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Mitchell (the other one)

Roof Trusses

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Good afternoon, I am a long time Vectorworks user, new to the Tech Board, (this is my first posting), I am a subscriber to the older Vectorworks User Discussion List. 

My first question is for those that create models of buildings that will be built with roof trusses.  How are you modelling and controlling (manipulating) the profile of the roof trusses?  

Here (in western Canada) the vast majority of our houses are built with roof trusses.  During the design I may adjust the depth of the truss heel and the roof slope several times as needed to meet the overall building height allowed within the site zoning.  Without a roof truss tool (if there is one I'm going to look pretty dumb) are you drawing a truss in elevation and then extruding it for the model?  Creating a roof face and then positioning it to allow for a heel depth?  As for the final building section, I'm not looking for the software to suggest a truss type (Howe, Fink, etc.), just provide a profile using the parameters I control as the designer and then the truss manufacture can build to fit the profile.  

Thanks.

 

 

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This would be a hard one to have a plugin without engineering input because of the grade of timber you have available to you would affect the size of members.

I use the framing member tool a lot which will get all the rafters and ceiling joists in and if i really need to model then its a tedious task of building a few symbols.

As I model a lot of building with exposed rafters on the eaves the framing tool works for me.

HTH

Edited by Alan Woodwell
Added a bit more

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3 hours ago, Alan Woodwell said:

This would be a hard one to have a plugin without engineering input because of the grade of timber you have available to you would affect the size of members.

That doesn't seem to be an issue in our market.  Trusses here all use 2x material, 2x6 being standard.  Occasionally we will use a 2x8 cord but with a minimum heel height of 11" to get the code required insulation values at the exterior walls, top and bottom cord dimensions have never been an issue with a flat bottom cord truss.  I agree with you for a mono slope truss or a scissor truss, there is less space within the truss to work with and member size is important.

 

3 hours ago, Alan Woodwell said:

I use the framing member tool a lot which will get all the rafters and ceiling joists in

I look upon the Create Roof tool with lust - I love what it can produce.  But it dimensions to a birds mouth cut, I haven't figured out a easy way to pervert this tool to calculate heel hight which is measured to top of cord at face of wall.

its a tedious task

Agreed - and this is why I have raised the question.

Thank you for your reply.

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Here's what I do. I create a Roof, then cut a section. In the Section (Annotations) I draw the actual truss profile, then measure the distance (height) between the Roof I already have and the top of the truss. Then I go back and move the Roof higher by that amount. Obviously the Walls will need to be made taller to close the gaps in the model. Subsequently, if I need more detail, I may use the 2d Poly truss profile from the section to create actual 3d Trusses in the Roof Layer. When I do that, I modify the original Roof so that it is only 5/8" thick (same as the Sheathing) and is placed just above the Trusses. Of course once that is done then I can delete the original 2d Truss shape from the Section, and future Sections will have highly accurate trusses already in place. Yes there is some upfront time involved, but for me it pays off.

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There is a plugin on http://www.vectordepot.com/older_plug-ins.html by John Greaney which has a standard truss and a gable end truss which I use as a model for the majority of a truss roof, however the options are limited and you can't do a half truss so I don't end up modelling the hips of the roof - enough to make sure heights are correct and create a shape for a section.

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The last time a seriously used the roof framer was to produce the framed model shown.  I used the trick described above regarding modeling the roof with the Create Roof tool until I got it where I wanted it, then reduced the thickness to use it as sheathing.  I then used a combination of running the framer plus modeling trusses as extrudes.

 

Screen Shot 2016-09-06 at 9.57.22 AM.png

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