Medical Office CAM Charges: What Physicians and Healthcare Practices Pay
TL;DR: Medical office buildings (MOBs) have CAM rates of $15-20+ per square foot, roughly double the norm for retail. Healthcare tenants also sign longer leases — averaging nearly nine years — which means a billing error that goes unchallenged in year one compounds through every renewal cycle. After testing reconciliation samples from published audit cases through CAMAudit, the categories that generate the largest overcharges in healthcare leases are consistently the same: HVAC upgrade misclassification, shared medical gas system billing, parking lot denominator errors, and management fees applied to a base the lease excludes.
40% of CAM reconciliations contain material errors (Tango Analytics / PredictAP, 2023)
Physicians and practice managers who sign medical office leases are not commercial real estate specialists. They are clinicians and administrators focused on delivering patient care, managing staff, and navigating a regulatory environment that has nothing to do with landlord-tenant accounting. The result is predictable: CAM charges go unaudited, billing errors compound over multi-year lease terms, and overcharges accumulate into six-figure losses before anyone notices.
This guide covers what healthcare tenants legitimately pay in a medical office building, what they should not pay, and the five billing categories where errors are most concentrated.
The MOB CAM Structure: Higher Rates, Longer Leases, Higher Stakes
Medical office buildings have cost profiles that push operating expenses well above general office benchmarks. The drivers are real: hospital-grade HVAC systems require more maintenance and more frequent filter changes, building security must handle controlled substances and vulnerable patient populations, electrical infrastructure supports imaging equipment with power demands that standard offices never see, and parking must accommodate the patient-volume throughput that a physician practice generates.
CAM rates of $15-20 per square foot are typical in MOBs. Combined with base rent, a 3,000 SF primary care practice may pay $85,000-$100,000 per year in total occupancy costs before utilities. NNN obligations — CAM, taxes, and insurance combined — often represent 25-40% of total lease cost.
Healthcare lease terms average 107 months (nearly nine years) according to JLL data. That term is a direct consequence of buildout economics: medical tenant improvements cost $80-200+ per square foot for plumbing rough-ins, lead-lined X-ray rooms, medical gas lines, and specialized HVAC. A practice that invested $500,000 in tenant improvements is not moving at lease expiration over a CAM dispute — and landlords know it.
The combination of high per-SF rates and long terms makes billing errors in medical leases uniquely damaging. A $2/SF allocation error on a 4,000 SF suite costs $8,000 per year. Unchallenged across a nine-year lease, that is $72,000 — before accounting for annual escalators that grow the underlying expense pool.
Shared Medical Gas Systems: Who Pays When the Bill Is Indivisible?
In multi-tenant medical office buildings, piped medical gas systems — oxygen, nitrogen, nitrous oxide, medical vacuum — are sometimes distributed building-wide, with individual tenant connections rather than separate systems per suite. Maintenance, certification, and periodic testing of these systems creates real costs.
The billing error scenario: the full annual maintenance cost for the building's medical gas distribution system is allocated to a single tenant — usually the one with the highest gas usage, usually a surgical or procedural specialty — rather than distributed proportionally among all tenants who connect to the system.
Under standard pro-rata share principles, shared infrastructure costs should be divided among all tenants who benefit from that infrastructure. If six suites connect to the central oxygen system, each should bear approximately one-sixth of the annual maintenance cost (subject to the allocation method specified in each lease). Billing the entire cost to one tenant is an allocation error.
The reverse error also occurs: some landlords pool the full medical gas system cost into the general CAM pool and allocate it by square footage to all tenants, including non-medical tenants who have no connection to the medical gas system. A billing services company on the second floor of a mixed-use MOB pays for oxygen system maintenance serving only the medical suites on floors three and four.
What to look for: Request a breakdown of any "mechanical systems maintenance" or "building infrastructure" line item in your reconciliation. Ask specifically whether medical gas system costs are included, and if so, how they are allocated and which tenants share that allocation.
