Dutch Gable Roof Bracket

[medeek]

I'm looking at a dutch gable roof right now for a local client and it occurred to me that I have no idea how a roof like this is traditionally framed (no trusses). Has anyone ever seen something like this used?

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

http://www.medeek.com

 

[jimstructures]

Medeek,

As a retired roof framer and without running any numbers, I would double the last common rafters that the dutch hips are attaching to or I would extend the doubled hip rafters all the way back to the ridge beam and leave the ridge beam uncut and running all the way to the end of the shown dutch hat at the end of the current ridge beam and then install jack rafters down to the hip roof on the end wall. The would require compound cuts on the bottom end of the jack rafters.

I haven't run any numbers to see if this works for stress but they are both common prescriptive framing solution and should be shown in traditional framing sources.

Jimstructures,
former carpenter and timber framer and current steel structural designer.

 

[medeek]

Any recommendations on traditional framing sources? All of my books on carpentry and the WFCM don't really get into this particular configuration (dutch gable). Most everything I see anymore is done with trusses so I'm out of my comfort zone on this one.

I get the doubling of the last common rafter, it is essentially filling the role of the girder truss in a typical hip truss scenario. However, I'm trying to determine how they are going to connect the ledger/header board (supporting the end jack rafters) to the last common rafters. The connection detailing there has me stumped. I'm looking for a prescriptive approach that might be employed by a framer/carpenter.

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

http://www.medeek.com

 

[XR250]

I honestly have never worried about it and they seem to hold up fine (in my neck of the wood that is). If it was a really big roof, I might look into it a little more.

 

[chicopee]

"...I would double the last common rafters that the Dutch hips are attaching to ..." that a very point. If you go on line you'll have many topics and pictures which you can evaluate and feel comfortable about the project.

 

[chicopee]

That's what it should have said: "...I would double the last common rafters that the Dutch hips are attaching to ..." that's a very good point.

 

[medeek]

I probably would have not even gave it a second thought until the client asked me about using a special bracket, similar to that shown above. That got me thinking about how is this type of framing done traditionally (prescriptive). It would be easiest to simply redirect the client to a prescriptive approach and avoid doing a bunch of unnecessary engineering. At the very least I need to educate myself on the best way to frame this out so I can present a coherent and sensible solution to the client.

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

http://www.medeek.com

 

[XR250]

Come to think of it, I have done something special previously. Doubled the last rafter and installed a ceiling joist on each face to make a truss. Then added (4) collars up at hip level. Two in between the double rafter and one running long on each face. This gives a stout band to nail to. The hips and jack rafters are then just toe-nailed to this. Generally, the hips are not long enough on these to required special connectors. Maybe with all this snow, I might re-think that.

 

[medeek]

@ XR250

I like the method you've described. I also found a paper by Larry Haun, Mar. 1995 "Framing a Dutch Roof" that was published in Fine Homebuilding magazine. Both methods are very similar. A quick model in SketchUp would look something like this:

Disregard the common rafter sizes they are undersized but look at the method of sandwiching the dutch ridge/ledger between the last common rafters. I would probably also install some blocking between the double gable common rafters. I'm also not showing all of the ceiling joists and bird blocking etc...

If the roof gets large enough then one could go to a double ply dutch ridge like you've described above, or even a deeper LVL member, assuming there is no internal support available from internal walls.

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

http://www.medeek.com

 

[jdgengineer]

Is the central space vaulted? If not I would frame as a hip and overframe the dutch gable.

 

[jimstructures]

Medeek

The "Journal of Light Construction" has had several articles, over the years, on framing hips. Maybe they could give you some ideas on how these are traditionally framed.

Jim

 

[medeek]

If the dutch gable is small then I agree it makes more sense to frame as a hip and overframe the dutch gable. However, if the roof is large and the dutch gable is 4-6' from the gable wall I think it makes more sense to frame it as above.

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

http://www.medeek.com