Hip roof joint at upper end

[grweldon]

In a previous post, Jim gave great illustrations of a dragon and cross joint for the corners of a hip roof.  I am wondering what the joints would look like where the rafters all came together to form a point.  I'm specifically talking about a small square structure, say 8-12 feet square.  I can't even picture what this joint might look like.  Can anybody point me in the correct direction, or better yet, provide a picture?

[Jim_Rogers]

Well, the easy answer is: "it depends"...... on how the roof is being designed. Are you going to have a ridge beam? Are you going to have this ridge beam supported?

A supported ridge beam may look like this:



 


With a post coming up under the ridge beam.

If the ridge beam is not there then you will have a pair of rafters that butt or connect with each other at the peak. Then a common rafter will lean against them from the gable end roof.
The hip would then lean against the two main roofs and the gable end rafter with two cuts, one on each side for the sides where it rests against the other common rafters. These may be only held in place with nails or screws.

I don't seem to have a good picture of this on file.

I hope someone else who has more experience with hips can post a picture for you.

Jim Rogers

[giant splinter]

Here are some photos of hip intersections, it is not uncommon for most timberframers to not have built very many of these. This set of photos is closer to hybrid timberframing and as you can see after a close look the is hardware used in it as this structure is in a public park. I am not sure who built it and the primary timberframer in that part of Idaho for the most part does not deviate from the traditional style of timberframing.






Apparently I made some sort of error in downloading my photos, sorry for the inconvenience ...... they can be viewed in my album under traveling photos till I get this straightened out. I suspect i have chosen a file format that is not recognized though they are in my gallery.

It looks like I may have messed up something bigtime and loaded them a bunch of times in my gallery. I hope no one is inconvenienced by this as its obvious I still have a lot to learn about the gallery photos and adding them to my post. I hope you can find them in my gallery ...... if not Tuff ;D

[grweldon]

Giant Splitter,

Those photos are about 3/4" tall and 1" wide in my browser.  Got anything bigger?

[beenthere]

GS
You should follow the posting suggestions in the "Behind The Forum" forum and if they are in your gallery in .jpg format, they will be easy to post.
They are thumbnails, and do not have the [img ] [/img ] brackets around the url's that you copied. You are close tho.
Go back to the messed up post, and click on modify. Work on it until you see what you want when you check it in "Preview" .  When correct, then re-post it.

[canopy]

I hope this is what you are asking about. Below are pictures of what the joint looks like on a frame I made. You can see the finished version in my avatar. There are also other ways of making this joint.


rafter to ridge beam joint, top view


bottom view


exploded view of rafters from the bottom.

[giant splinter]

I ran out of time today, looks like the admin. did some damage control for me (thank You) I will get a handle on it one of these days 

[grweldon]

Canopy, that is close to what I was picturing, but I'm thinking about a completely square structure where all four hip beams come together in the center and join.  I'm thinking that it might be necessary to just cut compound miters on the ends of each of the hip beams and nest them together with no mortise and tennon joints.  They cold be fastened with timber screws or wooden pegs.  Would that be feasible?

[D L Bahler]

where all four hips join at a single peak, I would think it best to use a key timber, that is instead of all timbers coming together, which requires some complex joinery and compound angles, you use a key timber that captures all 4 hip rafters into joints, or even which they are simply nailed to. It simplifies thing a bit, and if done right adds a good deal of stability. Also if you would have a post underneath, the key gives a convenient support mechanism. In the case of a king-posted pavillion type roof (4 hip with a king post in the middle) the post itself doubles as the key.

Around here, there are many houses that appear to be full hip right up to a single peak, but closer inspection reveals a short ridge cleverly oriented so that you don't always see it. Sometimes there is even a small flat at the very top (these are the oldest farmhouses, which a square structures built of solid brick, with timber roof structures) This was done to simplify the joinery at the top.

[Jim_Rogers]

If the post in the middle of the four rafters comes down to a beam I think it's called a king post. But if it comes down and doesn't touch a beam it maybe called a king pendant.

I have drawn one like this:



 

But I don't have any joinery details to go with it.

Jim Rogers

[Carpenter]

If the post in the middle of the four rafters comes down to a beam I think it's called a king post.

Jim Rogers

I've heard it called a bos pin before.  I was in an old barn in Illinois that had a roof similar to your sketch-up drawing.  The bos pin was supported by the hip rafters with struts going from the bottom of the bos pin to the hip rafters.  I don't have the actual dimensions of the building but it was approximately 45'x45'.  The whole roof was a freespan.  Obviously it can be a very strong system. 

    This is a little off subject, but, I would like to build an octagon gazebo with a hipped roof and a bospin.  I just haven't been able to figure out how to join eight hipped rafters to the pin.  I could use lag bolts of course, but, if there's a way I would prefer to do it with wood joinery.

[jueston]

If the post in the middle of the four rafters comes down to a beam I think it's called a king post.

Jim Rogers

I've heard it called a bos pin before.  I was in an old barn in Illinois that had a roof similar to your sketch-up drawing.  The bos pin was supported by the hip rafters with struts going from the bottom of the bos pin to the hip rafters.  I don't have the actual dimensions of the building but it was approximately 45'x45'.  The whole roof was a freespan.  Obviously it can be a very strong system. 

    This is a little off subject, but, I would like to build an octagon gazebo with a hipped roof and a bospin.  I just haven't been able to figure out how to join eight hipped rafters to the pin.  I could use lag bolts of course, but, if there's a way I would prefer to do it with wood joinery.

let us know what you come up with, I've been working on a octagonal hammer beam in my head for months and have not figured out all the joinery yet.... I figure if I think about it enough, one day I will wake up in the middle of the night and the answer will seem obvious.... 

[Jim_Rogers]

To do the joinery into a "Boss" pin you have to make it very large. Something like a 12x12 or so. That way you can have 3 or 4" tenons on each rafter into the boss pine and still have some wood there to hold them all together.

I don't know if I've got a good picture of a "pin" or not.

I'll have to do a search and see.

Jim Rogers

[giant splinter]

Jim, it looks like the Boss Pendant that your drawing employs would work if it had eight contact faces, it would surely be a great deal larger to allow all the mating surfaces to have room for proper connections. I like the way yours looks and can visualize an eight or even a six point version of it in place. I would bet that if any of our forum Structural Engineers had a look at the full hip you have shown they would agree that the ridgepoint connection with your hip rafters and supporting jack rafters would comprise a very sound roof framed structure. Once a connection point gets overcrowded it makes for some special consideration in how to make it work, in some cases  fabricated metal brackets are the answer and can often be covered with a wooden surround so as not to detract from the original timber frame design.
The frame joinery that Canopy shows is very nice and almost leans towards the Japanese timberframe joinery with its complex and beautiful workmanship, always more to look at and "dream about building".