Minimum Slope For Flat Roof

Flat roofs which aren t perfectly flat require a small slope to allow for water runoff.

Minimum 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. 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. The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. The minimum roof pitch for shedding snow is around 30 or a 6 12 or 7 12 slope although this is not a definite as the material of your roof the direction of the snow and wind are some factors that can affect whether or not snow will slide as roofs of as little as 10 have been reported to shed snow.

However you can only use this pitch with built up roofing or specialized synthetic roofing. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run. 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.

Generally such roofs have a pitch ranging from 1 2 12 to 2 12. The minimum slope for a flat roof is 1 4 per foot or 1 4 12 but some owners or insurance companies require a minimum slope of 1 2 per foot. In general the minimum slope for a flat roof is 1 0 but as stated earlier this is only possible in theory. Asphalt shingles minimum roof slope roof pitch r905 2 2.

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 is the basis for calculating the angle which is approximately a 1 19 degree slope. This means for every 12 horizontal units the roof must rise a minimum of 2 vertical units. They provide excellent weather resistance great value and now more than ever a tremendous range of beautiful designs and color blends.

Asphalt shingles continue to be the most widely installed roof covering option in north america. Asphalt shingles can only be installed on roof slopes of 2 12 or greater.