Roofs are one of the universal structures found on all buildings. Their purpose is primarily to shed water off the building and to prevent it from accumulating on top. To achieve this goal, Roofs may be highly pitched (sloped) or low sloped in form. Low sloped roofs are commonly found on industrial/commercial type structures. Pitched roofs are the primary design found on residential homes. The most common type of low sloped roof for industrial/commercial structures are the conventional built-up-roof (BUR), modified bitumen, or single plies (EPDM, PVC, TPO). Metal standing seam roofs are becoming increasingly common on low sloped roof assemblies.

Residential roof designs in mild climates or where there is little precipitation tend to exhibit lower pitched roofs and drainage at the exterior wall; an example of residential flat roof is that of the adobe construction in the American Southwest. In northern climates, where temperatures drop below freezing, or in southern climates with high temperatures, the need for greater thermal resistance will dictate the type of roof design as well as the waterproofing membrane specification. In areas that have a high accumulation of snow, such as Buffalo USA or Montreal Canada, a minimum slope of 6 inches in 12 inches (6/12) of roof surface is required. Roof pitches may exceed 45 or 50 degrees.

Cool roofs and green roofs are becoming increasingly popular, and in some cases are mandated by local codes. Cool roofs are defined as roofs with both high reflectivity and high emissivity. Green roofs have soil placed over the waterproofing membrane in which plants and even trees are planted.

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