Spike's Calculators

# Construction Math

## Solving Unknown Lengths and Angles # II Dual Pitched Roof

Solving for length's aa and ab
Solving it Spikey style!!

Before you can find the angles and different lengths you first need to solve for length's aa and ab to find where the roof peak is located in relation to the side walls.

To do that: add the values of both rises from the pitches together.

An example:
What is Known:
Roof pitch no 1 = 9/12
Roof pitch no 2 = 5/12
length a = 20'

Adding the two rise values together: 9 + 5 = 14
Divide "length a" by this number:
20 / 14 = 1.4285714286, this becomes the
multiplier

To solve for "length aa" take the rise of the opposite pitch, pitch #2 = 5 and multiply it with the multiplier:

Length aa = 5 * 1.4285714286 = 7.14285714' = 7' 1 11/16"

To solve for length ab take the rise of the opposite pitch, pitch #1= 9 and multiply it with the multiplier:

length ab = 9 * 1.4285714286 = 12.8571428' = 12' 10 5/16"

Roof Pitch One / 12
Roof Pitch Two / 12
Length a ft in n
d

#### Results:

 Length aa in Decimal Format ft Length aa ft in Length ab in Decimal Format ft Length ab ft in