Building a workshop....

[Piston]

I decided I need to build a workshop.  I started with a 16'X24' frame that I modified from the Sobon Shed, then I added a farmer's porch on one side.  I want it to look more like a small cozy cabin than a workshop!  I designed it using Sketchup and have detailed most of the joinery using the program(not finished with it yet).  I tried using a few different types of joints as this will be my first frame and I want to get some exposure to different joints, all basic though, but I'm sure still challenging. 

Here is my design so far, not completely done with the model but getting close.  I would like to know your opinion on a few things, just the frame in general, but also I'm not sure what kind of joint I should use to join the porch rafters to the main frame? 
Does it look like the way I lined up my joints will interfere with others, or weaken the timbers too much? 

Here is the basic frame.....













I want to use the loft for storage and the 4 collar ties for some light weight storage.  I want to be able to use the porch as a workspace too by using mobile workbenches for certain tools.  I will have a barn type sliding (or opening) door on the gable end and a dutch door on the front wall (I love dutch doors!)

For the foundation I'll most likely use piers, 3 under each sill and 3 in the center of the main frame, with a long sill to help support the longish span of the floor joists. 

I'm looking to make this a woodworking shop as I want to get more into woodworking as a hobby.  It will also by my 'hang out and relax' room so a small fridge and woodstove is mandatory. 

Here is a pic of the tie beam connection.....I'm not sure if I should use pegs or just the wedge, I will use a wedge on the top of the joint (not shown in pic) regardless. 




The Tie beams are 8X12, the posts are all 8X8, the sills are all 8X8, the floor joists are all 5X7, as are the rafters, although the porch rafters are 3X6 but I may bump that up to 4X6. 
I haven't done any structural calculations yet so these are subject to change. 


For the floor joists I used dovetails on two joists and the rest just joist pockets with the underside adzed to spread out the stress.







'


Any thoughts?  I plan on starting to mill the timbers in the fall and cutting the frame over the winter....who knows if this will actually happen or not!   :D

[Raphael]

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.

One approach (belt and suspenders) to the tie beam is use just the wedge until the timbers have well dried in then tighten the wedge up real good, bore and add a peg.  But in theory a good wedge is usually sufficient... what sort of snow loads do you see there?

[Brad_bb]

Build it bigger.  I've never heard anybody complain about their workshop being too big, but sure have about it being too small.  That's pretty small.

[Raphael]

Build it bigger.  I've never heard anybody complain about their workshop being too big, but sure have about it being too small.  That's pretty small.

Ain't that the truth!  ;)
I've got something similar in mind only a bit more dutch barn like.
It'd be something like adding another porch on the other side of your design.

[Jim_Rogers]

Piston:
I can understand your wanting to build yourself a frame.

As for the choice of joints, a dovetail joint isn't the best for holding things together.
I believe I have a couple of threads here about that, but maybe a search will bring them up to the top.

Timbers dry out, and when a timber has a dovetail on the end and the dovetail shrinks it allows the dovetail to pull out.



The dovetail will shrink and the distance shown as the red dimension line will get shorter. This will allow the sills to spread further apart if something else, like the floor boards aren't holding it together. To prevent this from happening some framers pound in hard wood wedges in the areas shown as blue lines. This compresses the green wood, and then, it is thought, that when the wood shrinks the compressed wood expands and doesn't pull out. Or that the hardwood wedge takes up the future gap and doesn't allow it to pull out.

A better joint would be a standard tying joist joint.

This joint is not hard to cut and it does the job very nicely, if done correctly.

Here is a picture of the sill mortise for a tying joist:



And here is the tying joist tenon:



During the assembly of the frame, it is just a matter of sliding the tying joist into the mortise at the same time the long sill is slid onto the two cross sill's tenons and then the pegs are driven in pulling the entire side into place:



It may seem difficult but it's not really hard to line up all three tenons at the same time, especially when you have several others there helping you.

Jim

[John S]

Piston,
I am hoping to do the same thing and was planning on taking the Sobon shed (14 x 16) and doubling it to 14 x 32, but think that may not be large enough.  My current shop is a 16 x 26 walkout benind my ground floor garage ... it is too small.  The most efficient use of material (to maximize interior space) is a square footprint, so the closer your dimensions are to a square, the more interior floor space.  Your current design (an excellent job, by the way) at 16 x 24 = 384 sq. ft. while a 20 x 20 = 400 sq. ft.
John

[Piston]

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.

