Commercial Lease & CAM Glossary

Plain-English definitions of the 12 terms that show up most often in commercial leases and CAM reconciliation statements — the ones that determine whether your bill is right.

Informational only · Not legal advice

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CAMRSFUSFLoad FactorPro-Rata ShareOPEXTIQCTGLAGBAGross-UpBase Rent

CAM— Common Area Maintenance

The operating-cost passthrough every commercial tenant pays on top of base rent.

Common Area Maintenance (CAM) refers to the ongoing operating costs a landlord incurs to run a commercial property — and passes through to tenants on top of base rent. Typical CAM line items include landscaping, parking-lot maintenance, security, common-area lighting, HVAC for shared spaces, janitorial services, common-area utilities, property-management fees, marketing or promotional fund contributions, and (in some leases) property taxes and insurance. Tenants typically pay a pro-rata share of CAM based on the ratio of their leased space to the building's total leasable area. CAM is the largest single source of lease-overcharge disputes in commercial real estate, because most leases give the landlord broad discretion in what counts as 'CAM' and how costs get allocated. Annual reconciliation statements (where the landlord trues up estimated CAM payments against actual costs) are where tenants most commonly discover errors.
Related:OPEXPro-Rata ShareGross-UpBase Rent

RSF— Rentable Square Feet

The square footage a tenant pays rent on — includes common-area share.

Rentable Square Feet (RSF) is the leased footprint that shows up on a commercial lease and drives most rent and CAM calculations. RSF includes the tenant's actual occupied interior space (USF) plus a proportional share of the building's common areas — lobbies, corridors, shared restrooms, mechanical rooms, and similar non-leasable space. The relationship between RSF and USF is captured by the building's Load Factor (RSF ÷ USF), which is typically 12-18% for office buildings and lower for retail. Because RSF determines both the tenant's rent bill AND its pro-rata share of CAM, an inflated RSF — whether through aggressive load-factor application or through misrepresenting the building's total RSF — compounds across both rent and CAM billing. This makes RSF verification (against the lease, the building's BOMA measurement, and the county tax-record Gross Building Area) one of the highest-leverage checks a tenant can run.
Related:USFLoad FactorPro-Rata ShareGBA

USF— Usable Square Feet

The actual interior space a tenant occupies, excluding common areas.

Usable Square Feet (USF) measures only the interior space a tenant actually occupies and uses for its own business — excluding shared common areas like lobbies, corridors, and building-wide restrooms. USF is what you'd measure if you stood inside the demising walls of the tenant's suite and counted the floor area. USF is the denominator underneath the building's Load Factor calculation: RSF ÷ USF = Load Factor. Most commercial leases price rent and CAM in RSF (the larger number), so the gap between USF and RSF is where the load-factor multiplier hides. Tenants negotiating a new lease should always confirm both the USF and the RSF, ask for the load-factor calculation in writing, and verify the building's load factor matches the Building Owners and Managers Association (BOMA) standard for the asset class.
Related:RSFLoad FactorBOMA standards

Load Factor— RSF ÷ USF Multiplier

The ratio that determines how much common-area space gets added to a tenant's billable footprint.

The Load Factor (also called Add-On Factor, R/U Ratio, or Loss Factor) is the ratio of Rentable Square Feet to Usable Square Feet in a commercial building. It expresses how much of the building's common-area footprint gets allocated into each tenant's billable space. A load factor of 1.15 means a tenant occupying 10,000 USF is billed for 11,500 RSF — paying rent and CAM on 1,500 SF of common area allocation. BOMA standards typically result in load factors of 12-18% for office, lower for retail and industrial. A drifting load factor across years — e.g., the same tenant's RSF growing while USF stays constant — is a classic red flag for re-allocation games. ReCAM's free Pro-Rata Share Check compares your lease's stated load factor against BOMA benchmarks and flags outliers.
Related:RSFUSFBOMA standardsPro-Rata Share

Pro-Rata Share— Tenant's Allocation Percentage

The percentage of building-wide CAM costs a tenant is billed for.

Pro-Rata Share is the percentage of building-wide CAM costs allocated to a single tenant. The standard formula is tenant RSF ÷ building total RSF (or in some leases, building GLA — Gross Leasable Area). For example, a 10,000 RSF tenant in a 100,000 RSF building has a 10% pro-rata share — so if total annual CAM is $1,000,000, the tenant is billed $100,000. Pro-Rata Share is the single most common origin of CAM overcharges: a 1% inflated share (e.g., billing 10.5% when the lease specifies 10%) on a $1M CAM pool is $5,000/year. Compounded across a 10-year lease, that's $50,000 — more than enough to justify a 5-minute cross-check. The free ReCAM Pro-Rata Share Check verifies the math from three numbers off your lease and most recent reconciliation.
Related:RSFCAMGLALoad Factor

OPEX— Operating Expenses

The full set of building operating costs a landlord incurs.

Operating Expenses (OPEX) refers to the complete set of building costs a landlord incurs — most of which become CAM passthroughs to tenants. Different leases use OPEX and CAM interchangeably; others split them, with OPEX encompassing the broader category (including property taxes and insurance) and CAM referring specifically to physical-maintenance items. The distinction matters for lease interpretation: a 'CAM exclusion' for taxes only works if the lease defines CAM and OPEX as overlapping rather than equivalent. When reading an OPEX clause, look for: explicit inclusions, explicit exclusions, the definition of 'controllable' vs 'uncontrollable' OPEX, annual caps on increases, and the gross-up provision (if any) for variable expenses in partially-occupied buildings.
Related:CAMGross-UpPro-Rata Share

TI— Tenant Improvement Allowance

A landlord-funded budget for the tenant's build-out work.

