Quick Answer: Apartment-style condominium units are generally measured along the interior perimeter, while townhouse-style or detached condominium homes may follow single-family ANSI measurement rules. These methods, and the boundaries or areas described in a master deed, can produce different figures in a condo's deed, listing, and appraisal. Confirm both the property design and the measurement method.
Last updated: October 1, 2026
Condominium square footage generates more confusion than any other measurement question, and the reason is structural rather than careless. A single-family house and an apartment-style condo unit are measured by different methods, for sound reasons, and the figures recorded in a master deed were often produced for a purpose entirely unrelated to how a home gets valued today. Three different numbers for the same unit is common.
How Are Condominium Units Measured?
For a single-family home, gross living area is measured from the exterior walls, which includes wall thickness. For an apartment-style condominium unit, Fannie Mae requires interior perimeter measurements. The master deed defines ownership boundaries; condominium ownership alone does not determine the measurement method. That difference alone produces a smaller number for a condo than the same footprint would produce for a house, and it is correct in both cases. The distinction follows building design: single-family-style condominium homes, including townhouses, may require ANSI measurement rather than the apartment-unit method.
Why the Master Deed Number Is Often Different
The square footage recorded in a master deed or unit deed was typically produced when the condominium was created, sometimes decades ago, by a surveyor or architect working to a standard that may not match how residential appraisers measure today. It may include areas that are not finished living space, or exclude areas that are. The deed defines legal ownership boundaries, which may not match the finished-area figure used in an appraisal. How records and reality diverge is examined in the difference between what the town records say and what your home actually measures.
Balconies, Storage, and Deeded Parking
A balcony or deck is not living area. A deeded storage unit in the basement is not living area. A parking space, deeded or assigned, is not living area. All three have real value and a competent appraisal addresses them, but they are reported separately rather than added to the unit's square footage. Listings that combine them produce a figure buyers cannot compare against anything.
Why the Discrepancy Surfaces at the Worst Time
A seller lists using the master deed figure. A buyer runs a price-per-square-foot comparison from it. The lender's appraiser measures the unit and reports a different number. Now there is a conversation nobody planned for, days before a closing. Having the unit measured before listing can identify discrepancies early, although different standards or reporting conventions can still produce different figures. The timing argument is made in measure before you list and why the square footage question should be settled before the buyer's appraisal.
If you own or are listing a condominium in Greater Boston, do not assume the deed figure is the measurement a buyer's lender will use. Have the unit measured, know what does and does not count, and market the space accurately rather than optimistically. We measure condominium units across Eastern Massachusetts, including Waltham and the neighboring communities.
Why is my condo smaller than the deed says?
Because apartment-style condominium units use interior perimeter measurements, while the deed figure may have been produced to a different standard, sometimes decades ago, and may include areas that are not finished living space. The deed is a legal description of ownership rather than a valuation measurement.
Does a balcony count toward condo square footage?
No. Balconies, decks, patios, deeded storage, and parking spaces are not included in living area. They contribute value and a competent appraisal addresses them separately, but combining them into the square footage figure makes the unit impossible to compare against other units.
Who should measure a condominium unit?
A qualified appraiser or measurement professional should identify the correct method for the unit's design and intended use. Fannie Mae calls for interior perimeter measurements for apartment-style units and ANSI for single-family-style dwellings, including townhouses. Documenting the method makes comparisons clearer.
If your square footage is uncertain or disputed, our property measurement service provides a sketch and floor plan using the method appropriate to the property.
