There are three major types of flat roofing used in residential home applications. These include Built-Up Roof, Modified Bitumen and Rubber Membrane. Below you’ll find a brief explanation along with some pro’s and con’s of each material.
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.
Pros: Gravel is an excellent fire retardant. Attractive for windows and decks that overlook the roof. It’s the cheapest of the four roof varieties.
Cons: Very heavy. Joists sometimes have to be strengthened to sustain the weight. Messy and difficult to install and installation is not recommended for occupied homes. This type of roof is often hard to find the source of leaks.
A single-ply rolled roof similar to ice-and-water shield, but impregnated with a mineral-based wear surface. Torch-down style systems involve heating the adhesive as the material is unrolled. There are also peel-and-stick systems which are potentially safer and easier.
Pros: Its light-colored mineral surface reflects heat and cuts energy bills. Its price is in the middle of the pack.
Cons: Torch-down application is a fire hazard, and not recommended for occupied buildings. It’s not as scuff- or tear-resistant as rubber-membrane roofs (as discussed below).
EPDM (short for ethylene propylene diene monomer) is true rubber. This 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 in place.
Pros: Material is relatively light yet highly resistant to scuffs and tears. Leaks are easy to patch.
Cons: Costs more than BUR or modified bitumen. It’s also more vulnerable to punctures than other choices.