sept1951

Creating Purlins for Roof Plan

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How do I create purlins for the roofing plan? It is required that purlins are located in the roofing plan if the joists are over 12'. And it has to be in the Roofing Layer. Please help me if you can? Thanks!

 

 

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I use lookouts edited to the size of the purlins that are lowered to just below the rafters. Just stretch them across the width of the roof plane. I use the transform replicate tool if I have multiple purlins.

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I just use the roof beam tool, it places them right up against the bottom of the rafters.

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Hi Perry,

I think it depends on whether you want it vertical, or perpendicular to the rafter. 

post-62-0-14153400-1434663195_thumb.jpg

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To me a purlin is a beam breaking the span of the rafters, so for me they are always vert. you can also change a roof beam to show any size you want.

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Hi Perry,

This is a purlin shown in the Oregon Residential Specialty code.  They can be vertical as well; but then I would likely call it a roof beam.

post-62-0-37652500-1434664041_thumb.jpg

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Thanks Bill, A vert. beam can also be a purlin around here. I very rarely do those anymore with all the structural stuff we do.

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Hi Perry,

Although this is still in the code book, we rarely see them in new construction here.   We also see them in agricultural pole buildings.

 

I looked up the definition, and it can be any horizontal member that breaks the rafter span.

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Hi Perry,

This is a purlin shown in the Oregon Residential Specialty code.  They can be vertical as well; but then I would likely call it a roof beam.

 

Bill,

I do it the same as you have it here in your section. But I don't try to get it in the framing because we don't need to see the purlins in 3D so its just as easy to draw the purlins with bracing into the section.

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I just use the roof beam tool, it places them right up against the bottom of the rafters.

 

Perry,

 

Once you put the beam in can you rotate it in the section to get what Bill is doing? Not that you need to do that but was curious if you ever tried it. You would the one that showed me how to edit in section views.

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Downunder, Now I see, they just like to cause trouble.

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Hi Mick,

We also call the horizontal members on top of the rafters, purlins in my region as well. These are used mostly in agricultural pole buildings.

I use modified lookouts for these as well.

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I guess it figures that they would put the purlin on the wrong side of the rafter downunder

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I am actually surprised there is no automated way to do this , I 'd think fairly easy to implement since as you say Bill a modified Lookout would do the job , fair bit of work to do them all manually every 900mm or so.

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Mick,

You can automate the process.  Just stretch one lookout, then use the multiple copy tool.  They will follow the roof plane.   Then group select, and raise them  as necessary.  You'll have to raise the roof plane an equal amount.

 

The only downside is you'll have to turn off auto roof framing.

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To me a purlin is a beam breaking the span of the rafters, so for me they are always vert. you can also change a roof beam to show any size you want.

 

Yeah, but if vertical, you really should be cutting a birdsmouth into the rafter to avoid introducing lateral forces.

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Hi Richard,

If you're referring to the cross section that I posted; I simply showed where Chief shows a roof beam by default.  I would have to raise it to create the birdsmouth; but I just posted it as a quick comparison of vertical, compared to perpendicular.  That seemed to be the essence of the discussion between Perry and I.

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It kind of funny when someone post a question and then you never hear from them again after several replies are going back and forth. :huh:

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Yeah, but if vertical, you really should be cutting a birdsmouth into the rafter to avoid introducing lateral forces.

Not if you use an "A35" clip

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Perry,

 

As a Framer I have to ask this question:

 

How do you put a diagonal brace under a vertical beam?

post-2478-0-45860600-1434732371_thumb.png

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I would just nail a 2x block under the purlin, that's the old way, now we just extend posts up inside the wall to a beam with an approved steel connection. most of the time an interior shear wall has to extend to the roof anyway. and for me at least purlins are 4x and bigger depending on the situation.

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Not if you use an "A35" clip

 

Huh? Unless you use a birdsmouth, the rafter forces will be normal to the slope of the rafter. A clip doesn't change that.

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It works for my structural engineer.

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This is common way we construct hones in our area, I use roofs as purlins, it takes no time.

post-2517-0-88354800-1434737671_thumb.jpg

post-2517-0-39009500-1434737703_thumb.jpg

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