Building a workshop....

[Piston]

So is that the right way to do it  ???
I got that from Benson's book and basically copied it right out of there, however he recommends a 2" thick tenon on the collar tie and a minimum of 4" left on the rafter itself, so I would need to increase my rafter to 6" wide instead of the 5" that I have now. 
I saw somewhere else that someone had used a 1" thick tenon so I went with that at the time.  I have been meaning to update the model with a thicker tenon but had forgotten about that. 
Should I make the tenon at least 2" thick and increase the size of my rafters to 6x8?

[Jim_Rogers]

I thought he was talking about this joint:



And as far as I can see, it is laid out right.

The only thing I would change is to drop the top peg, you don't need three.

I'm not sure what you're talking about.....

[Piston]

Yup, he was definately talking about that one...
I read that too fast and had the collar tie dovetail on my mind, that's the one I was thinking about.  ;D

Oops

[swampfox]

Hey Piston,

It looks like your wedge for your dovetail is actually a rectangle.  Make sure you cut a wedge with an angle on it.  Angle the corresponding surface on top of the mortise as well.  That way you can set the wedge further after shrinkage.  If you just insert a rectangle (as drawn) it most likely will be doing nothing after wood shrinkage.  5 degrees should work.

[Rooster]

Swampfox and friends,

Should we also be advising Piston to cut his wedges large enough so that they don't "bottom out" or stick out of the frame from the inside?...and even go as far as having them come 2"-3" short of the outside reference face so that they can be adjusted or driven further later after shrinkage?  The outer skin or siding will definitely be in the way if the wedges are cut flush with the outside surface of the post when or if they needed to be adjusted.

Yay, or Nay?

Rooster

[Piston]

Swampfox and friends,

Should we also be advising Piston to cut his wedges large enough so that they don't "bottom out" or stick out of the frame from the inside?...and even go as far as having them come 2"-3" short of the outside reference face so that they can be adjusted or driven further later after shrinkage?  The outer skin or siding will definitely be in the way if the wedges are cut flush with the outside surface of the post when or if they needed to be adjusted.

Yay, of Nay?

Rooster

I vote Yay  ;D

Swapfox,
Good eye ;).... it is a rectangle in the drawing.   The reason I did that was so when creating the shop drawing for the receiving post in Sketchup it would cut a full square mortise for the wedge.  If I had made the wedge a "wedge shape" it would have cut that same shape into the post. 
Just to clarify though, I am supposed to cut the top of the mortise square in the post right?  Or should it match the slope of the wedge?

[Raphael]

  Ideally wedges should be dry so they don't shrink and the channel they are in is cut across the grain so shrinkage there is minimum, keeping the tip back any more than an inch is overkill and leaves you that much less bearing surface.

I'd cut the slope of the wedge into the timber.

[Piston]

  Ideally wedges should be dry so they don't shrink and the channel they are in is cut across the grain so shrinkage there is minimum, keeping the tip back any more than an inch is overkill and leaves you that much less bearing surface.

I'd cut the slope of the wedge into the timber.

I just confirmed this in Chappell's book, he states ,

"...the bottom of the tenon (and corresponding mortise) is cut with a 1-1/4 to a 1-1/2 inch half dovetail, depending on the length of tenon.  A common ratio of shoulder cut to tenon length is 15 to 1."

He then goes on to say,

"The top of the mortise must be enlarged the same amount to allow the tenon to be inserted and then dropped onto the corresponding angle on the bottom of the mortise.  The space left at the top is then wedged snugly with an oak wedge, locking the tenon and mortise securely.  The addition of two or three pegs, depending on the loading condition, make this one of the strongest mortise and tenon joints to be found in traditional European timber joinery."

I also have a question about his diagram, but I need to scan it so it makes sense....I'll do that now.

[Piston]

In this diagram, the wedge is going in from what I would consider the outside face, but in the description it says inside face....

I know the good thing about inserting the wedge from inside is you can  drive it further after the timbers shrink, whereas from the outside you wouldn't be able to.
So what is the proper way?

[Jim_Rogers]

Inside pushing out....

[Rooster]

So, what if you want to put decking on top of the tie beams?  How would y'all deal with the wedge, when it is from the inside out, and you still want to adjust the tenon because of shrinkage? :-\

Oh, what a pickle!! ;D

You know me, always thinking ahead!

Rooster

[Raphael]

I'd just slot the decking around the wedge.  You don't need very much wedge sticking out, once it's initially locked into place any subsequent adjustment is going to be in the fraction of an inch range.

Of course if you've got access to the far side you could change the joint to make it a dutch tying beam, a wedged through tenon.  That's the approach I've got in mind for my shop.

[Rooster]

...make it a dutch tying beam, a wedged through tenon.  That's the approach I've got in mind for my shop.

Raphael,

Care to share a sketch of that joint?  I don't know them all by name. haha

Rooster

[Brad_bb]

Dutch tying is a through tenon.  It's held on the outside of the post with 1 or two wedges perpendicular to the tenon, not parallel like in the half dovetail example, and the end of the tenon is usually rounded and not squared off like a regular tenon.  This can only be used when there is nothing on the outside of the posts, like a tie beam holding two interior posts.

One great little book to have that shows most joints in pictorial form is "Historic American Joinery" A graphic guide by Jack Sobon.  It's only $10 through the guild.  Here's a link to order:
http://tfguild.stores.yahoo.net/hiamtijo.html

[Dave Shepard]

Here is an anchorbeam to purlin post joint from a New York state Dutch barn I'll be restoring this coming winter:

[Rooster]

So, it's typical to use both trunnels and wedges to secure these joints?

