Flat Roof Slope Requirement

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Flat roof slope requirement.

The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. However you can only use this pitch with built up roofing or specialized synthetic roofing. Since they vary in quality as well as method of installation the choice preferred for a flat roof will ultimately have an effect on the final slope of the flat roof. For metal panel roof systems with nonsoldered seams with applied lap sealant ibc 2018 prescribes a 1 2 12 minimum roof slope.

The slope of a roof or pitch is determined by how many inches the roof rises over 1 foot or 12 inches. To put it in perspective the angle of this slope would be around 30 degrees. Let us recap on the minimum roof pitch required for each type of roofing material. Asphalt shingles require a minimum roof pitch of 2 12 or greater.

Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling. The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code. In order to achieve this drop a slightly steeper angle of 1 40 1 44 should be the aim when installing a flat roof as this accounts for surface. Cold roofs and warm roofs.

Metal roof shingles require a minimum roof pitch of 3 12 or greater. For standing seam metal roof panel systems a 1 4 12 minimum roof slope is prescribed. A roof of pitch 7 12 30 is manageable but caution should be taken. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.

An example for a steep sloped roof is 8 12. A roof pitch of 6 12 26 5 or less is considered easily walkable and no extra precautions are required. Asphalt shingles continue to be the most widely installed roof covering option in north america. The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems.

In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. This means that the rise of the slope goes up or down 8 inches for every 12 inches. In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. Normally 1 80 0 72 is the recommended minimum angle for a slope and this is universal across the vast majority of flat roofing systems regardless of the materials that they incorporate.

There are two types of flat roof.