Revit Element Hierarchy
In this post we’re going to look at the organizational structure and hierarchy of Revit elements. It’s important that all Revit users understand this organizational structure so that they can efficiently create and document a building model. If you prefer to watch a video, check out this YouTube video…
Let’s start with the Revit hierarchy to begin. There are categories, and then you have families, family types, and then instances, which are individual elements. So when you place an element, you place a single instance. That element is of a certain family type and the type belongs to a family. Those families are organized into a category.
Let’s take a closer look at these terms and what it means when you’re working in Revit.
Categories are Revit’s main organizational structure for families. Categories are high-level groupings of elements, and the good thing is they are intuitive to buildings. In other words, there are categories like walls, windows, doors, ducts, pipes, structural framing, structural columns and so on. If you actually went to a construction site and started pointing out individual objects, you would likely be calling out the category.
Categories also determine the available parameters and how elements behave. What is happening is the category is telling Revit what the element is and how it’s going to behave in an actual Revit project.
Next, there are families. Every element in Revit belongs to a family. There are actually three kinds of Revit families. There are system families, loadable families, and in place families.
System families are defined within a Revit project or project template. In other words, when you have a Revit project or even a project template, the system family is defined within that file. Some examples of Revit system families are walls, roofs, floors, ducts, and pipes.
Loadable families are defined in RFA family files. These files are created and modified in the Revit Family Editor. For that reason, they are considered external files, or external to Revit project files. These RFA family files must be loaded into a project before they can be used to create a building information model. For that reason, they are called loadable families. Some examples are windows, doors, columns, beams, air terminals, plumbing fixtures, and lighting fixtures.
Distinguishing Between System Families and Loadable Families in Revit
Typically, a good way to distinguish between system and loadable families is to think about the construction process. System families are the elements that are created on a construction site. If we look at what is being constructed on site, we have objects like walls, roofs, floors, ducts, and pipes. I know that example can break down a bit as we get into prefab, and there are things like duct and piping spools created off site. But typically or historically, system families are created on site.
Loadable families are typically the elements that would be purchased and then shipped to the construction site. For example, windows, doors, plumbing fixtures, lighting fixtures, and so on. But once again, that example does break down a little bit when we get to structural elements. To me, using this example, I would put columns and beams under system families. However, that’s not the case. Columns and beams are loadable families.
Nonetheless, this analogy should give you a decent framework to begin distinguishing between system families and loadable families.
Lastly, there are in-place families. In-place families are not used very much, and really, they shouldn’t be. The reason is because in-place families are intended for unique components that need to be created in a project that are specific to that project. It’s almost like creating a loadable family inside a project. I say that because when you create an in-place family, you use some of the same tools that are in the Family Editor. They become available in the project for you to create that family within the project. You should stay away from creating in-place families unless it is absolutely necessary.
Revit Family Types
When you create a family, it can have multiple types. Those types can be created for different sizes, materials, or really any other parameter that you want to vary. In the case of a door family, you can have several types for the various sizes. Everything else could remain the same. In other words, the same material and hardware. Then when you switch between the types, you switch between various sizes of doors. Another example is air terminals. You can have an air terminal that includes types for a 24”x24” square face as well as a 12”x12” square face.
Once again, family types do not just have to mean different sizes. Any type parameter can vary between family types. Nowadays people get very creative with families. But for the most part, families are elements with similar geometry and a common set of parameters. Then the types are developed by adjusting the parameters.
It’s important that all Revit users understand this organizational structure so that they can efficiently create and document a building model.