How To Work Out The Slope Of A Roof

Access one of the rafters then take the measurement this way.

How to work out the slope of a roof.

Rafter rise run 1 5 6 2 25 36 38 25rafter 38 25 6 18 m. Locate the level s 12 inch mark. Use a level against the underside of the rafter you re measuring to get the most accurate value. The horizontal distance in the ratio will be 12 while the vertical distance is the measurement you took from the rafters.

Formula for calculating the slope the length of a slope is calculated using the pythagorean theorem. Recalculate this value into an angle. Finally you can find the roof pitch in the form of x 12. The slope of your roof is the ratio of the vertical distance or rise of the roof to the horizontal distance or run.

The most precise way to find the roof s slope is by measuring it from the underside. Calculate the roof pitch as the proportion of rise and run. Calculating roof slope is done by calculating the number of inches your roof slope rises vertically for every 12 inches it extends horizontally. The standard pitch of most residential roofs ranges between 4 in 12 and 9 in 12.

For example if your roof rises 7 inches for every 12 inches of horizontal run then your roof has a 7 in 12 pitch. Angle arctan pitch arctan 0 25 14. Square root width x width height x height slope length.