Help with rafter span


Old 02-17-14, 01:40 PM
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Help with rafter span

I'm planning on adding a lean-to on the end of my pole barn. It is going to be 10' deep and 40' long. With that said... I have a 10' run. I want a 1' overhang and a 4/12 pitch. I am putting metal roofing on it.

My question is: Would 2x8's 48" o.c. with 2x4 roof purlins be adequate for this?

I live in central Ohio so we do get snow.

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Old 02-17-14, 07:13 PM
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Without knowing your region's snow load design value, and the species/grade of lumber you'll be using, none of us can tell you if what you're planning will work. My gut feeling is that the 2 x 8 rafters will be over-spanned.

You would do well to get an engineer involved. He/she can come up with a practical and economical design. You'll probably need a stamped set of plans when applying for the building permit anyway.
Old 02-26-14, 03:29 PM
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Though BridgeMan45's opinion about the engineer IS NOT wrong (hope he doesn't take offense because as I said he isn't wrong), I wouldn't get one involved. Especially with a metal roof, the 4 on 12 pitch is fine, but the rafter span with a 2x8 should be 16 inches with the snow. I can almost guarantee the zoning doesn't require 16 inches, it would probably fall at 2 foot. But I would put it at 16 inches to be safe with a 2x8. It is a lean to and not a house, so they aren't going to require the same span. But to be safe, I would go a little beyond the requirement because of the snow.
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