What is the advantage of this joint?  
Does it have signficant holding strength?  
Would it look out of place in a small structure like Piston's workshop?

And is that a diagonal brace that got cut out below and perpndicular to the anchor beam?

It seems large...like 4x8?  

And are the bent nails that are located under the anchor beam to catch your clothing on?..or to help get a good grip with your jersey gloves? ;D

Rooster

[Raphael]

yup, wedges and pegs both is typical.
One big advantage is you can put a serious vertical load on the beam.
IMHO a lot of dutch barns have survived primarily due to the strength (and protected nature) of this joint.
In a smaller structure the beam would be correspondingly smaller so I don't think it'd look to out of place.

[Piston]

I really like the way this joint looks and have always thought that if I were to build a barn that it would be the Dutch style barn that the anchorbeam is used in.  I believe (and correct me if I'm wrong) that in my workshop I want to build it wouldn't be smart to use this joint, because it would be exposed through the siding, which would be much more susceptable to rot if blowing rain were to get into the joint.  It seems like you mostly only see this joint when there is another, outside wall and the anchorbeam is restricted to the interior portion of the bent. 
This way, if the outer walls deteriorate and the sill plates rot out on the outside of the building, the interior bent is strong enough to hold up the remaining portion of the rafters and the building won't collapse.   I really love the look of the MASSIVE anchorbeam holding those old barns together.  8)

[Dave Shepard]

Do you have Jack Sobon's first book, the red one? In the back is a dutch style two bay garage. He and Paul Martin put a little pent roof over the through tenons. That garage is about 12 miles from me.

[Piston]

Dave,
Yes I do have his books, I just checked out that 2 car design in the back of his book.  I like salt-box design in the back makes a good spot for firewood.  I might have to incorporate some sort of additional roof overhang just for that purpose.  The back wall will be facing south so it would be a great place to stack wood. 

[Piston]

I'm back at it again  ;D

Now that winter is here and I'm finally not too busy with everything else I'm going to try and devote some time to actually getting this thing started  8)  I have a few of the major timbers milled and ready to get cut into and plan on milling a few more when I get home in 2 weeks. 
I've been going over my highly modified Sobon 'shed' design and have run into a couple problems that I never got around to fixing before. 

Hopefully one of these days this thread will turn into pictures of actual progress rather than planning, but for now its still in the 'design' stage  :D



You can see I added another sill down the center of the main portion of the frame.  I also adjusted some heights of the porch ties and increased the center main tie beam to 10x12 to give me more room for the loft joist pockets. 
I increased the size of the center posts to 8x10 to match the width of the tie beam, as well as give me more room for the two brace's and half dovetail for the tie beam. 



Here is my first major issue. 
In this center bent.....(with timbers removed for clarity)


On the right side of the frame...


where the porch tie beam (center) meets the center post, I can't think of a good way to fit all the joints there. 

Here it is close up....


.....and here is an end view....


I may need to move things around but I'm not sure what/where to move.  I don't want to lower the porch tie beam or raise the main tie beam, so that pretty much leaves me with either going with what I have, or changing the length of the braces? 
I offset the porch tie beam tenon so it wouldn't be directly under the half dovetail as you can see.  I didn't want to remove wood directly underneath it because it is only 7" between the two. 

Am I trying to remove too much wood from this post by adding the porch tie beam? 

[Don_Papenburg]

Piston ,  I do not know how much neat stuff and tools you have to use in your shop. But if it is like mine I would insulate beforeI put anything inside .  I want to insulate mine now and I have a month of moving to do just to get access to my walls.   

[fred in montana]

I'd tie the corner posts on the porch to the shed posts.
There's little or nothing resisting thrust from the porch roof right now.

You had mentioned that you would rather not have to put in ties or braces due to wanting to park a tractor in there. I think you should leave them out. You will need to have strong connection where your porch rafters tie into the plate. The connection you have in the drawing looks as if it would need to be beefed up though.


As long as the main structure is rigid and the rafter is securely fastened to the plate, there is no way that the porch post can be thrust outward due to roof load.

I guess a joist hanger is out of the question but maybe someone could suggest an alternate connection detail for the porch rafter/plate connection?

[icolquhoun]

First off, I'm currently in the design stages for a small cabin almost EXACTLY like what you are doing off the sobon shed idea.  Therefore, this thread is very appealing to me.  I also plan on having a porch off the back, and have run into the same exact issues as you have.

Maybe I'm missing something, but how does the porch roof have any outward thrust?  The main roof/plate yes, but the let-in collar ties take most, if not all of that away.  Being a single plane, how is the porch roof generating enough outward thrust on the porch plate to be considered more than negligible?  I still see the need to tie the porch plate in with the main frame, but see below for how I plan on doing this.

Also, I have seen where the braces where put from the sill to the post where you have a large number of joints all fighting for space on a crowded post with a dropped tie beam, although this makes the raising a bit of a chore I'd imagine.  You could also lengthen the braces to drop them below the braces tying the tiebeam to the post.  On that center bent, you could get rid of them altogether on that one post and probably be fine.

Just thinking out loud here, and I've never seen this done, but what about for the porch portion, raising the tie, making it a half of an english tying joint with rafter/porch plate?  It would then be on the same vertical height as the main framing tie-beams.  You then have an issue with the dovetail tenon being in the same place as the porch tie beam, but what if the porch tie beam were also dovetailed the other way and offset?  Has anyone seen a joint like this before?  I realize there would be quite a bit of material removed, but you said you were making the center post a 10" anyway, correct?  Let me draft up the joint and post it up. 

[jamesamd]

If that post is 10" wide and your brace housings are 1/2" deep
and the brace tenons are 2" long.
There should be 5" between thier ends!
Jim