Truss Designer 2015 Updates

[medeek]

Version 1.5.5 - 04.29.2016

- Added Gambrel Attic truss type, configurations: (AUTO w/ piggyback trusses).

- Added a graphical user interface (GUI) for gambrel attic geometry input.

[medeek]

I am wondering how many of your designers/architects/contractors/builders out there have used Open Joist products?

http://www.openjoisttriforce.com/

I was thinking I might add their product line to the Floor Joist/Truss module.

[Marc]

It's common here.

Marc

[medeek]

Version 1.5.7 - 05.15.2016

- Added Scissor truss type, configurations: (4/2, 6/4).

- Structural outlookers (vert. & horz.) enabled under advanced roof options for Scissor (4/2, 6/4) truss types.

View model here:

https://3dwarehouse.sketchup.com/model. ... 25b4cc17fc

I also updated the pause in the truss selector GUI from 700 ms to 400 ms. Still more work to be done with raised heels and structural outlookers for some of these configurations but its getting close.

[medeek]

Coffer Truss Algorithm:

This is assuming that the coffer span is centered on the truss. A non-centered coffer algorithm could get significantly more interesting and difficult.

[medeek]

Version 1.5.8 - 05.22.2016

- Added metric input for Gambrel Attic truss type.

- Added a graphical user interface (GUI) for metric gambrel attic geometry input.

Gambrel Attic (metric) GUI

I also show the industry standard feet-inches-sixteenths.

[medeek]

Version 1.5.9 - 05.29.2016

- Increased top chord pitch limit from 12/12 to 18/12 for the following Scissor truss types, configurations: (2/2, 4/4).

- Heel web logic revised to accommodate steeper pitches for bottom and top chords of scissor trusses.

- Increased top chord pitch limit from 12/12 to 18/12 for valley truss sets.

16/12:12/12 Scissor Truss with an 18" raised heel:

Notice that the steep pitch of the bottom chord changes the way the heel web and bottom chord meet at the bearing point. The additional logic listed in the changelog notes deals specifically with this issue.

View model here:

https://3dwarehouse.sketchup.com/model. ... 771fbfa936

[medeek]

Various configurations of a 16' King Post Truss:

View model here:

https://3dwarehouse.sketchup.com/model. ... c43148d958

With a raised heel note the use of either a wedge, slider or vertical web with strut.

[medeek]

Version 1.6.1 - 06.11.2016

- Added Coffer truss type, configurations: (AUTO).

- Metric input enabled for coffer truss type.

- Added gable end trusses for coffer truss type.

- Structural outlookers (vert. & horz.) enabled under advanced roof options for Coffer truss type.

- Building parameter menu (2nd) and advanced options menu for trusses now default to last picked options of the session for that sub-menu item.

Various configurations of a 40' coffer truss shown below:

The web triangulation algorithm automatically determines which configuration is appropriate based on the span between panel points. This simplifies the geometry input menu but does take some control from the user.

View model here:

https://3dwarehouse.sketchup.com/model. ... bdfdd078f4

[medeek]

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

View model here:

https://3dwarehouse.sketchup.com/model. ... 41b47a636f

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?

[Marc]

I've never seen this type of roof configuration done right with trusses. In your drawing, there's not enough support for the decking near the apex. What I usually see is some stick framing jutted in there to make it look better but there's no accommodation in the IRC to mixed stick framing with truss framing. Neither has any builder ever shown me an engineered certificate on a roof design that mixes these two, whether Jerkin Head roof or other.

Marc

[medeek]

Hip Truss Algorithm:

[medeek]

I've never seen this type of roof configuration done right with trusses. In your drawing, there's not enough support for the decking near the apex. What I usually see is some stick framing jutted in there to make it look better but there's no accommodation in the IRC to mixed stick framing with truss framing. Neither has any builder ever shown me an engineered certificate on a roof design that mixes these two, whether Jerkin Head roof or other.

Marc

I agree there will have to be considerable blocking added to make this work, in particular the triangle of sheathing at the apex of the hip. I've actually never seen a jerkin head truss set in the field and to what lengths the contractor had to go to make it work. As noted previously I rarely ever consider this situation since we engineers usually leave the truss set to the truss manufacturer and pretty much ignore it completely. Now that I'm looking at it in some detail I realize that I am in the dark on how this thing actually goes together.

I appreciate the perspective of the code enforcement official since it is up to you guys to give the framing its final blessing. You have probably seen all sorts of crazy things, some that work and some that don't. I try to get out in the field as much as possible these days, it never quiet goes together like it should have on paper.

[medeek]

Version 1.6.3 - 06.19.2016

- Added Gable Dormers to the Minor Roof Sub-Menu (dormer walls only).

For now only the walls of the dormer are created:

View model here:

https://3dwarehouse.sketchup.com/model. ... b6484e8f08

I am still ironing out the details on how to best model the roof geometry. I will probably offer either a rafter or truss option. Other details such as multiple windows will also come later.

For now please test the metric and imperial wall creation. I will probably need to post a tutorial video on how to use this feature since it involves selecting the main roof plane (top of a rafter or truss) and then two points that define the width/exterior corners of the dormer.

[medeek]

Testing the dormer (wall) feature out with a gambrel attic truss:

These dormers have a typical gable profile but it might be useful to have a gambrel dormer option as well to match with a gambrel style roof. Note that I have not shown all of the ladder framing in the model. On a roof like this it could get quite extensive.

