Slope Of A Roof Pitch

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

Slope of a roof pitch.

Most roof s have a pitch in the 4 12 to 9 12 range. The run is the measurement from the outside of one wall s top plate to a point directly below the center of the ridge picture 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. Squaring building lines example 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.

A pitch over 9 12 is considered a steep slope roof between 2 12 and 4 12 is considered a low slope roof and less than 2 12 is considered a flat roof. 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. How do you calculate the slope of a roof.

Use a level against the underside of the rafter you re measuring to get the most accurate value. The slope is the measurement of the rise of the roof to the run of the roof and is expressed as inches per foot in a ratio format. 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.