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 slope multiplier table.
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.
800 multiplied by 1 16.
Also see our page quick reference.
It s just a little math.
And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier.
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 varies according to the slope of the roof as shown in the table below.
Step 1 multiply 20 and 40 which equals 800.
For example if you measure 4 inches the pitch of your roof is 4 12.
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.
Degrees to roof pitch rise in run to see a table.
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.
Typically the steeper the roof is the higher the price will be.
If the home measures 20 x 40 and has a 7 12 roof then to calculate the slope of the roof follow these steps.
Step 3 multiply step 1 and step 2 i e.
Divide the rise by the run the run is 12.
For any roof slope expressed as x in 12 rise in run the hip and valley factor is determined by finding the square root of rise run 2.
This will give you the rise over run or pitch.
This is useful since the area of the roof itself is often difficult to measure by hand.
Find the square root of the result.
The roof pitch multiplier is a number that allows you to find the total surface area of your roof.
Notes to the table above.
Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118.
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.
Low slope roofs are from 0 to 3 12 in pitch.
Understanding the roof pitch chart process.
Simply multiply this number by the area covered by a sloped roof to obtain the total surface area of the roof itself.
Roof pitch refers to the measurement of the slope of a roof and you express this as a ratio.
Some sources consider low slope to include 3 12 pitch roofs.
Step 2 find the value of 7 12 from the roof slope multiplier table which is 1 16.
That gives you 5 590 square feet which is the actual area of the surface of the roof.