To generate the dormer roof I just used my rafter roof feature and then trimmed the elements back manually.

View model here:

https://3dwarehouse.sketchup.com/model. ... 891371c77c

https://www.kubity.com/p/uCN2F6

[medeek]

Same barn with a few more details. For gambrel attic advanced options I should also include the option for a crow's beak as shown in this model and the option to set the extension.

View model here:

https://3dwarehouse.sketchup.com/model. ... e28b9f477e

https://www.kubity.com/p/hNVovS

[medeek]

Under advanced options for gable roofs (truss and rafter) I am thinking about adding a "roof return" option. Any thoughts on "greek returns":

The images above shows a roof return with a gable termination, alternatively this could end with a hip termination as in below:

Or with a full greek which stretches across the entire span:

Does anyone have any specific framing details on how best to frame these roof elements?

As far as the logic to add them into the plugin it won't be a big deal, just an additional module that plugs into the advanced roof module.

To simplify things I would used the same pitch on the returns as on the main roof. The three variables would be:

1.) Return Type: Gable, Hip, Full

2.) Length of the Return

3.) Extension beyond Rake

[Marc]

Under advanced options for gable roofs (truss and rafter) I am thinking about adding a "roof return" option. Any thoughts on "greek returns":

I call them 'cornice returns' since it's just the cornice that's actually coming around the corner.

Marc

[Marc]

Does anyone have any specific framing details on how best to frame these roof elements?

As far as the logic to add them into the plugin it won't be a big deal, just an additional module that plugs into the advanced roof module.

To simplify things I would used the same pitch on the returns as on the main roof. The three variables would be:

1.) Return Type: Gable, Hip, Full

2.) Length of the Return

3.) Extension beyond Rake

Cornice returns, whether ending in a gable or a hip, are done the same way as a hip roof i.e. band board (nailing base for top of rafters)/structural frieze (nailing base for lookouts)/rafters/lookouts/structural fascia, with the hip added for returns ending in a hip configuration. The only difference is that it's just the cornice that continuing around the corner, not the whole roof.

Marc

[medeek]

Version 1.6.4 - 06.27.2016

- Added roof return option within the advanced options menu for common, scissor and vaulted trusses, configurations: (HIP).

View model here:

https://3dwarehouse.sketchup.com/model. ... 7da0209a02

This option is available for most typical triangular shaped trusses.

I will be adding the gable and full return at a later date, currently only the hip return is available. Another limitation is that the return roof pitches currently default to the main roof pitch. I need to add some additional code that will allow the pitch of the return portions to be set independent of the main roof pitch.

[Marc]

Version 1.6.4 - 06.27.2016

- Added roof return option within the advanced options menu for common, scissor and vaulted trusses, configurations: (HIP).

View model here:

https://3dwarehouse.sketchup.com/model. ... 7da0209a02

This option is available for most typical triangular shaped trusses.

I will be adding the gable and full return at a later date, currently only the hip return is available. Another limitation is that the return roof pitches currently default to the main roof pitch. I need to add some additional code that will allow the pitch of the return portions to be set independent of the main roof pitch.

The rake soffit of the gable wall is going to look strange and burden the framer with a lot of detail if the slope of the return is greater than the main roof.

No problem with making the return slope lower than the main roof because the gable rake soffit gives you a break on how to slope the return - as long as it isn't greater than the main roof.

Marc

[medeek]

12:12 main roof with a 8:12 hip roof return. The interesting part is the hip rafter

where the return meets the main roof plane. The dropped hip rafter is off center so that it supports the sheathing from both planes. The calculations might prove challenging.

Typically I think the return pitch is usually less than or equal to the main roof pitch. I don't think I've ever seen a situation where it exceeds the main roof pitch.

[Marc]

12:12 main roof with a 8:12 hip roof return. The interesting part is the hip rafter

where the return meets the main roof plane. The dropped hip rafter is off center so that it supports the sheathing from both planes. The calculations might prove challenging.

The wide rake cornice and that little return hip are generally exclusive. Use the little return hip when the main rake is nothing more than a 1x (or sometimes 2x) nailed on top of the gable siding. If you want the wide main rake, leave that little return hip off and run the barge rafter down to the fascia. The return framing depends on whether the main cornice is boxed or whether the finish soffit is secured directly to the bottom of the main commons. Both are common in my area.

I've never seen a cornice return pitch that was any different than the main pitch but every region is different.

Typically I think the return pitch is usually less than or equal to the main roof pitch. I don't think I've ever seen a situation where it exceeds the main roof pitch.

Marc

[medeek]

Roof return pitch can now be set independent of main roof pitch:

The calculations for a hip rafter that handles two pitches was insane as expected. I've also made some other minor adjustments and bug fixes related to the sheathing and rake board when the roof return extension equals the gable overhang.

I've set it up so that the return pitch can also be greater than the main roof pitch but its doubtful if this will find any usage.

[medeek]

Looking at the lumber and I-Joist floor module this morning and thinking it might be nice to make an option that allows one to specify something other than a rectangle for the floor outline. For example an L-shaped floor outline:

View model here:

https://3dwarehouse.sketchup.com/model. ... e7cb74e0c5

https://www.qrvr.io/p/HlnqPF

Or even more exotic shapes with non-orthogonal corners. I'll be giving this some thought over the weekend.