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Round pole timberís and basic joinery design

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Hi Iíve got a few basic questions about a timber frame build (round poles) mainly to build confidence and hopefully gain some new insights. It is a 16x20 with a loft on half of the frame. I am using wood from my property most of which Iím milling with an Alaskan chainsaw mill. Iíve already finished the basement and first floor decking with round log joists and chainsaw milled flooring - I left a gap filled the gaps with 1/4Ē - 1/2Ē (3/8Ē looks best) sisal rope it worked great and looks cool but beware every roll of sisal is different size but itís cheap enough to just buy lots of rolls and bigger is better to jam in gap with white rubber hammer if itíll go. 

So my basic confidence issue is in the joinery on round poles. I want to use mortise and tenon but my poles arenít very oversized (6.5-7.5Ē for 6 posts) but big ole 8x10 plates and tie beams. The posts are a little bigger on the opposite end (around 8Ē) and Iím thinking of flipping them upside down and lagging the joists to the floor with 9Ē 1/2Ē lag bolts at an angle. Iíll have sips all around the outside plate to sill. The posts are made of yellow birch and good grade. 

To put it all frankly Iím intimidated by the outward force on the tie beam pins and since 2Ē tenons seem to make the most sense Iím concerned about the amount of meat removed from my post. I made a drawing and the tenon only goes in halfway and leaves some room on the side but I just wonder about it. Iím using Will Beemers book as my original first plan and he doesnít use a ridge beam and so I was planning to just butt the rafters at a 45 degree angle and bird mouth them at the plate although his book shows yet another cut in the plate as angling the rafter further into the plate I wonder also how necessary that will be. Iím going to add collars to every other rafter except for on the loft and I figured that would be the extra reenforcement but Will only does that on the end walls Iíd love to get some other opinions on outward thrust. When I calculate it the thrust is in the thousands and Iím just saying to myself who wants to put that must faith in a few tie beam pins and sip screws on the corners. I might just add king posts on the two ends with a ridge beam I just wonder is all of that really necessary.

If anyone has input on outward thrust without a ridge beam involved Iíd love to hear it?

Also what are your thoughts on two or three braces coming together almost at one spot removing all the meat from a post?? Iím actually planning to make my brace tenons only 1 1/2Ē deep and putting 1/2Ē threaded rod recessed a little in and trimmed over to alleviate that concern I just wonder how itís normally considered, even with 7Ē or 8Ē Square posts it can be a lot of wood removed? 

Any thoughts on round post building ideas would be greatly appreciated - I have great ideas to square everything but my worries are in what I donít yet know?? I would like to  also reenforce with steel plates or lags but round logs to steel plates seems like itís gonna look crappy or maybe Iím just over worrying. 


Don P:
That's gonna take some sketches to sort out. I'm not going to assume I understand what a loft on half the frame means.


--- Quote from: Don P on October 21, 2021, 04:50:10 PM ---That's gonna take some sketches to sort out. I'm not going to assume I understand what a loft on half the frame means.

--- End quote ---
I think it means a loft will be half way down the length of the cabin.
There is a discussion right now, in this section, about the need for collar and rafter ties on cabins.  

I tried uploading a few pictures but they wouldnít upload but yes itís basically a loft on half of the length of the cabin and yes if I join the floorboards right I can seemingly reenforce the outward force strength , maybe if Iím worried Iíll just install a small tie beam across the unlofted side just for extra security although the collars should do it. I know it should be fine I just wonder on like a pavilion or something that without a ridge beam or collar ties if the outward pressure becomes an issue or if itís just something to keep in mind. I tried using the outward force calculator but Iím not certain I was seeing it right if I remember it said I had like 3000ib of outward force and Iím thinking thatís s lot of trust in tie beam pins. I know most people add lags and screws and such but in the Old days I wonder if outward force on plates caused common problems.

Don P:
It is not something I would assume will take care of itself, well actually it does take care of itself. The theory of gravity has my vote  :D.

The ends of this plate, were pinned with 1-1/4" pegs, they sheared and it was sliding.


The half dovetail with packing piece on the tie here was withdrawing, The pin into the log below and alls that shimming and whatall was sheared and sliding. Not the best design going on right there anyway, but no shortage of that. 



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