BOMA 2024 vs 2017: How Measurement Changes Affect Your CAM Charges

BOMA publishes the standard that defines how commercial buildings measure rentable square footage. When that standard changes, the total rentable area of a building can change — and when the total rentable area changes, every tenant's pro-rata share changes with it, even if the actual CAM expense pool stays the same.

BOMA 2024 (ANSI/BOMA Z65.1-2024) made several changes to how space is classified and measured. For tenants in affected buildings, the practical question is not whether the standard changed — it is whether your landlord adopted the new standard, what your lease says about it, and whether the change in your pro-rata share is legitimate.

What changed: BOMA 2024 vs. BOMA 2017

Net effect across a typical commercial portfolio: a 2–5% increase in total rentable SF per building when adopting BOMA 2024 from BOMA 2017.

How this affects your pro-rata share

Your pro-rata share is calculated as:

Your RSF ÷ Total Rentable SF = Pro-Rata Share %

If the total rentable SF increases because the building adopted BOMA 2024, the denominator gets larger. A larger denominator means a smaller percentage for each existing tenant — which means a smaller CAM bill, assuming the total expense pool stays the same.

That sounds like good news. But the math only works out that way if your own space is measured consistently with the new standard. If your lease locked in your square footage under BOMA 2017 measurements but the building's total RSF is now calculated under BOMA 2024, the denominator and numerator are using different standards. The shares no longer add up to 100%.

To see the math: a 150,000 RSF office building where a tenant occupies 10,000 RSF starts at a 6.67% share. Under BOMA 2024, the building remeasures to 157,500 RSF (a 5% increase). If the tenant's space stays at 10,000 RSF, the share drops to 6.35%. On a $500,000 annual CAM pool, that's the difference between $33,333 and $31,746 — a $1,587 annual reduction. If the landlord adopted the new building total but did not adjust the tenant's share, the tenant may be overpaying by that amount each year.

The reverse problem also occurs: if the landlord adopted BOMA 2024 for the building total but also remeasured individual tenant spaces under the new standard, some tenants may see their square footage (numerator) increase, which increases their share even if the denominator grew proportionally.

The Non-Allocated Tenant Area problem

The most impactful single change in BOMA 2024 is the reclassification of balconies and rooftop terraces as "Non-Allocated Tenant Areas."

Under BOMA 2017, these spaces carried a load factor — the same way interior tenant areas did. The load factor distributed common area overhead across all tenant spaces. Under BOMA 2024, Non-Allocated Tenant Areas are measured at 100% of their actual area with no load factor applied.

This reclassification changes the rentable square footage of any tenant whose space includes a balcony or rooftop terrace, and it changes the building total for any building that has these features. In a mixed-vintage lease book — where some leases were signed under BOMA 2017 measurements and others under BOMA 2024 — the two standards produce different denominators, and those denominators cannot be directly compared. The pro-rata shares no longer sum to 100%.

If you are a tenant in a building with balconies or rooftop terraces, and your landlord adopted BOMA 2024, verify whether your own space was remeasured and whether the pro-rata share in your reconciliation reflects a consistent measurement methodology.

What to check in your lease

First, find out what measurement standard your lease actually references. Many commercial leases specify the BOMA version governing measurement — "per BOMA 1996," "per BOMA 2010," "per BOMA 2017." If your lease specifies BOMA 2017 and the landlord adopted BOMA 2024 unilaterally, the landlord may not be entitled to apply the new standard to your space without a lease amendment.

Also check whether your lease auto-updates. Some leases tie measurements to "the then-current BOMA standard" or "BOMA standards as amended." If yours has this language, the landlord may have the right to adopt BOMA 2024 without a lease amendment. If it specifies a fixed standard year, the landlord likely cannot change it unilaterally.

Beyond the measurement standard itself, look at how the lease defines the denominator. Language like "total rentable area of the building as currently measured" is different from "total rentable area as measured on the lease commencement date." Frozen denominators protect tenants from arbitrary remeasurements.

Finally, compare the square footage figures in this year's reconciliation to last year's. If your numerator changed without a lease amendment, ask the landlord to explain why.

What to do if your landlord adopts BOMA 2024 mid-lease

If you receive a reconciliation showing a changed pro-rata share with no explanation, and you suspect the landlord adopted BOMA 2024:

1. Ask the landlord for the BOMA measurement certificate for the building and your space. The certificate identifies which BOMA standard version was used and when.

2. Check whether your lease specifies a BOMA version. If it does and the landlord adopted a different version without a lease amendment, that change may not apply to your space.

3. Determine whether the changed denominator increased or decreased your share and quantify the annual dollar impact.

4. If the change appears unauthorized by your lease, document your objection in writing within your lease's dispute window. A mid-reconciliation BOMA standard change that's not authorized by the lease is a pro-rata share error.

For the full context on why pro-rata shares change and what to do about it, see why did my CAM share change?. For the broader pro-rata share calculation framework, see pro-rata share calculation errors.