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Half Hip Truss Set

Half Hip Truss Set

Half Hip Truss Set

(OP)
Modified an existing truss roof to make it a half hip truss set:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=6e2...

This will be my first venture into more complex truss systems. I figured I would cut my teeth on the half hip (Jerkin Head, Tudor Hip) truss set first before attacking the more complex full hip variants of which there are many.

After sketching this model up and examining the geometry I now have a number of questions:

1. Are my roof planes correct? Note that I have drawn the apex of the hip roofs at the edge of the last full truss and not at its centerline. Not entirely sure what is common practice in this regard.

2. I've shown some non-structural outlookers along the rake. What would the outlookers along the half hip portion look like?

3. If I use structural outlookers how would those be framed in over the hip section?

4. Does the apex of the half hip typically coincide with the next truss or could it land somewhere between trusses? ie. the half hip length is some multiple of the truss spacing.

5. Is the hip section usually the same pitch as the rest of the roof? There is really no reason why it has to be.

6. As the length of the half hip increases the depth of the gable end truss decreases as does the first inboard truss. What is the practical limit for the minimum depth of the first inboard truss?

7. Does anyone have some shop drawings of this type of truss set that I can study?

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

I would call that a tudor hip. To me a half hip is a mono-sloped hip truss. But names are very regional, so that doesn't mean much.

When I get plans with a hip like that, they rarely specify the flat top, height, or setback. So I would typically adjust it to something that suited me.

The gable lookouts on the sloped area - I have typically seen them stuck on the face of the gable sort of like the overhang on a truss.

RE: Half Hip Truss Set

(OP)
I find it strange that the customer or architect/designer would not specify the setback, seems like a cosmetic element of the structure like this would be closely scrutinized.

With non-structural lookouts do you mean something like this?

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

The people who draw plans seem to just draw what's visually appealing. They don't have to worry about things like how the framing fits together.

The way you drew the outlooker blocks is what I would typically see around here. (Although they might have a brace going back to the gable) But I'm sure it's a very regional thing.

RE: Half Hip Truss Set

(OP)
Non-structural outlookers like this seem rather pointless to me. They aren't doing a whole lot, much better to drop the top chord of the gable end truss and extend the outlookers back to the first in-board truss.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

(OP)
Oriented horizontally:



With the gable end truss dropped.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

FYI - I'm not trying to tell you what I think is best - Just what I typically see.

RE: Half Hip Truss Set

(OP)
I appreciate that. There is always more than one way to do something. I'm just trying to nail down the most widely accepted method(s) of handling this type of roof shape.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

Step down hips are the typical way of doing them here. The girder truss normally has an 8 ft set back from the outside wall. One manufacturer goes with a 6 ft set back.

RE: Half Hip Truss Set

(OP)
Does anyone have some PDF's of shop drawings for a California Hip Set that they would not mind sharing with me. The standard stepdown, midwest and northeast variants are pretty straightforward but the California is a bit of mystery to me, how it goes together.

On the example shown I used a 8 ft set back for the girder but I am curious what drives this number, I'm assuming the overall span and roof pitch has something to do with it.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

(OP)
This is the California Hip Set:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=c17...

The problem I am having with this variant is the conflict between the 2x6 hip rafter and the top chords of the step down hip trusses.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

Your step-down hip -

I'd say you have it about right. But I have never seen a manufacturer stick with a specific setback, like 6' or 8'

What I've always done here (Central Illinois) is something this: There's a common truss at the peak. The first step-down has a 4' 1 1/2" flat top. Next one has an 8' 1 1/2" flat top. And so on down to where the setback is 8' or less.

For instance - A 32' hip set. Trusses are stepped down until the girder, which has a 16' 1 1/2" flat top. That leaves a setback of 7' 11 1/4".

The reason for the 7' 11 1/4" setback is so that the jacks work at 2' O.C. all across the end. Otherwise you'd have an odd space and the framer would have to cut plywood.

On long span hip sets (Like 60 feet or more) the setback sometimes has to be greater so the hip girder has more depth. Then you have to get creative in how you do the corner sets.


The california hip -

We always figured the plumb cut of the hip rafter, and made the flat top of the hip girder low enough so that it passed over it without a birdsmouth.

The trusses behind the hip girder were often the same as one ply of the girder, with the top chords extended to meet the hip rafter. That reduced the number of setups.


The Northeast hip -

I've only seen drawings of it. Never have seen it done in practice. But things are very regional, so it might well be popular elsewhere.

RE: Half Hip Truss Set

(OP)
I've just measured the dimensions on the stepdown hip set and they match your numbers exactly as outlined above.

The problem I'm having with the california hip set is that I'm using a 2x6 hip rafter. If I drop the flat top of the hip girder so that I don't have to birdsmouth cut the rafter then the top chords of the end jack trusses do not bear on the top of the hip girder. I've seen some examples of the california with the trusses beyond the hip girder all the same as the hip girder except for the top chords extending up to the hip rafter. It would seem better though to have the flat tops of the hip trusses so that the jack trusses bear directly on them otherwise additional blocking will be required to provide support for the top chords of these end jack trusses. However, I do see the economy in making them all the same size and reducing manufacturing costs.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

(OP)
Reading various threads and blogs on the internet I came across the stacked hip rafter, I think this is the solution to the conflict between the hip rafter and girder truss top chord:



A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

(OP)
A stepdown or midwest hip set with a drop-in purlin frame:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=5d0...

There is some minor conflicts at the top chord of the frame with the hip trusses and at the peak but I don't think it is worth worrying about.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Half Hip Truss Set

(OP)
A smaller (16' span) standard terminal hip set attached to the main roof with girder truss and valley set.



View model here:

https://3dwarehouse.sketchup.com/model.html?id=beb...

From what I've read the standard terminal is only used on smaller spans.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

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