Minimum Slope For Flat Roof

This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units.

Minimum slope for flat roof.

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. This is the basis for calculating the angle which is approximately a 1 19 degree slope. In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.

The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code. 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. The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. For example the international building code 2018 edition ibc 2018 prescribes a 1 4 12 minimum roof slope for asphalt built up polymer modified bitumen thermoset and thermoplastic single ply and liquid applied membranes in new construction.

Minimum roof slope roof pitch r905 4 2 metal roof shingles can only be installed on roof slopes of 3 12 or greater 25 slope.