Click File tab › New › Family, pick a template such as Generic Model, and set Family Category and Parameters. Draw reference planes, label their dimensions as parameters, lock geometry to them, add sizes in Family Types, then save and Load into Project.
Or, just describe a simple family and Mira builds it and places it in your model.
How to do it in Revit
Step 1: Start from a family template
Click File tab › New › Family. In New Family - Select Template File, choose the template by how the element is hosted, not by its name. Pick a wall-, ceiling-, floor- or roof-based template if the element needs that host, a face-based one if it can sit on any surface, or a standalone template such as Generic Model for furniture or equipment that stands on its own (Autodesk Help: About Family Templates). Click Open. The Family Editor opens, usually with two or more dashed green reference planes already drawn (Autodesk Help: Create a Family from a Template).
Step 2: Set the family category
Click Create tab › Properties panel › Family Category and Parameters, choose a category and click OK (Autodesk Help: Specify Family Category and Parameters). Autodesk's rule of thumb is to pick the category by how the part is ordered from a manufacturer. The category decides which schedules the family appears in.
Step 3: Lay out the reference planes
Parameters move reference planes, and planes move geometry, so draw the planes first. Click Create tab › Datum panel › Reference Plane, draw one at each edge a parameter will control (say the left, right, front and back of a desk top), and give each a Name in the Properties palette (Autodesk Help: Lay Out Reference Planes).
Set Is Reference to Strong Reference on the planes people will dimension to in a project; new planes start as Weak Reference, which people may have to press Tab to pick (Autodesk Help: Define Priorities for Reference Planes). In many templates, two crossing planes already define the origin, the family's insertion point. Leave them where they are, and pin them if they aren't pinned (Autodesk Help: Define the Family Origin).
Step 4: Dimension the planes and label them
Click Annotate tab › Dimension panel › Aligned and dimension between the planes each parameter will drive, such as left to right for width. Select the dimension and click Create Parameter on the Label Dimension panel. In Parameter Properties, name it and choose Type (one value for every instance of that type) or Instance (each placed copy can differ) (Autodesk Help: Label Dimensions to Create Parameters).
Flex it before there is geometry: open Create tab › Properties panel › Family Types, change the value, click Apply and check that the planes move (Autodesk Help: Flex the Family Framework).
In Revit 2025 the dimension options, such as Prefer and Pick, sit on the Options Bar. Revit 2026 moved them to the Modify | Place Dimensions tab, and Revit 2027 has no Options Bar at all.
Step 5: Build the geometry and lock it to the planes
Click Create tab › Forms panel › Extrusion (or Blend, Revolve, Sweep or Swept Blend) and sketch a closed loop over the planes. Lock each edge to its plane: start Align from the Modify panel, pick the plane, pick the sketch line and click the padlock. Set the height with Extrusion End in Properties and click Finish Edit Mode (Autodesk Help: Constrain Family Geometry).
Lock geometry to planes, not to other geometry. Autodesk warns that constraints between pieces of geometry behave unpredictably when parameters change.
Step 6: Add family types and flex them
In Family Types, click New Type, name the size, enter its dimensions and fill in standard parameters such as Manufacturer, Model and Type Mark (Autodesk Help: Create Family Types). Click Apply after each change and watch the geometry follow. If a face stays put, check that it is locked to its plane (Autodesk Help: Test the Family).
Step 7: Save it and load it into a project
Click File tab › Save As › Family and name the .rfa for what it is, in title case: that name shows in the Project Browser and the Type Selector. Then click Create tab › Family Editor panel › Load into Project (or Load into Project and Close). With several projects open, Revit asks which ones get it (Autodesk Help: Load the Current Family into a Project).
Check it in a test project, in plan, elevation and 3D at Coarse, Medium and Fine, before you save it where others can load it (Autodesk Help: Test the Family).
What to watch for
Hosting is the one choice you can't undo. Autodesk's advice is to pick the template for the hosting you need and fix the category afterward. The category can be changed later in Family Category and Parameters, but the hosting can't once the family exists (Autodesk Help: Video: Select a Family Template). A recessed light starts ceiling-based; a fixture that can go on any surface starts face-based.
Custom parameters need to be shared to be tagged. A tag can read built-in parameters such as Type Mark and Width, but a parameter you add to the family shows in a tag only if it's a shared parameter, and a schedule across several categories needs one too. For any custom value that will be tagged, choose Shared parameter in Parameter Properties and pick it from your firm's shared parameter file (Autodesk Help: Shared Parameters).
In-place and system families are a different job. In a project, Architecture tab › Build panel › Component › Model In-Place makes a one-off element inside the project. It holds a single type, and Autodesk warns that in-place elements can increase file size and slow the model (Autodesk Help: In-Place Elements). Walls, floors, roofs, ducts and pipes are system families: you can't create one, only duplicate and edit its types (Autodesk Help: System Families).
Build in the oldest release you still run. Families aren't backwards-compatible: once an .rfa is upgraded and saved in a newer release, older releases can't open it (Autodesk Help: About Opening Models that Require an Upgrade). If any project is still on Revit 2025, build shared families in 2025.
Settle type names before the family ships. When you reload a family, types missing from it stay in the project, so a type renamed in the Family Editor comes back as an extra type (Autodesk Help: Reload a Family into a Project).
At firm scale building the family is the easy part. The hard part comes after: people build their own versions of the same desk, a renamed type shows up twice and a family saved in 2027 won't load into a 2025 project. That is what Revit family management is for: one approved version of each family, which people can find by what is inside it. When a family really is new, Mira, the AI agent for Revit, can build a first version from a description, such as a desk's top size, height and legs, and place it in your model once you approve its plan.
Or, just ask Mira to do it.
Mira is an AI thinking partner for Revit that automates the work you repeat and builds tools your team needs.
- Type this in Mira
Build a simple desk family: a 60 by 30 inch top, 29 inches high, on four legs.
Mira describes the family it will build and waits for your OK, then builds it, places one desk and checks it with a screenshot.
What is a family in Revit?
Where are the Revit family templates located?
How do I change the family category in Revit?
How do I add a parameter to a Revit family?
Can I save a Revit family to an older version?
Which Revit versions does Mira work with?
Try it yourself.
Or bring it to the firm.
The download is free and takes a minute. The firm conversation is where your standards, your library, and your rollout get built. Start wherever makes sense.