A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a 4 in 12 slope.
2 inch per foot roof slope.
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.
Strangely enough if a pitch of 6 inches rise per foot is entered then the degrees generated is not 22 5º it is 26 6º.
However roof pitch is technically measured and defined differently.
The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.
Feet inches enter run the flat level length then click pitch angle or rise to select then enter other known dimension angle or 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.
If the rise is 6 inches for every 12 inches of run then the roof slope is 6 in 12 the slope can be expressed numerically as a ratio.
A roof with a 6 rise for every 12 run has a 6 per foot or 6 in 12 pitch.
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 this is very useful information for many purposes especially for roof framing the slope sometimes called pitch is calibrated on speed squares.
Roof pitch or slope is a measure of vertical rise to horizontal run expressed in inches per foot.
I e 4 inches of rise per 12 inches one foot of run.
Roof pitch calculator results explained.
This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
This is the basis for calculating the angle which is approximately a 1 19 degree slope.
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.
Note that roof pitch is sometimes used in parallel with roof slope.
The triangle diagram will be re drawn to scale with all dimensions marked.
According to the international building code the typical built up flat roof that uses tar or asphalt goes by the guideline that for every foot 12 inches of a flat roof a minimum of inch must step up or down.
A 12 12 roof pitch would be selected as 12 inches of rise per foot with no fraction and the value generated by the calculator would be 45º.
However you can only use this pitch with built up roofing or specialized synthetic roofing.