Understanding Construction Drawings

Construction drawings are used to show how a structure should be built. These drawings are created by architects and engineers based on the functional and design needs of the building occupants.

While they can appear complex, it is actually fairly easy to understand the basics of these plans and the information they provide about the building's design.

Plan Overview

Construction drawings may range from a single page to hundreds of pages. Most sets of building plans are divided into five categories that cover different aspects of the job. They include civil, structural, architectural, mechanical and electrical sections topped by a title page. The title page lists all the drawings included in the set, as well as a legend that can help you interpret symbols found throughout the drawings.

Construction drawings are equipped with a grid system similar to the ones used on road maps. Each page features horizontal rows labelled with numbers, and vertical rows labelled with letters. These rows are known as "column lines" and represent the structural columns within the building. You can use column lines to help you compare different plans to one another.

Architectural Drawings

Although they are located in the middle of a set of drawings, architectural plans should be reviewed before other drawings because they are the easiest to understand. Each drawing in the architectural set will have a number starting with "A," such as A6.11. The first few drawings in this set show the floor plans of the building. These floor plans provide the basic layout of each floor, including wall and door locations, as well as the name and number of each room. Take time to see where rooms are located in comparison with one another, and to find major features like stairs, elevators and entryways.

The rest of the architectural plans provide close-up details of each area as well as flooring, paint and other finish selections. You'll also find interior and exterior building elevations.

Civil and Structural Plans

Civil plans show the building in relation to the surrounding area, and include things like earthwork and environmental protection. The first drawing in this set is generally a site plan, which shows the entire construction site along with the outline of the building. Get an idea of how the building is oriented, and which direction the entrance or other major features are facing. Review grading plans to see where dirt will be added or removed from the site, and check for things like landscaping and fencing.

The structural drawings provide details on the buildings framing system. Unless you are responsible for framing or steel work, it is usually sufficient to understand where columns are located and how roof and floor framing will be constructed.

Mechanical and Electrical

The most complex drawings in a set of blueprints are the mechanical and electrical plans. Mechanical drawings show duct layout, piping and equipment locations. Review the path that ducts and pipes take through each floor, and check to see how they connect to mechanical rooms and to other levels of the building. Use the symbols legend to understand where air enters each room through a grill or diffuser, and where it exits to return to the mechanical room.

Electrical drawings rely heavily on symbols and notes. Review the symbols used by the architect for receptacles, light switches and other equipment. Determine the locations of electrical rooms and panels, and follow the path of the wiring from these panels to areas throughout the building. Pay attention to the path the electrical service takes from outside transformers to inside the building.