how to figure the length of a false gable ridge

How to Determine the length of a False Gable Ridge

This one is easy! As easy as this is I can't tell you  how many times I've seen good carpenters put a level cut on a ridge board; stick it up there and mark it with a level. While you may still want to check your work this formula will make quick work of framing a false gable.  Study the diagram below. Click the image to enlarge into a new window.

    To determine the length of the ridge for a false gable when the pitches are different;  first: find the "total rise" by of the false gable by multiplying the run in feet by the rise after subtracting 1/2 the ridge thickness. Next divide the "total rise" by the other roof pitch.

For example 10/12 on a 8/12

Run - 1/2 ridge thickness = 5'

10/12 run = 5': 5 x 10 =50

50 ÷ 8 = 6.25' or 6' 3"

note* to change tenths of a foot to inches multiply the decimal portion by 12. For example .25 x 12 = 3"

You can even cut all the other rafters in advance by using the tables on the framing square " difference in length of jacks" if the pitches are the same. Of course if the pitches are the same then the ridge will be the same as the run (minus 1/2 the ridge thickness). 

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How to determine the length of the ridge on a hip roof.

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