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Revit families deep dive 2: Elements and their classification

As you start diving deeper into Revit families, you will need to understand the different elements and their classification. This post will bring you closer to becoming a Revit pro!

In our recent Revit deep dive, we expanded on the different types of Revit families. If you are not familiar with Revit families yet, we recommend you check out this article before you continue reading. Already familiar with Revit families? Let’s deep dive into elements then!

Revit families and their element hierarchy

First of all, it’s crucial to understand the Revit element hierarchy. When it comes to Revit families, there are 4 main elements within the pyramid:

revit families elements hierarchy pyramid

  • Category: this is located at the top of the hierarchy within the Revit families. Categories control the organisation, visibility, graphical representation and scheduling options of a particular set of families within the project. Examples of categories are doors, windows, columns, ducts, etc.
  • Family: this is the next element in the hierarchy. Each category typically contains several families. As we know, families are the key building blocks of every BIM project in Revit. They contain 2D and/or 3D information which represents a specific building or documentation element within the project. Examples of families can be ‘single flush door’, ‘single window’ or ‘rectangular duct’.
  • Type: this is the next element of sub-division under families. A type is a specific element within a family which has distinct parametric, graphical and documentation characteristics. This makes it unique from other types within the same family. For example, under the family ‘single flush door’ we could have ‘800×2100 single flush door’ and ‘1000×2300 single flush door’. In many cases like this, types represent different sizes of the same family.
  • Instances: these represent the bottom of the hierarchy. They are the individual representation of a type within the project. Unique parametric, graphical and documentation characteristics make an instance different from any other instances of the same type. For example, each single flush door that we can see in the 3D model is an instance.

The Revit element hierarchy explained visually

And because a visual description is worth a thousand words, we’ve put together the image below to effortlessly help you understand the hierarchy of elements. As you can see, the top element is the category, which in this case is ‘doors’. Then, we move down to the individual families, like ‘single-flush’. Then the individual types, like ‘800×2100’. And once we use this type within the model, we have an instance. The instance in the image is a ‘door: single-flush: 800×2100’ representing a real single flush door, 800mm wide and 2100mm high, in a particular location within the 3D model.

Revit families elements and parameters

Revit elements: classes and sub-classes

Once we understand the hierarchy of Revit families, we can dive deeper into classes and sub-classes. Families are classified into distinct groupings, depending on what they represent. Everything in Revit is an element or family. The elements classification includes:

  • Classes: elements are classified into a Model, Datum or View-specific class.
  • Sub-classes:
    • Model elements include hosts and component sub-classes.
    • View-specific elements have annotations and detail items sub-classes.

Revit families element classes and sub-classes

Model elements

Model elements represent 3D elements in Revit that are visible both in 2D and 3D model views. Their sub-classification includes hosts and components:

  • Host elements generally represent elements that are constructed on-site, like walls, floors or ceilings. Generally, host elements are system families. They can host component elements.
  • Component elements typically represent manufactured elements that are installed on-site, rather than constructed on-site. Generally, component families are loadable families. Component elements need host elements. For example, when you want to insert a specific door family into the model, you will need a wall host family – typically a system family. Other examples of component elements could be windows, chairs, tables, columns, beams, etc.

Datum elements

Datum elements, on the other hand, are 3D elements in Revit that are only visible in 2D views. These are generally levels, grids and references. They are contextual elements that help define elevations in model elements or that link to other views of model elements. For example, typical datum elements would be section planes or detail windows.

View-specific elements

View-specific elements are 2D elements which are specific to the 2D view in which they appear. Sometimes they can also be shown in 3D views, as 2D representations. These can be further sub-classified into annotations and detail items:

  • Annotations: these represent 2D documentation elements that provide additional information in a specific view. They are the standard text annotations that we generally see in construction drawings. They help clarify information and identify different elements in a drawing or detail.
  • Detail items: these are 2D elements that can be overlaid on model elements or stand alone to describe particular items. For example, they can be specific hatching to represent particular materials in a cross-section.

Have we missed anything about Revit families and elements? Let us know in the comments!



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