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Building on a budget (zero) Rafter size

Started by Jeff, October 17, 2022, 04:10:37 PM

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Jeff

Guys, this is just a tractor quad shed. I would ile to use some of the small fir or spruce I have dor 2 sided rafters. What size and spacing could I get away with?  Im using log screws for fastners. I have 9, 10, and 12" screws.

Span is 12ft.  
 Would 5"  every 4' do it?   I have some downed aspen I want to cut roof sheeting, and put a tarp over that for winter as no way I can afford steel this year.



 

 
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Jeff

Front wall beam is 7x8. The back is 5.5x5.5
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

barbender

Idk about spans Jeff. Iirc, B. Allen Mackie, who wrote a lot of books about full scribe log building, had a book about round log rafter spans. From what I recall, full round rafters have way more strength than a comparable size board- a 4" pole is way stronger than a 2x4.
Too many irons in the fire

Jeff

I had planned on flattening them on 2 sides.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

thecfarm

You don't want to know what I keep my tractor in.  ::)
But I will tell you anyways.
I took some cedar, left them round, maybe 8" across and I ran them across what you have, I think I only used 3. One on each end and one in the middle. Than I ran some hardwood trees about 6 inches on the big end and ran them long ways. One every 3 feet.
More then 20 years later and I never shoveled the snow off it is still standing. 
keeps the tractor dry.
My FIL calls it two by tree building.
I did brace the corners, but I used wire to hold everything down.
Budget building at it's best.  ;D
I even used an old wide belt from work for the roof. Then I had some old tin kicking around.
This building brought the value of my place down.  ;D  
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Southside

Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
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Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
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Don P

Is Goetzeville close enough? Snow is 70 lbs per square foot + 5 psf dead load.
12' rafter span x 4' spacing= 48 square feet.
48 square feet x 75 lbs per square foot = 3600 lb snow load per rafter, uniformly spread out.

Assuming I can talk you into skimming just enough to make a flat on the top only, don't saw the underside fiber and double the strength ;), use this calc and lets see;
Log Beam Calculator (forestryforum.com)
... for just bending I'm getting a midspan dia needed is 9.5" in #2 Aspen

Cutting the spacing to 2' centers drops the midspan diameter to 7.5"

Southside

What about not sawing them at all, and using a 2x as a purlin come spring when it's time to put metal on it? The 2x could be shimmed to get a flat surface.  
Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
Riehl Edger
Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
White Oak Meadows

breederman

You are not using the tractor etc in the winter? I'd use what you have and wedge a couple temporary posts on the middle of the span for the winter and call it done.
Together we got this !

Jeff

This is what I want to use for rafters. Leaving them whole, seems like you would not want to cut a birds mouth. How would i handle how they pass over the beams? Connecting is no problem. I have plenty of log screws



 

 

 
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Hilltop366

Whatever you end up doing you have lots of them so don't skimp over build, the load tables are the minimum to pass code/safety.

 To me the span stops at the point were the joist contacts the beam so the birds mouth is not part of the equation on the lower side, could cut a wedge to set the upper side on. At some point you may decide that cutting dimensional lumber may be easier but on the other hand we are not always looking for easier.

Don P

Yup, tighten up the spacing and use plenty. Try to stay fairly consistent in diameter, butts go low.
Skim to create an upper flat. Yes it is marginally stronger to leave it full round. Having done the shim it thing before, take the hit and skim the top surface.

Now saw a pair of rafters out of 2x boards of the same depth as your logs, roughly, birdsmouth, top cut and all, 2 finished rafters. You want to make the birdsmouth big enough to land on the beam well but never extend the heel of the notch inboard, don't over notch.

Screw a plank the length of the rafters across a pair of horses. Set your dimensional rafters top edge down on the plank and screw them from underneath the plank. Line up the birdsmouth cuts with a framing square across the plank You're making a trough to set the log rafter in.

Set the log rafter in the trough, smooth surface down on the plank, index surface to index surface, the top surface of the roof is what its all about so that is what this is all about. Line it up straight in the trough, butt end to the birdsmouth end. Using opposing wedges or screws up from the plank secure the rafter in the trough. Fire up the chainsaw and use the trough as your guide, try not to eat it before the last cut but you can screw on a patch pattern if you do. How would I know :).



 


Joe Hillmann

Are you planning to put a bottom chord on the rafters?

Without a bottom chord tying the sides together I think the rafters will push the top of your walls out.

Right now I am building something similar.  Mine is 12 x 16.  I put up 3 log trusses that are triangles.  One at each end and one in the middle.  The rafters are 4 to 6 inch logs flattened on one end.  They are all slightly rotten cull logs from my house build.  I am using insulated garage door panels for the roof sheeting so I hope they can span 8 feet between rafters.  

Since you are checking it with boards you should probably go 16 inches or 2 foot on center to do it correctly but you could probably get by with 4 feet on center if you font need to walk on the boards

Hilltop366

Me thinks it's a shed roof not gable end, well that is what I based my comments on so I hope I was not too presumptuous.

Joe Hillmann

I took "two sided" to mean a peak in the middle.  But if it is a single sided shed roof my suggestion would NOT be strong enough.

Jeff

Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Jeff

Rafter factory open. Skim cuts complete. Need to make another jig board. The sawmill bed is working nice for this. There is hardly any birdsmouth to cut

 .
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Jeff

Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Southside

Dosen't scare me at all. Of course it's not my tractor parked under there.  :D
Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
Riehl Edger
Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
White Oak Meadows

Jeff

That crooked shed next to it with the same span using 2x6s on joist hangers has lasted 20+ years.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Southside

I can think of countless old buildings that were built like what you are doing that survived massive piles of snow growing up. As long as the roof kept the water off the lumber they never moved.
Franklin buncher and skidder
JD Processor
Woodmizer LT Super 70 and LT35 sawmill, KD250 kiln, BMS 250 sharpener and setter
Riehl Edger
Woodmaster 725 and 4000 planner and moulder
Enough cows to ensure there is no spare time.
White Oak Meadows

Walnut Beast


Ianab

Quote from: Southside on October 29, 2022, 10:39:22 PMAs long as the roof kept the water off the lumber they never moved.


That's the important thing for long term life. Keep wood dry and it stays intact for centuries. Let it get damp, and the clock starts ticking. Then some last 2 years, some last 30, but eventually the rot gets them.  
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Old Greenhorn

Looks great Jeff! What's the spacing on the rafters, I think I missed that? What is your plan for purlins? Have any siding planned, or is that next year? You could hang tarps to keep the snow drifts to a minimum inside, just for the winter. I hear it can snow up there. ;D
Tom Lindtveit, Woodsman Forest Products
Oscar 328 Band Mill, Husky 350, 450, 562, & 372 (Clone), Mule 3010, and too many hand tools. :) Retired and trying to make a living to stay that way. NYLT Certified.
OK, maybe I'm the woodcutter now.
I work with wood, There is a rumor I might be a woodworker.

Jeff

I had cut one decent spruce log into full 6 by heavy 6/4 because the log size lent itself to that. My plan this morning is to split them into 3"  wide to use for purlins.  The rafters ended up around, 38" center to center. Im thinking the purlins every 2ft.

That is exactly my plan. If I can't get walls up before the weather croaks out on me, i have the big heavy duty tarp I covered everything with last winter. If I can get purlins up for the walls, I could use that for this year.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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