You can use the following equations to find the length of the rafter and the slope.
Measuring slope of roof.
This is very useful information for many purposes especially for roof framing the slope sometimes called pitch is calibrated on speed squares.
Slope the slope of a roof is represented as x 12 where x is the number of inches in rise for every 12 inches of run.
A roof with a 6 rise for every 12 run has a 6 per foot or 6 in 12 pitch.
This ratio is always expressed as inches per foot.
The most precise way to find the roof s slope is by measuring it from the underside.
Generally roof pitch is calculated from the same formula that describes a right triangle.
A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a 4 in 12 slope.
Access one of the rafters then take.
Roof pitch or slope is a measure of vertical rise to horizontal run expressed in inches per foot.
Pitch is thus the ratio of the rise in inches to a 12 inch run and is often expressed using a semicolon for example 6 12.
Use a level against the underside of the rafter you re measuring to get the most accurate value.
Rafter rise run from the pythagorean theorem.
We use the level to measure out from the roof surface horizontally for a distance of 12.
Then from that point on our level we measure the distance straight up to point of contact with the roof surface.
Locate the level s 12 inch mark.
How do you calculate the slope of a roof.
How to calculate roof pitch.