Custom truss option to model a tied roof

I am trying to use the truss module to design an additional lower tie (node 2 to 5) to a deficient roof. The model worked okay until I tried to change the lower portion of the rafters to an LVL product as if member reinforcing is being added. The Member Data section now shows with a “NaN” error code and the results will not calculate. Did I do something wrong or is there a bug in the software?

On a related note, the member selection page would be easier to use if the drop-down options worked or if they were set up more like the member selection pages in other modules. The filters option does work well as an option. That’s just my opinion…

Hey Jim,

Thanks for the post! The NaN is definitely a bug → I’ve filled it with our team and we’ll be lining up to prioritize and action. Just looking at it quickly, I believe it’s because we’re using the “effective elasticity” here which accounts for shear deflection. However not all LVL manufacturers provide such a value, and for those ones, our database just has them marked as empty. So as a workaround, you can try using another brand - I see that we currently have the data filled out for Versa-Lam, Kerto-S, RigidLam, and Global LVL.

As for the selection - I’m guessing you mean these filter boxes. Those aren’t the right one. It’s a simple fix on our end and you can expect to see those fixed in the next few days. It’ll now match what you see in the Wood Beam calculator.

@WilsonEngineers - wanted to let you know, we’ve now fixed the filters and they’re live on our Truss and Frame wizard calculators :slight_smile:

It looks like I have to recreate the truss from scratch. The change only shows if I create a new frame.

Hi @WilsonEngineers you can upgrade your existing truss sheet manually and then you’ll be able to access the new version without needing to create a new truss from scratch. This is automatically prompted when there’s a high-class bug, but since this was a minor issue, you have to do it manually. See below:

Project Details > Add “/upgrade” to the URL and press Enter > Select the sheet you want to upgrade

I hope it helps :wink:

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Your recommendation worked, but there is still something not right…

This part did not update:

FWIW, member #2 is defined for the lower 2 rafter segments on each side of the frame.

Hi @WilsonEngineers can you please send the URL of this sheet to Then I’ll be able to open your calculation and investigate the issue. Thank you!

The model is here:

This is an odd set up - but it is because I am modeling the lower portions of the existing rafters to add reinforcement (LVL material) to the existing 2x8s in the region of the lower ties.

Follow-up… The Weyerhauser LVL product results in “NaN” material errors, but VersaLam does not. So perhaps there is something in the internal product database that is causing the issue.

Hi @WilsonEngineers this is related to the above. We just filed a bug ticket and we’ll let you know when this is fixed. Thank you!

On a related note, since we are talking about a custom truss option, I recommend detuning some of the descriptions, such as those for materials “top chord”, “bottom chord”, “webs”, etc. Maybe just use “material 1”, “material 2”, etc.

My custom truss, which is nothing more than a double-tied roof, appears to be calculating accurately, but I do worry that those labels might reflect some internal aspect of analysis where I shouldn’t be doing what I am doing.

For instance, the results are all printed out with maximums per each of the three material types. In my case, however, the lower half of the rafter is the bottom chord material and the top half of the rafter is the top chord material. The two rafter/collar ties are the webs. Alternately, maybe there is a way to color code the members based on the screen based on material type.

I know, this is perhaps a rare usage of the truss option and not a high priority. I’m just thrilled that I can perform this here without needing to jump to RISA or some other FE program. I’ll take the labels as they are.

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