Grow Your Building Without Pulling a Permit: The Math of Unrecognized Rentable Area

Additional rentable area increases building value through a three-step chain: found SF × rent per SF = new recurring revenue.

Recurring revenue flows to NOI, and that NOI divided by the cap rate capitalizes into asset value.

On a 400,000 SF Class A building at $40/SF and a 6% cap rate, a 3% finding is worth roughly $8M in asset value.

That’s the entire thesis. The rest of this piece shows the math, where the area comes from, and why it’s sitting in buildings owned by sophisticated institutions.

Where Does “Found” Rentable Area Come From?

From two forces that run continuously and belong to no one’s job description.

Standards evolve. BOMA has revised its office standard progressively, most recently in 2024. That standard allowed ground-level outdoor amenity areas and tenant-exclusive shafts to become countable rentable area. A building measured under the 2010 standard leaves area unrecognized by 2024 definitions, and unrecognized area is revenue the building never bills.

Buildings change. Tenants redesign, corridors get reconfigured, and demising walls shift. Each change can alter usable area, common area, and load factors. Unless someone manages the remeasurements and reconciles against the source records, the rent roll keeps quoting a rentable area that no longer exists.

The same average holds in medical office buildings.

What Is Found Area Worth? The Worked Example

Take a representative Class A office asset:

• Building size: 400,000 RSF (stated)
• Found area at 3%: 12,000 RSF
• Average rent: $40 per RSF
• Cap rate: 6%

Step 1: Revenue. 12,000 RSF × $40 = $480,000 per year, recurring, as leases roll and reset to the corrected area.

Step 2: NOI. Found area carries almost no incremental operating cost. The lobby was already cleaned, the elevators already ran. The revenue lands on NOI nearly intact.

Step 3: Valuation. $480,000 ÷ 0.06 = $8,000,000 in capitalized asset value.

Over a 10-year hold, the position is roughly $4.8M in cumulative revenue plus the valuation uplift at exit. For a measurement engagement priced in the tens of thousands, the multiple explains itself. Measurement behaves like an investment because it is one.

“We measured a Class A tower last quarter. The owner was leaving $1.2M a year on the table. Not because of mistakes, because standards and tenants change.”

Why Hasn’t Someone Already Captured This?

Capturing it requires three things that rarely coexist.

Whole-building measurement. Most measurement work happens suite by suite, whether at a lease event or by whoever is closest. Nobody returns to the source records, so suite numbers and building numbers stop reconciling. Found area resides in the gaps between fragments. SSI measures everything that may or should be included as rentable: the entire building, against the current standard, and every suite.

Standards authority. Edge cases decide the margin: does the covered terrace count, how does the shared loading dock allocate, where does the dominant portion line fall. Our team co-authors the BOMA standards, and Peter Stevenson is one of only two official BOMA Standard interpreters internationally. Our reading of an edge case is the definitive one, which is what you want under a number a lender will scrutinize.

Capture follow-through. Area found on paper isn’t revenue until it’s in lease documentation. SSI runs a dedicated revenue-capture team for exactly this step, so the findings are converted instead of sitting in a report.

How Does This Hold Up With Tenants and Lenders?

This is the first question careful owners ask, and the right one.

The number holds because the methodology is the one the lease references. Leases cite BOMA; we apply BOMA as its co-authors, with field verification behind every figure: an accurate snapshot of what’s currently built, suite TIs, demising walls, all of it. Our measurements are accurate enough to stand up in court, and they’ve been presented to the largest institutional owners and lenders in the world.

A pre-disposition remeasurement deserves a special mention: sellers who correct their RSF before going to market price the found area into the exit instead of donating RSF to the buyer’s upside.

Frequently Asked Questions

How much does additional rentable area increase building value?

Found SF × rent per SF gives annual revenue; dividing that by the cap rate gives the valuation impact. A 3% finding on a 400,000 SF building at $40/SF and a 6% cap is roughly $8M in asset value.

Is finding 3 to 4% additional area realistic?

It’s SSI’s average across Class A engagements over the last five years, stated as an average rather than a guarantee. Some buildings yield more, some less, depending on measurement vintage and building history.

Does found area mean my last measurement was wrong?

No. Standards evolve and occupancies change continuously. A measurement can be correct for its day and still leave area uncounted by today’s standard.

How do I estimate the opportunity before committing?

Start with the building’s current measurement and standard, then model found-area scenarios against your rent and cap rate. SSI’s Revenue Capacity Calculator does this in minutes, and a verified number also de-risks the Argus model built on top of it.