I like the idea of tying the corner posts to the porch, but the only reason I don't want to, is in case I want to use the porch for storage of a small tractor or something, If I put a tie there I will only have about 6'or maybe a bit more of overhead clearance.  Do you think it will be okay without one?  Although I guess I'd rather be safe than sorry.
(I'll have extra support under the porch joists if I'm going to be planning on parking a few thousand pounds on there)

what sort of snow loads do you see there?

40psf is code, but I want to overbuild by a good margin.



I wish I could go bigger, but for this one I have to limit the size because of where I'm putting it on my land.  I'm hoping this is the first of many frames to come.

Jim, I'll change joinery as suggested, do you think I should change all my joists or just the ones I have dovetailed? 

Thanks all for advice, I'm a complete rookie at this stuff and need all the help I can get  :D

Any thoughts on what joints I should use for the porch rafters?  I'm using a step lapped rafter seat for the rafter connection to the top plate, should I do the same for the porch or is the pitch not steep enough? 

[Dave Shepard]

I framed an 8' addition to the 14'x16 Sobon/Carlon shed from Hancock last winter. We used a 6/12 pitch, and that seems to be about as low as you can go on the step lap. The laps are very close to the post top tenons. We will be running the rafters over the top of the main building rafters, and simply lapping on the top. This may work for you to raise up the porch plate height, allowing you to put a tie beam at each post location to the plate. What is the height of your tie beam, 8' like in the book? That may mean you have to raise the porch plate over the tie beam, or just below it. How much headroom do you need for the tractor on the porch?

[Piston]

Yes, 8' to the tie beam.  The tractor's ROPS is 7'2" high, which is foldable so I can go lower if I have to.  I placed a few tie beams in there just to see how it looked, aesthetically, I'm not too happy with the looks of the tie beams.


They just don't look right?  Is my porch to wide?  Maybe I should go with 7' instead of 8'?  Do I need braces on the porch tie beams?  Also, how close to the top of the porch posts can I join the tie beam? I have it at 12" below now.
This is with a 3:12 pitch.

I like the way it looks with the 4:12 on the porch roof and no tie beams, but I don't think I'll be able get around that.



I don't want to raise the porch roof up any higher mainly for looks, I think it would look too 'tall'.
I may just have to put in the tie beams and go that route.  Honestly I don't think I'll park the tractor under there much so it shouldn't be much of an inconvenience....I'm just trying to have my cake and eat it too!   ;D

[Piston]

I played around with the model a little more and like it a lot better after putting some braces in, although it seems a little crowded on the porch now with so many braces....



As you can see I changed to curved braces and made the cross sill one long timber instead of breaking it up into two. 

I'm a little concerned that my tie beams for the porch are too close to the top plate? 

There's only about 4 inches above the tie.

Also on the other side, it sure seems like I have a lot 'going on' there.  It looks to me like I would be removing too much wood by having so many joints cut into my corner post? 



I found some more details on the half dovetail tying joint in Steve Chappell's book and updated those joints.



I tried attaching my sketchup file in case anyone wanted to check it out but the file is too large...

[Raphael]

  What I did for the extension I put on Sobon's classic house frame was put the tie over the plate to maximize headroom, but that'd mess with your complementary rafter-tail design...

  And I only put braces from the outer posts to ties as the entire main body of the frame resists the extension wracking in the other direction.

[mmhailey]

This is a really educational post for me. I have plans in hand for a 16X24 kingpost cabin. I too am adding a porch to the long side. My idea was to not tie into the 16X24 frame at all, but build a free standing porch. Much like your drawing, but add posts, and a beam, on the inside of the porch, after you have built the exterior wall.   The grade difference can be taken into account when you put in your foundation for the 16X24 structure, then a step down to your porch.

Just my idea, but I am interested in how ever one else feels.

[Raphael]

This is a really educational post for me. I have plans in hand for a 16X24 kingpost cabin. I too am adding a porch to the long side. My idea was to not tie into the 16X24 frame at all, but build a free standing porch. Much like your drawing, but add posts, and a beam, on the inside of the porch, after you have built the exterior wall.   The grade difference can be taken into account when you put in your foundation for the 16X24 structure, then a step down to your porch.

