Formula Roof Pitch Multiplier

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.

Formula roof pitch multiplier. Now solving for c in the equation above gives. Rafter rise run this formula is from the pythagorean theorem. Here are the equations you may use to solve for the length of the slope and the rafter. Image 1 12 to 12 12 roof pitch 7 12 pitch.

Step 3 multiply step 1 and step 2 i e. The pitch of this roof is 4 8 12. Take the area of the roof s footprint say it s 5 000 square feet and multiply 5 000 by 1 118. If your roof is flat or has no more than a 3 in 12 pitch you can calculate its total square footage by simply multiplying the length by the width.

That gives you 5 590 square feet which is the actual area of the surface of the roof. 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. 48 10 4 8. Let s say it is equal to 1 5 m.

Step 2 find the value of 7 12 from the roof slope multiplier table which is 1 16. 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. You can also calculate roof pitch even without using a roof slope calculator. Use the following formula which also describes a right triangle.

And for a roof with a slope of 6 12 that number 1 118 is your roof slope multiplier. Roof pitch degree table. For example a 4 12 pitch roof that is 100 square feet. 800 multiplied by 1 16.

Calculate the roof pitch as the proportion of rise and run. Rafter rise run 1 5 6 2 25 36 38 25rafter 38 25 6 18 m. The formula for the roof pitch multiplier comes from the famous pythagorean theorem. 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.

Calculate the rafter length substituting these values into the following formula. The calculator above can handle much of this math. 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. Step 1 multiply 20 and 40 which equals 800.

Steep roofs measure your house at ground level then add in the roof s overhang for greater accuracy. Next multiply the footprint of the roof by the multiplier below for your roof pitch to find the overall roof area. Measure the rise of your roof. 100 1 054 105 4ft2.

Use our roof pitch calculator to find the pitch of your roof.