How to Read Blueprints of Buildings

Locate the scale -- either at the top of the blueprint page, usually next to the title, or at the bottom of the page -- to identify what each unit on the paper translates into in actual building feet. A 1/4-inch scale is common, meaning every 1/4-inch on the blueprint is equal to 1 foot in actual building length.

Understand how elevation is represented on blueprints and that elevations are not indicated according to perspective. Look for front, rear and side elevations that indicate ridge heights, exterior finishes, roof pitches and the final grade of the lot.

Examine the floor plans represented in the blueprints. A floor plan gives an overhead view of the completed building; look for parallel lines that show how wide walls are required to be and for dimensions in between those lines that indicate room sizes and wall lengths. Observe fixtures such as sinks, water heaters, furnaces and showers throughout the rooms.

Locate the legend on each page, which tells you what electrical symbols drawn on each page represent. Look for the symbols for fans, lights, light switches, doorbells, thermostats, telephone jacks and outlets so that you can note where these items plan to be placed. Use a dictionary to look up any terms you do not understand.

Look for cross-sections that give overhead, detailed views of the building's special areas that are out of the ordinary or require non-standardized methods to complete. A cross-section shows what the building looks like if it were sliced down the middle. Observe rafter lengths and floor heights in relation to each other through a cross-section drawing.

Observe the plot plan to understand how the structure will sit on its building lot. Look for the location of utility services, how far the building is set back from the streets and topographical data indicating the slope of the land.