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Timber Framing: mortise and tennon vs. lots of carriage bolts.  RSS feed

 
Dave Zoller
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Location: Kentucky
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  I am presently wading through steve chappell's "a timber framer's work shop" with a growing sense of trepidation. i am decently handy but still easily classified as a wood butcher. so i'm thinking of chasing this book with "timber framing for the rest of us" by rob roy.
   
  my goal is a robust structure to hold a metal roof and a roughly 15x24 loft. our walls will be strawbale for the straight bits and cob for the curvy parts but i'd prefer to have them remain non load bearing. i'm aware this may be overbuilding but in the long haul i think it'll pay off.

that being said, it's proving difficult to find salvagable structures, and i'm concerned that when they do turn up the size beams i'm looking for ( biggest being two 7x12x24s) are going to be less common here in kentucky than they would be further north.
 
  my plan at present is to go ahead at cull timbers where i can,  do a practice mortise and tennon chicken coop, and if i'm just not up to it come build time rework things to include a lot of metal plates and carriage bolts.

  so how much am i losing here? structurally, asthetically? any body have any encouraging words regarding the learning curve on traditional joinery?
 
                    
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Im a wood butcher too. Im great with cabnitery, but never actually got to school up on larger scale joinery. its invaluable to work next to someone who has that in their body.

all that said, jigs jigs jigs.

make jigs for your joints. maybe not the way a pro would do it if you were side by side, but as fool with some of a cabinet makers background, jigs have made my life easier than it would be otherwise. and run practice joints on scraps. and yes, explore with the chicken  coop. Ive never done a whole building in traditional TF, but Ive played here and there with incorporating large dimension lumber into some of my projhects, as well as roundwood. and it always helps to make some firewood in a dedicated fasion before heading into the wood that matters.

looking forward to hearing about your projects

and, welcome to the boards!
 
Irene Kightley
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Hi Mule tree !

I don't know if these photos will help you - the dimensions will be overkill for a light roof but they should help give you some motivation. Fabrice my partner has never done this before and the first set of beams took ages but once he's gained confidence he was flying. These aren't all real mortice and tenon joints but they do the job - the roof's still up after a year!

Measure up and make a good scale plan. (Treat yourself to a new pencil !! )



Trace the plan out somewhere full scale.



Little by little add the pieces as you make them.



There are lots more detailed photos here. Click on them if you want to make them bigger.

http://www.flickr.com/search/?w=25918339%40N00&q=green+oak&m=text

I hope that helps.
 
            
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Archetect Frank Lloyd Wright built a number of buildings using the mortise and tennon technique.
 
Dave Zoller
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Location: Kentucky
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yeah! that helps tons! it'll take a while for me to get though the photos ( rural internet) but i've enjoyed what i've seen so far. looks lke a fine place to work as well. thanks again!
 
Dave Zoller
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allright, feeling a lot better about things. irene's photos boosted moral and deston's suggestion of jigs made things seem a lot more do-able. also i think the timber framers workshop book may have been written backwards...towards the end i feel theres a lot more practical approach, the begining seems to be more of an appendix.

i feel confidant enough to overlay a framing design on my floor plan, which was my most pressing goal. i'll put up the image when i finish, and when i find a way to put sprawling .pdf files onto the interweb

thanks!
 
dave brenneman
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Location: london, england
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Thanks for the link; those are some inspiring photos. You've got a great place there, congrats!
 
Irene Kightley
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Thank you Dave and Mule tree I'm so glad the photos were useful ! 



 
                    
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Just a note on carriage bolts.

Carriage bolts are usually threaded all the way from the end to the head. This reduces the effective diameter of the carriage bolt and effectively reduces its strength. Building codes generally do not recognize carriage bolts.

A standard hex head bolt, on the other hand, is only threaded near the end, more or less enough space for a washer and nut and enough protruding thread for safety. When used on wood a flat washer should be placed under the head.
 
dave brenneman
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mountainDon Miller wrote:
Just a note on carriage bolts.

