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Custom Family Type - BuiltIn Parameters

Message 1 of 14
1287 Views, 13 Replies

Custom Family Type - BuiltIn Parameters


I am using Revit API 2023 to create a Family ( something similar to what is referred to in The Building Coder: SVG, In-Memory Family, RevitLookup BoundingBox (  ) .  Family is getting created just fine. Then I load that family and lastly I create a FamilyInstance of type StructuralColumn and StructuralFraming.  So far so good.


The problem I am facing is when I try to set the Offset related parameters e.g.  FAMILY_TOP_LEVEL_OFFSET_PARAM and FAMILY_BASE_LEVEL_OFFSET_PARAM . These are null when I try to retrieve them via   familyInstance.get_Parameter  before trying to set the values to it. 


I am not sure if I have to specify something specific at the time of Family creation to let API know to associate the builtin Parameters to the Family or FamilyInstance. 


Any help is much appreciated. 

Labels (2)
Message 2 of 14
in reply to: rnilay81

HI @rnilay81 
Are you trying to create FAMILY_TOP_LEVEL_OFFSET_PARAM and FAMILY_BASE_LEVEL_OFFSET_PARAM custom parameters to Built-In-Parameters ?

Thanks & Regards,
Mohamed Arshad K
Message 3 of 14
in reply to: Mohamed_Arshad

Hi @Mohamed_Arshad 


Thanks for the reply. These are not custom parameters. but BuiltinParmeters ( BuiltInParameter Enumeration ( .As per the Revit Documentation I read that I can't create the BuiltinParameter because they are "BuiltIn"  ( Solved: Add built-in parameter to family - Autodesk Community - Revit Products)  .   Of course the link talks about adding Builtin Params to the existing family and the answer is NO, we can't.   But I want to know if we can add BuitlinParameter for newly created family through API.  


For more details, below are the steps to give an idea as to why I want to have this functionality 

1) I create the FamilyInstance and apply the offset.  Once the entire model is built with API in this way then

2) I read the model for some post processing in another use case.  As the normal Revit API flow is to read the offsets through FAMILY_TOP_LEVEL_OFFSET_PARAM and FAMILY_BASE_LEVEL_OFFSET_PARAM BuiltInParmeters, I need to have the values set to it at the time of creation of the model creation( Step 1 above) . 


I can easily create the custom parameters and assign the values to it but the worry is that Revit won't be able to understand those parameters and won't be having the same offsetting effect on the 3D model. 


Not sure what the way forward is.  

Message 4 of 14
in reply to: rnilay81

Hi Mohamed, 


Thanks for helping me out. So I have tried to have these values SCHEDULE_LEVEL_PARAM

set . The problem I faced is when I try to do this through API, then the value SCHEDULE_LEVEL_PARAM

 is coming as ready only and can't be set..  Then I am trying with having different families for Columns ( Structural column family ) and for Beams ( Structural Beam & Truss family) and trying to set these values. Still trying these things and will update by today. 

Message 5 of 14
in reply to: rnilay81

For an introduction to programmatically creating a family, please work through the Family API labs:



You will probably also find the other family creation articles useful:



You cannot create built-in parameters. They are built in to Revit, hard-coded.


You can however create family parameters and make use of those to control the types and symbols generated by by your family definition. 


Jeremy Tammik, Developer Advocacy and Support, The Building Coder, Autodesk Developer Network, ADN Open
Message 6 of 14
in reply to: rnilay81

HI @rnilay81     

One thing you have understand. You're Using Structural Framing Category with Line Based Family so below parameters are must.

1. Curve

2. Level 

3. Which Type of Family

4. Structural Type or Non Structural Type

By using this create New Family Instance by using the NewFamilyInstance Method, Then Access the below two parameter for offset from the level. SCHEDULE_LEVEL_PARAM can accessed at the time of creating Instance. Once Instance is created. It will not accessed.



Hope this will Helps 🙂

Thanks & Regards,
Mohamed Arshad K
Message 7 of 14
in reply to: jeremy_tammik

Thanks @jeremy_tammik  for replying. I have followed these posts already to create the families . They are getting created fine. The place I am struggling is - I want my Column to have the constraints as "Base Level" and "Top Level" with values to be set as Levels from the model ( Snapshot is from Sample model and I want it similar for my own model through API )  .


As the existing values of the "Top Level" parameter such as SCHEDULE_TOP_LEVEL_PARAM I get from the existing templates is coming as readyonly, the values can not be set. So I tried to add the parameter through below method


fmgr.AddParameter("Top Level", GroupTypeId.Constraints,


but I am struggling to understand what the other parameter of ForgeTypeId would be for Type Level so that it would be displayed under Constraints when the model is ready . All the examples I get is either for ParameterType.Length or Material or Text. But I don't understand how to add parameter with type for ElementId as Level so that when I get the custom Parameter then it can be set as 




Basically I want to create the custom family parameter but want it to behave exactly like BuiltInParameter of base level and top level because they are readonly. 


