How Big Is Your Condo? There Is No Right Answer.

Q: We are under contract to purchase a downtown condominium unit. The seller's real estate agent has said the unit contains 860 square feet. However, when my wife and I measured the apartment, we came up with only 830 square feet.

Is there a formal method of making these measurements? Obviously, we do not want to pay for more than we are actually getting.

A: There is an old saying that when there are two lawyers, there will be three opinions. When you are trying to analyze square footage, you may actually get four or five opinions.

How to measure multifamily condo square footage has become a hotly debated question to which there is no real answer. There are industry standards when measuring single-family houses, offices buildings and rental apartment buildings, even though they are often ignored. However, to the best of my knowledge, there are no such standards for measuring condominium and cooperative apartments.

The American National Standards Institute (ANSI) has published a document titled "Square Footage -- Method for Calculating." It applies to single-family attached and detached houses. For attached properties such as townhouses, ANSI states, "The finished square footage of each level is the sum of the finished areas on that level measured at floor level to the exterior finished surfaces of the outside wall or from the centerlines between houses, where appropriate."

Note the words "exterior" and "centerlines."

In a condominium unit, however, lawyers who prepare documents for developers tell me that they try to get the engineer who is preparing the measurements to follow the unit boundaries as they are spelled out in those documents.

There are two important legal records in a condominium: the declaration and the bylaws. The former creates the condominium and contains basic concepts, including a definition of units, common elements and limited common elements.

Here's an example of a definition of a unit in one D.C. condo's declaration: "Each Condominium Unit includes the horizontal space between the Unit side of the exterior walls of the building and the finished walls separating the Unit from corridors, stairs, and, where applicable, to the surface of the finished walls of those interior walls which separate one Unit from another Unit. Each Condominium Unit also includes the vertical space measured from the (topside) surface of the subflooring to the finished (exposed) surface of the ceiling of such Unit."

Note that this refers only to the inside of the unit, not the exterior or centerline. In my opinion, that is how condominium square footage should be measured.

However, many developers have opted to go the ANSI route -- that is, measuring from the centerline of the walls between the units. If, for example, the outside wall is 12 inches thick, that would add half a foot in one dimension used in calculating the area.

The basic formula for square footage is to multiply a room's length by its width. Thus, a room that is 12 feet by 18 feet contains 216 square feet. However, if you add the six inches to our example for each dimension, you get 231 square feet but no more usable space in your unit.