HVAC: Hospital-Grade Infrastructure Meets Capital vs. Operating Disputes
Medical office buildings run more intensive HVAC than standard offices. Positive and negative pressure zones for infection control, higher air change rates in exam rooms, separate exhaust systems for procedure areas, and continuous 24/7 operation for equipment that requires stable temperatures all drive legitimate cost increases.
The CAM overcharge is not about whether HVAC costs are higher — they are. The overcharge is about how HVAC capital improvements are classified.
When a landlord replaces a rooftop unit serving a multi-tenant floor, that is a capital improvement. The replacement cost should be depreciated over the unit's useful life (15-20 years for commercial HVAC equipment) and the portion passed through to tenants should reflect annual amortization, not the full replacement cost in year one.
Landlords frequently expense HVAC replacements as operating costs. The full invoice hits the reconciliation in the year the work is done. If a rooftop unit replacement cost $80,000 and your pro-rata share is 12%, you pay $9,600 in that year instead of $576 (1/20 × $9,600 = amortized annual share). Over a 20-year amortization period you pay the same total — but the year-one lump sum overstates your legitimate operating expense by $9,024.
HVAC upgrades mandated for infection control compliance — HEPA filtration, negative pressure room infrastructure, UV germicidal systems — are capital improvements even when they are required by code. Capital expenditures do not become operating expenses because a regulation requires them.
Parking: The Patient-Volume Denominator Problem
Healthcare practices generate more parking demand per square foot than most tenants. A 4,000 SF family practice turning 25-30 patients per day creates more daily vehicle trips than a 4,000 SF accounting firm that sees 4-6 clients.
Standard CAM allocation uses square footage as the denominator. Your 4,000 SF suite pays the same parking cost share as any other 4,000 SF tenant, regardless of patient volume. For most tenants, this allocation is roughly proportional to actual use. For medical tenants with high patient throughput, it may actually understate your impact — which is why landlords rarely push back on the standard methodology for healthcare tenants.
The overcharge is not in that relationship. The overcharge is in how the denominator is calculated.
In a MOB with non-tenant space — lobbies, common corridors, examination corridors shared by multiple practices, building administration offices — the denominator question is whether that non-leased space is included or excluded from the total square footage used to calculate pro-rata share.
If the building has 100,000 SF of total space and 75,000 SF is leased to tenants, the pro-rata denominator should be 75,000 SF (tenant-leasable area), not 100,000 SF. Using the total building footprint makes every tenant's percentage smaller, which is favorable to the tenant — but some landlords exclude vacant space from the denominator, which inflates every occupied tenant's share.
What to look for: The reconciliation or lease should specify whether pro-rata share is calculated on total leasable area or occupied area. The difference matters: a 20% vacancy rate that inflates occupied tenants' shares by proportional amounts can shift a $6,000 annual share to $7,500.
Building Engineering Charges: The Hidden Overhead Line
Medical office buildings employ building engineers — licensed professionals who maintain HVAC controls, medical gas systems, electrical infrastructure, and fire/life safety systems. Their salaries, benefits, and overtime appear in the operating expense pool.
The overcharge pattern is not that building engineering costs are passed through — they are a legitimate operating expense. The issue is when the billing includes the cost of engineering time spent on tenant-specific work that should be charged directly to the requesting tenant rather than pooled.
If the building engineer spends 30% of their time on HVAC modifications for one medical tenant's procedure room expansion, that 30% should be billed directly to that tenant, not pooled into the building-wide engineering expense shared by all tenants. When the full engineering cost is pooled without adjustment for tenant-specific work, every tenant subsidizes every other tenant's buildout-related service calls.
The secondary issue: some landlords include corporate real estate management overhead — asset management fees, regional management costs, ownership-level administrative expenses — in the line items labeled as "building engineering" or "building management." Corporate overhead is a landlord cost that should not be passed through as a building operating expense. CAMAudit's landlord overhead pass-through detection rule (Rule 13) flags this pattern specifically.
