How do Revit trusses really work?

[Base12]

I'm trying to make simplest truss you can imagine and it's giving me nothing but problems.  A: Is there a way to just designate a slope (pitch) to the trusses instead of a height?  That would solve my problem.  B: For reasons that I don't understand the truss won't (errors) attach to the underside of the simple roof I've created.  C: When I enter the height of the truss, which is the bearing plate to the underside of the roof deck... the top of the truss is correct, but the top chord comes just slightly up through the roof deck at the base (see attached image and properties).  If I raise the roof deck, then I have to raise the truss height value and the problem perpetuates.  The only way I could get it to work was by dragging with width of the truss to the inside of the walls, which obviously isn't correct.  How the heck do you work this thing?

[barthbradley]

Understand Screenshot? 

[Base12]

If I understand, to set the slope by pitch/angle then you have to do it in the family, not the project file, yes?

[ToanDN]

You might not need to concern about the pitch of the height at all if you attach the truss to a roof.

[Base12]

I tried this, a lot and it would never work for me.  It kept returning an error that said something like "creates an invalid profile" or something.  Item B in the OP

[ToanDN]

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@Base12 wrote:

I tried this, a lot and it would never work for me.  It kept returning an error that said something like "creates an invalid profile" or something.  Item B in the OP

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Share your file here if you want to know why it doesn't attach.  With that said, you can change the pitch in the project if it is an instance parameter, not just an angular dimension in the family.

[barthbradley]

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@Base12 wrote:

If I understand, to set the slope by pitch/angle then you have to do it in the family, not the project file, yes?

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No, you add those instance parameters/formulas I showed, and then you can set the Truss Instances "Slope" Parameter it in the Project to whatever suits your fancy. Basically, no different than setting the "Truss Height".  

Still, I agree with @ToanDN on this one.  By the time you get to Trusses, you will have your roof already. Just place a single Truss, Attach it to the Roof and then array the Truss. 

[barthbradley]

Try attaching a Flat Truss to your Sloped Roof.  Does it still not work? 

[Base12]

I did try a flat truss, and it didn't work either.  Here's the file.  To note, this not how I would typically model this building, but the client wanted to see all the members of the built-up roof modeled with the outriggers and various overhang layers, etc.  The trusses here are "eyeballed" so while they look good, they aren't actually attached or tied to anything.  Directly above the trusses is the "3/4" PLY ONLY" roof element that I'm trying to attach the truss to.  All of the other roof stuff above that element are irrelevant to this task. 

[barthbradley]

It's not you, it's the Truss.  Try another.  Try Fink.   

"...Not all truss families properly attach to a roof..." 

https://help.autodesk.com/view/RVT/2023/ENU/?guid=GUID-A77B218C-3EC7-4D60-AA69-B23CA115F5C4

Help | Edit a Truss Profile | Autodesk

BTW, Flat attaches fine in your Project in my testing.   

[Base12]

I'll give it a shot.  Thanks for taking the time to look into it for me!

[jay_colc]

There is a Structural Framing > Truss Member which is a very simple Truss Family which i have seen used more in Architectural applications rather than Structural.  It is more driven from the Properties Palette than the Structural Truss Families - it may be a simpler solution? 

[Base12]

@jay_colcwhere did you find that family?  I don't have a "Truss Members" category by default, only "Structural Trusses" and there's not a generic one in there by that name?  Is it maybe from a version of Revit that is not 2023?

[jay_colc]

Structure Tab > Beam > Insert Family > Structure Framing > Truss

You can also use the Insert Family from library option on the Insert Tab and search for Truss

[Base12]

I know how to load families, I'm saying that family doesn't exist in my installation.  Not even the folder.  Would you mind just sharing the family here?

[jay_colc]

Sorry I’m not at me laptop but will try and get this over to you!

Can you use the other Method as this is all the regions Revit Content online

[jay_colc · Accepted solution]

Here it is not sure why you cannot find it?

[Base12]

I have plenty of other structural trusses - but not that one, and as I mentioned that folder does not exist for me.  Thanks for uploading the file however!

[Base12]

While some of the other options in this thread 'may' have worked, the family uploaded by @jay_colc was the best solution for me as that family had the parameters already in it that I would have had to create otherwise.  Thank again Jay!