Rise Over Run Roof Pitch

If a roof slope rises say 4 inches when measured 12 inches along the bottom of a horizontal roof truss the roof slope is said to be 4 12.

Rise over run roof pitch.

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. Roofers express roof slope as rise or pitch measured in inches of vertical rise per foot of horizontal distance or run. The triangle diagram will be re drawn to scale with all dimensions marked. 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 run is the distance from the outside of the wall to the inside of the ridge. Visit this page using a phone or tablet to directly measure pitch and angles. Enter run the flat level length then click pitch angle or rise to select then enter other known dimension angle or pitch. 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.

Roof slopes are most commonly defined by the rise over run ratio. The same pitch is also sometimes written as 4 12 4 in 12 or 4 over 12. 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. It just means the top of the roof has to end out at a specific place.

Roof pitch is simply the slopecreated by the rafter. Enter the rise and run for the pitch length and angle of the rafter. For example a roof that rises 4 inches for every 12 inches of run has a 4 12 pitch. This is rarely is a whole number it is not a rare event and it is not a nightmare.

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. A a roof with a 6 rise for every 12 run has a 6 per foot or 6 in 12 pitch. It can be assessed in two ways either as the angle the rafter makes with the horizontal or the proportion between the rise and the run of the roof. Drag sliders to animate the results and diagram.

For example if the roof rises 4 feet and the span is 16 feet twice the run then the pitch is 4 16 or 1 4. Pitch is the incline of the roof represented as the ratio of rise to the span twice the run. Here is an online rise and run calculator which helps to calculate pitch slope and angle with the help of rise and run values. Roof pitch or slope is a measure of vertical rise to horizontal run expressed in inches per foot.

Roof pitch is often expressed as a ratio between rise and run in the form of x 12.