Revit Family Modeling: 3 common mistakes


We delve into three prevalent mistakes frequently encountered during the process of modeling Revit families. These errors, made by well-intentioned creators, can impede the efficient use of Revit families and, in some cases, lead to complications in BIM projects.

Revit families are the cornerstone of Autodesk Revit, offering a powerful means to model and document architectural projects with precision and efficiency. A Revit family encompasses parametric 3D models and 2D symbols, acting as digital representations of real-world building components and objects. Everything from doors, windows, and furniture to lighting fixtures finds its virtual existence within these meticulously crafted entities.

Revit’s dominance in the Building Information Modeling (BIM) industry is indisputable. This dominance extends beyond Revit itself, as its proprietary family file format, “.RFA,” has gained recognition and acceptance within the broader BIM software ecosystem. Renowned software platforms such as Graphisoft’s Archicad and Bentley’s AECOsim have embraced this format, further solidifying the importance of Revit families in the BIM landscape.

Professionals across the architectural, engineering, and construction spectrum rely on Revit families as invaluable tools for their projects. These families are the building blocks for generating project templates and comprehensive project documentation, serving as the blueprint for specifying and realizing common and complex designs. Manufacturers of building products also harness the potential of Revit families to convey essential product information, facilitating seamless integration into professional designs and construction plans.

However, even though the Revit family concept is adaptable and can accommodate a wide range of product categories, it’s essential to recognize that many common pitfalls in family modeling stem from the actions of the family’s creator rather than inherent limitations within the family template itself.

In this article, we delve into three prevalent mistakes frequently encountered during the process of modeling Revit families. These errors, made by well-intentioned creators, can impede the efficient use of Revit families and, in some cases, lead to complications in BIM projects. By identifying and addressing these challenges, we aim to empower designers, architects, and BIM professionals to harness the full potential of Revit families in their endeavors.

Too much geometric definition

This toilet family is composed of Free Form elements, which are not necessarily needed because Revit’s default modeling tools can produce this type of geometry. In this particular example 1) there is a double curvature surface at the back of the toilet, which represents the product exactly but adds no value to the family since this type of detail will go unnoticed by the user while it will still add to the file size.

The first mistake is over-modeling the family. It involves introducing overly complex geometry or excessively defining the geometry of the family model. It’s true that the Revit family editor offers a set of rather rudimentary modeling tools, which can make modeling double-curvature surfaces particularly challenging. Overcoming this limitation can be difficult, but it’s a rare case that one would need to define a parametric family with double-curvature geometry without resorting to an advanced family template.

The most common scenario that leads to the mistake of over-modeling is the desire to faithfully represent the product that the family will depict. This can manifest as an attempt to precisely recreate geometry based on the actual product or by adding intricate details to the model that may never be visible in practice.

Regardless of whether the modeler’s objective is achieved, this scenario consistently results in an increased file size. The family’s size can balloon up to 1.2 MB for a family model that would typically weigh around 600 KB. The issue with an enlarged family file size is that it can adversely affect project performance. When a Revit project contains numerous heavy families, working on the project can slow down to a crawl.

The unfortunate reality is that most of the effort put into over-modeling a family will likely go unnoticed by professionals when they specify it in a project. This is primarily because of two reasons: 1) The view may never cut to display the extent of modeling precision, and 2) When line thickness settings are activated, all the intricate modeling details turn into a solid black area.

How to avoid this mistake?

Consider how professionals will visualize this family in plan and 3D views, taking into account the scale of each view. It’s important to remember that a family is just one element of the project design, not the central focus. In this sense, the family should resemble the product it represents, but the finer details may not be visible, as professionals will generate plans, sections, or 3D views of the entire design, not just of a single family component.

Making a Monster-Family

This window family includes 3 nested families: 1) The window panel, 2) the handle, and 3) the sill. Including nested families is a good way to give your family a huge amount of flexibility and interchangeable capabilities, this window’s nested families only contain 1 type.

A possible reason for this is that the manufacturer may have wanted an easier access to modifying or changing parts of the family; the result is another family that is heavy and clunky to use for the end-user. The price the manufacturer paid for convenience was to reduce the quality of the files that will help its products specified more in projects.

When we refer to a “monster family,” we’re talking about a family that was originally conceived as a “super” family capable of handling any scenario. While Revit’s Family Editor does allow for the creation of highly configurable families, this point primarily pertains to authors who are well-versed in the Family Editor’s capabilities and intend to leverage its full potential in crafting a Revit family.

A monster family is typically the result of creating a family with numerous parameters controlling geometry, often including formulas and nested families. While these ingredients and combinations are not inherently disastrous, there’s a likelihood that the family will exhibit one or more of the following issues:

  • Large file size
  • Sluggish performance when switching between types or adjusting values
  • Complexity in usage

The last point is crucial as it underscores a key aspect of the design process that shouldn’t be overlooked: Who will use this family, and what purpose should it serve?

This might appear to be a straightforward question, but if there isn’t a clear answer, it can be reflected in the family model itself.

