A commercial-zoned parcel is improved with a single-story office building. The appraiser measures the building per BOMA Office Standard and calculates a rentable area of 12,500 sq ft. The same building, measured per ANSI Z765-2021 for a hypothetical residential conversion, yields a GLA of 9,800 sq ft. What is the primary reason for this difference?
Correct Answer
C) BOMA includes shared restrooms and corridors in rentable area; ANSI excludes all non-living space
BOMA Standard Method for Office Buildings (ANSI/BOMA Z65.1) defines rentable area as usable area plus a proportionate share of common areas (e.g., lobbies, restrooms, corridors). ANSI Z765-2021 defines GLA strictly as *finished, above-grade residential space* used for living purposes — excluding all circulation, mechanical, and common areas. Thus, the 2,700 sq ft difference primarily reflects inclusion (BOMA) vs. exclusion (ANSI) of shared non-occupiable spaces. Option C correctly identifies this core distinction. Option A is incorrect: ANSI excludes below-grade space, but the building is single-story — no basement. Option B is false: both BOMA and ANSI measure to the *exterior* face of permanent walls for gross area calculations. Option D misstates ANSI: mezzanines are included in GLA only if ≥ 5 ft headroom and enclosed — not at 50%.
Why This Is the Correct Answer
BOMA rentable area deliberately includes a proportionate share of shared restrooms, corridors, lobbies, and similar common space, because those are costs the landlord recovers through rent. ANSI GLA deliberately excludes anything that is not finished above-grade living space. That inclusion-versus-exclusion difference is both the correct explanation and the only one that can produce a difference of this size in a single-story building. Option C names it precisely.
Why the Other Options Are Wrong
Option A: BOMA includes basement storage; ANSI excludes all below-grade space
The building is described as single-story, so there is no basement storage for BOMA to include and no below-grade area for ANSI to exclude. The option describes a real difference between the standards but attaches it to facts the stem does not contain. It is tempting because the below-grade exclusion is the most famous thing about ANSI Z765.
Option B: BOMA measures to the outside face of exterior walls, while ANSI measures to the inside face
ANSI Z765 measures to the exterior finished surface of exterior walls, not the inside face, so the second half of the statement is simply false. Even if a wall-line convention did differ, the thickness of a perimeter wall on a building of this footprint could account for only a small fraction of 2,700 square feet. Run the magnitude check and this option collapses on its own.
Option D: BOMA counts mezzanines at 100%; ANSI counts them at 50%
ANSI Z765 does not apply a 50% factor to mezzanines; a mezzanine level is either included in full when it is finished, enclosed, and meets the ceiling height requirement, or excluded. Half-counting rules of that sort belong to other conventions, not to Z765. The stem also never mentions a mezzanine, so the option imports a fact that does not exist.
Rentable Rides Along
Rentable area rides along with the common areas: the tenant pays for a slice of the lobby, the corridor, and the restrooms even though nobody's desk sits there. GLA is Guests Living Area, only the finished rooms people actually live in. Rentable rides, GLA lives.
How to use: When two measurement standards give different numbers for the same building, first ask what each standard is for. A leasing standard adds shared space to recover cost; a residential standard counts only livable finished space. Then check whether the size of the difference matches the explanation you picked.
Exam Tip
Before selecting a reason for a measurement discrepancy, estimate whether that reason could plausibly produce the stated magnitude; wall-thickness explanations almost never survive that test.
Common Mistakes to Avoid
- -Comparing a rentable-area figure to a usable-area or GLA figure without converting to a common basis
- -Assuming ANSI Z765 measures to interior wall surfaces when it measures to the exterior finished surface
- -Reaching for the below-grade exclusion rule on a single-story building that has no below-grade space
Concept Deep Dive
Analysis
This question tests whether you understand that a measurement standard is a definition of what counts, not merely a technique for holding a tape. The BOMA Office Standard produces rentable area, which is a leasing construct: usable area occupied by the tenant plus a pro rata share of building common areas such as lobbies, public corridors, shared restrooms, and janitorial closets. ANSI Z765 produces gross living area for residential use, and it counts only finished, above-grade space intended for living, excluding common circulation and mechanical space. Because the two standards answer different questions, the same building yields two legitimately different numbers. The 2,700 square foot gap, roughly 22% of the BOMA figure, is far too large to come from a wall-line convention and is exactly the order of magnitude you expect from a common area load factor.
Background Knowledge
You need to know that BOMA rentable area equals usable area plus a share of building common area, expressed through a load or R/U factor, and that ANSI Z765 defines gross living area as finished, above-grade living space measured to the exterior finished surface. You also need the habit of checking whether a proposed explanation is large enough to account for the stated difference.
Real-World Application
An appraiser valuing a multi-tenant office building receives a rent roll stated in rentable square feet with a 15% load factor. To compare it against sales expressed in usable area, the appraiser strips out the common area load before deriving a price per square foot, and states clearly in the report which measurement basis each figure uses.
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