Is a hip roof a timber framing nightmare?

[Jim_Rogers]

That is a cool joint ,but how do you cut the hip beam if you want a large or small over hang?

The dragon beam, the one the hip connects to, can extend out beyond the outside surface of the plate and tie, which is or could be the outside of the walls.

The above drawing was for a small shed with no large overhang.

Jim Rogers

[nas]

I would not recommend the corner joint where the dovetail is but that's what the client wanted.


Jim Rogers

So what would you recommend for that corner?  I am putting a porch on my house and it needs some corner joints, and I'm wondering what would work best.  The posts are 7x7 and the beams 7x9.
Thanks,
Nick

[Jim_Rogers]

I would not recommend the corner joint where the dovetail is but that's what the client wanted.


Jim Rogers

So what would you recommend for that corner?  I am putting a porch on my house and it needs some corner joints, and I'm wondering what would work best.  The posts are 7x7 and the beams 7x9.
Thanks,
Nick

Normally you don't design a three way joint.

A three way joint usually takes away too much wood from all of the members.

You would offset one or two of the pieces so that the height of the plate or the height of the tie beam is lower then the other.

You have to consider the order in which things are going to be put together and design so that it can be put together easily.
Some things can be drawn that can't be assembled.
You have to consider all aspects of the design, including raising it.

There are joints that could work, but each frame has to be reviewed for the entire structure.
And I can't say for sure what will work best for you without knowing all the details about the complete design.

If you have a sketchup plan of it you could post it in the plans section and we could look at it.
If you don't have one, but you have paper drawing of it, you could take pictures of the drawing and post that.

Let me know if I can be of any further help to you.

Jim Rogers

[nas]

here is my attempt at the drawing.  I'm not great with sketchup so bear with me
I can't figure out how to draw the hips and valleys.  The joints in question are the corners on the beams.  I don't want to use a lap or tongue and fork because one side will not bear on the post.  Any suggestions?

Nick

[Jim_Rogers]

  Any suggestions?

Nick:
I reviewed the Historic American Joinery series from the guild and found a joint that may work for you.
You can download the free pdf's from the guild site.
In section 2 on page 5 and 6 are some corner joints where the tie and plate meet at corners at the same (or nearly same) elevation.

I opened your sketchup plans and got your dimensions of your post and plates and made up a version of your joint using one of the corner joints shown in the above pdf.

Here is one way you can make your corner joint:



Here you can see that the post tenon is set back from the end of the first plate. And that there is a housing under the plate for the top of the post to fit up against the plate so that there is plenty of bearing area.
Next is the second plate attaching to the first one. This is where there maybe some problems.
If the post shrinks then the bearing area of the second plate onto the top of the post is going to get reduced. I have drawn it with a 1/2" housing but you may want to make it a lot deeper. Maybe even 1", or more. So that there is plenty of bearing area for the second plate onto the top of the post.
If you don't when the second plate shrinks in height the plate could lift up off the post until the tenon splits the plate and lets it sit back down.
I would make sure that the second plate's tenon is loose in the mortise so that it has room to move down if the second plate shrinks. And not split the second plate.

I'm not sure what type of wood you're using so you may need to modify the tenon sizes and lengths to allow for more relish and pegging.

Here is a picture of the joint with the pieces all together but "see through" so you can see everything inside:



I hope this helps.

Jim Rogers

[nas]

Thanks Jim, that is exactly what I was looking for.  I am using white pine timbers.  It's funny how you can over think something, and when you ask someone, the solution is fairly simple.

Nick

[Brian_Weekley]

Jim,

Would you peg those connections?  What's the best way to do that since the pegs can't go all the way through without penetrating the adjacent timber?

Thanks, Brian

[Jim_Rogers]

If you go to the section of the Historic American Joinery series mentioned above you can see how it was pegged.

You would blind peg the post tenon to the first plate and then blind peg the second plate to the first plate.

A blind peg is one that has the long tapered end cut off so that the peg is nearly the same shape from tip to end.
Draw boring would be a challenge with such a peg.

Jim Rogers

[creekyphil]

I needed 14 ft of 6"x8" per mare and colt, with 42" decks.

[shinnlinger]

http://keeperbarn.com/2012/05/17/plymouth-hip-roof/

[Brian_Weekley]

Pretty cool.  The photo labeled "Hip Rafters-1" is pretty funky.  Looks like that joint would just snap off, but apparently it held up quite well since 1790!

[moorerp]

WoW!  I feel like such a slacker for starting this thread and only just now getting back to it; so much new information!  Sorry for the long absence, but my life becomes one big blur of work in the 4 months of late spring/early summer, but I'm back in the saddle now and gearing up to think about the design of this frame again.

Jim:  Thanks a zillion for posting the pictures of the dragon and cross.  That joinery will look amazing, be relatively easy to cut (or so it looks), will make the hip rafter-to-plate joinery much easier than it would have been, and I'm assuming it will make the whole structure much more sound than without it? 

If that last point sounds like a question, it is....  I'm assuming that the hip rafters cause unwanted thrust at the corner joints, and that the piece of this dragon and cross that spans the plate/tie works to counteract that thrust ('thrusting the tie and plate back together)?

cheers,
randy

[Housewright]

Hi Randy;

You are probably well on your way but I thought I would mention that historically it was common in 19th century framing in my area (Maine) for the common rafters which join to the hip rafters to be tenoned at the bottom but nailed to the hip rafter. Nailing these rafter tops makes life much simpler.  If that sounds too easy you can always make your own nails!

Good luck;
Jim

[moorerp]

You are probably well on your way but I thought I would mention that historically it was common in 19th century framing in my area (Maine) for the common rafters which join to the hip rafters to be tenoned at the bottom but nailed to the hip rafter. Nailing these rafter tops makes life much simpler.  If that sounds too easy you can always make your own nails!

Hi Jim,

Hey, my whole family lives just down the way from you- Mom in Rockland and everybody else near Camden!  I'm out that way pretty regularly.

And my brother (the one who thinks I'm crazy to try a hip roof on my first frame) had the same suggestion; make it a hybrid by cutting the main roof elements and essentially stick framing the minor elements.  As I get further into the framing process, I'm sure that suggestion (minus the making my own nails) will start to look more and more attractive....

And just for full disclosure, I haven't even started on my way.... :