Minimum Roof Pitch Angle

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.

Minimum roof pitch angle.

However you can only use this pitch with built up roofing or specialized synthetic roofing. The 2 12 number is rise over run or two units of vertical for every 12 units horizontal. 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. However it is regrettable that many installers usually ignore this requirement due to the desire for a quick installation process.

Use the following formula which also describes a right triangle. This means if a roof rises 4 in the length of 12 your roof pitch would be 4 12 or 18 43 degrees. So if your roof rises 4 inches for every 12 inches of horizontal length then the pitch of your roof is expressed as 4 12. They have a pitch ranging from 4 12 to 9 12.

This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement. Find the inverse tangent of the pitch to find the angle in degrees. Asphalt shingles continue to be the most widely installed roof covering option in north america. Roof pitch and corresponding angles.

You can also calculate roof pitch even without using a roof slope calculator. A 12 12 pitch roof has a pitch angle of 45. High pitched roofs often need extra fasteners and their pitch can be as high as 21 12. To convert between american roofing ratios and pitch degrees follow these steps.

Divide the first part of the ratio by 12 to work out the pitch. 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 minimum requirement is 2 12. What is the minimum slope for an asphalt shingle roof.

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. The recommended minimum roof pitch for shingles is 2 12 or simply two units of vertical rise to every twelve units of horizontal span. The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles. That works out to about nine degrees if that works better for you.

A 4 12 pitch is around 18 5 degrees but not exactly.