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Hello, I’m doing my first timber frame project for my boss. I have been timber framing for 3 years and this is my first arched beam I just want to know if this will hold up over time. It is holding a 6x 12 ridge beam and 2x10 rafters over a 12 foot span. The arch itself spans 8.5 ft
424405
 

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Hello, I’m doing my first timber frame project for my boss. I have been timber framing for 3 years and this is my first arched beam I just want to know if this will hold up over time. It is holding a 6x 12 ridge beam and 2x10 rafters over a 12 foot span. The arch itself spans 8.5 ft View attachment 424405
I would run that by an engineer. The only weak point I see is the grain direction at the beginning of the arches on the left and right side.
 

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Fascinated by this.

What other options are for the grain direction you guys mention on the sides?
 

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It looks like the arched member is 2 separate pieces of wood joined together at the central point with a long key set into vertical slots and cross pinned. There may be some half lap joint there; but without seeing both sides, I can't tell.
If that is the case, it isn't a candidate for beam calculations since it isn't a full length member. Visualize it without the vertical post there and ask yourself if 2 straight pieces joined like that in the middle would be a good beam.
To me it looks like 3/5ths of a good truss. With the addition of rafters and a joint at the top of the post that will resist tension it could be triangulated into a very rigid structure.
It reminds me of some window mullions I did structural testing on. The company wanted to reinforce the center of a 4 way joint with a key like you have rather than a full length stiffener. We framed it up and put a bit of a wind load on it in the lab, maybe 5-10psf. It ripped apart. The code requirement was 50psf wind load.
 

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what joint do you have at the top? personally i think that is your weak link...

are those blocks on the end? what joint do you have for the blocks on the ends? at the very least, that should all be one (piece) timber, with the vertical post sitting underneath and above the arch, not cut into it.
 

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I'm going to go out on a limb and say OH HELL NO!
Just scaling it with 8.5 feet length, I see a 4×6 cut in half with no real reinforcement
No no no

Timber framing uses beefiness or triangulation for strength 💪
You obviously used a piece of 6x12 similar to the ridge and cut most of the 'beef' out
This is why you typically need a civil engineer's stamp on any design
Not only would it fail, it would look wrong holding up a 6×12, rafters and roof
 
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