How to Read CAD House Plan Drawings

By Nicholas Pell

You've got your contractor. You're excited about your new home or remodel. Then the contractor hands you a set of computer-aided drawings (CAD) and the whole thing looks like Greek to you. If you have trouble reading computer-aided drawings you aren't alone. Many design and architectural schools have entire classes dedicated to learning how to do just that. However, taking a class isn't necessary for the non-professional. Reading CAD drawings is a lot easier than you think.

Tools and model house on blueprints
credit: Jupiterimages/Comstock/Getty Images

Step 1

Look at the legend. The legend or key, usually located near the lower right-hand corner of the drawing, should explain all of the symbols on the drawing. Take a minute to acquaint yourself with the symbols. The legend will also tell you what different kinds of lines--dashed, thick, thin-- mean in this drawing. Remember that it is there for reference if you see something that you don't understand.

Step 2

Look at the title block. The title block is the part along the very bottom of the drawing or in either the lower right or lower left corner that tells you what you are looking at. You will probably know what project you are looking at. But you must know what aspect of the project you are looking at. For example, you could be looking at an elevation (one side of the project), a plan (a bird's eye view), or a section (a drawing that allows you to see "inside" the project, as if it were cut in half).

Step 3

Read the notes. Particularly near things like windows and doors, CAD drawings have lots of notes. These are usually letters or numbers in circles or hexagons that refer to a specific material or product to be used. Remember that when you are looking at a specific part of a CAD drawing with one of these notation marks next to it, there will be an explanation. This explanation can be either on the page you are looking at or on a page of its own.

Step 4

Pay attention to lines. Different line weights or thicknesses refer to different parts of a project. For example, interior walls and exterior walls are typically delineated with different line weights. Pay attention when you are looking at a CAD drawing to what a line looks like. This is perhaps the most important part of know what you are looking at.