How to Read a Blueprint for a House

Blueprints are detailed specifications of a structure created by architects and designers and used by builders and contractors during construction.

A blueprint contains all of the information necessary to construct a house.A blueprint contains all of the information necessary to construct a house.
Before the age of the computer and computer-aided design or drafting (CAD), blueprints were painstakingly drawn on semi-transparent film referred to as vellum. By overlapping the vellum drawing on top of blueprint paper, a blueprint is created when these are processed through a blueprint machine. Blueprints are generally 18-by-24 inches or 24-by-36 inches in size.

Locate the scale key of the blueprint, generally beneath the drawing or next to the title. Most blueprint plans are drawn to 1/4-inch scale of the actual size. This reads as every 1/4-inch of measurement on the blueprint represents one foot in reality. Some of the finer details, such as framing layouts, may be reduced to 1/8-inch scale or 3/4-inch scale, but the scale key of the drawing will note these differences. Contractors and builders consult with the scale key when making changes to the blueprint.

Identify the location of load-bearing walls, steel rebar placement and footings on the foundation or basement blueprint drawing. This depicts the placement of the structural elements that support the upper levels of the house.

Inspect the blueprint floor plans to determine the position of closets and room dimensions. Other features of the floor plans include the location of fixtures, such as the furnace, water heater and sinks. Specific types of finishes, symbols for electrical fixtures and construction methods are other notes that appear on the blueprint.

View the final appearance of your home with the four elevations blueprint drawings. These show the look of each side, the front and the rear of the house when completed. Items such as roof pitches, ridge heights, exterior finishes and other special design aspects also appear on the elevations blueprint. The elevations blueprint is drawn to scale and used by contractors, as needed, for specific measurements.

Consult the detail plans for plumbing, heating and electrical included as part of most blueprint sets for houses. These give the contractor the information as to the location of electrical outlets and include legends for heating systems and plumbing fixture locations. Some blueprint plans will include cross-section views of the house cut in half. This provides the contractor with even more structural information.

About the Author

Keith Allen, a 1979 graduate of Valley City State College, has worked at a variety of jobs including computer operator, medical clinic manager, radio talk show host and potato sorter. For over five years he has worked as a newspaper reporter and historic researcher. His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines.