Intermediate Support in a Mono (slant) Shed Roof
I’m Will, and apologies beforehand – I’m an amateur builder looking for something to do during the lockdown. Basically every time I ask google a building question it sends me here, so I figured I’d ask the one question I can’t seem to get good answers for here as well.
We have the foundation for an old shed, approximately 40′ x 17′ 4”. The old shed had a single slope roof with a decline of about two feet from front to back. My question is, can I safely rebuild it without using intermediate support? What I mean is, would it be safe to use 20′ 2x10s or ibeams to span the 17′ 4” gap without having intermediate support beams or any support besides the walls? I’m based in very southern New York – so will have some snow.
I am thinking about framing with 2×6 on 24” inch spacing. Appreciate any guidance or input.
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Replies
Will,
Yes a variety of materials can span that length. Whether dimensional lumber will work depends on your local snow loads. Our code has span tables for rafters, perhaps yours does too.
I-Joists, or manufactured trusses both come engineered specifically for your roof. They will be more expensive, but can also provide more depth for insulation and ventilation.
My guess is in your location 36 inches of snow on your more or less flat roof is somewhat likely. I would call that a major load.
I think you can find a local truss company that engineer and build a merry nice truss that will work for less money than the 2x14 you are likely to find in a span table for your load.
Walta
Except in heavy snow area, you are probably in the range of 2x12 rafters, you would have to check your local code for exact size and spacing.
I joist is probably a better bet as it is simpler to insulate. You can staple vent baffles to the underside of the top flange and either blow in loose fill or install batts for insulation.
I joist also give a higher whole assembly R value since they have much thinner cross section and significantly lower thermal bridging compared to dimensional lumber.