Minimum Roof Slope Angle

This is the basis for calculating the angle which is approximately a 1 19 degree slope.

Minimum roof slope angle.

Express the slope of a metal roof by a ratio which indicates the pitch of the roof. Metal roof shingles can only be installed on roof slopes of 3 12 or greater 25 slope. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. Roof slope equivalents as rise.

Determine the minimum slope of the roof based on the roofing material. According to this code the minimum slope for asphalt shingles is 17 degrees or two vertical units to twelve units in the horizontal. That works out to about nine degrees if that works better for you. The picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7.

Remember metal roofing is more expensive than shingles. What is the minimum slope for an asphalt shingle roof. You need to consider the slope requirements of each panel to determine this minimum slope. The minimum slope of a roof depends on the roof s profile.

The profile is the shape taken by the sheets when you bend them to form panels. The minimum requirement is 2 12. This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units. The 2 12 number is rise over run or two units of vertical for every 12 units horizontal.

The following table provides the minimum required. Asphalt shingles continue to be the most widely installed roof covering option in north america. In case a slope greater than this is necessary then a double underlayment application must be used as per the requirements of the international building code. 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.

Run in degrees and as percentage 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 pitch for shingles is 1 6 which is equivalent to 4 inches rise to 24 inches run. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. They provide excellent weather resistance great value and now more than ever a tremendous range of beautiful designs and color blends.