How do you scale Geometry in Revit?

In Revit, you can scale geometry primarily by utilizing the Scale tool, which supports both graphical and numerical methods for adjusting the size of various elements. This tool is especially useful for loaded families, detail items, and imported CAD data.

Understanding the Revit Scale Tool

The Scale tool, found on the Modify tab, allows you to resize selected elements uniformly. It offers two main approaches: graphical scaling and numerical scaling.

Graphical Scaling (The 3-Click Method)

This method provides an intuitive way to scale elements by visually defining the scale factor.

Select the Elements: Choose the geometry you wish to scale in your view.
Activate the Scale Tool: Go to the Modify tab, click on the Scale icon (often represented by a square with arrows pointing outwards).
Define Origin (First Click): Click to place the first point, which serves as the origin or base point from which the scaling will occur. All selected elements will scale relative to this point.
Define Base Vector (Second Click): Click a second point to establish the starting length of your scale vector. This point, in conjunction with the origin, defines the "before" length.
Define New Vector (Third Click): Click a third point to set the new, desired length for the scale vector. This point defines the "after" length. Revit then calculates a scale factor by determining the ratio of the lengths of the two vectors (the "after" length divided by the "before" length) and applies this factor to the selected geometry.

Numerical Scaling (Inputting a Scale Factor)

For precise control, you can enter a specific scale factor.

Select the Elements: Select the geometry you intend to scale.
Activate the Scale Tool: Click the Scale icon on the Modify tab.
Choose Numerical Option: On the Options Bar (usually located below the ribbon), select the "Numerical" scaling option.
Enter Scale Factor: Type in your desired scale factor. For example, enter 2 to double the size, 0.5 to halve it, or 0.25 to reduce it to one-quarter.
Define Origin Point: Click on the screen to set the origin point from which the scaling will occur. The selected geometry will then resize according to the factor you entered.

What Geometry Can Be Scaled in Revit?

While powerful, the Scale tool has specific applications in Revit. You can typically scale the following types of geometry:

Loaded Families: Most loadable families, such as furniture, equipment, generic models, and specialty equipment, can be scaled. This applies to their instances placed in the project or within the family editor itself.
Detail Items and Detail Groups: Lines, filled regions, masking regions, and detail components within a detail view or group are scalable.
Imported CAD Files: DWG or DXF files brought into a Revit view or family can be scaled. This is often necessary to correct unit discrepancies after import.
Groups: Both model groups and detail groups can be scaled as a single entity.
Sketch-Based Elements within Families: When working in the family editor, individual sketch-based forms (extrusions, blends, revolves, sweeps, swept blends) can be scaled.

Limitations: What Cannot Be Directly Scaled?

It's crucial to understand that not all elements in a Revit project can be scaled directly with the Scale tool. This is due to Revit's Building Information Modeling (BIM) nature, where elements are often defined by specific parameters and relationships.

System Families: Elements like walls, floors, roofs, ceilings, railings, and ducts are "system families." Their properties are defined by their type parameters (e.g., wall thickness, material layers), not by direct geometric scaling.
Entire Revit Projects/Models: You cannot scale an entire Revit model because it would break the integrity of relationships, dimensions, and coordinates.
Linked Revit Models: Linked models are typically placed and coordinated at specific locations, not scaled.
Dimensions, Grids, Levels: These are reference elements and their scale is tied to the view scale or specific parameters, not directly scalable geometry.
Revit Elements with Fixed Dimensions: Some elements have fixed internal geometry that prevents scaling.

Alternatives to Scaling System Families and Project Elements

When direct scaling isn't an option, you need to use alternative methods to adjust element sizes or properties.

Create New Types: For system families (e.g., walls, floors), duplicate an existing type and modify its type properties. For example, to change wall thickness, you would edit the wall's structure within its type properties.
Adjust Instance Parameters: Many loaded families have instance parameters (e.g., width, height, depth) that can be directly modified in the Properties palette for each individual instance.
Modify Family Geometry (Family Editor): For custom changes to loaded families, open the family in the Family Editor. Here, you can scale the internal forms or adjust parameters that control their dimensions.
Change Project Units: If scaling is needed due to incorrect unit interpretation (e.g., an imported CAD drawing appears 12 times too large), ensure your project units (Manage tab > Project Units) are correctly set.
Redraw or Rebuild: For significant design changes that affect system families or project-wide elements, it may be more efficient to redraw or rebuild parts of the model to the desired dimensions.

Practical Tips for Scaling

Selection First: Always select the elements you want to scale before activating the Scale tool.
Origin Matters: Be mindful of your origin point, especially during graphical scaling, as it dictates the anchor for the transformation.
Verify Results: Use temporary dimensions or measure tools to confirm that your geometry has scaled as intended.
Clean Imported CAD: Before scaling imported CAD, consider cleaning it of unnecessary layers or blocks to prevent unexpected behavior.
Uniform Scaling: The Revit Scale tool typically performs uniform scaling, meaning all dimensions (length, width, height) are adjusted proportionally.

Scalable vs. Non-Scalable Elements

Scalable Elements (Directly using Scale Tool)	Non-Scalable Elements (Directly using Scale Tool)
Loaded Families (Components, Generic Models)	System Families (Walls, Floors, Roofs, Ceilings)
Detail Items & Detail Groups	Entire Revit Projects
Imported CAD Files (DWG, DXF)	Linked Revit Models
Model Groups & Detail Groups	Dimensions, Grids, Levels
Sketch-based elements within families	Elements with fixed internal geometry

Understanding these distinctions allows you to effectively manage and modify your Revit geometry.