The lease language, not any single statute, controls what expenses are recoverable and how the math works.
What do you need before you start the calculation?
Before you run any numbers, pull three things together: a rent roll showing each tenant's rentable square footage, a clear definition of your total leasable area, and a complete list of expenses you intend to include in the CAM pool.
For industrial flex properties, the CAM pool is narrower than in retail or office. According to Wikipedia, Common Area Maintenance Charges, typical inclusions for this property type are exterior maintenance, parking lot upkeep, landscaping, lighting, water and irrigation, and administrative fees. Interior bay maintenance, roll-up door repairs, and loading dock work that serves only one tenant generally stay out of the pool.
Get your lease in front of you. The lease is the controlling document. Texas courts enforce commercial leases as written under a freedom-of-contract framework anchored in Texas Property Code Chapter 93, and California courts apply Civil Code § 1638 to enforce unambiguous lease language. If your lease is vague on what goes into the pool, you are exposed.
How do you run the calculation step by step?
- Confirm each tenant's rentable square footage from the lease or a current rent roll.
- Confirm the denominator: total leasable square footage of the property, whether occupied or not. Write this number down and note whether your lease specifies total leasable or occupied-only.
- Divide each tenant's square footage by the denominator to get their pro-rata share percentage.
- Add up every CAM expense for the year to build the total expense pool.
- Multiply each tenant's pro-rata share by the total expense pool to get their annual CAM obligation.
- At year-end, compare actual expenses to estimates and issue a reconciliation statement showing the overage or credit.
This estimate-and-true-up cycle is standard under NNN and double-net leases, according to Wikipedia, Common Area Maintenance Charges.
What is a gross-up provision and do you need one?
A gross-up provision adjusts CAM charges upward when the building is not fully occupied, so a small number of tenants are not stuck covering costs sized for full occupancy, according to Wikipedia, Common Area Maintenance Charges.
Each tenant's bill rises as vacancies increase.
If you have multiple bays vacant right now, check whether your leases include this language. If they do not, add it when you renew.
Hypothetical example: three-bay flex building
Hypothetical example.
That is a meaningful increase caused entirely by the denominator choice, not by any change in actual expenses. This is why the denominator definition, as noted in Wikipedia, Common Area Maintenance Charges, materially changes each tenant's bill.
What are the common mistakes and edge cases?
Using the wrong denominator is the most common error. If your lease says total leasable area and you calculate on occupied area only, you are overcharging tenants and creating a dispute.
Missing the audit window is the second. Most commercial leases give tenants a contractual audit window of 30 to 180 days from delivery of the annual reconciliation, according to CAM Audit Rights and Statute of Limitations, qtren.com. Courts in Texas, California, and Maryland have consistently enforced binding-and-conclusive reconciliation clauses when the lease language is clear, per the same source. A tenant who misses that window may lose the right to challenge the bill even if the state's limitations period is still open.
The state limitations period for a CAM overcharge claim varies significantly. Under Cal. Code of Civil Procedure § 337, California allows 4 years. Under Tex. Civ. Prac. and Rem. Code § 16.004, Texas allows 4 years. Colorado allows 3 years for contract actions under C.R.S. § 13-80-101, but potentially 6 years if the CAM charge is characterized as a liquidated debt under C.R.S. § 13-80-103.5. Tennessee and Georgia both allow 6 years for breach of written contract, according to CAM Audit Rights and Statute of Limitations, qtren.com. Georgia also permits parties to contractually shorten that period, meaning your lease language can override the state's 6-year default, per the same source.
No single national CAM statute governs any of this. The lease controls, and what the lease says depends on what was negotiated.
What should you measure and how do you collect it?
Track four numbers every month: total CAM expenses paid, the expense category breakdown, total leasable square footage, and occupied square footage. The gap between leasable and occupied is what triggers a gross-up calculation.
Collect actual invoices for every expense in the pool. Do not estimate from memory. At reconciliation time, your documentation is what stands up if a tenant audits you.
Compare monthly actuals to your budgeted estimate. If actuals are running more than 10 percent above budget, consider issuing a mid-year adjustment notice rather than hitting tenants with a large year-end bill. Your lease may require notice before you can do this, so check the language first.
What should you do next?
- Pull every active lease and locate the CAM definition section, the denominator language, and the audit-right window.
- Confirm whether each lease specifies total leasable area or occupied area as the denominator.
- Check whether your leases include a gross-up provision. If any do not, flag them for renewal negotiation.
- Build a simple spreadsheet with each tenant's square footage, the denominator, and the current expense pool. Run the formula now so you know where each tenant stands.
- Identify your state's statute of limitations for written commercial lease disputes using the state-specific rules above, and confirm whether your lease's audit window is shorter.
- Before you finalize any new lease, renew an existing one, or add a gross-up or audit-right clause, have a local commercial real estate attorney review the language. What is enforceable in Texas may produce a different outcome in California or Colorado, and the expense of a review is far less than a CAM dispute.