by John Flanagan
Introduction
Families are Revit files (.rfa) which you create and load into Revit Projects (.rvt) and use to create and populate your building model.
All the elements you add to your Revit model are organized into families. This includes walls, doors, structural members, mechanical equipment, or annotation elements such as elevation symbols, door tags, and column gridlines.
Revit Families
A family is a collection of elements with identical use, common parameters, and similar geometry. For example, although you may have varied sizes of desks, all the sizes can belong to a desk family. If you look in the Project Browser, you can see a branch called Families. All Families in the project are listed within this branch. When you expand the Families branch, you can see that families are organised into categories such as annotation, symbols, ceilings, columns, doors, windows and so on. Each element in Revit belongs to one of these predefined categories. Some family categories may have subcategories. For example, when you expand the Doors category, you see subcategories for double flush and single flush doors. Each of these is a unique family.
Revit Families in the Project Browser
You cannot create or delete family categories, but within a given family you can create new types. To illustrate this, in the project browser, when you expand the single flush door family, you see multiple sizes. Each size is a unique type within that family. In this case, each type includes type properties that give each door its specific size. But type properties are not limited to size. Type properties could also determine the material or appearance of a specific type of door.
When you place an element such as a door into a Revit model, you create an instance of that element. In other words, if you place twenty 910mm x 2110mm single flush doors in a model, each is simply an instance of that specific type of door. Each instance would have its own unique instance properties, such as its door number or sill height, but all would share the same type properties such as the size. Thus, if you were to change an instance property of a particular door, such as its sill height, only that one instance of the door would be affected. But if you were to change one of its type properties, such as the width of the door, every instance of that door would immediately change.
Single Flush Door – Instance and Type Properties
Family Types
There are three types of Revit Families.
System
System Families, such as walls, roofs, floors, text, and dimensions, have predefined parameters that you can modify. You create new types of these families by modifying existing parameters using element properties.
These are the building blocks of which you must have at least one in your Revit Project.
Again, although you cannot create or delete system families, you can create multiple types within a system family. For example, in the project browser, when you expand the Walls family, you can see that there are Basic Walls, Curtain Walls, and Stacked walls. And when you expand Basic Walls, you can see that there are already a number of wall types.
If you create a new type within the Basic Walls category, that new wall type will only exist within the current project, but you can copy that new wall type into another project or save it as part of a project template file so that it will be available for use in other projects.
Loadable
These are the building blocks that you can create from External Family files and load into Revit Projects. Revit includes family templates for most elements to help you get started. These families are loaded into a project.
Examples include Furniture, Lighting Fixtures, Windows, and Doors.
Since these .rfa files are created using the Revit Family Editor, you can also create your own custom components.
Autodesk provides a cloud-based library of loadable family files.
In-Place
These are the building blocks which you can create within the context of your Project without opening and reloading an external Family file.
Examples include Custom Mass objects, Casework.
They are only available in the project in which you create them. but you can copy an in-place family into another project or save it as part of a project template.