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The Ultimate Guide to BIM MEP Modelling for US Subcontractors

September 9, 2022


Construction subcontractors are a critical part of the BIM process. They fill the gaps that general contractors and designers cannot, either because of capacity issues or because of regulatory requirements. However, many subcontractors struggle to adopt BIM processes effectively. The majority of construction subcontractors do not have in-house CAD operators and 3D modelers. They tend to focus on niche areas within their sector, such as plumbing or electrical contracting. Thus, when working with a general contractor on a new project, they need to find another subcontractor to take on modeling responsibilities for their part of the build process. General contractors can’t provide detailed engineering drawings as part of their service offering. In addition, most general contractors won’t share proprietary data with an external third party due to competitive pressures and liability concerns. Therefore, if you are a BIM-savvy sub-contractor who wants to work optimally with other parties in the future, you need to understand how BIM modeling fits into your workflow so that you can adopt it as seamlessly as possible in your next project.

What does BIM MEP modeling involve?

BIM MEP modeling, image

BIM modeling is a collaborative process where different disciplines work together to create a single, integrated model. As such, BIM modeling can include traditional electrical, plumbing, and mechanical engineering disciplines. It also involves collaboration between different parties, such as architects, general contractors, and subcontractors. A BIM model is created using computer-aided design (CAD) software. The input data for a model can come from a wide range of sources; architectural drawings, as-built drawings, other BIM models, and spreadsheet data are just some examples. When you’re subcontracting out your MEP model, you’ll need to provide the modeler with information about your equipment and the location of your equipment in the building. You’ll also need to provide information about the building’s configuration, such as wall and column locations (i.e. the building’s “as-built” configuration).

How is BIM MEP modeling different to traditional MEP modeling?

traditional MEP modeling, image

Traditional MEP drawings are not collaborative and do not provide as much information about a building’s configuration and equipment. MEP drawings are generally created using commercial 2D CAD software and then imported into the BIM model. This means that the design team can only see what they’ve put into the BIM model. Due to the nature of 2D modeling, you can’t see any vertical penetrations, such as HVAC ducts, or horizontal components, such as plumbing pipes, in a traditional MEP drawing. Additionally, you can’t view the model in true 3D and walk through the model, as you can in a BIM model. For example, a BIM model can show how an HVAC system is designed and where the ducts run. It can also show how a plumbing system is designed, including where the pipes are located. You can use this information in a variety of ways when you’re working on the project, such as ensuring that your equipment is installed correctly and that it complies with regulatory requirements.

Why is accurate BIM MEP modeling important?

BIM modeling, image

Accurate BIM modeling is important for several reasons. - Regulatory compliance: In the United States, the parties who are responsible for ensuring compliance with the building code are the owner, architect, and general contractor. The subcontractor is responsible for ensuring that their part of the build process complies with the code, but they do not have the same level of responsibility. If the BIM model is not accurate, the code compliance checks may not pass, and the contractor may need to redraw the model to correct the issues. - Avoid delays: If the BIM model is not accurate, it can affect the project schedule. For example, the building may need to be inspected before it can be occupied. If the BIM model is inaccurate, the inspection may not pass, and the project may be delayed until the model is corrected. In addition, if the building has been designed based on the BIM model, any changes to the model will also need to be communicated throughout the project team. Above all, we need an accurate BIM Model to execute and install the MEP services at the construction site accurately.

Most important things to consider when doing BIM MEP modeling

Most important things to consider when doing BIM MEP modeling, image
  • Use a BIM-savvy Company: When you’re subcontracting out your MEP model, you need to find a top BIM company that is familiar with BIM processes and has experience working with other subcontractors. A modeler whose experience is primarily with single disciplines, such as 2D engineering, may struggle with the level of collaboration and information exchange that is required when creating a BIM model.
  • Stay on top of changes: You need to stay on top of changes to the BIM model during the project. When changes are made to architectural drawings, you need to ensure that the changes are reflected in your BIM model. You also need to ensure that any changes that you make to the BIM model are communicated to the other parties on the project.
  • Ensure that the model is accurate: Finally, you need to ensure that the BIM model that is created is accurate. If it is not, all of the above issues are likely to arise.

Common mistakes to avoid when doing BIM MEP modeling

Common mistakes to avoid when doing BIM MEP modeling, image

Not being involved in the BIM process: If you’re not involved in the BIM process, it’s unlikely that your model will be accurate. You need to be involved in the BIM process from the beginning. This includes attending the design team meetings where the architectural drawings are being created, attending the concept model meetings, and reviewing the model as it develops. If you do not participate in these meetings, you will not be aware of the decisions that are being made and it will be difficult for you to ensure that your model is accurate.

Doing the model yourself: You may think that you should do the BIM model yourself, but this is not recommended. The modeler has a different focus from you; they are creating a model that they need to work from. Unless you are an experienced BIM modeler, you may not be aware of the best practices that need to be followed to ensure that the model is accurate.

Not communicating with the BIM Subcontractor: When you’re subcontracting out your MEP model, it’s important to communicate with the modeler. Let the modeler know what information you need in the model, and communicate any changes or clarifications that you need to be reflected in the model.


BIM modeling is a critical aspect of the BIM process. Coordinating the work of different disciplines is challenging when they are working in silos. However, when everyone is working together in a single model, the project is delivered more efficiently and with a reduced risk of error.

BIM modelers are often working with a different team of people than the design team, there is a need to establish trust and clear communication early on in the project.

The best way to do this is to engage with the modelers (BIM Consulting Companies ) throughout the project, making sure that they have all the information they need to create an accurate model. We at Desapex understand the entire process and have multiple project experiences in helping General Contractors and MEP Sub Contractors, if you want to explore subcontracting for your upcoming project or have a project where you need an immediate team to be mobilized, please don't hesitate to contact us.

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