Wood Shed Questions

[Derek_PNW]

Hello. I've been waiting a long time to own property that allows me to tackle some timber framing projects, so I'm excited to finally stop lurking and start posting. The first project I'd like to tackle is a lean-to wood shed. Before getting in the weeds and drawing the joinery for the mortise/tenons and knee braces, I thought I'd first get a sanity check on the basic design. I've used the calculators and this is over-engineered as far as I can tell, but timber framing with 4x4 posts just seems wrong.  Anyway, any input will be greatly appreciated.
 
- Material will be douglas fir milled by me.
- Snow load is 25 PSF and wind load is 110 MPH with 3 second gusts
- Posts/plates/girts are 6x6
- Rafters and knee braces are 4x4
- Structure is 26'x6' and each bay is 8'x5'
- Roof pitch is 2/12. 1x or 2x purlins to be added later.
 
Questions:
1. Knee braces: I'm unsure when and where knee braces are necessary. Is there a general rule for that? Do I need knee braces connecting the front posts to the top plate? How about on each girt connected to the front/rear posts?
2. Since this is such a small structure, would smaller knee braces still be beneficial, say 24" (or even 12") rather than the customary 36"?
3. Could I get away with going 4x4 with the girts?
4. Local code calls for 24" max overhangs. But based on my 4x4 rafters at 24" oc, I'm forced to bring my overhangs out to 26" for the rafter spacing to work out properly. What is the standard practice to reconcile rafter spacing vs roof width? Do you tweak the overhang or just make the rafter spacing a little narrower somewhere?
 
Thanks in advance for any input/suggestions.
~Derek

[Don P]

A modern building has braced walls around the perimeter, don't do less than the worst allowed by law.
Others don't care to hear it but a 36" brace is already a reduction in the proper full height brace. You are desiring to reduce inadequate. At a certain point the brace is simply a fulcrum to jack the lever arms of the post and plate apart.
What is the girt doing? Quantify load and provide resistance.
I prefer a rafter or something to close off the roof/wall line, after that the overhang can be whatever. Dock yours to under 2'.

Uplift is one concern, tie the rafters to the plate well, carry that thought down to the foundation. Overturning of parts or the whole is what the bracing is for. If the wind hits one wall the bracing in the adjoining walls keeps that wall upright. If the wind quarters, the force flows down to ground through 2 adjoining braced walls. Shaking is the same in reverse.

I don't go under ~ 4/12 without VERY good reason, it will leak and is probably a waste of time and material.

And last, our on center spacing revolves around sheet goods and lumber lengths rather than some engineering need. You are making lumber, you are a wood.. well just use the little g  :D.

[Derek_PNW]

Thanks for the insights Don, they're greatly appreciated.

I'll add exterior knee braces (at minimum) and keep them as long as possible, increase my pitch to 3/12 or 4/12, and incorporate hurricane ties/etc for wind.