Minimum Roof Pitch Angle

Asphalt shingles continue to be the most widely installed roof covering option in north america.

Minimum roof pitch angle.

To convert between american roofing ratios and pitch degrees follow these steps. Roof pitch and corresponding angles. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. Use the following formula which also describes a right triangle.

Find the inverse tangent of the pitch to find the angle in degrees. A 4 12 pitch is around 18 5 degrees but not exactly. The minimum requirement is 2 12. On blue prints architects engineers usually display the pitch of a roof in the format shown on the image where number 4 represents a rise and number 12 represents a length.

High pitched roofs often need extra fasteners and their pitch can be as high as 21 12. A shingle roof like this north dallas garage in the photo above may have a failure no matter how good a job the installer did. The 2 12 number is rise over run or two units of vertical for every 12 units horizontal. A ratio is the most common way of expressing roof pitch or roof slope but degrees are also possible.

Divide the first part of the ratio by 12 to work out the pitch. The recommended minimum roof pitch for shingles is 2 12 or simply two units of vertical rise to every twelve units of horizontal span. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.

This means if a roof rises 4 in the length of 12 your roof pitch would be 4 12 or 18 43 degrees. So the pitch of a roof is determined by how many inches the slope rises for every 12 inches it runs horizontally. However you can only use this pitch with built up roofing or specialized synthetic roofing. You can also calculate roof pitch even without using a roof slope calculator.

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. However it is regrettable that many installers usually ignore this requirement due to the desire for a quick installation process. If a roof increases in height by four inches for every foot of horizontal run it is considered to have a 4 in 12 pitch or just a 4 pitch talk in terms of pitches and you will always be understood in the roofing universe.

What is the minimum slope for an asphalt shingle roof.