Carriage bolts are usually threaded all the way from the end to the head. This reduces the effective diameter of the carriage bolt and effectively reduces its strength. Building codes generally do not recognize carriage bolts.

A standard hex head bolt, on the other hand, is only threaded near the end, more or less enough space for a washer and nut and enough protruding thread for safety. When used on wood a flat washer should be placed under the head.



what about a lag screw? Is there a particular reason why a bolt, nut and washer are preferable?
 
                    
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A bolt and nut, with washers at each end, resists pull out or pull through better than any other fasteners used to join wood wood.

A lag screw is sometimes the only easy thing to use when both sides are not readily accessible. Lag screws should be installed with a shank diameter clearance hole drilled through the member to be secured and a pilot hole drilled in the main member to accept the threaded portion. The main member should be penetrated by a minimum of 8 times the shank diameter in order to develop design strength. A washer should be used under the head.

Pilot hole chart HERE.

Last note on lag screws: Many folks start them with a hammer rather than drill a pilot hole. Sometimes the lack of a pilot hole will cause the screw to be twisted off before it is tight. Other times the fixed member may crack, maybe not right away but sometime down the road.

Carriage bolts can be used, just be aware of their reduced strength because of the full length threading. At times the carriage bolt head tears the wood and will not hold when tightening the nut. There are special washers available with square holes and "ears" that are bent to engage the wood to prevent turning. High density woods resist this tear out better than less dense.

Too much tightening, crushing the wood fibers more than the thickness of the washer, is not good practice.

 
solomon martin
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My house mate is a timber framer.  When he bids jobs, he figures a  full day of labor cost for each mortise and tenon connection.  The appeal of using carriage bolts and brackets becomes immediately apparent.  But who can argue with the beauty and craftsmanship of traditional T.F.?
 
Dave Zoller
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Location: Kentucky
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so after digging around on http://www.tfguild.org/forums/ubbthreads.php i think i'm a lot more comfortable with traditional joinery. one fella in particular dressed down gusset plate joinery in a pretty insightful way. it might be less time on the job but it's a lot more design time.

sol, that one day per joint is helpful...i'll figure on 2 or 3 for me but still it's nice to have a number in your head.
 
Mekka Pakanohida
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Location: Zone 9 - Coastal Oregon
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I have had the pleasure of visiting a Samurai Farmhouse that was brought over piece by piece from Japan and re-assembled in NY.  There was no nails ever in the construction of the building and it dates from somewhere in the mid 1500's I think.  Everything was joinery & it was beautiful. 

There are books on this kind of joinery that go from easy to follow to what the hell was the person thinking who came up with that level of joinery techniques.  Personally, I would go for the joinery over the bolts.
 
                                                                    
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Location: Nashville, Tennessee, USA
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I have done well using post and beam construction as follows:
1) use 6" x 6" wooden beams cut on my bandsaw mill
2) use 1/2" rebar as fasteners.  These are easy to find on jobsites.

Post and beam is much easier than Timber frame.
You put corner bracing in each corner and pre drill the holes for the rebar.
These can be pounded in with a heavy hammer.
Each corner brace uses four 12" rebar pins.

Bolt sets are very expensive.
 
Mark Vander Meer
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Here is one we put together yesterday.  Tight & square. 
P2040987.JPG
[Thumbnail for P2040987.JPG]
 
Irene Kightley
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We finished the tower roof of our house a few months ago and now we're working inside out of the rain - yeah ! 



Plan of the roof design from the top using the golden mean for the shape :



Plan from the side :



When we finished the tiles - you have no idea how excited we were !

 
                      
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Location: Spearfish SD
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Patience, patience, patience. Take you time laying out your joints, measure 22 times and cut once. Also educate yourself on how to PROPERLY sharpen you tools. It's worth the extra time to cut the joints and not use plates and bolts. It will be worth it I promise. 
 
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