The town assessor's record for your property contains a number for square footage. That number is probably wrong.

Not wrong in a conspiratorial way. Wrong in the same way that any data compiled at a moment in time and rarely updated is wrong: it reflects what was recorded when the permit was filed, the assessment was established, or the previous sale was processed. It may not reflect renovations that changed the home's actual GLA. It may not reflect the ANSI measurement standard that professional appraisers use. And it may not have been verified by a physical measurement at all.

Where Town Square Footage Numbers Come From

Municipal assessors compile property data through a combination of methods: building permits, field observations, transfer disclosures, and in some cases aerial measurements from remote sensing technology. The accuracy of each method varies, and the resources available to verify each property's square footage individually are limited.

In practice, the square footage number in the town record for most Greater Boston properties was established years or decades ago and has been carried forward in the database without physical re-measurement. Renovations that change the GLA are supposed to trigger an assessment update, but the update is only as accurate as the information the assessor's office receives, which may not include a professionally measured floor plan.

Why ANSI Measurement Produces Different Numbers Than Town Records

Even when the town's square footage figure was established by a field visit from an assessor, the methodology used may differ from the ANSI Z765 standard that professional appraisers apply. Mass appraisal methodology does not always distinguish between above-grade living area and below-grade finished area. It does not always apply the ceiling height criteria that determine whether an attic or bonus room counts as GLA. And it does not always exclude non-qualifying spaces like enclosed but unheated sunrooms.

The result is that the ANSI-compliant professional measurement almost always produces a different number than the town record, and the difference can be significant. Cases where the discrepancy exceeds 300, 400, or even 500 square feet are not rare in Greater Boston's varied housing stock.

When the Discrepancy Costs You Money

If the town record overstates your GLA, and you are assessed based on that inflated figure, you are paying property taxes on square footage that either does not exist or does not qualify as above-grade living area. This is a correctable over-assessment.

If the town record understates your GLA, and the lender's appraiser measures it at a higher figure during a refinance, the lender may require an explanation for why the public record is lower. This creates delay and documentation burden during a transaction.

And if you list a home with a square footage figure from the town record, and the buyer's appraiser or the buyer's agent's floor plan service produces a lower number, you may face a renegotiation after listing or a contract issue during due diligence.

The Professional Measurement as the Definitive Record

A professionally produced, ANSI-compliant floor plan measurement establishes the authoritative GLA figure for your property. It is the document that appraisers, lenders, attorneys, and tax authorities accept as the accurate measurement. When you have it in hand, you control the square footage conversation, rather than being subject to it.

Ready to Get Started?

Whether you are a homeowner, estate attorney, realtor, or investor in Greater Boston, Adam Wiener and the Aladdin Appraisal team deliver USPAP-compliant appraisals you can rely on. Call today: (617) 517-3711 | info@aladdinappraisal.com | aladdinappraisal.com