Popular author Dan Brown once said, ‘Knowledge is a tool, and like all tools, its impact is in the hands of the user’. Similarly, Revit-based parametric BIM (Building Information Modelling) tools have had a significant impact on the AEC (architecture, engineering and construction) industry recently in the hands of well-qualified professionals. Specifically, Revit families have driven the progress of this industry with their range of components, the ease with which those components can be manipulated, their cache of accurate data and the resultant savings in time and cost. They are, in essence, the building blocks of AEC design. Revit families are also known as content creation or component modelling or Revit family creation.
Just what is a Revit family?
The simple definition for families in Revit is that it is a group of components used to build a model, for example, walls, windows, stairs, doors, bathrooms, fixtures, showers, etc., with a common set of properties, or parameters, and a related graphical representation. In general, each family has multiple types, for example, different sizes, materials and more. Changes to a particular family item are updated parametrically throughout entire projects. To understand through an example, consider a window. If the height of the window is changed, all windows of the same type within a project are updated automatically. Revit has many family items already built in.
In case a new family must be added, this can also be done. Family files, also known as RFA files, can be loaded using Revit Family Manager. Parameters of exported elements can be added to an external database such as familit dbManager for Revit. These exported elements can be linked to the Revit project. Several database engines, such as Oracle, MySql, MsSql, SQL Express, Access and XML, can be supported by dbManager. Parametric values that are changed in the database are updated in the Revit project’s elements, such as rooms, floors, roofs, walls, and other families. Useful functions of dbManager include searching, grouping, sorting, zooming, exporting, importing, calculating and selecting. Using dbManager for Revit is the ideal tool for generating facility management, resource management, statistical analyses and reports.
The Family Editor tool is used to alter existing elements and create new ones, if a project has specific requirements. Examples of elements created by families include structural members, walls, roofs, windows, doors, fixtures, tags and detail components. Using predefined, or in-built, families or creating new families in Revit enables the addition of both standard and customised elements to building models. Design changes can be made easily, since families facilitate the control of similar elements.
Revit 3D modelling involves families that can be broadly classified as:
- System Families – family types to create basic building elements, such as walls, floors, ceilings and stairs
- Loadable Families – created in external RFA files and imported into Revit projects
- Annotation Families – families loaded for annotation purposes, such as text, dimensions or tags. Annotation families display only in the view in which you place them.
- In-place Elements – customised elements created by Revit professionals for specific client and project requirements, with parameters such as size, materials, dimensions, etc., intended for limited use in a model.
These families also have certain properties, which are known as:
- Category – A Revit family classification which includes doors, curtain walls, furniture, lighting fixtures, etc. Families are grouped and separated by category in content libraries and in the Project Browser.
- Type – Types are variations of the family element. An example would be a family of a door with a light. There may be 3 types of that family category in 3 different sizes.
- Instance Property – This property specifies data for a specific instance of the family element. For example, instance properties for a door may include sill heights and frame materials. Modifications to instance properties solely affect that particular instance of the family.
- Type Property – This property specifies data for all instances of the same family type. For example, a door’s type properties could include its thickness and width. Changes made to these type properties, or the thickness and width, affect all instances of that type.
The diverse and significant building components of Revit families are necessary for the creation of accurate 3D models. Effective and accurate families contribute to the successful and timely completion of BIM modelling projects.
Revit family modelling contributes 4 top benefits to precise design in AEC projects. They are:
- Increased accuracy – Dimension tools in Revit assign exact and specific dimensions to various components of a Revit family. When a family item is placed, Revit automatically assigns dimensions to the elements in the family.
- Flexibility – Family Editor creates 2D and 3D families, which can be parametric or non-parametric. Changes and variations of materials and sizes are edited in parametric families. Several variations in a single family can be stored as types. Non-parametric families have unique properties in shape and size, which cannot be altered. Both parametric and non-parametric families are useful at different times and for different reasons in 3D architectural modelling.
- Easier modification – Families can be easily modified with the relevant Revit tools, thus enabling designers and engineers to design and build with precision.
- Savings of time and effort – Revit families enable professionals to spend less time on modifications. The components of the family can be reused for other projects, saving valuable time and effort.
In conclusion, Revit family creation is at the very foundation of architectural 3D modelling and MEP modelling in the AEC industry. Revit family creation increases the accuracy of the project models, enables variations of types of components and changes on those variations and saves time and effort spent on recreating this data for future use. As a result of these advantages, AEC projects ultimately see significant benefits from these cost-effective processes.