It’s not uncommon for us to be asked to perform BIM coordination or create additional models using preexisting design models from architects. However, clients are sometimes unclear about why enhancing or even recreating the architectural model could benefit the construction coordination or BIM coordination process. This does not imply that the provided model is poorly done or entirely useless. Rather, it’s a matter of assessing the model’s condition and determining how it can best support the coordination required for the construction phase.

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Understanding Design Models vs. Construction Models

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Before diving into the coordination aspects of the construction phase, it’s important to understand the critical difference between a model created for the design phase and one adapted or created for construction coordination. The key to this understanding lies in one fundamental question that every BIM technician should ask before starting any modeling task: What is the end goal for this model? This question is essential because the model’s purpose dictates its structure and content. In short, we model for a specific outcome—whether it’s to inform design decisions, support construction logistics, or facilitate coordination. Each phase of a project has its own objectives, and the model must be tailored to meet those needs.

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At its core, BIM stands for Building Information Modeling, meaning we can input as much data as needed. However, the model’s purpose changes depending on the phase. Having worked as an architect using Revit through all project phases—from schematic design to construction and project closeout—I can confidently say that the design phase focuses on materializing the concept in a virtual space. During this phase, the emphasis is on showcasing the core idea, not on addressing the finer details that may arise during construction, unless the team is working on the Construction Documentation (CD) phase.

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In the design phase, the focus is on aesthetics and presenting a client-friendly model. We often use tools like photorealistic rendering to communicate the design vision effectively, while detailed plans and specifications may be developed in 2D, without requiring intricate 3D modeling.

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The Role of Construction Models

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In contrast, a construction model must be as close to reality as possible. Accurate details and robust data are essential because these models serve as tools to inform and facilitate the on-site construction process. If BIM coordination was done previously, it can help streamline processes before construction even begins. Ultimately, the construction phase in a BIM mindset focuses on identifying potential conflicts between disciplines, saving time and reducing errors on site.

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The primary distinction, therefore, is this:

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- A design model focuses on conceptualizing and visualizing the design.

- A construction model is used to coordinate and execute the design during construction.

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Construction Models: More Data, More Detail

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During the construction phase, the model requires more data. The richer the model is in terms of information, the better it can support tasks such as conflict resolution, scheduling, cost estimation, and planning. Throughout this phase, the model may be adapted to support coordination, clash detection, and real-time updates. Ultimately, the model must serve its intended purpose, providing the necessary information at the right time. Essentially, we treat the construction model as a virtual representation of the project, translating floor plans into a constructible framework.

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In Conclusion: All Models Are Valid

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In the end, the purpose of the model determines its value and the phase it’s intended for. Design-phase models are primarily used to showcase ideas, create renderings, support client presentations, and deliver design-phase floor plans. In contrast, construction-phase models require more detail and robust data to address real-world construction challenges.

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This is why, in some cases, we prefer to either redo or significantly enhance design models for construction purposes. Even when working with preexisting design-phase models from others, adjustments and additional data are often necessary to align the original design with the practical realities of construction. This process helps prevent issues, streamline project delivery, and ensure that the needs of other disciplines are accommodated, facilitating effective BIM coordination as those disciplines become involved.

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