Rise Over Run Roof Pitch

Measure from the attic.

Rise over run roof pitch.

Pitch is written assuming a run of a foot or 12 inches so the ratio describes how much the roof rises for every foot of its run. The rise is the distance from the top of the roof to the bottom. Rafter rise run 1 5 6 2 25 36 38 25rafter 38 25 6 18 m. How to calculate the pitch of a roof method one.

Other than the 45 roof slope which is 12 in 12 none of the standard roof pitches 5 in 12 6 in 12 etc are equal to a whole degree. The run is the distance from the outside of the wall to the inside of the ridge. Angle arctan pitch arctan 0 25 14. So a 3 inch rise roof also described as a 3 in 12 roof means that for every 12 or foot of horizontal distance the height of the roof increases by 3.

This is rarely is a whole number it is not a rare event and it is not a nightmare. The same pitch is also sometimes written as 4 12 4 in 12 or 4 over 12. It just means the top of the roof has to end out at a specific place. The rise is basically the distance from the top of the roof to the bottom.

One method to find the pitch is to climb on the roof and measure the rise for a 12. Here is an online rise and run calculator which helps to calculate pitch slope and angle with the help of rise and run values. For example a roof that rises 4 inches for every 12 inches of run has a 4 12 pitch. Calculate the roof pitch as the proportion of rise and run.

Finally you can find the roof pitch in the form of x 12. A roof pitch that is based on a fixed rise and run and does not end up with a whole number is known as a bastard pitch. Measure from the roof. Recalculate this value into an angle.

The following table shows the roof pitch rise in run equivalents for all roof slopes in degrees from 1 to 72. Pitch rise run 1 5 6 25.