I am constructing a timber outbuilding with a shed roof that is cantilevered towards the peak. The main beam will support about 600 sq ft, I am keeping it a free span of 30' with no interior posts, the roof is a 6/12 pitch. I have trees that I will cut into beams onsite but I think the largest beam I can cut is 10" or 12" wide X 30" high. Can you shed any light if I am in the ballpark of making this work?
Nothing, but this is going to be cut out of high grade douglas fir logs
Hi, I can hellp
Give me a minute to read the question completely
What do you mean by cantilevered toward the peak?
Post on lower eave wall and in the middle of the building (about 2/3rds across on the side walls) and the rafters free hanging over the cant beam as they rise towards the peak, there will be no enclosed walls on this structure.
The rafters cantilever past the ridge beam?
The ridge beam spans 30'? And that is the beam you need designed?
No ridge beam, they free hang towards the peak, rafters will be 8" X 12" with purlins on top to attach roofing. Think of a boyscout emergency shelter built with a shed roof only on a much larger scale
Is it a monoslope roof?
Ok. So it starts low at the eave and slopes up to the other wall?
Now I'm with you.
and the span is 30'?
you might call it a ridge beam but it is canted over by the rafters
It's a wall, though, not a beam, right?
Yes 30' wide. Thats the width of slope and building
Ok, where are you located, so I can look at snow loading.
No wall just open working space to drive into with forklift to move products
Do you have a spacing in mind or do you want me to work that out?
Do you want to use purlins between these or just span the sheathing directly over it between adjacent beams?
I figured 600-700 sq ft of roof will be carried by the beam. the other 200 or so sq ft of roof will be carried by the lower eave posts and beams
Ok, so just one beam? Give me a few minutes to run some numbers
What type of trees do you have to cut?
Just the beam size, rafters are about 8 ft center and 4"x4" purlins that will have metal roof fastened to
Douglas fir, should make number 1 or better. I went to grading school
If you can put it as No. 1 Doug-Fir, then you can cut it 13" x 26", assuming dressed and dried dimensions of 12.5" x 25"
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That keeps deflection to span/300.
Not terribly stiff, but it's already a very big beam.
No, I would expect to have alot of bounce in it
It's just a roof, right?
It works for strength and is within acceptable limits for deflection. If you want it more stringent, let me know what kind of deflection you are looking for and I'll size it for that.
Yes, an oversized machine shed type structure. It will be open workspace to build timber frame trusses for my home, thats why its free span
This is a great service, just lets me know I am not totally unrealistic before I get complete engineering for the structure. Thanks alot
No problem. Best of luck with your project