Pole barn metal roof purlin


LeoSweeney
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Hi, I don't know about any where else, but in my area, pole barn roofs have the purlins on top of the rafter or truss when metal roof is used. I can't find anywhere how to draw them this way in CA. Should be drawn as one continuous member, not broken up at each rafter or truss like blocking is drawn.As long as CA has been around this should have been a common design option. Please help if there is an easy way of doing this I don't know about. Thanks

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Let's think that through.  What you essentially have is a roof with 2 framing layers right?  One perpendicular to the other.  The problem is that Chief doesn't allow for 2 framing layers to be defined so we must frame one of them manually.  There are probably other methods but here's where I would start...

  1. Define your roof structure to have 2 layers, one layer for the rafters and one layer for the purlins.  Set the purlin layer to a framing material and and the rafter layer to a non-framing material for the time being.
  2. Make sure to check Lookouts in the roof Structure tab and then auto build the roof framing.
  3. Select one of the lookouts, block it, and add it to your library.  Name it purlin or something you'll otherwise remember. 
  4. Hit Undo a couple times to get rid of the roof framing. 
  5. Go back into your roof structure tab and change the structure layers so that the rafter is a framing material and so that the purlin layer is an air gap.
  6. You can now frame your roof as usual.
  7. Drop your Purlin block into the plan and explode it.  You can now multiple copy that around, resize it as necessary, and use various CAD tools (extend, trim, etc.) to create your purlins.  Because it was originally framed in the second layer of the roof structure it should always automatically return to that second layer when you drop it into the plan.

NOTE:  The top of your purlin will always automatically align itself with the top of your upper structure layer and will resize about that point if you change the depth.

 

Maybe Chopsaw will chime in.  I know he's spent a bit more time than I have working with this method and may be a little more familiar with some of the nuances.  

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Yes thank you Micahel.  A automatically generated lookout is the only member that has the properties you will need and unfortunately chief does not yet have a manual lookout or Purlin tool but you can create an automatic lookout in a test plan if you design does not have any and copy it into your plan or save it in the library as a cad block. It has been a while since I have worked with this but I believe that you can temporarily set an alternate framing level to manually frame in after you have auto framed the main structure.

 

Just give us a shout back here if you run into issues and we will do our best to try and help.  If you need a quick demo we can hook up on Skype if you like or send your plan file.

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If you do a session would you be able to record it?  I am just finishing up a design that is going to require cross purlins for ventilation on the sloped roof sections.  I am redoing this plan because it was started 2 versions ago and while setting up I wasn't sure how to do that portion of the roof.  This sounds exactly what I need to know.  If not, I will try doing a trial plan the way both you and Michael suggest.

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Sherry,  Are you looking for one layer on top of your rafters or two for the best venting.  I originally developed this for a 1 1/2 story design that was extremely difficult to vent and needed cross ventilation.  Let me know how it goes and maybe we could do a combined session.

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I believe it will be one layer of 3" timber purlins.  The builder is a timber craftsman but is doing his own home on a budget with leftover materials.  Venting on this area is fairly straight forward (open gables) but I am meeting with him later this week to confirm final design changes and will ask.  On the design drawings I just thickened the roof layers to get everything lined up but on this final plan I want the structure to be correct for sections and detailing.  (Or as close to correct as possible.)

Thank you for the offer and if you do a session I would appreciate participating.

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Leo,

I think we were all assuming that you were running X9 and and and that is why the instructions would have not made much sense.

 

I only developed this system of automation using the new roof layers tool that was introduced in X8 however there are a couple of other guys that I learned the basics from that were doing this before X8 so it will be a lot more work but it can still be done in X7 which I believe the plan file you posted is ??

 

Would it be possible for both of you to PM your Skype names and maybe we could set up a meeting tomorrow evening Saskatchewan Time.

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I would have really liked to have attended but I am out with clients all afternoon and then have to curl tomorrow night.  I haven't had a chance to try but I may be able to handle this with the explanations you and Michael gave.  Sounds like Leo needs this to work much sooner than me.  I'll post again if I can't work it out.

 

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18 hours ago, country said:

I believe it will be one layer of 3" timber purlins.  The builder is a timber craftsman...

 

If you're talking about true timber framing the purlins may very well be dovetailed into the rafters or otherwise dropped in and aligned on the top side. In these cases I've found using just plain old lookouts is the best method....unless of course you actually need to show the joinery in which case a series of solids may be the best method.  

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This will just be standard framing.  The builder doesn't have the time or materials to do his own house in timber so we are using a vault with false timber beams over the main living space.  I was just going to try using solids until I read this thread.  Learning to do something so it shows properly in section would be ideal.

Normally, around here, I would be using full vault trusses and not be worried about the venting but he wants to stick frame.

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Basically the same thing I already spelled out in the posts above but here's a quick video on the subject...

 

 

As always, if you find this or any of my tools, tips, or videos helpful enough please consider sending a small donation my way by clicking on the PayPal link in my signature below.  It will go a long way in ensuring I continue to make and share them.  Thanks : )

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  • 2 months later...

Hello Alaskan Son, 

 

I tried your video several times but when I have made the block of the one lookouts and saved it in my library, it doesn't work to get it to show up in my framing view again.  It shows up on my plan view as a cad block but that is it.  What am I doing wrong?  

 

 

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1 minute ago, QualicoreHomes said:

Hello Alaskan Son, 

 

I tried your video several times but when I have made the block of the one lookouts and saved it in my library, it doesn't work to get it to show up in my framing view again.  It shows up on my plan view as a cad block but that is it.  What am I doing wrong?  

 

 

 

You aren't exploding the block when you drop it in your plan.

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