles an inner tube, but it’s engineered to resist damage from sunlight. EPDM can be mechanically anchored with fasteners, ballasted with stone, or glued.

The material’s relatively light yet highly resistant to scuffs and tears. Leaks are easy to patch.