Commercial lease types are defined by one question: who pays the operating expenses. In a triple net lease, the tenant pays base rent plus its share of taxes, insurance, and maintenance. In a gross lease, the landlord pays the operating expenses out of a single rent figure. A modified gross lease sits between the two, splitting specific expenses between the parties by negotiation. The label matters because the same base rent can mean very different total occupancy costs depending on which structure governs.
Why Lease Structure Determines Real Cost
Base rent is only part of what a tenant pays. Operating expenses, taxes, insurance, and maintenance can add several dollars per square foot on top of the quoted rate. The lease structure decides whether those costs are inside the rent, added on top, or shared. Two spaces quoted at the same rent can carry very different real costs once the structure is known.
This is why comparing offers by base rent alone is misleading, and why the structure is one of the first fields captured in a lease abstract. A quote of thirty dollars per square foot net and thirty-eight dollars gross may describe nearly identical economics once the pass-throughs under the net deal are added in. The structure translates the quoted number into a real number.
The Triple Net Lease
A triple net lease, often written NNN, requires the tenant to pay base rent plus its pro rata share of the three nets: property taxes, building insurance, and common area maintenance. The landlord receives a rent stream largely insulated from expense volatility, and the tenant bears the risk and benefit of changing operating costs.
Triple net structures are standard in retail, single-tenant, and industrial properties. Because the tenant pays actual costs, the base rent is typically lower than a gross quote for comparable space, but the total is variable. When taxes rise or a major repair falls into a passable category, the tenant absorbs it. The tenant's key protections are clear expense exclusions, caps on controllable expenses, and the right to audit the common area maintenance statement each year.
Reading a Triple Net Lease
When abstracting a net lease, capture the tenant's pro rata share, the expense categories passed through, any caps, and the exclusions. Confirm how the pro rata share denominator is defined, because a small denominator inflates the tenant's share. Also note whether the lease is truly net or an absolute net, where the tenant carries even structural and roof obligations that a standard net lease leaves with the landlord.
The Gross Lease
A gross lease, also called a full-service lease, bundles operating expenses into a single rent figure. The landlord pays taxes, insurance, maintenance, and often utilities and janitorial from the rent it collects. The tenant's cost is predictable, which is the structure's main appeal.
Pure gross leases are common in multi-tenant office buildings, where the landlord controls building services and prefers to manage expenses centrally. The predictability comes at a price: gross rents are quoted higher because the landlord prices in expected expenses and a cushion for increases. Most modern gross leases are not fully fixed, though. They use a base year to shift future expense growth back to the tenant.
The Base Year Mechanism
Under a base-year gross lease, the landlord absorbs operating expenses up to the level of a reference year, and the tenant pays its share of increases above that base in later years. The base year functions as an expense stop. It is the most consequential figure in the lease, because a low base year means larger pass-throughs every year after. The related gross-up provision should apply consistently to the base year and later years, or the tenant quietly overpays.
The Modified Gross Lease
A modified gross lease is a negotiated middle ground. The tenant pays base rent plus some, but not all, operating expenses, with the split defined in the lease. A common arrangement has the tenant pay its own utilities and janitorial while the landlord covers taxes, insurance, and structure. Another has the tenant pay increases in specified categories over a base year while the landlord retains others.
Because "modified gross" is not standardized, the label tells you little on its own. Two leases both called modified gross can allocate expenses very differently. The only reliable way to understand a modified gross lease is to read the expense provisions line by line and record exactly which costs each party bears. This is where careful abstraction earns its keep.
Side-by-Side Comparison
The three structures form a spectrum of who bears expense risk, from the tenant under net to the landlord under gross, with modified gross negotiated in between.
Feature | Triple net | Gross | Modified gross |
Base rent level | Lower | Higher | Middle |
Taxes | Tenant share | Landlord | Negotiated |
Insurance | Tenant share | Landlord | Negotiated |
Maintenance | Tenant share | Landlord | Split |
Utilities | Tenant | Often landlord | Often tenant |
Cost predictability | Lower for tenant | Higher for tenant | Middle |
Common property type | Retail, industrial, single-tenant | Multi-tenant office | Office, flex, mixed |
Expense risk sits with | Tenant | Landlord | Shared |
Comparing Offers Across Structures
Because the structures are not directly comparable at the quoted rent, an apples-to-apples comparison converts each to a fully loaded cost per square foot. Follow a consistent sequence.
Start with the quoted base rent for each option.
Add the estimated pass-throughs. For a net lease, add taxes, insurance, and CAM. For a base-year gross lease, add projected increases over the base year.
Account for rent escalation over the term, since fixed and CPI-indexed increases compound differently.
Factor concessions such as free rent and the tenant improvement allowance.
Reduce everything to net effective rent so the structures compare on one number.
Cost element | Triple net example | Gross example |
Quoted base rent | Lower | Higher |
Explicit pass-throughs | Added on top | Bundled in |
Visibility of expenses | High, itemized | Low, embedded |
Budgeting certainty | Requires estimates | More fixed, base year aside |
Comparison method | Add nets to base | Add base-year increases |
The point is not that one structure is cheaper. It is that the structure changes where the cost lives, and only a fully loaded comparison reveals the real difference. For the underlying calculation, see net effective rent and how it normalizes concessions and escalations.
How Structure Interacts With Other Lease Terms
Lease type does not stand alone. It shapes how other provisions should be read. Under a net lease, the rent escalation clause applies to a lower base, so a fixed percentage increase compounds off a smaller number, while the separate pass-throughs float on their own. Under a base-year gross lease, escalations apply to a higher base rent, but the pass-through exposure is limited to increases above the base year.
Retail leases add percentage rent, where the tenant pays additional rent above a sales breakpoint, almost always on a net structure. Across all types, the rent roll should record the structure for each tenant, because a portfolio that mixes net and gross leases cannot be analyzed on base rent alone. Capturing the structure accurately during abstraction is what makes portfolio-level comparison possible.
Frequently Asked Questions
What is the main difference between a triple net and a gross lease? In a triple net lease the tenant pays base rent plus its share of taxes, insurance, and maintenance, so cost varies with actual expenses. In a gross lease the landlord pays those costs out of a single, higher, more predictable rent.
Is a triple net lease cheaper than a gross lease? Not necessarily. The base rent is lower, but the tenant adds pass-throughs on top. Once taxes, insurance, and maintenance are included, the total cost can equal or exceed a comparable gross quote. Only a fully loaded comparison shows the difference.
What does modified gross actually mean? It means an expense split negotiated between full net and full gross, with no fixed standard. The lease itself defines which costs each party pays, so two modified gross leases can allocate expenses very differently.
Why does the base year matter so much in a gross lease? The base year sets the expense level the landlord absorbs. The tenant pays its share of increases above it, so a low base year raises every future pass-through. It is often the most financially significant figure in a gross lease.
Which lease type is most common for office space? Multi-tenant office typically uses gross or base-year gross leases, because the landlord controls building services and tenants value predictable cost. Retail and industrial lean toward triple net structures.
Conclusion
Triple net, gross, and modified gross leases describe one thing: how operating expenses are allocated between landlord and tenant. Net shifts expense risk to the tenant with a lower base rent, gross keeps it with the landlord inside a higher rent, and modified gross splits it by negotiation. Because the same quoted rent can mean very different real costs, the structure must be identified precisely during abstraction and every offer reduced to a fully loaded, net effective figure before the numbers can be compared.