What General Contractors Need to Know About MEP Drawings

This article is part of our new Onsite Insight series, where we focus on content to help the construction industry modernize its operating practices to improve safety, schedule predictability, and, ultimately, profit.

General Contractors need to know a lot about a lot! There are many moving parts in a fast-paced environment. The complexity for a General Contractor is partly because they are at the helm of the project, orchestrating the various trades. Approximately 93% of workers on a job site are subcontractor trades, and some of the more complex work involves MEP (Mechanical, Electrical, and Plumbing). Think of MEP as the ‘central nervous system’ of a building. Much of what General Contractors need to know is tied up in MEP drawings, which provide a visual representation and the detailed information necessary to install Mechanical, Electrical, and Plumbing systems. For General Contractors, understanding MEP drawings is crucial to ensuring the project stays on schedule and adheres to the specifications outlined by the design team.

MEP drawings contain detailed information, including many sub-systems, such as the layout of HVAC systems, electrical outlets, wiring, plumbing fixtures, and piping. They are instrumental in coordinating the efforts of different subcontractors, ensuring that the installed systems do not conflict with each other or the architectural and structural elements of the building. BIM (Building Information Modeling) and VDC (Virtual Design and Construction) have made the coordination of MEP much easier in recent years. However, it is still a complex task, and design changes happen.

Now, let's delve into the key aspects of MEP drawings that General Contractors need to be proficient with:

1. Symbols and Legends: MEP drawings are filled with symbols representing various components. The symbols and legends used in MEP drawings can be standardized to a certain extent, especially within a particular country or region, as they often follow national or international standards. For instance, organizations like the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) provide guidelines on symbols to be used in technical drawings. However, there can be variations from company to company or even from project to project, especially if there are specialized or unique systems involved. Some firms may have their own set of customized symbols and legends that they have developed over the years or across different projects. It's important for General Contractors and other stakeholders to ensure that they are familiar with the specific symbols and legends used in the drawings for a particular project. This often involves reviewing the legend section of the drawings meticulously and communicating effectively with the design team and MEP subcontractors to clarify any ambiguities. This practice is crucial to ensure everyone involved in the project has a clear and unified understanding of the drawings, which in turn helps in preventing misinterpretations and costly errors during the construction phase.
2. Scales and Dimensions: MEP drawings are scaled to provide a sense of size and distance. Accurate interpretation of scales and dimensions is crucial to avoid costly mistakes during installation.
3. Drawing Titles (Plan, Layout, Coordination, Sections etc): Understanding the difference between plan drawings and coordination drawings helps delineate the scope and details entailed in each. Layout drawings depict the layout of mechanical, electrical, and plumbing systems, showcasing how they traverse through the building and interact with other structural elements. Coordination drawings emphasize the coordination between different MEP systems, ensuring they are integrated seamlessly without conflicts.
4. Specifications: Detailed specifications for materials, equipment, and installation procedures are often included to ensure construction safety and adherence to building codes.
5. Common Pitfalls: Navigating through MEP drawings can sometimes take time due to the complex nature of these systems. Some common pitfalls include misinterpretation of symbols, overlooking dimension details, and needing to be updated with revisions. Misalignment or discrepancies in the drawings can lead to costly and time-consuming corrections on-site. Identifying and addressing these common issues can significantly streamline the MEP installation process.
6. Building Information Modeling (BIM) and Virtual Design and Construction (VDC): BIM and VDC are revolutionary technologies that have reshaped the construction industry. BIM provides a digital representation of a facility's physical and functional characteristics, facilitating a shared knowledge resource for information about the project. On the other hand, VDC encompasses the management and application of multi-disciplinary performance models, including geometry, spatial relationships, geographic information, and quantities and properties of building components. General Contractors can utilize BIM and VDC for better visualization, coordination among trades, and clash detection in MEP systems. These technologies enable a virtual prototype of the building to be created before it’s built, allowing for potential issues to be identified and resolved before they reach the construction site.
7. Clash Detection: Clash detection is an integral part of the coordination process in construction, especially concerning MEP installations. This process identifies clashes or conflicts between different building systems, such as ductwork clashing with structural elements or plumbing lines intersecting electrical conduits. Utilizing BIM for clash detection allows General Contractors and MEP subcontractors to identify and resolve these issues in the design phase, significantly reducing the time and cost associated with on-site alterations. It ensures that the MEP systems are installed seamlessly without hindering the construction project's progress.
8. Revisions: Keeping track of revisions and ensuring all stakeholders are working with the most updated version of the drawings is fundamental to project accuracy.

Modern technologies, such as construction time lapse cameras, can visually document the MEP installation process, ensuring the work aligns with the MEP drawings. Especially a 4K construction camera can capture high-resolution imagery that could be utilized for detailed analysis post-installation, serving as a valuable resource for reviewing the accuracy of installations against the MEP drawings.

In conclusion, a robust understanding of MEP drawings is indispensable for General Contractors. It serves as the roadmap for accurate MEP installations and forms the foundation for effective coordination among various trades involved in the project. Embracing modern technologies can further augment the capabilities of General Contractors, enabling a meticulous adherence to MEP drawings and fostering a culture of precision and efficiency in construction projects.

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