What’s the first thing that comes to mind when you think of the utilities in a building?
Well, if you answered lighting, the bathroom, or your kitchen sink, then know that this was included in the MEP drawings.
What are MEP drawings?
Simply put, MEP drawings represent the mechanical, electrical, and plumbing drawings for a project. In the construction industry, these drawings will normally come together as a set.
In this article my goal is to inform you of the different sections of the MEP drawings. This way when you review the plans you will know what you’re looking at and how it translates to a project.
Before I dive into the nitty gritty of the MEP drawings, I want to first cover their importance to a project. Understand that without MEP you have a building without any functionality. MEP provides building occupant with the amenities for normal day-to-day activities.
For example, your mechanical will provide you information for the HVAC system. This give occupants comfort while they’re working in the office or relaxing at home.
Electrical provides you with your power to the building. Not only do they cover power to the building, but this can also include fire alarm, lighting, and data systems.
Plumbing allows you to have a shower, running sink water, and a toilet.
You get the gist, without MEP you can’t have a well functioning building. But let’s take a step back and look at how these systems get developed in the first place. Also, we will look at why these drawings typically are associated with one another.
When an owner wants their construction project to begin, they need to reach out to a design team to engineer the job. This way they can develop a set of construction plans to issue with an RFP. Depending on the project, it can require engineering of the MEP systems.
During the design phase, MEP engineers need to maintain a high degree of interaction. When they’re selecting locations for new equipment and material, they need to make sure there’s no interference during install. This can include breaker panels, plumbing fixtures, control panels, and more.
Careful planning needs to be done during this phase to avoid this issue. If this is missed, then this creates conflict in the field. If the contractor recognizes the discrepancy, then they will require a change order to correct it.
Another thing to consider during the design process of the MEP plans is how everything ties together. Let’s imagine an HVAC system, you have your equipment but it requires a power supply and piping for chilled water. The electrical engineers will need to make sure they show the power connection to the unit.
If during the electrical design they forget to include a detail, then the electrical contractor likely did not include this cost. If that’s the case, they might ask for more money for running additional electrical conduits to power the equipment.
In commercial buildings this situation is a more likely scenario, that’s why you need to look at all the sections in the drawings. By only looking at the drawings you think pertain to your trade, you risk running into problems in the job.
As the general contractor, it’s your duty to consider all of the trades and how they intertwine. When this information is missing it can affect the MEP installations in the project. Plus this is all just added construction cost in the grand scheme of things.
Understanding the Drawings
Symbols and General Notes
A lot of these the items in a MEP drawing set but you need to understand what the different symbols and abbreviations mean. The tile sheet is where you will find this information. If you look in the example below, you’ll see the symbol and some information next to providing you with an explanation.
It’s important that you don’t just gloss over the notes on this page, it can contain valuable information. Things such as phasing, installation requirements, building codes, and more to follow. This information can be crucial in some situations, so make sure to review the notes throughly.
Floor plans are the most common drawing that you will come across in any plans. Depending on the trade you’re looking at, the appearance of the drawings will change. The information that each sheet provides is pertinent to the trade or labeling.
When it comes to floors plans, you will have your demolition, then new construction sheets. Items to demolish are typically shown as greyed out or a hatch appearance to it, see image below.
In your new construction floor plans, there are many different type to consider.
The mechanical drawing will show you locations for your ductwork for any mechanical ventilation. Piping connected to HVAC systems, providing either chilled water or refrigerant. As well as location for new equipment, chillers, air handlers, exhaust fans, etc..
Plumbing will display the approximate piping routes along with fixtures and equipment.
Electrical is a bit different, there’s many different types of floors plans that can be included in the electrical section. The two most common types you will come across is lighting and power. You can also expect to see sheets for data (telecom & internet) and fire alarm systems.
This type of drawing will provide you with a three dimensional view of the piping layout, also know as an isometric view. This type of drawing provides the contractor with information if the piping elevation varies in certain locations. This helps to mitigate confusion when construction begins.
The equipment schedule is valuable information, this tells the contractor what piece of equipment to purchase for the job. Usually, the design data will be included in the schedule should the contractor decide to use a different manufacturer.
