size rafters to use for roof

Discussion in 'Coop & Run - Design, Construction, & Maintenance' started by jmc, Jun 25, 2010.

  1. jmc

    jmc Chillin' With My Peeps

    Jul 22, 2008
    South Central MA
    roof will be 9' x 10', with 1/2 in. cdx sheathing. plus felt and either roll roofing or 'regular' asphalt shingles. i think 2 x 6 would be better; but if i could bring cost down and have 2 x 4 work well, i'd like to do that. but i don't want to risk having it sag over time........
    ?
     
  2. Hugerat

    Hugerat Out Of The Brooder

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    Well that depends on the spacing of the rafters the pitch of the roof and whether or not you need to worry about snow load.
     
  3. patandchickens

    patandchickens Flock Mistress

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    Ontario, Canada
    Yup, can't say for sure without knowing where you live (and may also need to know what pitch you are proposing).

    Generally 2x6s are more appropriate for that size roof though -- you would have to use more 2x4s to get the same strength and so unless you happen to have a lot of good sound straight rafter-quality 2x4s lying around it's liable to not really be much more expensive to use (fewer) 2x6s *anyhow*.

    Pat
     
  4. jmc

    jmc Chillin' With My Peeps

    Jul 22, 2008
    South Central MA
    oh yeah, sorry.

    pitch is 3/12; i am in massachusetts
     
  5. twentynine

    twentynine Chillin' With My Peeps

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    Okay I'll play.

    Gabled roof or lean-to?

    Gabled roof the span of the rafter would be 1/2 the width of the building-- plus pitch.

    So if you have a 9' building your rafter run would be 4'6". Adding an over hang and rise to the rafter, unless you want 12 on 12 pitch or more, you would end up with a rafter 5'6" or so long. A span of 4'6" can be done with 2x4s on 16" centers easily.

    Lean-to roof. 9' wide building your span would be atleast 9' plus pitch, in addition to overhangs. 9' span I would go with the 2x6s on 16" centers.
     
  6. jmc

    jmc Chillin' With My Peeps

    Jul 22, 2008
    South Central MA
    single pitch roof, no gable. coop is 8 x 8. six in. overhangs on east and west; one foot overhangs north and south. wondering whether 16" or 24" rafter spacing would be better.
     
  7. owler

    owler Out Of The Brooder

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    Jan 11, 2010
    Northen NJ
    I would be careful with 1/2 plywood on roof if you plan to space the rafters 24" on center. You will feel the plywood bend when you are up there putting shingles on.
     
  8. greathorse

    greathorse Chillin' With My Peeps

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    You (I) will always be happier with 16 inch centers. I started framing back in the day when 24 inch centers were unheard of. I think you will only be buying like three more rafters in a 12 foot span so I dont think it will make much difference in the cost of the coop.

    eta: last I heard Mass can have a pretty fair snow load LOL
     
    Last edited: Jun 25, 2010
  9. patandchickens

    patandchickens Flock Mistress

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    wondering whether 16" or 24" rafter spacing would be better

    Unquestionably 16" is better; you presumably already know that, and REALLY are asking whether you can reasonably *get away with* 24" spacing [​IMG]

    I wouldn't, myself, certainly not with 1/2" decking. But I tend to build on the more conservative, not-wanting-it-to-fall-down-even-when-sternly-tested side of things. If you are more adventurous and cavalier and gambling-inclined, you *could* do it with 24" spacing. But to me, it's an awful lot of work to go to, to try to save like $20 on risking the whole thing getting saggy or coming down [​IMG]

    Good luck, have fun,

    Pat​
     
  10. greathorse

    greathorse Chillin' With My Peeps

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    Yep I used 2x4 for my floor joists on a six foot span on 16 inch centers. I really wish I had used 2x6 as if feels spongy when i walk in the coop. I am sure it is fine but Ilike it to feel like a rock.
     

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