Miniumum Slope For Flat Roof

The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.

Miniumum slope for flat roof. The minimum slope for standing seam of roof systems shall be one quarter unit vertical in 12 units horizontal 2 percent slope. Depending on the roof profile there are minimum roof slope requirements for each panel which need to be considered. Asphalt shingles minimum roof slope roof pitch r905 2 2. 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.

This is the basis for calculating the angle which is approximately a 1 19 degree slope. 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. Asphalt shingles can only be installed on roof slopes of 2 12 or greater. 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.

In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code. For standing seam metal roof panel systems a 1 4 12 minimum roof slope is prescribed. Asphalt shingles continue to be the most widely installed roof covering option in north america.

The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run. Flat roofs which aren t perfectly flat require a small slope to allow for water runoff. This 1 4 12 minimum roof slope requirement also applies to spray polyurethane foam spf roof systems in new construction. 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.

For metal panel roof systems with nonsoldered seams with applied lap sealant ibc 2018 prescribes a 1 2 12 minimum roof slope. Low pitched roofs are generally difficult to maintain and you need special materials to prevent leaks. However you can only use this pitch with built up roofing or specialized synthetic roofing. This means for every 12 horizontal units the roof must rise a minimum of 2 vertical units.

The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems.