Revit LT Roof Scissors Trusses

[Anonymous]

Does anyone know the best way to create roof scissors trusses with 2' top chord extensions in a Revit LT model?  For instance: a 10/12 top chord and 7/12 bottom chord, with an 18" high energy heel at the outer face of a 2x6 bearing wall.  it would be nice to have these as parametric objects so that sloped ceiling finishes can be applied to them, ceiling insulation, as well as have the truss underside (bottom chord) be the plane that interior partitions clip themselves to.  Thanks for you input.

[Anonymous]

Here's my response to your question and it's not a very strong one. Roof trusses are usually created with the add-in framing extensions. Revit LT doesn't allow any of those add-ins. But anything can be created in the family editor. If you want to use that automatic framing stuff, you'll need the full version of Revit.

[Anonymous]

Thanks for your comment.

I have seen some response in this forum going back to 2005 that have workarounds for Revit LT and would appreciate hearing from others that are using these successfully:

Namely: I saw one forum response in which a Revit user (LT?) said to simply model 2 roofs in your Revit model: one roof at 10/12, and higher than your "inner roof" (the bottom plane of the scissors trusses) at 7/12.  In that manner, you would be modeling 2 roof planes.  The bottom roof (ceiling) would have no overhang.  The top roof would have whatever overhang was needed for the project.  Haven't tried this yet, but hope to soon.

I guess I probably asked the wrong question.  I should have asked:

When using Revit 2013 LT, what's the best and easiest method to model the top roof plane of a sloping gable roof and to also model the bottom sloping plane of the ceiling at a different and lowe slope, set several inches (or feet), below the main exterior roof plane?

[loboarch · Accepted solution]

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@Anonymous wrote:

Thanks for your comment.

I have seen some response in this forum going back to 2005 that have workarounds for Revit LT and would appreciate hearing from others that are using these successfully:

Namely: I saw one forum response in which a Revit user (LT?) said to simply model 2 roofs in your Revit model: one roof at 10/12, and higher than your "inner roof" (the bottom plane of the scissors trusses) at 7/12.  In that manner, you would be modeling 2 roof planes.  The bottom roof (ceiling) would have no overhang.  The top roof would have whatever overhang was needed for the project.  Haven't tried this yet, but hope to soon.

I guess I probably asked the wrong question.  I should have asked:

When using Revit 2013 LT, what's the best and easiest method to model the top roof plane of a sloping gable roof and to also model the bottom sloping plane of the ceiling at a different and lowe slope, set several inches (or feet), below the main exterior roof plane?

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Here is an example of what this might look like if you used the approach of an upper roof at one slope and a lower ceiling at a different slope.  I also placed some insulation and an interior partition wall attached to the inner ceiling.  This method would not let you see individual truss members and may require some detailing work in the section view to get it to appear exactly as you would like, but it might be close enough.  If you need to see individual truss elements then you would need top make a family for this and then place them into the project.  It would still require you to place a roof element and ceiling elements like I have done in this example.

[Anonymous]

Hello Lobo,

Yes, I think that's along a workable approach.  The bottom truss chord (ceiling) should precisely intersect the interior side of the top of the 2x6 bearing wall, to give the truss a flat bearing position over the wall, but that is just an adjustment, isn't it?  You could have the lower roof (ceiling--truss bottom chord) join at the inside core face of the wall, correct?

Thanks for taking the time to try that.

[Anonymous]

Oh, I forgot to mention, it is not problem not showing truss struts because those are engineered by the truss plant and it is generally not wise to guess about such things, rather I always have a note over the middle of the truss (annotation in Revit) that would read: "Truss plant to provide structurally engineered, signed and sealed shop drawings for this truss profile with all truss struts calcluated and sized per project load specifications in Division 1 and Division 6 Prefabricated Trusses."

Meaning: that this open truss profile approach could work quite nicely. Thanks.

[Anonymous]

Lobo: did you use 2 roofs or were you able to accomplish this using a separate setting with a ceiling?  And was that in Revit LT?

[loboarch]

You are correct the bearing point of the truss (bottom chord position) could be moved to the interior face of the wall.  It is just a matter of where the sketch line for the ceiling is poistioned.  I happened to use the outside face of the wall.

This was created with a roof as the upper portion and then 2 ceilings for the bottom chords.  The reason I needed to use 2 deilings is because a ceiling object can only be sloped using 1 slope arrow so it can only slope in 1 direction.  So the celing boundaries are drawn from the outside wall to the center point of the room (peak of the truss)  Once I had one in place I used the mirror tool to create the other side of the bottom chord of the truss.

I happened to do this in Revit because the computer I am working on today does not have Revit LT installed (not sure why that is?  )   The tools to do this are exactly the same in Revit LT and it would work exactly the same way. 

[Anonymous]

Oh!  You're Jeff Hansen.  You're one the guys with AutoDesk that handled many of my questions when I participated in Project Spark, last summer, aren't you?  Thanks for your help back then and sorry for my continuing ignorance of the software. I have had a mental block about databases in general and that's exactly what Revit is, but for drawing.  This time around, I am determined to learn Revit and instead of the typical macho guy approach that I tried decades ago with ArchiCad, and failed, I am this time purposely not even downloading the software until I have learned just about everything I can about how Revit works, including some of the most important procedures for me: I design custom homes and believe that Revit LT may be the best tool for me.  I am almost done studying Eric Wing's excellent Revit 2013 Architecture book and have also just about finished Infinite Skill's Revit Architecture 2012 Bundle.  Thanks for helping me to understand how to accomplish various things in Revit LT and Revit, so that I won't be making a big mistake when I finally buy one or the other this time. 

