If you try to include all building systems in the same drawing, it will become confusing and difficult to understand. For example, consider that offices have lighting fixtures, electrical wiring, air conditioning ducts and communication networks above the dropped ceiling. A smarter approach is to create separate sets of drawings for each construction system – this makes design requirements easier to understand while avoiding misinterpretation.
As you would expect, the number of drawings needed to describe the building and its systems increases proportionally to the scale of the project. To simplify construction plans, they are divided into sets of drawings such as the following:
- Architectural
- Structural
- Electric
- Mechanic
All construction projects must be submitted to a local authority to be checked for compliance with code and zoning requirements before a building permit is issued. In the case of New York City, only a Professional Engineer (PE) or Registered Architect (RA) can submit plans for approval, and the responsible authority is the New York City Department of Buildings.
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Architectural and Structural Drawings
Architectural drawings show what the building will look like: floor plans, interior and exterior elevations, sections, and any details necessary to provide the contractor with a clear picture of what the completed project should look like. By working with a qualified architect, you can ensure that drawings are easy to understand and comply with building codes.
Structural drawings describe how the building is physically supported. At first glance, these drawings appear similar to architectural drawings in that they feature the same floor plans, elevations, sections, and details. However, the main difference is that structural drawings specify the construction elements needed to support the dead load of the building, plus the live load of its contents and occupants. Buildings must also be strong enough to withstand weather conditions such as wind and snow, and extreme events such as tropical storms and seismic activity.
All structural designs are subject to federal and local building codes, and there must be an exact match of shape and dimensions between architectural and structural drawings.
Electrical Drawings
These drawings describe the power system that provides electricity to the building's appliances and equipment and are prepared by electrical engineers.
- Electrical layouts indicate the location of visible elements, such as outlets, light fixtures, and switches.
- They also specify the wiring and conduits for the circuits that supply voltage to these elements, which are typically hidden in walls or above ceilings.
- Additionally, electrical drawings provide a detailed description of the switchboards from which circuits obtain power, including the capabilities of circuit breakers and main feeders.
Even combustion-based heating systems have electrical components such as fans and pumps, and their power supplies are specified on electrical drawings. If the building uses heat pumps or resistance heaters, the electricity demand associated with heating increases and the circuits must be sized accordingly.
All electrical installations are subject to standards and codes, and only compliant designs are approved by the New York City Department of Buildings:
- The National Electrical Code NFPA 70 provides the requirements for all electrical installations in the US. In the case of New York City, there is a New York Electrical Code that includes the entire NEC with specific requirements and changes.
- Electrical components must be labeled by Underwriters Laboratories (UL) or Intertek Electrical Testing Laboratories (ETL). The marks of these laboratories prove that the component has been rigorously tested for safety.
Electricians working on the project must be familiar with codes, materials, and equipment to ensure they can install the electrical system as described in the design documents. If the building is affected by a fire and the electrical system is not installed up to code, insurance companies will not provide coverage.
Energy efficiency marks such as ENERGY STAR and NEMA Premium Efficiency are not required, but you can achieve a significant reduction in operating costs if you purchase equipment with these marks. Also consider that most energy efficiency incentives only apply to labeled equipment – for example, Con Edison lighting rebates are only for bulbs and fixtures with the ENERGY STAR or DesignLights Consortium (DLC) mark.
Mechanical Drawings
As the name implies, mechanical drawings provide the layout and technical specifications of mechanical works, which include plumbing, heating, ventilation, air conditioning, sheet metal, and fire protection. As multiple systems and types of equipment are involved, many of these drawings are provided by subcontractors, with approval from the architect.
Plumbing drawings provide the layout for drinking water and sewer piping. These designs also cover domestic hot water (DHW) systems, which typically use natural gas as a heat source. Additionally, they cover aspects such as ventilation openings and manholes.
- The Uniform Plumbing Code is the national standard to follow during the design process, and there are also city-specific regulations such as the New York Plumbing Code.
- For combustion-based hot water systems, the New York Fuel Gas Code also applies.
Plumbers must study the corresponding drawings in detail before proceeding with the installation. Because many plumbing elements are embedded in walls and floors, they are more difficult to modify than electrical and HVAC installations.
Because a plumbing system provides clean water and removes wastewater, malfunctions can create health risks in a very short time. There are heavy penalties for New York plumbing code violations, and plumbing contractors go through a rigorous licensing process before they can work on real projects.
HVAC drawings specify the location and installation details of all heating, cooling and ventilation equipment. They also provide the layout for sheet metal ducts used in air distribution systems.
- The sheet metal design must be highly detailed to ensure correct installation: ducts have many turns and connections and must be supported at multiple points.
- Depending on how HVAC systems are designed, they may involve hydronic or steam piping.
- Both air ducts and pipes must be sized appropriately to provide the space heating or air conditioning output required for each area of the building.
- Because sheet metal and hydronic piping design depends on heating and cooling loads, an accurate load calculation is very important. Unfortunately, a correct design procedure with inadequate data does not lead to a satisfactory design.
Installing exposed equipment such as furnaces, boilers and chillers is not the main challenge in HVAC systems. The most difficult part of the installation is the hydronic pipes and ducts, which must travel long distances with changes in direction and accessories. Mechanical drawings must clearly indicate the layout and assembly details of these systems.
HVAC design is strongly related to the performance of the building envelope: if the building is well insulated and airtight, heating and cooling loads are reduced. Adding a high-performance building envelope to a new project is much simpler than updating an existing property where the walls are already built.
Sheet metal work is primarily associated with the air ducts of HVAC systems, but also includes the following construction elements:
- Flashing, to protect components from water damage
- Gutters
- Roofs and decks
- Conveyors
- Machine guards and hoods
Additional Documentation: Factory Drawings and As-Built Drawings
Shop drawings describe work performed outside the construction site and are typically prepared by subcontractors. Shop drawings should be highly detailed, large enough in scale to indicate all relevant features. These drawings must be approved by the project architect before any corresponding work is manufactured.
As-built drawings indicate exactly how all building systems are installed upon completion of the project. Many components can be installed in slightly different positions without affecting performance, and contractors make small changes for ease of installation or convenience. However, these changes must be indicated on construction drawings and submitted to the architect.
The following are some examples of components that tolerate small changes in their location:
- Underground piping
- Conduits, junction boxes and conductors
- Cleaning
- Overhead valves
As-built drawings provide a reference for maintenance and changes. These drawings are important for all building systems, but especially for electrical, plumbing and HVAC installations.
Conclusion
Construction drawings are important throughout the life cycle of a building. Together with technical specifications, they enable effective communication of project requirements to contractors and their staff.
Once the project is complete, the design documents are used to inspect the building and its facilities. Once buildings are in operation, construction plans are very useful for maintenance activities or system upgrades – just make sure the drawings are updated appropriately after each change.
