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Flat Roof

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Flat roofs, also known as Low Slope roofing has a surface which is almost level in contrast to the many types of roofs with defined slopes. The slope of a roof is properly known as its pitch, and flat roofs can have up to approximately a 10 degree slope.

The National Roofing Contractors Association defines a low-slope roof as having a slope of 3/12 or less (3 feet of "drop" in a 12 foot span). Most modern roofing materials and codes require a positive slope that will dry out within 72 hours, thus even a "flat" roof needs some slope nowadays.

Flat roofs are an ancient form mostly used in arid climates, in some places allowing the roof space to be used as a living space. Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world, due to the fact that a significant savings in square foot cost is achieved by avoiding building expansive framed truss systems found on large conventional structures.

Traditionally the smelly, hot, physically demanding and sometimes dangerous work of hot tarring built up gravel ballasted flat roofs [BUR] has often meant that uneducated fitters of doubtful reputation have done work to a poor standard: This together with a lack of regular inspection and maintenance has meant that flat roofs have a poor reputation and there can be a unwillingness to invest in or to build them, which is unfortunate, given the potential usefulness of flat areas, the more so with the excellent performance of modern membranes, many of which come with long warranties, superior wind uplift and impact resistance, and provide an durable roof covering.

Modern flat roofing membrane systems tend to be sensitive to human traffic. Anything which produces a crack or puncture in the waterproofing membrane can quite readily lead to leakage, though our favorite low slope EPDM roof system resists this type of damage.

Flat roofs can fail, for example, when subsequent work is carried out on the roof and incompatible repair materials are used (asphalt rain patch on TPO for example), when new through-roof service pipes/cables or hot gas ducts are installed, or when plants such as air conditioning units with curbs are installed. A good roofer should be called to make sure the roof and curb flashings are properly watertight before the HVAC unit is left as complete. For one-off work, old carpet or smooth wooden planks for workers to walk or stand on will usually provide reasonable temporary protection of a membrane surface.

In trafficked areas, proper advisory/warning signs should be put up on flat roofing (they can be slick), and walkways of rubber matting, wooden or plastic duck-boarding etc. should be installed to protect the roof membrane. Stone or concrete paver blocks can be fitted some Low Slope Roof membranes. There are designer membranes for flat roofs that are specifically made for use on exterior decks abutments for additional living space, particularly in urban environments.