Shed roof

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Old 03-14-00, 01:26 PM
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I am building a 12'x16' shed and have no clue how to do the roof as far as pitch and all. I live in the Northeast, so I have to be concerned about snow in the winter. Is there some sort of formula I can use to determine the proper pitch and therefore the length of the rafters? I thought I would make the center 2' high, and run 9' 1/2 rafters to give me about a 1' overhang on the walls. But I dont know the proper angle to cut them where they meet the center beam. I have little construction experience. Any help would be most appreciated.
 
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Old 03-15-00, 04:16 AM
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what you have to do if you are making your own rafters, is to lay them out on the ground to make a pattern. Lay them out like you want them, nail together, and you have your pattern, and your angle. If you would like some good advice, I would buy ready made trusses. You can buy a truss for less money then you can buy the lumber for rafters. They are all the same, easy to put up, and no lumber waste. From your dimensions, you will have to waste, about 12 2x4's, at a minimum. Also no snow load problem. Good Luck

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Jack the Contractor
 
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Old 03-18-00, 12:33 PM
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The roof you describe has a 4:12 pitch. Rafter length is 6'4". For snow load that may not be steep enough. Are you going to use metal roofing or shingles? I would cut them at 6:12. Rafter length 6'8 1/2", and still not waste much more than the shallower roof. This would put your ridge at real close to 3'

If you took geometry in high school. Remember the Pythagoreum Theorem? A sq x B sq = C sq

Or: A equals the height of the right triangle. B equals half the span of the building. C equals the rafter length (without overhang).

Rafter length is measured from the top of the common cut (where the top of the rafter meets the ridge board) to the point directly above the outside of the wall it is attached to. Reduce the number 3/4" to account for a 2xX (I would use a 2x8) ridge. I almost always use 2x6 for rafters and leave 3" inches above the top plate or HAP (height above plate). The 3" is the wood remaining after you cut the bird's mouth.

If you leave the rafter cut long (do not remove for tail) you can cut them all at the same time.

If you haven't purchased a "Speed Square" that's the tools that will make this job go much smoother for you. It comes with a little blue book full of instructions. There are lots of imitations, but the Swanson brand is by far the best one.

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MTAC - Van Buren,MO
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Home repair & Construction

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[This message has been edited by More than a Carpenter (edited March 18, 2000).]
 
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