Measurement standards
ANSI Z765 vs BOMA square footage
Short answer
ANSI Z765 measures finished living area in single-family homes and is what listings and appraisals expect. BOMA standards measure commercial and multi-tenant space, separating usable from rentable area. They count different things on purpose, so the same building can carry two different, equally correct figures depending on which standard applies.
What ANSI Z765 counts
Finished, heated living area in a single-family home, measured to the exterior faces of exterior walls. It sets out how to treat stairs, how to handle sloped ceilings, and what to exclude - garages, unfinished basements and open areas below are not living area regardless of how usable they feel. Because the rules are written down, a figure calculated to ANSI Z765 can be defended, which is why appraisers and listing services expect it.
What BOMA counts
Commercial and multi-tenant space, and critically it distinguishes usable area from rentable area. Usable is what a tenant occupies. Rentable adds a share of the common areas - lobbies, corridors, shared facilities - which is what the tenant actually pays for. That load factor is the difference a landlord and a tenant negotiate over, and it is why a lease figure is almost never the same as the space you can walk around in.
Why two correct figures can disagree
They are answering different questions. A house measured to ANSI Z765 and the same house measured under a commercial standard will not match, because one is counting finished living area and the other is counting leasable space including a share of what is shared. Neither is wrong. The error is applying one standard's number to the other's question - quoting a rentable figure as living area, or a living-area figure in a lease.
Which one your figure needs
Match the standard to the decision. Selling or appraising a home: ANSI Z765. Leasing commercial or multi-tenant space, or preparing a lease exhibit: BOMA. If a figure will be relied on by a buyer, lender or tenant, state which standard produced it and on what date, because an unattributed square-footage number is the one most likely to be disputed later.
At a glance
Side by side
| ANSI Z765 | BOMA | |
|---|---|---|
| Applies to | Single-family residential | Commercial and multi-tenant |
| Measures | Finished, heated living area | Usable and rentable area |
| Includes common areas | No | Yes, as a proportional share in rentable |
| Typically used for | Listings, appraisals, disputes | Leases, lease exhibits, service charges |
| Excludes | Garages, unfinished basements | Varies by the specific BOMA standard applied |
Questions
Common questions
Which standard should a real estate listing use?
ANSI Z765 for a single-family home. It is the standard appraisers apply, so a listing measured the same way avoids a contradiction appearing later in the transaction, which is one of the more common causes of a deal stalling.
Does a garage count toward square footage?
Not as finished living area under ANSI Z765, however well finished it is. It can be reported separately as garage area, which is the honest way to give the space credit without inflating the living-area figure.
Can you certify a square-footage figure?
We measure on site, calculate to the stated standard and note the basis of measurement so the figure is transparent and checkable. We do not certify square footage for legal or lending purposes; where a certified figure is required, that is a matter for an appraiser or licensed surveyor.
Related services
What this applies to
Last reviewed: 2026-08-20 · Asheville, NC
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