Shed roof truss design

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  #1  
Old 10-03-06, 11:22 PM
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Shed roof truss design

Greetings,

I am about to embark on the construction of a 10x12 shed. It will be set on a concrete pad, and I have most of the design finalized with the exception of the roof trusses. I want 12/12 pitch so that I can get ample storage space at either gable with a shelf area at the height of the top plates. I had picked up a set of plans (3/12 pitch) which featured trusses that utilized plywood gussetts and the crossmember (between the two rafter sides) was above the height of the top plates (about half way up the trusses/rafters). That would allow me to build without having to include joists between the side walls at the height of the top plate. (I hope this makes sense....). So... does anybody have any ideas as to how I should go about this? Again, I don't want to have joists between walls at top plate height as that only leaves me with 24" spaces for shelves between the joists. I want the crossmember between the opposing rafters as high as possible.

The plans I got don't use a ridge board. The trusses are all separate and only joined with the roof sheathing. Could I utilize a ridge board, and possibly increase the size of the rafters to 2x6 and not have to run a joist at each rafter point to connect the walls? If I do this, how do I resist the tendency for the walls and trusses to pull apart? Any other suggestions? Snow loads are a concern here. That's another reason I want a bit of a steeper pitch. Or am I stuck with having to tie the walls together at the top plate height?

I'm confident in my construction abilities, having designed and built a big deck this summer and from numerous other house projects that I've tackled. However, I don't have any experience in designing truss/shed type structures. In a nutshell, how do I design a 12/12 truss?

Hopefully this is clear enough to give a picture of what I'm trying to do. I'd appreciate any advice or insight anybody could give me.

Regards,
Patrick
 
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  #2  
Old 10-04-06, 09:06 AM
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Join Date: Jul 2006
Location: St. Louis Missouri
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First thing I am going to suggest is that you stick-build the roof for this shed - I'll explain. A truss that will give you a 12/12 pitch on the inside (because that's where you want the storage), would be a "scissor truss", with an outside pitch much greater than 12/12 - probably more like 20/12. It would eat a lot of material and probably look pretty strange on your little shed. If you build it using rafters and ceiling joists, you can leave that same area open on the inside, and still only have 12/12 on the outside.
I don't know which direction your ridge will be running - 10' direction or 12' direction - this will work either way. You are looking for storage area above the top plate, and don't want to be restricted to the space between joists 24" on center. You could frame regular rafters and ceiling joists, on 24" centers, but box two of the joist spaces together in the middle of the shed. That would leave you with the ceiling joists at either end to support your shelves (sort of like a mini-attic), and the boxed space as an over-sized scuttle hole. To box the scuttle hole area, you double the joists on either side of the opening, frame headers (also double) to either side of the hole, then run joists from the top plates to the headers. Use joist hangers to connect the headers to the joists, and to connect the shortened joists to the headers.

Here is a simple drawing to explain:


Hope this helps.
 
  #3  
Old 10-08-06, 11:52 AM
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Hi Ubob,

Thanks for the suggestion! That's exactly what I'm looking for, and I'll revise my plans to accomodate the scuttle hole. (Why didn't I think of that?!) I'm just finishing up the foundation, so I should be building soon. Thanks again,

Pat
 
  #4  
Old 04-07-08, 06:31 AM
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What size of lumber & Y/N-Gussets?

Given the information, already posted, I am assuming that there are only the rafters and the ceiling joists. What size lumber should be used for each - for those of us who don't have a lot of experience with stick framing?

Also, should you use the plywood gussets between the rafters and joists?

Thanks in advance!!

Eric
 
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