Roof Pitch and rafter length


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Old 07-03-09, 02:11 PM
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Question Roof Pitch and rafter length

Hello, we are planning on building a 12x12 storage building and we want to put a 3/12 roof pitch on it with a 1 foot overhang, but we are having trouble trying to find the length we need for the rafters and being a bit mathmatically illiterate (lol) we are having some trouble, can someone please tell me what the length would be? Thanks in advance!
 
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Old 07-03-09, 02:52 PM
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Would the rafter length be 7.21 feet?
 
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Old 07-03-09, 03:13 PM
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Rafters

8 ft. lumber (2x4?) will work for the rafters.
 
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Old 07-03-09, 03:25 PM
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Thank you for your helpBeer 4U2
 
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Old 07-04-09, 09:03 AM
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This is the basic rundown on how to size your rafters
Your building is 12’ wide, which means each rafter has a 6’ span, plus 1 foot for projection



You want a 3/12 pitch. If you draw a triangle and find the unknown side, it works out to 12.37



So for every 12” of run, you need 12.37” of rafter
Since you had a 6 foot span, plus 1 foot projection, you need to multiply 7 x 12.37 = 86.59”
Since an 8’ board is 96”, 8 footers will work

If you’re going to use 2x4’s, space them on 16” centers and you should be ok, as long as you don’t get massive amounts of snow

Good luck, let us know how it goes

(sorry about the huge images)
 
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Old 07-04-09, 11:26 AM
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Ridge Board

If you want any overhang at the ends, you will need a 14 ft ridge board cut to correct length. The ridge board should be located such that the top of the ridge board is 18 inches plus the distance from the top of the birds' mouth to the top of the rafter(around 3 in.). If you plan to build trusses, then forget the ridge board.
 
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Old 07-22-09, 02:37 PM
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Thanks to all that helped
 
 

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