size rafters to use for roof

[jmc]

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........
?

 

[Hugerat]

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.

 

[patandchickens]

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

 

[jmc]

oh yeah, sorry.

pitch is 3/12; i am in massachusetts

 

[twentynine]

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.

 

[jmc]

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.

 

[owler]

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.

 

[greathorse]

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

 

[patandchickens]

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

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

Good luck, have fun,

Pat​

 

[greathorse]

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.