If you can’t match the design data shown, then chances are your equipment will not perform as the engineer intended. This can be a major issue when it comes to commissioning or turnover of the building project.
As the heading might suggest, these drawings provide exact details on how the engineer expects installation to be completed. This can include things such as pipe supports, penetration drawings, roof curbs, etc..
The mechanical engineer will provide a section or side profile view of the interior of the building. This will display the elevation of the ductwork to best show the design intent.
This will appear in the form of a matrix, and tells the DDC contractor what is required for the system. It will include different field sensors and devices which will be used in the system control, known as hardware points. You also have software points which provide additional information to the users monitoring the system.
Shown as a schematic, it includes all of the sensors and control devices that will be included with a specific piece of equipment. There’s a lot of symbols here so remember to refer to the title page of the drawings.
Sequence of Operations (SOO)
Basically, this tells you how the engineer wants the HVAC equipment to operate for the building. This is valuable information when it comes to testing out the equipment with the controls in place. The mechanical engineering team of commissioning agent will want to see that the SOO is met.
One Line/Riser Diagram
More commonly with HVAC controls you will have physical controllers which require low voltage wiring to operate. Included with the low voltage wiring is wires for communication between the controllers. The one line/riser diagram gives the contractor information on how the communication bus needs to be wired.
This schedule is intended to tell the electrical contractor what type of breakers he will need for his breaker panel. It will also provide information on what will be tied to the panel, the power requirements, and how to label the breakers.
The electrical engineering team will check this during their final inspections so make sure what was installed matches the schedule.
One Line/Riser Diagram
Like the mechanical controls section, this provides the contractor with information on the intended power distribution for the building.
This information can also be valuable if you need to perform work on some equipment and need to de-energize it. If you need to remove or work in the equipment disconnect then referring to the one line diagram can help. From there you can turn off the breaker to safely work on the equipment.
The MEP shop drawings are another part of the construction process. Don’t get this confused with the design drawings because they’re very different.
This can act as the coordination drawings. It tells the other trades and engineers how the contractor intends to perform the work. You can coordinate exact locations for installing equipment, piping, ductwork, etc.. based on the comments you receive.
Team members need to provide their feedback when it comes to the shop drawings. This helps to prevent conflicts in the field.
When are Shop Drawings Needed?
Shop drawings might not be required for every project. If you have a small job then including the drawings might make the job too expensive for the customer.
For commercial buildings and federal projects, it would be wise to include drafting time in your cost estimation. You keep installation costs to a minimum when you have drawings that everyone has agreed upon.
Contractors cannot rely on just the design drawings to complete the work because the design is not perfect. There’s some field verification that needs to be done before drawings can be made and work can proceed.
Mechanical installations will typically have shop drawings associated with their work. Along with the shop drawings, they may use a virtual model to assist with placement of the ductwork and piping. This would be the most accurate representation of how the work will be carried out for MEP coordination.
When the work has been completed, the post construction/close out phase begins and as-built drawings are needed. As the name implies, these drawings need to include the final record of how the project has been built.
These drawings will act as a reference for the building maintenance and future contractors doing work on the building. This way they can look back at the drawings to understand what was done if repairs are needed.
How Are As-Builts Made?
During the course of the project, the field team is required to mark up/redline the shop drawings. These mark ups are done to show what changes were made during construction. It then goes back to the drafting team to edit the shop drawings converting them to as-built drawings.
As you can see there’s a lot that can go into the MEP drawings. Building contractors need to make sure they’re familiar with all the plans for a project if they want to succeed. If not then you will not know the types of mechanical systems or electrical systems of the buildings.
With anything, it will take some time before you can grasp how the different systems tie together. It might be difficult to comprehend just by looking at the plans.
So, my recommendation if you’re just starting out is to get into the field. Once the work begins, go out there look at the drawings and compare it to what was installed. If you can start to visualize in your head what the finish product will look like, it will help to communicate with the field.
Also, know that the design drawings are not the final say in how things will be installed. They’re just guidelines to help the contractor determine what will be the best fit. This is why shop drawings are so important, engineers sometimes rely on the judgement of the contractor.
Thank you for reading.
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