Building Information Models (BIM) represent real-life objects like walls, floors, pipes, and equipment. While it may seem logical to model as much as possible to harness BIM’s full benefits, doing so can be time-consuming and costly. So, how do you determine the "right" amount to model?

For housing projects, if BIM is requested, the typical expectation is to create Architectural, Structural, and MEP (Mechanical, Electrical, Plumbing) models, often excluding external utilities and landscaping. It’s also common to limit the modeling of certain elements, like structural rebar or wiring. But is this a good or bad practice?

The answer depends on who will use the information and for what purpose. As I’ve discussed in my pevious blog posts on building my house, even small projects can benefit from focusing on four core BIM uses: design review, drawing creation, constructability analysis, and quantity takeoffs (QTOs).

To maximize these benefits while controlling costs, it's essential to keep two key principles in mind when modeling.

Highly detailed models often offer little value for the four core BIM uses. For instance, accurate external dimensions, counts, and locations of objects are usually sufficient. Modeling small, low-value components like small plastic water pipes or their fixtures in great detail and accuracy is typically unnecessary. Contractors will likely build these differently based on available materials and real life situation.

When it comes to QTOs, you don’t need to model every single item. You can either extract quantities directly from modeled elements or link quantities to other modeled objects. For example, instead of modeling individual bolts, you can link their quantity to other structural components.

For my house I modelled most of the furniture as boxes with correct external dimensions. The purpose: to check if everything fits and understand interfaces with other objects such as electrical sockets.

Model progression refers to starting with minimal detail in early design phases and gradually adding complexity. In the concept stage, you might only need a simple model—such as a building represented by a basic shape—to make decisions about its location or overall form. As the project progresses, the model can evolve in detail to serve other purposes.

Sketching layouts in 3D at the very start of the project can be very beneficial and it does not take very much time.

Finding the right balance in building information model creation is about aligning the level of detail with the project's goals and the intended use of the model. Over-modeling can lead to unnecessary costs and time, while under-modeling can result in missed opportunities to leverage BIM’s core benefits. By focusing on key elements, limiting geometric detail, and allowing the model to progress in complexity as the project evolves, you can ensure that your BIM efforts deliver maximum value without overshooting the budget or schedule. Ultimately, the right amount of modeling depends on how well it supports informed decision-making and the practical needs of your project.