Need to calculate rafter ties or collar ties at two different gable roof pitches

Hello all,

I am concerned about the stability of this roof of a gable roof with two different pitches, 8:12 meets 12:12 with 12:12 being the major span. I tried calculating collar ties and averaging the two pitches but I do not feel that is correct. I think I need rafter ties as cj’s are perp to rafters but the calculation for collar ties blows up


I’ve posted before about challenges with the tied roof modules - you can search on those in this forum to perhaps add some more context.

I do recommend you try to model the roof a couple of different methods (custom truss analysis, hand analysis, and the two tied roof design options. You may even have to think of each roof half individually with two separate models. Compare notes and you will find usable results even if they don’t all come from one module.

Thank you @Jeannie and @WilsonEngineers for your feedback on the Roof Tie Calculator. Having different pitches for a roof would be a new feature for the roof tie calculator I have mentioned this to our team and we will contact you is we had further questions for implementing the feature.
Thanks again for your valuable feedback!

I am not a structural engineer and have no idea how to do these calculations. I have a 8:12 meeting a 12:12- very concerned and trying to avoid changing the whole design. Would a structural ridge help in this case? Maybe treat it like a cathedral?

A ridge beam is one option but I recommend that you consider discussing the plans more specifically with someone who is experienced with the ins and outs of roof design.

The Truss Analysis Wizard would be a great design tool in this case, but that’s not a plug-and-chug solution unless you are familiar with the concepts.

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