Gross living area is one of the most consequential numbers in any appraisal and one of the least understood outside the profession. It is not the total size of the structure. It is not what the town record says. It is not the number in the listing. It is a specific, defined measurement, and because price per square foot is calculated from it, an error in GLA distorts everything built on top of it.
What GLA Actually Measures
Gross living area is the finished, heated, above-grade space in a home, measured from the exterior walls. Every word in that definition does work. Finished excludes unfinished storage. Heated excludes a three-season porch. Above-grade excludes anything below ground level, regardless of how nicely it is finished. Measured from the exterior means wall thickness is included, which is why a home almost never matches the sum of its interior room dimensions.
What Gets Excluded and Why People Are Surprised
A finished basement does not count in GLA even when it is drywalled, carpeted, heated, and used daily. Why below-grade space causes so much confusion is covered in the finished basement question and why below-grade space confuses Greater Boston sellers, buyers, and listings. Neither does a converted garage that lacks proper heat, an enclosed porch on a slab, or a finished attic with insufficient ceiling height. This is not the appraiser diminishing your home. Excluded space still has value and is reported separately. It simply is not counted in the same bucket, because comparing a home with 2,000 square feet above grade to one with 1,400 above grade plus 600 below is not comparing like to like.
Why the ANSI Standard Changed the Conversation
For years, two competent appraisers could measure the same house and produce different numbers, because there was no single mandatory standard for how to do it. The ANSI standard, now required for most lending work, defines the method: what is included, how ceiling height is treated, how to handle stairs and openings. The background on that requirement is in ANSI Z765 and the measurement standard Fannie Mae made mandatory. The result is consistency, and consistency is what makes square footage arguable in a productive way rather than a matter of opinion.
How an Error in GLA Distorts Everything
If a listing advertises 2,400 square feet and the home measures 2,150, every price-per-square-foot comparison is off by more than ten percent. Buyers who ran the numbers feel misled. The lender's appraiser measures independently and reports the real figure, which can create a gap at exactly the wrong moment. And in Massachusetts, an agent who advertises square footage that turns out to be materially wrong carries genuine professional exposure. That risk is examined in why listing agents who advertise incorrect square footage face legal and professional risk in Massachusetts.
Where the Wrong Number Usually Comes From
Most bad square footage figures are inherited, not invented. The town record was created decades ago and never corrected. A prior listing used a number nobody verified. An addition was built and never re-measured. The figure passes from listing to listing, gaining credibility with each repetition, until an appraiser measures the house and everyone is surprised.
Square footage feels like a settled fact. It is actually a measurement, and measurements can be verified. If a number is going into a listing, a filing, or a negotiation, it is worth knowing that it is right. We measure homes to ANSI standards across Eastern Massachusetts, including Medford and the surrounding communities.
If your square footage is uncertain or disputed, our property measurement service delivers an ANSI-compliant sketch and floor plan you can put on the record.
