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Brettny
Member
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# Posted: 11 Mar 2024 07:46am
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Check what the minimum pitch is for your roofing of choice. 3/12 is about minimum for shingles/metal roofing.
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oldpops
Member
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# Posted: 12 Mar 2024 12:32pm
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Thanks everyone & keep the info coming! I have to admit I am learning a LOT about roof trusses, rafters, gussets, and even the size of the wood I should use. We do live in southern California so there' always the chance for a big earthquake.
If the shed I'm planning is going to be 18 feet wide x 18' wide, with a 6" inch overhang, with a gable roof design, using at least 2x6 (or 2x8) spaced 16" inches apart, with a bottom cord from side to side, would that work for the shed roof? Would it be better to 5/12 instead of 4/12?
As far as storage above, I see (in pictures of sheds built by local shed company's) that they use 2x4 rafters and with no cross support. If the customer wants storage above, then they build mini-beams to span from side-to side of the shed, resting on the top of the walls (with plywood on top), but they don't attach to or use the 2x4's above for any type of support. If this will work, I suppose we could do that for additional storage above?
Or would it just be better, cheaper, easier, to to a lean-to style shed with a sloped roof?
Thoughts? And as always. thanks again to all who offer help, suggestions and advice!
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gcrank1
Member
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# Posted: 12 Mar 2024 07:35pm
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Think about the shed sizing; ie, your 18x18.
Best to use multiples of 4 to minimize waste since stuff like 'sheet goods/plywood' (for decking and wall sheathing) is in 4x8.
So, maybe 16x20 or 24?
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oldpops
Member
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# Posted: 13 Mar 2024 10:34am
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Thanks everyone. I originally had planned a 20x20 shed, but the city gave me set-backs that made the largest shed I could build an 18x18. Maybe they knew it would cause some waste, but as a woodworker I can tell you there isn't any real waste (as long as you have a good place to store wood cut-off's), there's just pieces of wood that haven't been used for a future project.
What do you think about switching to a lean-to style shed & roof design?
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ICC
Member
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# Posted: 13 Mar 2024 03:20pm - Edited by: ICC
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Quoting: oldpops What do you think about switching to a lean-to style shed & roof design?
Using the 18 ft dimension for width, a simple monopitch shed roof would need 2x10 DougFir rafters (roof joist) or 2x12 in some of the commonly available species 24" OC with a DL = 10 PSF and a LL = 20 PSF. If you were willing to push the limits and lower the LL to= 10 PSF, then DougFir 2x8 or 2x10 of many other common species could work. .
Or you could run a support wall down the center, with a beam and footings under that too.
I don't worry about working in multiples of 4 feet. Many times if a panel needs to be cut on one side to make an 18' wall the cutoff is used on the other side.
There are times though when I will narrow a building by a few inches to accommodate the loss due to the loss in coverage when using several sheets of T&G subfloor across the width.
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oldpops
Member
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# Posted: 14 Mar 2024 10:44am
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Thanks again ICC & everyone! Ultimately, as long as both options are do-able (gable vs lean-to designs) the final choice will come from my boss of almost 40 years.
I have to admit I am a little ignorant about everything that DL & LL mean. If I had to guess I'm assuming that DL = Dead Load & LL = Live Load, with PSF meaning Pounds Per Square Foot. But what does that mean in designing a roof for a shed?
We don't get snow where I live, & only occasionally have heavy rain. Other than when we're building the shed and roofing it, I don't know that anyone would ever be on top of the shed.
I have to say now, after learning of all these things needed to design a roof, that I am more impressed with how my father would figure all this out. in the days before calculators, he would always carry a slide rule, a measuring tape, a plumb bob, a compass (for drawing), a level, graph paper and pencils. He would sit and work on all this stuff, then sketch out what what needed to be built & how.
I also want to say thanks to all here who have offered help, advice, and suggestions! Obviously I don't want the shed roof to collapse or be unsafe. So any and all help I can get from you folks to help me design and build the shed roof is greatly appreciated!
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Brettny
Member
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# Posted: 14 Mar 2024 12:02pm
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With a 18' wide budding I would use a ridge board and common rafters. Have you thought about doing a gambrel roof? With a 18' width you gain alot of attic space.
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oldpops
Member
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# Posted: 14 Mar 2024 01:26pm - Edited by: oldpops
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I did think of a gambrel roof design, and my boss of 40 years would greatly appreciate the extra storage room. But I must admit that I don't know the 1st thing about designing such a roof. Certainly if anyone here has some idea how to design that kind of roof for our 18x18 shed, or possibly some design software that can knock a plan out, I can can certainly upgrade my plans to build it. I guess when it comes to building roofs, I am happy to follow a plan - but not so knowledgeable to lay one out myself.
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Brettny
Member
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# Posted: 14 Mar 2024 03:48pm
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Blocklayer.com has a prety good gambrel roof calculator. I used it for my 20' wide cabin. I made the trusses in half out of 2x10 at home then trailered them up and finished the assembly on site. It was only 3 different piece of wood to cut but alot of each one. We made jigs to cut each piece along with a pattern piece to get every truss the same.
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