So far, its sounds like Revit LT may work just fine for custom home design, even thought LT doesn't come with "truss" tools, like full Revit does.  Also, for a one-man practice, I can't imagine having the time to learn 3DsMax and all the programs that come with the Bldg Des Suite, much less being able to learn Revit thoroughly. 

Any reason why you think a small, one-person Architect wouldn't be able to accomplish whatever he needs to with Revit LT?

And hey: if I bought the current deal on Amazon, which includes AutoCad2013LT and Revit 2013 LT and includes a subscription, wouldn't I also receive Revit 2014 LT and AutoCad LT 2014 when they are released sometime this year at no additional cost?  And: do the 2013 releases of AutoCad LT and Revit LT (as they come, in the box) work for BOTH 32 bit aging computers on XP AND on new 64 bit computers on Windows 7? Thanks for your guidance. 

[loboarch]

Yes I am the same Jeff Hanson from the Project Spark forum.

Project Spark became Revit LT.  Revit LT was designed with the kind of user you described in mind.  Small one person or a few person firm.  Custom home design was one of the use cases we looked at while designing the feature set for Revit LT.

If the deal on Amazon includes subscription you will recieve the current version of Revit LT and AutoCAD LT and also have access to the next releases of both applications.  Both AutoCAD LT and Revit LT will be able to be installed on 32 and 64 bit PCs.

[Anonymous]

Thanks Jeff, that is very much appreciated. Sounds like the roof in a residential design is the toughest thing to throw at Revit LT in terms of geomtery and it appears that there is at least one way of handling that, per your example, so that would probably remove any other objections to Revit LT. Do you know of any other situations in which an Architect, designing and detailing a timber frame house might get into trouble with Revit LT as opposed to using full Revit?

[loboarch]

Revit LT does not include in-place modeling tools.  These can be used to create new or modify existing geometry in the context of the project.  Most things that you might use in-place models for can be done with the component family tools, but if the context of the project is needed to create the family it can be a bit difficult in the family editor.  In the long run component families are going to be a better choice but the in-place tool make things quicker and immediate for the really context specific situations.

Revit LT also will not allow for double curved geometry.  This requires massing and other tools in Revit.  In most cases this will not be a problem for all but the most custom of custom homes.

[Anonymous]

Thanks for the good information, Jeff.

By double curved geometry, I assume you are talking about Ghery and Zaha Hadid and the like? 

Not about two simple radial curved timber arched beams, one above the other (which I do include in my designs).

[loboarch]

Correct Ghery and Hadid like geometry.  Double curved meaning curving in 2 planes at one time.  As long as your radial arch beams are in one plane and curving multiple times it is ok.  If it bends out of plane and curve in an arch, that is much differnt geometry and will not be possible directly in Revit LT.

[Anonymous]

Got it.  I've never done that sort of thing anyway.  One plane arches are enough for me.  thanks.

[Anonymous]

Revit LT will not position the roof on the wall in a truss position like

the full version. Roof properties in Revit LT do not have the

rafter/truss roof positioning selector. It only has rafter. I don't

know what the work-around is for that or how to deal with it, yet.

[Anonymous]

Did you see Jef Hansen's (a Autodesk employee and Revit specialist) solution above?  My guess is his answer works for 3D modeling; the only question will be what happens to the BIM information in quantities (which for my needs, is a lesser concern), although if I really wanted to, I imagine I could, as Jeff suggests, model the roof trusses in the Family Editor and place them into the model and assign values to them, that hopefully would appear in any quantity takeoffs, if I really wanted to take it that far.

[Anonymous]

You would still need to manually position the roof even if you did create the trusses. Because Revit LT only puts the roof in a rafter postion.

[Anonymous]

Okay, and is there a particular problem, doing that?  And isn't that what Jeff Hansen did in his example?  For instance, I typically have an 18" energy heel on my roof trusses.  Is there any reason I couldn't do that (as Jeff appears to have done) in Revit LT?  Then position my ceiling at the 7/12 configuration similar to what Jeff shows?

If I have to move my roof up manually, couldn't I draw a horizontal  Reference Plane up 18" above the wall top plate, then use the move tool to move the roof underside to be at that position?

I realize that full Revit probably has a tool to deal with this in a tidy parameter adjustment/selector box, but I guess we don't have that in Revit LT, so what this thread is about is finding the solutions to draw scissors roof trusses.  Thanks for your input. And we must be dyed in the wool Revit people to be having this online communication on a Sunday morning, huh? 

[loboarch]

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@Anonymous wrote:

If I have to move my roof up manually, couldn't I draw a horizontal  Reference Plane up 18" above the wall top plate, then use the move tool to move the roof underside to be at that position?

I realize that full Revit probably has a tool to deal with this in a tidy parameter adjustment/selector box, but I guess we don't have that in Revit LT, so what this thread is about is finding the solutions to draw scissors roof trusses.  Thanks for your input. And we must be dyed in the wool Revit people to be having this online communication on a Sunday morning, huh? 

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IN my example I used a parameter to move the roof up 18".  Revit LT has a parameter to do this just like Revit does.