This will give you the rise over run or pitch.
Roof pitch factor multiplier.
Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118.
And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier.
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 2 find the value of 7 12 from the roof slope multiplier table which is 1 16.
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.
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.
For example if you measure 4 inches the pitch of your roof is 4 12.
Determine how many square feet of roof area a building has by measuring blueprints or plans.
Step 1 multiply 20 and 40 which equals 800.
A 10 slope roof should not be confused with a 10 pitch roof as a 10 slope roof means that the roof rises by ten inches for every foot of run.
The roof slope factor chart also consists of conversion factors to determine the slope of the roof.
Determine how many square feet of roof area a building has by measuring from the ground.
This roof pitch chart will give you your multiplier.
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.
It is sometimes called the roof pitch multiplier.
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.
The headache of using pythagoras and trigonometry can be spared by making use of these charts.
That gives you 5 590 square feet which is the actual area of the surface of the roof.