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Author Topic: Joinery Question on Center Post: Mortise & Tenon  (Read 464 times)

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Offline LimestoneWood

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Joinery Question on Center Post: Mortise & Tenon
« on: July 13, 2017, 03:21:20 pm »
Hello Everyone,

My name is Andrew and I'm new to the forum.  I have been working on a timber frame design for an 18x18 shed.  I have run into a problem joining the tie beams to the center post.  The post is 8x8 and I would like to inset the 8x12 tie beam by 1 inch into the center post along with a 4" long 2" wide tenon.  But that sets the tenon 5" into an 8" post and I have to fit another tie beam into the same place on the other side.  Should I simply make the post 12" wide or should I go for an over-under tenon?  Or is there something else that I should do? 



Please remember that this is my very first timber frame and I am not looking into getting into very complicated joinery.  That is why I am using a post in the middle in the first place.  However, I am a woodworker by hobby so I'm not completely lost.   

Any help that you can offer is greatly appreciated.

Thanks,

Andrew

Offline timberwrestler

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Re: Joinery Question on Center Post: Mortise & Tenon
« Reply #1 on: July 13, 2017, 05:40:00 pm »
Widening the post could work.  A free tenon would be the modern answer to your dilemma.  It would run through the post, and go maybe 12-16" into each beam. 

The beam splitting the center post is more of a problem.  It's a hinge point.  You'll also have a lot of cross grain shrinkage.  Even without that middle beam, you should leave a gap between the rafters.  So that when the ridge beam shinks, they'll still bear on the beam.

Offline Don P

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Re: Joinery Question on Center Post: Mortise & Tenon
« Reply #2 on: July 13, 2017, 08:53:30 pm »
Lose the lengthwise center beam under the ridge, run the ties continuous and tennon posts under and over the ties, brace upper posts to ridgebeam?

Offline LimestoneWood

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Re: Joinery Question on Center Post: Mortise & Tenon
« Reply #3 on: July 15, 2017, 07:21:02 am »
Hi,

Okay, so if I understand this correctly the center beam/plate should be removed.  I assume the posts underneath it would become taller and go all the way up to the very top plate/beam.  The tie beams meeting in the center post could then receive the floating tenons. 

I would still have nine posts but the center ones would be taller.  But now I would only have three beams/plates instead for four. 

As far as the rafters go, I don't understand the solution.  I understand wood shrinkage and now see the problem that has been posed but can't visualize how to fix it. 

Thanks for all your help!  I'll get a new design posted within the week to clarify the wording.

Thanks again,

Andrew

Offline LimestoneWood

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Re: Joinery Question on Center Post: Mortise & Tenon
« Reply #4 on: July 15, 2017, 07:24:51 am »
Oh never mind on the rafters.  I get it now!  Duh:)