Tenant Improvement Allowance (TI, also TIA or TI$/SF) is a landlord-funded budget for build-out work in the tenant's leased space — paint, flooring, partitions, fixtures, HVAC modifications, electrical upgrades. TI is typically quoted as $/RSF and varies materially by market, asset class, lease term, and tenant credit quality. For example, $40-80/RSF is common for Class A office in major metros; $10-30/RSF for second-generation retail; $80-150+ for medical or biotech lab buildouts. TI is one of the highest-impact pre-lease negotiation levers: a 5,000 RSF tenant getting an extra $20/RSF in TI saves $100,000 in out-of-pocket build-out costs. ReCAM's Pre-Lease Verification cross-checks your draft TI allowance against market-tier benchmarks by asset class and metro.
Related:RSFBase RentFree Rent

QCT— Qualified Commercial Tenant

Small commercial tenants protected under California SB 1103.

Under California SB 1103 (the Commercial Tenant Protection Act, effective January 1, 2025), a Qualified Commercial Tenant (QCT) is a small commercial tenant entitled to statutory CAM-billing protections including an 18-month look-back limit, itemized supporting documentation, a signed landlord attestation, prohibition on double-recovery from insurance, and treble damages for willful landlord violations. Three categories qualify: a microenterprise (≤5 employees including the owner, per California Government Code §12100.83); a restaurant with fewer than 10 employees; or a nonprofit with fewer than 20 employees. To activate QCT protections, the tenant must send the landlord a written self-attestation notice within the prior 12 months. Most California small commercial tenants qualify but have not yet sent the notice. ReCAM publishes a free QCT self-attestation template at recam.app/qct-template.
Related:CAMSB 1103

GLA— Gross Leasable Area

The total leasable square footage of a building.

Gross Leasable Area (GLA) is the total square footage of a building that is available for lease to tenants — the sum of all individual tenant suites' Rentable Square Feet plus any currently-vacant leasable space. GLA serves as the denominator in most pro-rata CAM allocations: a tenant with 10,000 RSF in a building with 100,000 GLA has a 10% pro-rata share. GLA is distinct from Gross Building Area (GBA, the county tax-assessor figure that includes mechanical penthouses, parking, and other non-leasable space). Discrepancies between the lease's stated GLA and the county tax-assessor's GBA — typically GLA > GBA-by-a-known-margin — are a strong indicator of CAM denominator inflation. ReCAM's county tax-record cross-check surfaces this gap automatically.
Related:RSFGBAPro-Rata ShareCAM

GBA— Gross Building Area

The total building square footage as recorded by the county tax assessor.

Gross Building Area (GBA) is the total square footage of a building as recorded by the county tax assessor and published on public assessment rolls. GBA is broader than GLA — it includes mechanical and equipment rooms, parking structures (if conditioned), and other non-leasable areas. Critically, GBA is a third-party verifiable number: county assessor records are public information and cannot be altered by the landlord unilaterally. This makes GBA the denominator-of-truth in ReCAM's county tax-record cross-check. When a lease's stated 'Building Total RSF' exceeds the county-recorded GBA, the landlord is effectively claiming the building has more leasable space than the tax record shows — which inflates every tenant's pro-rata share denominator and reduces their share. When the lease's stated total is LESS than GBA, the denominator is too small and CAM is overcharged. Either direction warrants investigation.
Related:GLARSFPro-Rata ShareCAM

Gross-Up— Gross-Up Provision

A lease clause that adjusts variable expenses to a stabilized occupancy level.

A Gross-Up Provision is a lease clause that permits the landlord to 'gross up' variable operating expenses (utilities, janitorial, certain repairs) to what they would have been if the building were 95-100% occupied. The intent is fair: if a tenant in a half-empty building would pay the same dollar amount for janitorial as a tenant in a fully occupied building, the gross-up keeps the per-tenant burden consistent with the building's design occupancy. The mis-application: many landlords apply gross-ups to FIXED expenses (real estate taxes, insurance premiums, base property management fees) where the calculation has no math basis — fixed expenses don't vary with occupancy, so 'grossing them up' just inflates the recovered amount. ReCAM flags gross-up applications outside the variable-expense category as a high-priority review item.
Related:OPEXCAMPro-Rata Share

Base Rent— Base Rent

The fixed rent component of a commercial lease — separate from CAM, taxes, and insurance.

Base Rent is the fixed rental amount a commercial tenant pays for the right to occupy the leased premises, expressed as a $/RSF/year rate. Base Rent is the most visible cost in a lease, but it is rarely the total occupancy cost. In a triple-net (NNN) lease, the tenant also pays a pro-rata share of property taxes, insurance, and CAM. In a modified-gross lease, some of those are rolled into Base Rent. In a full-service or gross lease, most operating costs are landlord-paid (with caps that trigger passthroughs). True annual occupancy cost = Base Rent + CAM + (in NNN) Taxes + Insurance + any other passthroughs. Tenants comparing two lease offers should always normalize to total occupancy cost, not just base rent — a $35/SF NNN lease can be more expensive than a $48/SF gross lease in the same building.
Related:CAMOPEXTI AllowanceRSF

Understanding the terms is step one

Step two: check whether your actual CAM bill is right. ReCAM's free Cross-Check takes three numbers off your lease and most recent reconciliation. 30 seconds, no sign-up, no upload.