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#34444 - 05/11/18 05:01 PM Reciprocal Roof Framing
Mark Davidson Offline
Member

Registered: 11/12/03
Posts: 1121
Loc: Keene,Ontario, Canada
Hello again,
I've gotten myself into a reciprocal roofed gazebo and I wanted to see if anyone here has done this framing style before. I've read up what I could find on the internet, and done some sketching which I will attach for reference. The gazebo has a diameter of 18ft.
cheers!




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#34445 - 05/11/18 05:17 PM Re: Reciprocal Roof Framing [Re: Mark Davidson]
Jay White Cloud Online   content
Member

Registered: 11/06/08
Posts: 535
Loc: Vermont
Hi Mark,

Yes to your question...

Lots of CAD experimenting and hand drawing of this and bridges, as well as modeling.

I've built a few small transient structures but not quite as big as yours.

If jointed...The layout accuracy is hypercritical...!!! Top of the game stuff to get the joinery to work in a structural capacity...Many ways to do it...

Lashing much easier (of course.)

No matter the method...some form of "band beam" with tension adjustable joinery or "perimeter banding" (cable, rope, webbing, forged strapping etc) is an absolute must if the structure is meant to last any length of service time...Also not that additional tensioning joinery and/or banding in the upper roof structure is highly recommended for this type of roofing system...Many are already showing signs of..."creeping sag!!!"

As always, if not well seasoned to this craft...do seek PE advise and guidance from an engineer with a timber framing background if at all possible...

Good Luck,

j
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#34447 - 05/13/18 01:28 PM Re: Reciprocal Roof Framing [Re: Mark Davidson]
Mark Davidson Offline
Member

Registered: 11/12/03
Posts: 1121
Loc: Keene,Ontario, Canada
Thanks Jay!, this is good information.
I've also contacted Gary Chaplin in the UK, whose webpage inspired me to consider this idea, and yes I have contacted one of my engineers in Ontario to do analysis once the configuration is figured out.
Right now I'm thinking that the opening at the peak needs to be a bit bigger, so I will redo the rafters with that in mind soon.

Jay when you say "band beam" do you mean the plates?
I'm thinking the plates would be connected with threaded rod(x2?) which passes through the post to to the adjacent plate.

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#34448 - 05/14/18 11:56 AM Re: Reciprocal Roof Framing [Re: Mark Davidson]
GaryChaplin Offline
Member

Registered: 05/14/18
Posts: 1
Loc: Suffolk, UK
Thanks for getting in touch Mark. I'll share my experiences on here when I get a moment.

Step one for me was to make a scale model, I used 2"x3" bearers. This was primarily to figure out how it would go together. Inserting the final timber can be really tricky if you have tight joinery.

However, this picture is of the frame. Timbers 7" x 5", 5m span.


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#34453 - 05/19/18 09:42 AM Re: Reciprocal Roof Framing [Re: Mark Davidson]
Jon Senior Online   content
Member

Registered: 05/04/11
Posts: 133
That's rather pretty Gary. If you don't mind my asking, what did you use to secure the timbers to one another. In the versions that I've made models of, I've always had the head of each bearer passing the supporting one to lock them in place. I suppose that you could include that in the joinery but I imagine they'd be even more fun to assemble in that case.
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Jon

Contemporary Norman longhouse in Normandy

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