Truss Plugin/Extension


For large agricultural buildings a double inverted truss can be employed to provide a large vaulted span for machinery:

I am wondering if this truss type is still commonly used by anyone for this type of application and whether it would be of interest, enough for me to add it into the growing list of trusses within the plugin.

Also if anyone has any shop drawings they could send me that would be very helpful.


A quick study of a double inverted truss by taking two 24’ howe trusses and joining them to form a double truss. Note that the 4:12 pitch of the original trusses is maintained and the interior vault is exactly 8:12 pitch.

View model here:

My question with this configuration is how the top and bottom chords at the peak should butt up? For example should the bottom chords at the peak have a double scarf cut or a single scarf cut? Some shop drawings would help in determining what is common practice.


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:

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.


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.


This map shows where the Truss Plugin is being utilized:

Note, this is only registered users and not all installations of the trial version. Also note that addresses have been dumbed down to City, State, Country so that the privacy of registered users is upheld.


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.


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:


I will probably add the symmetric cathedral truss type next:

View model here:

The web configurations will use an “auto” triangulation algorithm similar to the tray truss type.


Version 1.6.0 - 06.08.2016

  • Corrected a bug with raised heel fink trusses and structural outlookers.

This update may seem minor but underneath the hood it is a big change. I’ve rewritten a significant portion of the common truss module so that I can now offer raised heel trusses for all the other common truss types. Be on the lookout for this update in the near future.

Raised heel trusses (wedge, slider, vert) complicate things when combined with structural outlookers. I’ve had to add some significant logic to deal with all the permutations.


Various configurations of a 16’ King Post Truss:

View model here:

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


I was really hoping to make it to Basecamp this year but it does not look like it will happen, too much work and too little funds. Hopefully some of you can vouch for me there if you are attending this year. I’m going to try for next year and by then this plugin will be even more substantial and a little more polished.


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:


Version 1.6.2 - 06.14.2016

  • Added Symmetric Cathedral truss type, configurations: (AUTO).
  • Metric input enabled for symmetric cathedral truss type.
  • Added gable end trusses for symmetric cathedral truss type.
  • Structural outlookers (vert. & horz.) enabled under advanced roof options for Symmetric Cathedral truss type.

Various sizes and configurations of a symmetric cathedral truss:

View model here:


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

View model here:

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?


(Note that i’m going by what our roof truss manufacturer and engineer puts back to us - I just draw the things ;))
Most hipped roofs I see are more like a half-truss that has a “follow me” running around the perimeter rather than a trimmed shape as you show, so the following might not be of any use…

The common detail I see is that the hip timbers always meets at the top of a rafter and this position dictates the rafter spacing. I always see this rafter doubled up too.

Most of the time it does; aesthetically it looks nicer, but there are occasions where it has to change. (Such as matching an existing roof pitch or over-shadowing.)


With non-structural lookouts would you frame them something like this? This question is mostly directed at the contractors and carpenters out in the field who actually have to build these roofs. Typically as an engineer I never worry about these details especially when they are non-structural.

In my opinion they aren’t really doing a whole lot, much better to drop the gable truss and then cantilever them from the first in board truss (ie. structural outlookers).


Hip Truss Algorithm:


Outlookers oriented horizontally with gable end truss top chord dropped:

View model here:


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:

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.