Measure with a speed square.
1 8 roof factor.
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.
Image 1 12 to 12 12 roof pitch 7 12 pitch.
For example if you measure 4 inches the pitch of your roof is 4 12.
If the rise is 4 feet over a 24 foot span then the roof pitch was said to be 1 to 6 the pitch can be expressed numerically as a fraction.
8 1 x 12 scale factor 96.
Then multiply the square footage with the roof pitch factor to get the total area of the roof.
The pitch of this roof is 4 8 12.
The calculator above can handle much of this math.
1 8 1 0 invert the fraction and multiply by 12.
The maths behind this number is that it is the square root of rise run 2 1.
To convert an engineering drawing scale to a scale factor.
For example given a roof with.
Select the desired scale.
The roof slope factor chart also consists of conversion factors to determine the slope of the roof.
A roof that rises 8 feet over a 24 foot span was said to have a 1 to 3 pitch.
For example the roof layer that protrudes above the roof is 1 so add 1 to your tape reading.
That is if your tape reads 7 then add 1 that will give you 8 12.
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.
The headache of using pythagoras and trigonometry can be spared by making use of these charts.
The pitch fraction represents a certain amount of vertical rise over the entire span.
Valley hip factor.
Set the level on the edge of the speed square as shown below then place the heel of the speed square on a rafter or gable edge of the roof.
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.
This will give you the rise over run or pitch.
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.
20 x 12 scale factor 240.
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.
Select the desired scale.
A speed square and level can be used to easily find the pitch of a roof.