If you attempt to include all building systems on the same drawing, it becomes cluttered with information 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 drawing sets for each building system - this makes design requirements easier to understand, while preventing interpretation errors.
As you might expect, the number of drawings needed to describe the building and its systems increases in proportion with project scale. To make construction plans simpler, they are divided into drawing sets such as the following:
- Architectural
- Structural
- Electrical
- Mechanical
All building designs must be submitted to a local authority, to be checked for code compliance 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 authority in charge is the NYC Department of Buildings.
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Architectural and Structural Drawings
Architectural drawings show the appearance of the building: floor plans, interior and exterior elevations, sections, and any details required to provide the contractor with a clear image of how the completed project must look like. By working with a qualified architect, you can make sure the drawings are easy to understand and compliant with building codes.
The structural drawings describe how the building is physically supported. At a glance, these drawings appear similar to architectural drawings, since they display 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 have enough strength to withstand weather conditions like 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 delivers electricity to building appliances and equipment, and they are prepared by electrical engineers.
- Electrical layouts indicate the location of visible elements such as power outlets, lighting fixtures and switches.
- They also specify the wiring and conduit for the circuits that deliver voltage to these elements, which are normally hidden in walls or above ceilings.
- In addition, electrical drawings provide a detailed description of the distribution boards from which circuits obtain power, including the capacities of circuit breakers and main feeders.
Even combustion-based heating systems have electrical components like fans and pumps, and their power supplies are specified in electrical drawings. If the building uses heat pumps or resistance heaters, the electricity demand associated with heating increases, and circuits must be sized accordingly.
All electrical installations are subject to standards and codes, and only compliant designs are approved by the NYC Department of Buildings:
- The NFPA 70 National Electrical Code provides the requirements for all electrical installations in the USA. In the case of New York City, there is an NYC Electrical Code that includes the entire NEC with specific requirements and amendments.
- Electrical components must be labeled by either Underwriters Laboratories (UL) or the Intertek Electrical Testing Laboratories (ETL). The marks from these labs prove the component has been rigorously tested for safety.
The electricians working in the project must be familiarized 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 according to code, insurance companies do not provide coverage.
Energy efficiency marks such as ENERGY STAR and NEMA Premium Efficiency are not mandatory, but you can achieve a significant reduction in operating costs if you purchase equipment with those marks. Also consider that most energy efficiency incentives only apply for labeled equipment - for example, Con Edison lighting rebates are only for lamps and fixtures with the ENERGY STAR or DesignLights Consortium (DLC) mark.
Mechanical Drawings
As implied by their name, mechanical drawings provide the layout and technical specifications for mechanical work, which includes plumbing, heating, ventilation, air conditioning, sheet metal and fire protection. Since various systems and equipment types are involved, many of these drawings are provided by subcontractors, with approval from the architect.
Plumbing drawings provide the layout for potable water and wastewater piping. These drawings also cover domestic hot water (DHW) systems, which typically use natural gas as a heat source. In addition, they cover aspects such as vents and storm drains.
- The Uniform Plumbing Code is the national standard to follow during the design process, and there are also city-specific regulations like the NYC Plumbing Code.
- For hot water systems based on combustion, the NYC Fuel Gas Code also applies.
Plumbers must study the corresponding drawings in detail before proceeding with the installation. Since many plumbing elements are embedded in walls and floors, more difficult to modify than electrical and HVAC installations.
Since a plumbing system delivers clean water and removes wastewater, malfunctions can create health hazards in a very short time. There are hefty penalties for NYC plumbing code violations, and plumbing contractors undergo a rigorous licensing process before they can work in actual 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.
- Sheet metal design must be highly detailed to ensure a 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 properly sized, to deliver the required space heating or air conditioning output for each building area.
- Since sheet metal and hydronic piping design are dependant on heating and cooling loads, a precise load calculation is very important. Unfortunately, a correct design procedure with inadequate data does not lead to a satisfactory design.
Installation of exposed equipment like furnaces, boilers and chillers is not the main challenge in HVAC systems. The most difficult part of the installation is hydronic piping and ductwork, which must travel long routes with direction changes and accessories. Mechanical drawings must clearly indicate the layout and mounting details of these systems.
HVAC design is strongly related with building envelope performance: if the construction is well insulated and airtight, both heating and cooling loads are reduced. Adding a high-performance building envelope for a new project is much simpler than upgrading existing property where the walls are already built.
Sheet metal work is mostly associated with the air ducts of HVAC systems, but also includes the following building elements:
- Flashing, to protect components from water damage
- Gutters
- Canopies and decks
- Conveyors
- Machinery guards and hoods
Additional Documentation: Shop Drawings and As-Built Drawings
Shop drawings describe work that is performed away from the construction site, and they are normally prepared by subcontractors. Shop drawings must be highly detailed, with a large enough scale to indicate all relevant features. These drawings must be approved by the project architect before any of the corresponding work is fabricated.
As-built drawings indicate exactly how all building systems are installed after project completion. Many components can be installed in slightly different positions without affecting performance, and contractors make minor changes for ease of installation or convenience. However, these changes must be indicated in as-built drawings, and submitted to the architect.
The following are some examples of components that tolerate minor changes in their location:
- Underground piping
- Conduit, junction boxes and conductors
- Cleanouts
- Overhead valves
As-built drawings provide a reference for maintenance and alterations. These drawings are important for all building systems, but especially for electrical, plumbing and HVAC installations.
Conclusion
Construction drawings are important throughout the entire life cycle of a building. Along with technical specifications, they allow effective communication of project requirements to contractors and their staff.
Once the project is completed, design documents are used to inspect the building and its installations. When buildings are already in operation, construction plans are very useful for maintenance activities or system upgrades - just make sure the drawings are updated accordingly after every change.
