Roof Slope Defined

This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.

Roof slope defined.

Slopes greater than 18 12 are found on a frame roofs and some mansard style roofs. 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. 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. Roof slope is the amount of vertical change in height as a ratio of horizontal distance traveled also expressed as inches of rise per foot of horizontal run or cm of rise per m of horizontal run.

Roof slopes are most commonly defined by the rise over run ratio. A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a 4 in 12 slope. Slope is the incline of the roof expressed as a ratio of the vertical rise to the horizontal run where the run is some portion of the span. If asphalt shingles are to be installed on a low slope roof special steps are required to avoid short roof life and roof leaks.

The pitch of a roof is its vertical rise over its horizontal span. I e 4 inches of rise per 12 inches one foot of run. Definition of roof slope. Roof pitch defined and explained pitch is the term used to describe the angle slope or slant of your roof.

See low slope roofing. The ratio can be indicated by a division slash separating the numbers such as 2 12 or 7 12. In the roofing trade the go to term is pitch and it is expressed in terms of 12 inches so the pitch of a roof is determined by how many inches the slope rises for every 12 inches it runs horizontally. Low slope roofs are from 0 to 3 12 in pitch.

Some sources consider low slope to include 3 12 pitch roofs. Roof slope can also be described as the angle of change in elevation expressed in one of several forms. This ratio is always expressed as inches per foot.