Roof Pitch Factor Table

Notes to the table above 1.

Roof pitch factor table.

One medium to describe the roof pitch is in 12 runs. This will give you the rise over run or pitch. Roof pitch refers to the slope which the rafter creates. Two most common methods 4 12 or 4 12 are used for marking the pitch of a roof.

This numerical figure is significant as not everybody can understand the technical measurements. For roof slopes expressed as x in 12 rise in run the roof pitch multiplier is determined by finding the square root of rise run 1. The combination of two numbers are used to display or show the roof pitch. Often you express roof pitch as the ratio between the rise and the run in the form of x 12.

The hip and valley factor varies according to the slope of the roof as shown in the table below. Some sources consider low slope to include 3 12 pitch roofs. For example if the pitch of the roof is 6 then it is written as 6 12. Low slope roofs are from 0 to 3 12 in pitch.

Therefore it s important to understand the roof pitch chart process completely. The horizontal measurement or roof run and the vertical measurement the roof rise are the most important factors to get right when making the roof pitch calculations that you need to make. A roof pitch multiplier also called a roof pitch factor is a number that is multiplied by the area covered by a sloped roof to produce the area of the actual surface of the roof. On blue prints architects engineers usually display the pitch of a roof in the format shown on the image where number 4 represents a rise and number 12 represents a length.

The whole table of roof pitch and slope gives a conversion factor so as to obtain a numerical figure of the slope. Divide the rise by the run the run is 12. You can assess this in two ways either as the roof pitch angles which the rafters make with the horizontal or the proportion between the run and the rise of the roof. This means if a roof rises 4 in the length of 12 your roof pitch would be 4 12 or 18 43 degrees.