Manufacturer’s Warranty & Minimum Roof Pitch You should always check the manufacturer’s product data sheets for the actual product you intend to use, and always follow the manufacturer’s installation instructions. Recommended Minimum Roof PitchĮven though building codes state the minimum roof slope allowed for a material in general, specific roofing products may have different recommended minimum roof slopes. Read on to learn more about roof slope requirements, or scroll to the end to see the minimum roof slope chart with all the different roofing materials. Most other pitched roof roofing materials, such as clay tile or metal roofing panels, require minimum roof slopes from 2½-in-12 to 4-in-12. Pitched roofing materials (also called “steep-slope” materials) have a much wider range of minimum pitches than low-slope materials.Īsphalt roof shingles have a minimum roof slope requirement of 2:12 with a double application of underlayment, and 4:12 otherwise. These materials need a slope in order to function. Water would get through the roof under virtually every shingle. If shingles, tiles, or other pitched roof materials were installed on a low-slope roof, they would leak everywhere. Unlike low-slope roofing materials, which are put together to form a waterproof barrier on the roof, pitched roof systems are water-shedding, and depend on gravity to get water off the roof as quickly as possible. This low-slope roof is required to have a minimum pitch of 1/4 inch in every 12 inches to ensure water drainage. Coal tar pitch is an interesting case, since it also has a very low maximum recommended roof slope (½-in-12).Īll other roofing materials used on flat roofs require a minimum slope of at least ¼-in-12 (1.19°), which is why flat roofs are properly known as “low-slope” roofs. The lowest roof pitch allowed by code for any type of roof is ⅛-in-12 (0.60 degrees), applicable only to coal tar pitch roof systems. Long-term ponding water is detrimental to almost every type of roofing material. On a dead-level roof, the slightest bit of deck deflection or any obstruction will lead to water ponding in place on top of the roof. Some minimum amount of slope is required to ensure that water will drain off the roof. Minimum Roof Pitch for Low-Slope RoofsĪ truly flat roof with zero slope (a dead-level roof) is both undesirable and generally prohibited by code. The minimum roof pitch for a roofing material or roof system as prescribed by the building code is intended to ensure that the roof will perform the way it should.ĭue to the way different roofing materials or roof assemblies work to keep water out, some types of roofing simply don’t function properly if they are pitched too low (or too high, but that’s almost never an issue). (See the minimum roof pitch for all roof types in our chart below.) IntroductionĮvery type of roof has a minimum roof slope allowed by code.
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