Framing & StructuralQuestion 323 of 700
CALCULATION: A common rafter runs horizontally 12 feet from the wall to the ridge and rises 9 feet. Ignoring overhang and cuts, what is the approximate rafter line length?
a.13 feet
b.15 feet
c.18 feet
d.21 feet
Explanation
The rafter line length is the hypotenuse: the square root of (12 squared + 9 squared) = square root of (144 + 81) = square root of 225 = 15 feet. This is a 3-4-5 triangle scaled by 3. 13 feet ignores the rise, 18 and 21 feet overstate the diagonal.
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