Just my idea, but I am interested in how ever one else feels.

For an unheated porch attached to an often heated and occupied structure that's actually the best way to go.  Where timbers pass from a heated interior through to the outside is a point of heat loss and often condensation build up which over time can rot the timbers.

[ballen]

Raphael,
I'm glad you mentioned the thermal properties.  I want to apply the same thought to the roof where the main house rafters stop at the walls (and there is no gable overhang) so the whole house can be wrapped to provide a thermal break.  Then, I'd like to extend the gable and side overhangs via framing on top of the insulation on the roof to achieve a protective overhang all the way around.  Has anyone ever done this?
Bill

[swampfox]

Hey Piston,  not bad.  I like the lap joints on the collar, and the stout tie with the wedged dovetail.

As far as the shed rafters.  Someone mentioned there will be thrust and you would need a tie to resolve.  In my opinion there would be no thrust on those rafters because they are supported at the two plates.  (Just like if you ran a post to support a ridge).  I would not think you would need a tie there.  The rafters almost seem to be the "tie" that holds the two plumb planes stable.

[Jim_Rogers]

There could be thrust there, especially if some snow slides down the main roof onto the lean to roof.....

[Jim_Rogers]

do you think I should change all my joists or just the ones I have dovetailed? 

Just do the ones you have dovetailed, although I can't really see which ones those are from those pictures. If you want to send me the design I can open it and look at it here.

Any thoughts on what joints I should use for the porch rafters?  I'm using a step lapped rafter seat for the rafter connection to the top plate, should I do the same for the porch or is the pitch not steep enough? 

If you secure the lean to rafter to the top of the main frame rafter with something like a timberlok screw or two, and you cut the birds mouth rafter seat on the lean to wall so that it acts like a hook to hold that wall from moving out, that maybe enough to hold it all together.
You probably don't need braces in the lean to tie beam to main post as you already have two braces in that wall plane.

Move the lean to tie up until it is just below the wall plate or put it over the plate and hook it down on top, beside the rafter. Just an idea.

Jim

[ballen]

I found this picture on  the Vermont Timber Works page.  Looks pretty close to what you are proposing....

[Piston]

do you think I should change all my joists or just the ones I have dovetailed? 

Just do the ones you have dovetailed, although I can't really see which ones those are from those pictures. If you want to send me the design I can open it and look at it here.

Jim

Emailed you the model Jim. 


The pic Ballen posted looks like it would work for me as well.  I'll move some things around and see what I come up with. 

[Piston]

Okay so I ended up raising the main tie beam up a foot which gave me some more room to work with for the joinery.  I also placed the rafters so they'll be tying into the top plate on the side like the last pic posted.  Would I use a tusk tenon for this joint as well?  It seems like it would work good hear as long as I can use it with an angled connection like this. 
Thanks to all of you for walking me through this, it sure is a big help.  ;)

Here it is with the tie beam moved up and rafter's repositioned.  I also beefed up the rafter's to 5x7.













Other than the two end ones, the porch rafters will be staggered between the main rafters so the joinery won't interfere with one another. 

[mmhailey]

How are you planning on enclosing the Workshop?

Will it be insulated?

[Piston]

How are you planning on enclosing the Workshop?

Will it be insulated?

It will be insulated.....eventually  ;)

For the first year or so of it's life I think I am going to go with vertical shiplap siding, which will be both my interior and exterior wall.  When I decide to insulate it I will probably go with one of the method's I saw in one of Tedd Benson's books (I think that's where I saw it.)
I'll put 2x4's laid horizontally spaced 2' apart, and infill with rigid foam insulation, then vapor barrier, and then mabye board and batten over that.  I haven't really gotten this far yet but that's what I'm thinking for now.  Not sure what I'll do with the roof yet, I'll probably insulate that right from the start because it would be more of a hassle to wait until down the road.

[maineframer]

Piston,

Your dovetail on your tie beam is upside down.

[Raphael]

Piston,

Your dovetail on your tie beam is upside down.

You put yours in with wedges on the bottom forcing the dovetails up?

[Jim_Rogers]

Raphael: He must be joking...... the dovetail is right according to Steve Chappell..... maybe that do it that way in Maine (I'm joking..... ;D)