Roof Slope Multiplier Table

The hip and valley factor varies according to the slope of the roof as shown in the table below.

Roof slope multiplier table.

Step 3 multiply step 1 and step 2 i e. Roof pitch refers to the measurement of the slope of a roof and you express this as a ratio. If the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps. Simply locate a roof rafter board place the end of the level against the bottom edge and measure from the 12 inch mark vertically to the bottom edge of the rafter.

If asphalt shingles are to be installed on a low slope roof special steps are required to avoid short roof life and roof leaks. Notes to the table above. The first thing that you need to understand before picking any selections from a roof pitch multiplier chart is to ensure that it s affordable. 800 multiplied by 1 16.

Typically the steeper the roof is the higher the price will be. The roof pitch multiplier is a number that allows you to find the total surface area of your roof. Some sources consider low slope to include 3 12 pitch roofs. For example if you measure 4 inches the pitch of your roof is 4 12.

The following table shows how the same common roof slopes can be expressed using rise in run ratios degrees and percentages. Find the square root of the result. 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. So the actual roof surface if it were laid down flat on the ground would be 1 118 times larger than the footprint of the roof.

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. Low slope roofs are from 0 to 3 12 in pitch. Step 2 find the value of 7 12 from the roof slope multiplier table which is 1 16. Divide the rise by the run the run is 12.

Although there s isn t any standard pitch of a roof used on all kinds of sloped roofs you can determine the range of pitches by using a roof angle calculator and by considering factors like the local climate and roofing materials. See below after the table for directions on how to convert any roof slope from one form to another even roof slopes not shown in the table. That gives you 5 590 square feet which is the actual area of the surface of the roof. This is useful since the area of the roof itself is often difficult to measure by hand.

Step 1 multiply 20 and 40 which equals 800. And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier. Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118. Simply multiply this number by the area covered by a sloped roof to obtain the total surface area of the roof itself.

It s just a little math. Also see our page quick reference. Understanding the roof pitch chart process.