In the absence of any way to set base level and top level, my columns are just horizontally placed 




instead of expected Vertical 





Hope I am able to clearly put across the problem. 

Message 8 of 14
in reply to: Mohamed_Arshad

Hi @Mohamed_Arshad  for replying. Actually I am passing in the level at the time of creation of the instance as 



fi = m_revit.ActiveUIDocument.Document.Create.NewFamilyInstance(point1, fs, topLevel, st);



where topLevel is of type Level .  st is StructuralType i.e. Column or Beam  ,  fs is family symbol , point1 is the starting point in the base level. 


But unfortunately as I said in the above post, the columns are just coming in one level only ( Horizontal)  instead of  starting at base level and ending at top level (  Vertical ) .

Message 9 of 14
in reply to: rnilay81

You can only change the values of built-in parameter not add them to a family (they exist or they don't depending on category).


I tend to use




They are not read-only



The associated schedule ones are also not read-only but I would not use those since they were added for schedules. It doesn't make sense to me to use the schedule ones when the intended family ones do exactly the same thing, have existing for longer and were obviously created for that purpose.


Families placed on a level such as columns point upwards from that level this is unlike in the UI where the column ends up below the view level you place it on. So your 'toplevel' notation indicates to me that you are setting the bottom of your column onto the top level and also setting the top of the column to that same level after placement. 


To be honest that should trigger a warning i.e. the top and bottom level can't be the same.




Message 10 of 14
in reply to: rnilay81

Hi @RPTHOMAS108 for replying. I tried to use the FAMILY_BASE_LEVEL_PARAM and FAMILY_TOP_LEVEL_PARAM in my case but they are coming as null. Then I tried to use the inbuilt families in Revit and for them these parameters are coming as not null. As a next step I tried to see the code to create the custom family from sample code under 

Revit 2023.1 SDK\Samples\FamilyCreation\GenericModelCreation


and used that family in my code but for that as well these parameters FAMILY_BASE_LEVEL_PARAM etc. are coming as null. I have attached a reproducible case by combining the code from two samples given under Revit SDK ( CreateBeamsColumnsBraces and GenericModelCreation) . When I select the custom generated family in the dropdown of my solution, concerned parameters are always null but when I select the inbuilt families ( the ones we download/install from Revit ), these parameters are not null. 


This leads me to believe that something is missing from the family creation code which is controlling which built-in parameters should be present in the instance. 


Steps to reproduce the problem (  I have Revit 2023 and VS 2022) 

1) Download and unzip the attached file 

2) Run the solution from VS

3) Open any Revit file 

4) Go to Add-Ins --> External Tools --> Create beams,columns and braces(CS) 

5) From the "Type of Columns" dropdown , select "Generic Family"  

( this is family we have created in the code i,e. custom family)

6) In the PlaceColumn method of CreateBeamsColumnsBraces.CS.Command  , you can see baseLevelParameter and topLevelParameter are null at Line No. 367 and 368. 


Any help is much appreciated. 

Message 11 of 14
in reply to: rnilay81


Let me check and update you 

Thanks & Regards,
Mohamed Arshad K
Message 12 of 14
in reply to: rnilay81

If you are using the generic model template to create your column family then that isn't going to add those built-in parameters, even if you set the category.


That is the same as the UI.


To create structural columns you need to use

Metric Structural Column (or imperial equivalent)

Similarly to create a structural framing family you should use:

Metric Structural Framing - Beams and Braces (or imperial equivalent)

You should have an imperial and metric version of all your templates/content in reality (likewise versions with localised parameter names if you are localising).


So the problem is easier than you think i.e. if you don't see the built-in parameters in your family (when placed in the project) then you are using the wrong family template to create the family.


One of the most confusing things when people first interact with the Revit family environment is due to the incorrect assumption that any type of element functionality can come from the same RFT or RFA file. In reality the content of those templates is hard coded to suit a certain purpose and you can't change it to match another template type. In that respect it is a bit different to other programs where they would perhaps use a different file extension to note different template types.

Message 13 of 14
in reply to: rnilay81

@RPTHOMAS108  Thanks for the advice. I have now integrated the structural column template and it is giving me non null parameters for top and base levels. I am at least able to move it ahead. Thanks a lot for all your help. Also, a big thanks to @Mohamed_Arshad @jeremy_tammik 

Message 14 of 14
in reply to: RPTHOMAS108

Thank you for the nice illuminating explanation. I shared it on the blog for posterity:


Jeremy Tammik, Developer Advocacy and Support, The Building Coder, Autodesk Developer Network, ADN Open

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