How to read construction blueprints

Updated February 21, 2017

Construction blueprints serve as both instruction manual and map, showing exactly how a project should be constructed. They show the building plans, finish requirements and electrical and mechanical layouts, as well as information on any speciality requirements. Many people are intimidated by blueprints, believing they are difficult to interpret. But even people with little or no construction experience can learn to read building plans and use them to imagine what the project will look like or understand how it will be built.

Start with the title page. This is often the first sheet in the set and contains a list of all drawings included for the project. Take a look at what is included so you can get an overview of the job. The title page also usually contains a list of symbols and abbreviations used in the drawings. Review this list so you will know what these items refer to as you encounter them on the drawings.

Determine the scale of the plans. Scale is a way of representing a large building on a small sheet of paper and showing proportion at the same time. To accomplish this, most blueprints are drawn so that 1/8 of an inch on paper is equal to 1 foot of constructed material. This is referred to as 1/8-inch scale. Although this is a common value, some drawings may be drawn to 1/16-inch or even 1/4-inch scale. The value will be indicated somewhere on the drawings, usually on each page. Keep scale in mind as you examine the plans.

Review the architectural drawings. These are generally the first few drawings in the set and are numbered as "A" followed by a number. They show floor plans, exterior elevations, furnishings and finish selections. The architectural plans are easiest for the novice builder to understand, and they give a good overview of the project.

Examine the mechanical drawings. These will usually follow the architectural plans and will be numbered as "M" followed by a number. They will show the heating and air conditioning systems as well as plumbing information. Using mechanical plans, you can get a feel for where duct work will be located, how pipes will be run and where vents and diffusers will be located.

Understand electrical plans. These are typically at the end of the set and are numbered as "E" followed by a number. They show the locations of light fixtures, receptacles, switches and wiring. You can get a good picture of the building's electrical layout by examining these plans, even if you have no experience with the subject.

Refer to the specifications manual, often called the "spec book." Most blueprints come with a spec book that provides information about materials and methods for the project. Builders use both the spec book and the plans to construct the project, as there is typically a lot of critical information in the spec book that is not provided on the blueprints.


Few construction projects are completed without at least a few changes being made to the plans. Official changes are issued in the form of addenda, change bulletins or amendments. Be sure you have the latest changes when working with a set of blueprints. In most cases, the general contractor or architect will advise you on updates.

Things You'll Need

  • Building plans
  • Specifications
  • Any available addenda/modifications
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About the Author

Emily Beach works in the commercial construction industry in Maryland. She received her LEED accreditation from the U.S. Green Building Council in 2008 and is in the process of working towards an Architectural Hardware Consultant certification from the Door and Hardware Institute. She received a bachelor's degree in economics and management from Goucher College in Towson, Maryland.