How to Read a Blueprint

If you're building your own home, chances are you'll come across the blueprints at some point early in the process. This can be frustrating for many homeowners as they might not have an architect's background. However, you don't need to be an architect to understand the basics. We'll look at the various components of blueprints so you have a better idea of how to read them.

Types of Views

Most people think of blueprints as essentially a large piece of paper. However, there are different perspectives contained in these plans, including views from above, to the side and of a section of the home.

A plan view will show a birds-eye perspective from about 30 inches from the floor. It gives you a good idea of the full width and length of the structure. For elevation views, the perspective is usually from the side of one of the cardinal directions. As the name suggests, it's all about scaling the height dimensions. Section views will show you what the building would look like if you cut through it. So it might reveal the details of the building's envelope or the location of your basement pipes.

Blocks, Notes and Legends

The title block tells you the technical details of the blueprints. This can include the vendor, site specifications or approval signatures. It also identifies if there are related drawings to the blueprints. For instance, if you had an accessory dwelling unit (e.g., a guesthouse), this might be included in a second set of drawings.

The notes tell the builder if you have any specific requests about how the home is to be constructed. For instance, if you didn't want to pay for overtime under any circumstances, you might specify the hours in which the builders are allowed to work. The legend identifies the symbols and numbers that are used throughout the plans.

Scales and Grids

An architect's scale will be different from that of an engineer's scale. So if you're looking at plans that detail the size of the walls, it will likely be in fractions of an inch, such as 1/2 inch is equal to 1 foot. With an engineer's scale, it's usually a whole number (e.g., 2 inches is equal to 100 feet). There are no standards for scaling parameters so be sure to check the prints.

This is also a good time to take note of the grid. The goal of this feature is to assign numbers and letters to different areas of the home. This way, if you wanted to discuss a section of the basement with someone on the phone, you can direct them to D3 of the blueprints, instead of describing the section and risking confusion.

Line Varieties

There will be plenty of lines in your blueprints, and they each have their own meaning. A double line will indicate the wall. If it's a thick wall, the lines will be set further apart from one another. So an exterior wall will have more space between the lines than an interior wall because an exterior wall will have more insulation.

Thick single lines are object lines, while dotted lines are hidden lines. These two lines represent what you can and can't see. So the object lines might show the front of the stove and a hidden line might show the back of the stove (because you won't be able to see it from against the wall). Short, solid lines with arrows are dimension lines, named because they show you the distance between one object and another.

What to Look for

There are so many details in building a home and many go overlooked in the name of convenience. Learning to read blueprints gives you the chance to review the builder's works and potentially raise red flags now instead of when it's too late.

Again, you're not expected to have the same working knowledge as a professional. However, what you can do is try to spot any anomalies within the construction plans. For instance, you might see that the height of the upper floor's ceiling is lower than you expected, or that the refrigerator being too close to the stove. You can also check the materials being used for the home to ensure they're up to your standards.

If you're still unsure of the plans, try talking to a real estate agent, contractor or inspector. It is always a good idea to get a professional opinion from someone who has seen the perils of poor construction in the past.