In Revit, the fundamental unit is a family. A family consists of a group of elements that combine common properties (parameters) with graphical representations. Essentially, all elements in Revit are built upon these families, which serve as building blocks or “components” assigned with dimensions and physical attributes to facilitate editing and data extraction. The true power of a family lies in its ability to define varying dimensions and physical parameters based on the designer’s specific needs, allowing these parameters to drive dimensional changes. For similar components, adjusting parameters can quickly achieve the desired dimensions, making families highly practical for modeling tasks.
Revit families are mainly classified into the following categories:
(1) System Families: These are predefined within Autodesk Revit and stored in various template files and projects. Each template contains different types of basic component families. For example, building templates include families such as walls, columns, windows, stairs, and curtain walls that can be used directly. Users cannot directly create, delete, or modify system families themselves, but they can save or copy system family types. Custom family types can be created by modifying existing system families. System families are frequently used during the modeling process and satisfy most design requirements. However, they do have some limitations:
System families from different template types cannot be directly loaded into other templates or projects. Instead, they must be copied and pasted between projects to use multiple system families within a single template.
As a critical element of BIM models, the lack of localized components is a significant issue. Building templates include only a limited range of system family types, which often fail to accommodate the diverse architectural styles required for bridge structures and other complex designs. Relying solely on system families for BIM modeling of irregular structures is insufficient. Despite their importance, system families alone cannot meet all modeling needs in practice.
(2) Standard Component Families: These families can be created by copying or modifying existing components, or by building new ones from various family templates, enabling parametric-driven behavior. Family templates are divided into two types: host-based and independent. Accordingly, families created from these templates fall into either host-based or independent categories. Host-based families require a host element to be created and placed in a project—for example, window and door families are host-based because they depend on walls. Independent families include elements such as columns, main beams, and towers.
(3) User-Defined Families: User-defined families are custom-built components, primarily used for creating non-standard parts. Within the same model, users can customize size parameters that can be adjusted instantly to generate components that meet the specific design requirements of a project.
(4) Built-In Families: Built-in families exist solely within a specific project and can only be used as specific objects in that current project. They cannot be opened or saved for use in other projects, preserving intellectual property rights.
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