Miniumum Slope For Flat Roof

Generally such roofs have a pitch ranging from 1 2 12 to 2 12.

Miniumum slope for flat roof.

Flat roof slope minimum according to the international building code the typical built up flat roof that uses tar or asphalt goes by the guideline that for every foot 12 inches of a flat roof a minimum of inch must step up or down. Flat roofs which aren t perfectly flat require a small slope to allow for water runoff. It takes the manufacturer s recommendations the unique conditions of the roof as well as the skills and the expertise of the installer to arrive at the right slope. Low pitched roofs are generally difficult to maintain and you need special materials to prevent leaks.

Asphalt shingles continue to be the most widely installed roof covering option in north america. 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. Depending on the roof profile there are minimum roof slope requirements for each panel which need to be considered. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.

However you can only use this pitch with built up roofing or specialized synthetic roofing. In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. For metal panel roof systems with nonsoldered seams with applied lap sealant ibc 2018 prescribes a 1 2 12 minimum roof slope. The minimum slope for standing seam of roof systems shall be one quarter unit vertical in 12 units horizontal 2 percent slope.

The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. For standing seam metal roof panel systems a 1 4 12 minimum roof slope is prescribed. 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. This means for every 12 horizontal units the roof must rise a minimum of 2 vertical units.

This is the basis for calculating the angle which is approximately a 1 19 degree slope. The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. Asphalt shingles can only be installed on roof slopes of 2 12 or greater. The profile refers to the shape the metal sheets take when they bend to.

This 1 4 12 minimum roof slope requirement also applies to spray polyurethane foam spf roof systems in new construction.