The Best Flat Roofing Materials

Updated November 21, 2016

A flat roof, in contrast to the sloped form of a pitched roof, is horizontal or nearly horizontal. Both the design of a flat roof and the material used to cover it typically allow for water runoff from a very slight inclination. According to flat, more than 20 different types of flat roofing materials are available to homeowners and commercial building owners.

Built-Up Flat Roofs

Considered the most traditional of flat roofs, a built-up roof is constructed of three or more layers of waterproof material alternated with hot tar and laid in a crisscross pattern. Today's built-up roofs, usually ballasted with river stone, are made up of fibreglass materials rather than tar paper. The least expensive flat roofing option, a built-up roof includes a top layer of gravel, which protects the roof from UV rays and serves as an effective fire retardant.

Single-Ply Flat Roofs

Thinner and lighter than a built-up flat roof, a single-ply roof consists of a weatherproofing membrane that's adhered to a structure either with glue or fasteners and barbed plates. The most common type of flat roof for both residential and commercial use, today's single-ply roofs are available in an easy-to-use peel-and-stick material, making it a popular choice among homeowners who want to install a roof themselves. Types of single-ply roof materials include rubber roofing, TPO (thermoplastic polyolefin) and PVC (polyvinyl chloride).

Spray-On/Paint-On Flat Roofs

Spray-foam roofing requires a two-part installation process: a spray insulation is applied directly to the roof and then covered with a urethane or acrylic coating. In addition, a layer of sand or gravel is applied to the roof after both parts of the spray installation process is complete. Spray-on and paint-on roofing offers seamless insulation and provides a waterproof seal that spans the entire roof surface.

Flat Roofing Considerations

Flat roofs usually come with a 10- to-20-year warranty; however, if a flat roof is installed correctly and maintained properly through the years it can remain in good condition for as long as 25 years. When choosing a flat roof homeowners and building owners should consider which type of roof will best fit their budget, require the least amount of maintenance and repair, and be best suited to the prevailing climate. Choosing a supplier and an installer with expertise in flat roofing will help ensure the longevity of the roof and keep costs to a minimum.

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