In the previous chapter ‘Concept of Revit Elements‘, we discussed about how Revit elements are organized in a hierarchy:

Elements -> Categories -> Family -> Type -> Instance.

For many CAD users, families may sound similar to blocks or groups. However, the difference between CAD and BIM is the “information”. Thus, blocks and families are fundamentally different from each other because of the information they carry in their parameters and with which they can be controlled.

Each family is controlled by type and instance parameters within the project. Instance parameters affect individual instances only. Type parameters affect all instances of the same type in the entire project. To explain this, let’s go back to our example of chairs that we learnt in Concept of Revit Elements.

Now in this room, there are two types of desk chairs – blue and black. Let’s say that we want to change the color of all the blue chairs to red. If the color parameter is part of “type properties”of the family, then changing the value of the color in one chair would automatically affect all the 5 blue chairs present in the project. But, if the color parameter is part of the “Instance properties” then, changing the value of the color in one chair would affect only that particular chair. The remaining 4 chairs would remain blue.

In system families, type and instance parameters are pre-defined. For example, the thickness of the wall, by default, is a type property. Whereas, the height of the wall is an instance property.

For loadable families, you can decide which parameters to include as type and which as instance, depending on how you want to control the behavior of the family. This is typically done while you are creating a new family or editing an existing one.

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