Type vs. Instance Parameters — Edit type vs instance parameters and understand impact

Historical Context & Motivation

Before parametric modeling existed, architects and designers who wanted to change a door's width on a construction drawing had to erase every occurrence of that door and redraw it—a laborious, error-prone process that could consume hours of production time. The concept of parametric families arose from the desire to embed intelligence into building components so that a single edit could propagate logically throughout an entire project. Understanding this lineage clarifies why Autodesk Revit distinguishes between type parameters and instance parameters—two mechanisms that control the scope of change within a Building Information Model.

The central question that parametric families answer is deceptively simple: When I change a property of a building element, should that change affect every element of the same kind, or only the specific element I selected? Revit's answer—splitting parameters into types and instances—provides the granular control that makes BIM powerful for design iteration, documentation, and fabrication alike.

Core Principles & Definitions

In Revit's data architecture, every element placed in a project is an instance of a family type. A family type is a template that defines shared characteristics—dimensions, materials, and behavioral rules—while each instance is a concrete placement in the model with its own location, orientation, and instance-specific data. Parameters are the named variables that store this information, and their classification as type or instance determines the scope of any edit you make.

Visual Explanation — Type vs. Instance Hierarchy

Notice how the hierarchy fans outward from abstraction to specificity. The family sits at the top as the broadest container—it holds the geometric engine, the constraints, and the parametric rules that define how the element behaves. Beneath it, each type freezes certain values (width, height, material) into a named configuration that serves as a reusable template. Finally, each instance is a concrete occurrence in the model—tied to a specific host wall, assigned to a specific level, and carrying its own per-placement data like offset or orientation. This layered architecture is what allows Revit to manage thousands of elements efficiently while still giving designers element-by-element control when they need it.

How It Works — Editing Type vs. Instance Parameters

When you select an element in Revit and open the Properties palette (the panel typically docked on the left side of the interface), you see that element's instance parameters—values unique to that particular placement. To access the type parameters, you click the Edit Type button at the top of that palette, which opens the Type Properties dialog. This two-panel interface is the fundamental mechanism through which Revit separates local edits from global ones, and understanding when to use each panel is essential to effective parametric modeling.

Editing Type Parameters

The Type Properties dialog displays every parameter classified as a type parameter for the selected family type. When you modify a value here—say, changing the Width of a door from 900 mm to 1000 mm—Revit applies that change to every single instance of that type across the entire project. If your model contains forty doors of that type, all forty update simultaneously. This is powerful for maintaining design consistency, but it demands caution: an unintended type edit can ripple through hundreds of elements before you realize what happened. Revit does warn you with a count of affected instances when applicable, but cultivating awareness of this propagation behavior is a core professional skill.

Editing Instance Parameters

Instance parameters appear directly in the Properties palette when an element is selected. Changes here affect only the selected element (or the set of selected elements, if you have multiple items highlighted). Typical instance parameters include Level, Offset from Level, Mirrored, and Comments. These values inherently depend on the element's unique position in the model—no two doors necessarily share the same sill height or the same wall host, so it makes logical sense for these to vary per instance.

Duplicate Type Workflow

A critical workflow arises when you need a variation that differs from an existing type in one or more type parameters but want to preserve the original. Rather than editing the existing type (which would change every instance), you duplicate the type first. In the Type Properties dialog, clicking Duplicate creates a new type that inherits all current values. You then rename it, adjust the differing parameters, and assign the new type to the relevant instances. This preserves design intent for the original type while accommodating the variation.

Detailed Breakdown — Common Parameters by Category

Different Revit family categories assign parameters to the type or instance bucket based on the logic of how that property naturally behaves in a real building. A door's nominal width is a product specification—it belongs to the type. A door's position in a wall depends on the specific wall it is hosted in—it belongs to the instance. The following table maps commonly encountered parameters across several family categories, showing where each parameter lives and why that classification makes sense.

The decision diagram above encapsulates the mental model you should internalize every time you modify a parameter in Revit. Beginning designers often skip the "Does this change apply to all?" question and inadvertently alter a type parameter when they meant to adjust only a single element. Conversely, experienced practitioners leverage type edits strategically—for example, updating a window family's glazing performance data across an entire project in seconds rather than selecting each window individually.

Worked Example — Editing Door Parameters in a Gallery Project

Imagine you are designing a small art gallery in Revit. The gallery has twelve interior doors, all currently using the type "Single-Flush: 900 × 2100 mm" with an Oak material finish. The client requests two changes: (1) all interior doors should be widened to 1000 mm to improve accessibility, and (2) one specific door leading to a service corridor should have its sill height raised by 50 mm to clear a floor transition. Let's walk through both edits step by step.

Strengths & Limitations — Type vs. Instance Parameters

Connection to Advanced Topics — Shared, Project, and Global Parameters

The type-vs-instance distinction is the foundation of Revit's parameter system, but the platform offers additional layers of complexity that build on this foundation. As you advance in BIM authorship, you will encounter shared parameters, project parameters, and global parameters—each of which can be assigned as either type or instance. Understanding the base-level distinction makes these advanced tools immediately more approachable.

When creating custom families in the Family Editor—a skill you will develop as you progress in architectural visualization and design technology courses—you will make deliberate decisions about whether each parameter should be type or instance. For example, if you are authoring a custom gallery display case family, the overall cabinet dimensions (width, depth, height) might be type parameters so that all cases on one floor share a uniform appearance, while an internal shelf count could be an instance parameter if different cases need to accommodate artworks of varying sizes. This forward-looking perspective—designing the parameter structure before modeling the geometry—is a hallmark of mature BIM practice.

Practice Problems

Summary — Type vs. Instance Parameters