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.

So the pitch of a roof is determined by how many inches the slope rises for every 12 inches it runs horizontally. A 12 12 pitch roof has a pitch angle of 45. 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. The minimum requirement is 2 12.

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. Find the inverse tangent of the pitch to find the angle in degrees. To convert between american roofing ratios and pitch degrees follow these steps. However you can only use this pitch with built up roofing or specialized synthetic roofing.

They have a pitch ranging from 4 12 to 9 12. The recommended minimum roof pitch for shingles is 2 12 or simply two units of vertical rise to every twelve units of horizontal span. Roof pitch and corresponding angles. The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.

Divide the first part of the ratio by 12 to work out the pitch. Asphalt shingles continue to be the most widely installed roof covering option in north america. Use the following formula which also describes a right triangle. 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. 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. A ratio is the most common way of expressing roof pitch or roof slope but degrees are also possible. 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.

You can also calculate roof pitch even without using a roof slope calculator. High pitched roofs often need extra fasteners and their pitch can be as high as 21 12. What is the minimum slope for an asphalt shingle roof. The 2 12 number is rise over run or two units of vertical for every 12 units horizontal.

This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.