The consequence is often a family that requires tweaking a series of parameters, potentially leading to delays and even slowing down the computer when specifying it in a project.

If a family’s complexity distracts a designer from the project at hand, it ceases to be a helpful tool and starts hindering progress.Where once there were good intentions for making a family, now the result is something of a mess where it is used in one project and then discarded.

Most of these families are seldom reworked because they also tend to require a big time investment from the original author, and if the original author is not available another modeler may just prefer to start from scratch.The first step when embarking on family modeling is understanding how to shape it with forms and tailor it to align with its intended purpose.

Here are some tips to prevent the “monster” from emerging:

When a family involves numerous forms or imported elements, it tends to significantly increase the file size. When importing files or nesting families, it’s advisable to be selective. Ideally, nest one family with multiple types, ensuring that the nested family has the smallest possible file size.

If many parameters are linked to formulas, it’s best to keep the formulas as streamlined as possible. Try to clearly define all parameters in order to avoid confusion

Aim to have a limited set of parameters that need adjustment within a project, making it more straightforward to specify. To cover various scenarios, you may consider including a type catalog or, if feasible, dividing the model into multiple families to focus on specific project requirements.

Over-parametric & complex formulae

Another window family. In this case, the manufacturer has included not 3 but 10 nested families (Detail items). Each nested family includes only one type.

In a similar vein to the concept of the “monster family,” creating a family with complex formulas or making it overly parametric is a common pitfall that many modelers encounter. Parameters serve as the essential data connectors that enable us to craft families that serve specific purposes. These purposes could range from accurately representing spatial dimensions to generating valuable information crucial for defining the entire project.

From the same family as above, the result of too much detail of a window family in plan view at 1:50 scale. Because of the line width all of the detailing of the interior frames is lost.

At times, the design requirements may demand the calculation of specific values or the derivation of results based on a multitude of variables. This, in turn, necessitates the creation of numerous parameters dedicated to data input, alongside additional parameters housing the formulas required for these calculations. Depending on the complexity of the design and the number of variables involved, the family may end up housing an array of conditional statements within its parameters. While the use of these conditional statements can make a family highly versatile, it can also introduce performance issues. Families with an abundance of parameters containing complex formulas may experience difficulties when it comes to calculating results, potentially leading to software sluggishness.

This is a furniture family, that again uses Free Form Elements for geometry that can be easily done in the Revit Family Editor...
…And the long list of parameters to only modify 1 type configuration, even if it is done through a type catalogue

Furthermore, when a family involves more than two variables, it may require additional computational processing from Revit to incorporate these values and adapt accordingly.

How to achieve complexity while maintaining functionality:

While there may be no alternative but to create multiple parameters to achieve the family’s intended goal, the optimal approach is to organize them into distinct parameter groups. It’s also essential to make informed decisions about whether these parameters are better suited as type or instance parameters. By doing so, you can efficiently manage and manipulate sets of parameters, making it easier to fine-tune the family’s behavior to specific project requirements.

When dealing with complex formulas, keep in mind that the more conditional statements a formula contains, the greater the potential for making the family unwieldy within a project. To mitigate this issue, consider breaking down complex formulas into multiple parameters, especially when dealing with numerous variables. This approach not only enhances the family’s performance but also simplifies its management.

Another effective strategy for simplifying complex formulas is to create additional types or type catalogs. By doing so, you can streamline the use of these formulas and manage them more efficiently. Always bear in mind the intended methods for calculating and generating values as you make these considerations.

Tips for modeling Revit families…

In our journey through the potential complexities of Revit family modeling, it’s important to recognize that while we might not always escape every challenge, strategic planning can significantly enhance our success. To steer clear of the pitfalls we’ve explored, let’s proactively consider these three crucial questions:

Who Will Be the Primary Users of This Family?

Understanding your audience is paramount. Whether it’s architects, engineers, or interior designers, knowing who will interact with the family can greatly influence its design and functionality. By tailoring the family to the needs and expectations of its users, you can ensure it serves its purpose effectively.

What Specific Purpose or Objective Should the Family Serve Within the Project?

Every family should have a clear mission. Is it meant to represent a specific product, convey crucial information, or fulfill a unique role within the project’s design? By defining its purpose from the outset, you can streamline its development and align it with project goals.

What Level of Investment, in Terms of Complexity and Resources, Is Justifiable to Ensure the Family Meets Its Intended Purpose Effectively?

Balancing complexity against practicality is a key consideration. While it’s tempting to create families that can do it all, it’s equally important to assess the costs involved. By determining the acceptable trade-offs in terms of complexity and resource allocation, you can strike the right balance between functionality and efficiency.

Asking and, more importantly, addressing these questions in advance serves as our compass in the journey of creating Revit families. It not only guides us toward families that fulfill their objectives but also empowers us to craft them in the most efficient, user-friendly, and purpose-driven manner possible. By weaving strategic planning into our family modeling process, we pave the way for success and innovation within the world of BIM and design.

Have you had any encounters with these problems when modeling families, or using external families?

Reach out and tell us your story.

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