How Does BIM Work?

You’re likely familiar with the basic aspects of BIM by now. And if you’re not, make sure to read our article, “What Is BIM and Why Is It Important?”

In this chapter of the Beginner's Guide to BIM, we’ll be going more in depth to answer the question: How does BIM work?

BIM can feel like an intimidating process, so this article will explore the main aspects of a traditional workflow that BIM improves upon.

What Is the BIM Process?

• Predesign
• Schematic Design
• Design Development
• Construction Documentation

The term “BIM” in its most common use isn’t a single thing. It’s an entire workflow.

You may have heard someone refer to their model as their “BIM.” This is a valid use of the term, as a noun. More commonly the term is used to describe a holistic process — “Let’s do this project with BIM,” for example.

The words “process” or “workflow,” which imply action, should come to mind when considering BIM.

The key to understanding how BIM works is to avoid thinking of it as an entirely different process than what you’re used to. It’s an overlay to what you already know. This article will explore the things that are different from traditional design phases when overlaying a BIM process.

In a traditional building project, the predesign phase is where the key players in a project come together to discuss their needs and expectations and to perform feasibility studies. These studies include site analysis, program requirements and space analysis, and understanding cost versus budget. The BIM Execution Plan, or BIM PxP, is the big difference in this phase between traditional workflows and BIM.

During this stage, everyone involved agrees on how they want their project to look when it’s finished — in addition to budgeting constraints and timeline considerations — so that everyone is on the same page as far as what needs to be done throughout the rest of the process.

BIM provides structure and accountability for the predesign phase, which is where many of the important decisions are made — and shared digitally among stakeholders — in determining the success of the project.

A BIM Execution Plan clearly lays out roles, responsibilities, and timelines for those involved. It’s essentially a roadmap for everyone involved in the project on how information will be delivered, at what intervals, etc. It will also cover what software, hardware, and IT infrastructure are required, as well as name who’s responsible for information management.

The schematic design phase in a building project involves understanding and defining the project parameters, creating preliminary designs, and developing the overall project budget. A BIM process brings automation and more effective collaboration methods to the traditional workflow via common data standards.

Once all stakeholders have agreed on the project parameters, the next step is to create preliminary designs that meet requirements. This process may involve sketching out ideas on paper or using 3D modeling software to create detailed visualizations of potential solutions.

It’s important to note that changes or updates should be reviewed by all stakeholders as is outlined in the BIM Execution Plan. This is so that any necessary changes can be made before proceeding with further development. The BIM process — specifically, the BIM Execution Plan agreed upon during the predesign phase — determines exactly how and when to perform these information exchanges via the concepts of Level of Information Need (LOIN) and Level of Development (LOD).

The last step in this phase is providing a budget estimate based on cost per square unit to determine if the design is in line with the budget set by the project owner. By following a BIM process, schematic design becomes easier since the conceptual drawings and models will have relevant project information within them. Good BIM software can automatically pull this information into spreadsheets, making the process of budget forecasting automatic and faster.

During this phase, designers further develop the project by refining plans, sections, and elevations while also adding details to them such as window sizes, wall thicknesses, and material selections. BIM is an asset to this phase because having a central digital model ensures that stakeholders understand exactly how project elements interact with each other to create a unified whole that meets expectations.

Traditionally, this phase is all about refining earlier design decisions and creating more detailed models. The same goals are present with BIM workflows. The difference is that BIM allows everyone in the project to exchange information via a common file format, reducing the potential for costly errors since everyone will be able to coordinate their work in almost real time.

The construction documentation phase is when the project team creates detailed drawings and specifications that serve as instructions for building the actual structure. These documents are also used to solicit bids from potential contractors who want to work on the project, so they must be as accurate as possible. Using BIM reduces the amount of time associated with “drafting” details since most elements have already been created within a computer model which can then be easily accessed by anyone on the team.

During this stage, architects and engineers design each component of the building and its systems in detail and provide exact measurements for all components involved. This includes walls, windows, doors, plumbing fixtures, electrical systems, and more.

The plans must also include information on materials that will be used during construction.

BIM collaboration shines in this phase because project stakeholders can coordinate complex systems in 3D and address nuanced issues that would typically arise on the construction site.

One of the benefits of BIM in the construction documentation phase is the automation of quantity takeoffs and specifications. Because information is already present in the model, BIM software makes the creation of these items and others much less manual.

Permits often require specific drawings with information such as fire rating, egress, and occupancy load. These drawings can be easily generated with a BIM workflow because that information is already present within the model.