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On low-slope asphalt roofs, ponding water allows the oil solvent components of the asphalt to leach out and evaporate, leaving the roof membrane brittle and susceptible to cracking and leaking in the ponding location. [1] The time taken for water to saturate a zone, usually from rainfall, causing a pond to form, is referred to as the "ponding ...
Mechanically seamed metal with concealed fasteners contains sealant in seams for use on very low sloped roofs, suitable for roofs of low pitch such as 0.5/12 to 3/12 pitch. Flat-seam metal with or without soldered seams. Steel coated with a coloured alloy of zinc and aluminium. Stone-coated metal roofing.
Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world. The U.S.-based National Roofing Contractors Association defines a low-slope roof as having a slope of 3 in 12 (1:4) or less. [2] Flat roofs exist all over the world, and each area has its own tradition or preference for materials used.
The roof covering materials, siding, foundations, and all of the various penetrations through these surfaces must be water-resistant and sometimes waterproof. Roofing materials are generally designed to be water-resistant and shed water from a sloping roof, but in some conditions, such as ice damming and on flat roofs, the roofing must be ...
A flat roof includes pitches as low as 1 ⁄ 2:12 to 2:12 (1 in 24 to 1 in 6), which are barely capable of properly shedding water. Such low-slope roofs (up to 4:12 (1 in 3)) require special materials and techniques to avoid leaks. [4] Conventional describes pitches from 4:12 (1 in 3) to 9:12 (3 in 4). [4]
It protects the roof deck from rain before the roofing is installed. It provides an extra weather barrier in case of blow offs or water penetration through the roofing or flashings. It protects the roofing from any resins that bleed out of the sheathing. It helps prevent unevenness in the roof sheathing from telegraphing through the shingles.
Flat roofs actually slope up to approximately ten degrees to shed water. Flat roofs on houses are primarily found in arid regions. [2] In high-wind areas, such as where a cyclone or hurricane may make landfall, the main engineering consideration is to hold the roof down during severe storms. Every component of the roof, as of course the rest of ...
Bell-cast (sprocketed, flared): A roof with the shallow slope below the steeper slope at the eaves. Compare with bell roof. East Asian hip-and-gable roof; Mokoshi: A Japanese decorative pent roof; Pavilion roof : A low-pitched roof hipped equally on all sides and centered over a square or regular polygonal floor plan. [10]