Roof Pitch Multiplier Table

If asphalt shingles are to be installed on a low slope roof special steps are required to avoid short roof life and roof leaks.

Roof pitch multiplier table.

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. The hip and valley factor is a number that is multiplied by the actual run horizontal distance of a common rafter to determine the length of a hip or valley rafter. 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. If you know the pitch of a roof you can use the numbers in the following pitch table to do the following.

This table provides the hip and valley factor for common roof pitches as well as the underlying equation for the factor. Low slope roofs are from 0 to 3 12 in pitch. The formula for the roof pitch multiplier comes from the famous pythagorean theorem. This roof pitch table displays a multiplier for adding for different roof pitches.

Notes to the table above. Where a is the rise of the roof b is the run of the roof and c is the rafter hypotenuse of the triangle with side lengths a and b. 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. Roof pitch multiplier table.

Determine how many square feet of roof area a building has by measuring from the ground. How to find your what roof pitch category. A roof pitch multiplier also known as a roof pitch factor is a number that when multiplied by the area covered by a sloped roof gives the actual area of the roof. Since pitch is the rise over a 12 inch run divide the run by 12 to get the multiplier in this case 120 12 10.

Typically the steeper the roof is the higher the price will be. We excluded roof multipliers for pitch below 3 and above 12 for the following reasons. The total run is the distance from the peak to the edge of the roof which in this case is the total width divided in half which is equal to 10 feet or 120 inches. The roof pitch multiplier table is very helpful in giving correct and reliable roof measurements and uses pythagorean theory.

Accurate roof calculations are achieved using this table and all you need to do is measure the roof width and length and then you are ready to do a roof pitch measurement. Make sure that this is going to be affordable for you as more materials and time are needed to construct steeper roofs. Now solving for c in the equation above gives. Some sources consider low slope to include 3 12 pitch roofs.