Audit Rights and the Statute of Limitations
Medical leases typically include audit rights clauses granting tenants the right to inspect the landlord's books within a specified window — usually 12-24 months after receiving the annual reconciliation statement. Missing this window forfeits your right to dispute that year's charges regardless of how large the error.
Most healthcare tenants have never exercised their audit rights. That is not a strategic decision — it is the practical consequence of running a medical practice without dedicated lease administration staff.
The statute of limitations on CAM disputes varies by state, typically running 3-6 years for breach of contract claims. In states with a 6-year lookback, a practice that has never audited its reconciliations may have meaningful recovery potential across multiple prior years — but only if the landlord's records are available and the lease audit rights clause permits it.
The audit rights window and the statute of limitations interact. If your lease's audit rights clause limits disputes to within 18 months of receiving a reconciliation, that contractual provision may govern even if your state's statute allows a longer lookback. Review both your lease language and applicable state law before assuming you can recover errors from three years ago.
How CAMAudit Runs the Analysis
CAMAudit was built because the detection work — cross-referencing lease terms against reconciliation line items, applying the correct allocation formula, identifying capital-versus-operating misclassifications — is deterministic. Every rule either fires or it does not based on the numbers in front of it.
For medical office tenants, the detection rules most likely to generate findings are:
- Management Fee Overcharge (Rule 3): Verifies the fee base excludes capital items, taxes, and insurance if your lease requires that
- Pro-Rata Share Error (Rule 4): Checks the denominator against your lease's definition of total leasable area
- Gross-Up Violation (Rule 5): Identifies years where occupancy was below the threshold triggering gross-up adjustment
- Common Area Misclassification (Rule 12): Flags HVAC replacements and ADA upgrades expensed in a single year
- Landlord Overhead Pass-Through (Rule 13): Catches corporate management costs pooled into building operating expenses
Upload your lease and reconciliation statement. The scan runs automatically. If the tool flags overcharges, you get a line-by-line report and a dispute letter draft grounded in your lease language.
Frequently Asked Questions
What are typical CAM charges for a medical office tenant?
Medical office buildings typically have CAM charges of $15-20 per square foot, roughly double the $6-9.50 typical in grocery-anchored retail. Total NNN obligations — CAM, real estate taxes, and building insurance combined — represent 25-40% of total occupancy cost in most MOB leases. For a 3,000 SF primary care practice, that often means $30,000-$60,000 per year in CAM and pass-through charges on top of base rent.
Are HVAC upgrades in a medical office building a CAM charge?
HVAC replacements and upgrades are capital improvements, not operating expenses. If the landlord replaces a rooftop unit, the cost should be amortized over the equipment's useful life (typically 15-20 years) rather than expensed in a single reconciliation year. Even HVAC upgrades required for infection control compliance — HEPA filtration, negative pressure rooms — are capital items that must be amortized. Billing the full replacement cost in a single year overstates the tenant's legitimate operating expense obligation.
How is pro-rata share calculated in a medical office building?
Pro-rata share in a medical office building should be based on your rentable square footage divided by the total rentable square footage available in the building, as defined in your lease. The denominator is critical: buildings with non-tenant space (lobbies, shared corridors, administrative areas) must exclude that non-leasable space from the calculation. Buildings with vacancy may use total leasable area or occupied area depending on lease language — using occupied area inflates each tenant's percentage.
How far back can I dispute medical office CAM overcharges?
The lookback window depends on two factors: your lease's audit rights clause and your state's statute of limitations for contract claims. Lease audit rights typically allow disputes within 12-24 months of receiving the annual reconciliation. State statutes of limitations run 3-6 years in most states for breach of contract. The shorter of the two governs. If your lease's audit rights window has passed for a given year, you may be contractually barred from disputing that year even if the state statute would otherwise allow it.
This article is for informational purposes only and does not constitute legal or accounting advice. CAM rates, lease terms, and recovery amounts vary by market and building type. Consult a qualified commercial real estate attorney before submitting a CAM dispute claim.