Grow your building without pulling a permit: find the rentable area you already own
By Peter Stevenson, co-author of the BOMA standards · 6 min read
There is rentable area hiding in buildings you already own, and capturing it takes no construction. Over time, BOMA standards change and floors get reconfigured, opening a gap between the rentable area your leases charge for and what the building actually holds. A reassessment against the current standard routinely finds 3 to 4% of additional rentable area on Class A.
It is the lowest-effort square footage you will ever add to an asset, because it is already built. Here is why a building you have already measured tends to be bigger than your rent roll says, and how to tell whether yours is one of them.
Why a building you already measured is bigger than your rent roll says
A measurement is accurate the day it is taken. The report behind it has a shelf life. Standards evolve, tenants reconfigure floors, and walls move during buildouts, so the rentable area on your rent roll slowly stops matching the building in front of you. None of it involves anyone doing anything wrong. The gap accumulates on its own.
BOMA’s 2024 office standard (ANSI/BOMA Z65.1-2024) counts space earlier editions could not, including ground-level outdoor amenities and tenant-exclusive shafts. If your leases reference a 2010 or 2017 edition, the building is being charged under rules the standard no longer contains, and the current rules are frequently more favorable to the owner. The walls did not move. The definitions did. (What changed in BOMA 2024.)
The same floor, remeasured to the current standard, often holds more rentable area than the leases recognize.
What 3 to 4% is actually worth
Found rentable area is recurring revenue, and recurring revenue capitalizes into asset value. That is what moves measurement from a line item to a valuation lever. On a Class A tower, a few percentage points of newly recognized rentable area compounds across every year you hold the asset, then again at exit through the cap rate.
The mechanics are simple: we supply the verified square footage, you apply your own rent and cap rate. The result is an income stream you can underwrite, defend to a lender, and carry into a disposition model.
The 8 places unrecognized rentable area hides
After 12,500+ buildings, these are the gaps we find most, in rough order of frequency. Time causes all of them, and a single whole-building reassessment to the current standard resets every one at once.
1Common areas classified in ways that understate rentable areaFitness centers, conference facilities, and lounges allocate into rentable area differently depending on how they were classified, often years ago under different rules.
2Load factors built on outdated base measurementsThe load factor is only as current as the base measurement under it. When the base predates years of change, every suite inherits its age.
3Tenant spaces measured to the wrong boundariesDemising walls and lease lines disagree more often than expected after multiple generations of buildouts, and adjacent suites compound the difference.
4Vertical penetrations applied inconsistentlyShafts and risers are excluded by rule, but the rules have nuance, and different measurers across decades apply them differently floor to floor.
5Common areas allocated under an older BOMA methodologyAllocation rules changed across revisions. A building still allocating under its original methodology follows rules the standard no longer contains.
6The building was never brought current to the standardSometimes there is no methodology question at all. The building was measured under an older edition and simply never remeasured.
7Measurements that no longer reconcile to the source recordsA later remeasurement by a different party, done without referencing the original report, leaves you with numbers that cannot reconcile.
8Buildings measured in pieces instead of wholeSuite-by-suite measurement at lease events never captures the common area between the fragments, which is exactly where countable space goes unexamined.
The Math
Here is the calculation worked end to end on an illustrative Class A tower. The square footage is what SSI verifies. The rent and cap rate are your inputs; the figures below are illustrative, not a quote or a guarantee.
Illustrative: 500,000 RSF Class A tower
Stated rentable area (rent roll)500,000 RSF
Additional rentable area found (3.2%)+16,000 RSF
Your effective rent (illustrative)× $50 / RSF / yr
Added annual revenue$800,000 / yr
Capitalized at a 6.5% cap rate (illustrative)$800,000 ÷ 0.065
Added asset value≈ $12.3M
The annual figure recurs for as long as you hold the asset. The value figure is what shows up when you refinance or sell. On a 5, 10, or 20 year hold, those numbers compound, which is why a reassessment timed to a financing event or a disposition tends to pay for itself many times over.
Found rentable area only becomes revenue once it is documented in the lease. SSI’s revenue-capture team makes sure every recognized square foot reaches the lease record, not just the report.
The Rentable Area Self-Assessment
Is your building’s rentable area understated?
Check every statement that is true of the asset. Each one is an indicator. There is no email required for the result; it updates as you go.
0 of 8 indicators flagged. Check the statements that apply to see what they tend to mean.
One reassessment clears all of it
A whole-building remeasurement to the current BOMA standard, field-verified and reconciled to a single source of truth, resets every item on the list at once. Performed by SSI, it comes with a distinction that matters at the edges: our team co-authors the BOMA standards your leases reference, and Peter Stevenson is one of only 2 official BOMA interpreters internationally. Where an edge case has two readings, you get the definitive one.
From there, keeping the number current is a maintenance task. Every tenant change is processed against the source records, often in under 30 minutes, so the gap never rebuilds itself.
PS
Peter Stevenson co-authored the ANSI/BOMA office measurement standards and is one of only 2 official BOMA Standard interpreters internationally. Stevenson Systems has measured 12,500+ buildings representing $15B in verified asset value over more than 40 years focused exclusively on building measurement.
Keep reading
See the 8 places rentable area hides, the math, and the self-assessment
The 8 places unrecognized rentable area most often hides, from 12,500+ buildings measured
The revenue and valuation math, worked end to end
A 2-minute self-assessment you can run against any asset
Trusted by industry leaders
The questions asset managers ask first
We were already measured. Why reassess?
Against which standard, and when? A measurement is accurate the day it is taken, and the report has a shelf life. BOMA's 2024 office standard changed how common areas and amenities count, so a reassessment against the current standard routinely surfaces 3 to 4% on Class A.
Are you saying our prior measurement was wrong?
No. The opportunity comes from standards evolving and buildings being reconfigured over time, not from anyone getting it wrong. The area was always yours. It stopped being counted along the way.
How much rentable area do reassessments typically find?
On Class A office and on medical office, SSI averages 3 to 4% additional rentable area. That is an average across comparable engagements, not a guarantee for a specific building.
How do I know the new number will hold up with lenders and tenants?
Our team co-authors the BOMA standards your leases reference, so our interpretation is definitive rather than a second opinion. Our capture team then makes sure the recognized area is documented in the lease, where it becomes revenue.
Your building report has a shelf life
See what a reassessment finds on your asset
Book a Certified BOMA Measurement Review. We will show you where found rentable area capitalizes into value, both at hold and at exit.
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