3 sided shed

[trihounds]

Much more important then the rafter size is what you will use for a header.

Agreed - interestingly, the plan reviewer in our town made me use 4X2X12 built up beam to support my rafters. Largest span is 15 feet. Beam sits atop 6x6 PT posts. Snow load is 40 psf where I live.

For the OP, the opening of my 'lean to' faces trees and is somewhat in a forested area. Over the last 5 years, I have had minimal rain / snow come in the open side, BUT, a) I have yearned for doors for 4 years now (and building this summer), b) humidity condensates on my equipment on certain days. My rafters are 2x10 on 16" centers. Longest unsupported span is 11.5 feet. This might help your planning but a call to your county might be helpful too.

 

[Al 2]

Any chance of a cab for you tractor in the future? If so, you will probably need a higher roof. Also as others have said, go with doors or at least a tarp.
Al

 

[EddieWalker]

A cab tractor in a 12x12 shed?

 

[FTG-05]

According to Span Options Calculator for Wood Joists & Rafters , the minimum for a 12' span, 16" center, with a 40lb/sf snow load (this is Michigan, after all) using No.2 SPF wood (Spruce-Pine-Fur, typical wood) is 2"x8". I believe your area requires at least a 30lb/sf snow load rating, so you should be good to go using the 2x8's. If you used 2x10's, you could get the same rating @ 24" spacing.

Thanks for posting that link to that calculator, I appreciate it!

 

[flusher]

I' m planning on building a 3 sided shed or run-in shed that some might call it. Will be using rafters sloping the roof from 8' in front to 6.5' in the rear. Span will be 12' with 16" on center. Debating on size of rafter. Live in Michigan with snow in winter. Thinking 2 x 8 will suffice?

Just make a doubled 2x8 nail lam/gluelam for your rafters to handle the snow load.

Here's my 3-sided shed that I built about 8 years ago. It's 28 ft wide (two 14-ft bays), 20 ft deep, 10 ft high in front sloping to 9 ft high in the rear. 28 ga metal sides and roof.



I used doubled 2x12s glued and nailed together to span the 14 ft bays for the front, middle and rear beams that are carried by the posts.
The intermediate rafters are 2x10s.
No problem with snow loads in the North Sacramento Valley.

Good luck and be careful out there.

 

[KennyG]

I think everyone here is giving lots of good information and references so you should be in good shape on sizing. The only caution I would throw in is to be careful on the roof slope, with snow loading. A shallow slope will leak a lot quicker and the snow will not slide off so easily. Your plan looks like a 1 in 8 slope. The metal roofing companies will tell you that they are designed for a 1 in 4 slope as a minimum. If I were doing it, I would raise the front by another 1.5 feet and, if I felt ambitious, add an overhang, sloping back down like one of the examples posted, to provide a little more protection.

 

[Creamer]

I think everyone here is giving lots of good information and references so you should be in good shape on sizing. The only caution I would throw in is to be careful on the roof slope, with snow loading. A shallow slope will leak a lot quicker and the snow will not slide off so easily. Your plan looks like a 1 in 8 slope. The metal roofing companies will tell you that they are designed for a 1 in 4 slope as a minimum. If I were doing it, I would raise the front by another 1.5 feet and, if I felt ambitious, add an overhang, sloping back down like one of the examples posted, to provide a little more protection.

Most steel buildings are a 1:12 pitch. I just built one and had to argue to get them do a special 3:12 pitch.

1.5:12 is fine for a metal roof.

 

[KennyG]

Most steel buildings are a 1:12 pitch. I just built one and had to argue to get them do a special 3:12 pitch.

1.5:12 is fine for a metal roof.

Interesting. I'm attaching a sheet from a roofing supplier that says 1 in 4 is minimum recommended. I guess there are different approaches.

 

[Creamer]

It is different between heated interiors and cold storage. the other factor is the fact that this building has no laps - they are all single sheet.

Still if you drive around your area you will see a lot of steel buildings with roof under 3:12 pitch.

 

[EddieWalker]

Can't say for snow areas, but here in the South where we can get over an inch of rain in less then half an hour, 2:12 pitch for a roof is as flat as you can go. Anything less and water will build up on the roof and get through the overlap. Most metal buildings are 2:12 to 4:12 for R panels. On U panels or some version of a U panel without viable fasteners, it's not uncommon to see them 12:12.

For shingle roofs, 4:12 is the minimum slope. Anything less will allow water under the shingles if there is any wind blowing.

Does it really matter how much slope you put on a roof in snow country if it's less then 4:12? Seems to me that every time I'm in the mountains, all the buildings have much steeper pitches and they are covered in snow. At what pitch does snow come off a roof?