This method seems to make sense. In a nutshell you are extending the lower ridge past the joint until it meets the next jack rafter, then the flying hip and valley are miter cut to meet the lower ridge.
My only complaint or disagreement with your model would be the height of the valley rafter. Should it not be raised up so that the sheathing from both roof planes rest on its centerline?
I’ve created a version of the model above with this method of framing at the flying hip/valley/ridge joint:
My other concern is the way I have the valley rafter miter cut where it meets the fascia and the corner of the building wall (top plate). Is there a more practical way or better way of making those cuts?
This version of Hip Roof 4 has the flying hip extending as a full hip to the exterior wall and then the lower ridge framing into it with the valley rafter framed in last.
Rev. 5 is a slight variation of the previous roofs. I have shifted the secondary roof over by 24" to create a T-shaped building. The question is how to best frame the long and short valleys:
Maybe which valley is long or short doesn’t matter, but it is something I want to put out there for discussion.
yes you are correct, my bad. there are a few issues with the hip/valley DC that needs fixing. Its a project I started 2 years ago and found that the modelling was becoming too complex and gave it a rest. There was and still is a need to improve DC work ability, naivety I thought the Sketchup coders would resolve some of the issues and increase the DC abilities, I have since come to the conclusion that I need to incorporate some ruby scripts.
In regards to the valley - fascia ends, it depended on the fascia and eave type, for timber fascias and boxed we would cut off to one plane and send the fascia through. For exposed then one had to cut a fancy joint. The cut you show is correct, however in a practise, trusses and rafters are installed with extended overhangs, to be cut off after to a string line, this allows for any discrepancies in the walls and pitching points. If the fascia were steel then just plumb cuts just short of the fascia line, okay and could be done off the bench.
Personally I would leave this aspect of your modeling of the valley end as you have drawn. Then in the final takeoff or list, the option of overhang finish could be addressed
In regards to the broken hip designs, if possible I would incorporate both, one where the hip runs through the other where it is cut. The difference is dependant on size and how the roof is supported. For large spans the rafters can be supported with underpurlins, struts, strutting beams… generally a cut broken hip would require a strut.
My head is hurting just thinking about the programming and logic that will be required to make just one of these options work, giving the option for both is going to be insane. There will be a lot of conditional states, if the roof pitches are different that will make things even more interesting, the effects of which I have not even fully considered.
The most common secondary roof condition will be either an L-shape or a T-shape roof. Then there is the case where you have two offset rectangles.
Also note that the segment of the supporting valley rafter between the upper ridge and lower ridge would need to be beveled or “backed” otherwise it clashes with the sheathing. I noticed this when I originally added the supporting valley rafter but confirmed my suspicion when perusing DeWalt’s carpentry and framing handbook this morning. I probably should have pulled this book out before beginning this study but it only confirmed everything I had managed to discover myself once I started examining the model.
Now that I’ve got a gable and hip rafter roof I was thinking about adding in a dutch gable roof, but I’m a little unclear on the best method to support the end rafters. Has anyone ever seen something like this used?
I’ve checked all of my carpentry and construction books and there is absolutely no reference material on traditional framing of this type of roof, online is also quite scant, any resources, framing diagrams etc… would be quite helpful.
Doubled up gable common rafters with the dutch ridge/ledger is sandwiched between them. Found a paper by Larry Haun, Mar. 1995 “Framing a Dutch Roof” that was published in Fine Homebuilding magazine, that describes a very similar method of framing.
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, or even a deeper LVL member, assuming there is no internal support available from internal walls.
I’ve also realized that for hip roofs I need an option to set the depth of the hip rafters since they are often larger members than the common or jack rafters.
@thomgeal,
You should download the plugin and experiment with it. Although it offers a wealth of structural design material, I have not seen bolt and nut data displayed in this extension. I would not expect this add-on to calculate such connection requirements, but the author may provide definitive information as to whether or not it is (or could be) provided.
The plugin is integrated with the Truss Designer to provide limited information for MPC wood trusses. I am currently working on an option for plywood and OSB wood gusset plates with nails in double shear. At some point I could also look at bolted connections however I have not gotten that far yet.
My “todo” list is a bit overwhelming at the moment. On top of that the plugin is still very rough around the edges, the user experience could definitely be improved in a number of areas. A few things come to mind:
Interface remembers most recent settings with regards to overhang, pitch etc… This would speed up the creation of redundant roof structures where constantly re-entering the same parameters becomes tedious.
Ability to set global settings and defaults (ie. default rafter depth is 2x10 size).
Layer control: Currently everything is placed on layer 0, Have the ability to specify which layers certain items get placed on and make these layer names all user configurable.
I used this option to create a monitor style roof line but it can also be used for porch roofs, carports etc… I still need to add a standard shed roof with and upper and lower birdsmouth cut.
This roof was generated by first creating a hip roof primitive then deleting all but 3 components which were then copied and rotated into place for the lower roof hip corner. The shed roof /w ledger component was created with one primitive and then copied and rotated into place. Overall a fairly painless process now that I am somewhat familiar with navigating my way around SketchUp. The fascia required a couple of trims.
The pyramid at the top required no manual intervention. Approximately 10-15 minutes of work for a fairly substantial roof.
Testing the real world application of the Medeek Truss Plugin. This model combines a double fink truss, raised heel fink truss, monopitch truss and shed roof with ledger. While creating the shed roof special attention to the birdsmouth cut was required to ensure that the fascia height of the rafters and trusses lined up. Also note the use of the raised heel type truss on the upper roof portion. Structural outlookers were specified for all gable overhangs.
5:12 pitch roofs with rafters and trusses 24" o/c. I did not apply a level cut to the rafter overhangs but that would probably be a given. Span of the double fink is 48 feet with 2x6 top and bottom chords.
If anyone has some real world applications using the plugin that they are willing to share I would be very interested to see how it is being used and it would also give me some direction for further development and improvements.
I’ve ran into this structural question before, where you have a stairway next to an exterior wall. My first thought is to call out a balloon framed wall up to the 2nd story top plate(s) but then that makes the rim board and double top plate of the first story discontinuous. What is the preferred solution or how have you seen this done in similar circumstances.
Here is a quick mock up in SketchUp to better explain what the two options are:
In my experience, the typical approach for framing around a stairwell that is contiguous to an exterior wall is to use platform (or western) framing where the header and sole plate runs as a continuous element at each floor level (as depicted in your second illustration and as shown in the model on the left).
There are some issues with framing this using the platform method hence the balloon framing option was something I was exploring. However if some care is used in the connection, see detail below the hinge effect can be dealt with.
This discussion really belongs on a structural engineering board but I posted here to show how SketchUp combined with the plugin is helping me visualize some of these problems better.
