USF vs RSF: What Tenants Really Pay For in Commercial Leases

Understanding the distinction between usable square footage (USF) and rentable square footage (RSF) isn’t just a matter of definitions—it’s where many tenants either gain leverage or lose tens of thousands in avoidable expenses over the course of a lease. In commercial leasing, especially in suburban office parks, medical centers, and flex buildings, the RSF metric directly impacts base rent, escalations, and total occupancy cost. Yet, brokers and landlords often skim past the fine print, hoping tenants don’t challenge the numbers behind the numbers.

This article breaks down what experienced tenants should actually be looking for, how to spot manipulation in load factors, and the negotiating opportunities often hidden in plain sight.

The Real Cost of the Load Factor

Most tenants know the formula: RSF = USF + pro-rata share of common areas. But what’s missed is how variable that pro-rata share can be. The industry average for load factor typically floats between 15% and 20%, but it’s not uncommon to see figures over 25% in buildings with oversized lobbies, underutilized corridors, or inefficiently designed multi-tenant layouts.

When you sign a lease based on RSF, you're agreeing to pay rent on space you can't exclusively use. That’s fine in principle—everyone expects to contribute toward shared amenities—but inflated load factors mean you're subsidizing space that may serve other tenants more than you. For example, buildings with conference rooms reserved by select anchor tenants or executive-only lounges still pass the cost onto all occupants.

A 3% difference in load factor on a 10,000 RSF lease can translate into over $75,000 in extra rent over a 5-year term, assuming $25 PSF base rent with 3% annual increases. That’s not marginal. That’s capital loss that could have gone toward tenant improvements, headcount expansion, or tech infrastructure.

Measurement Standards Are Not Standard

One of the reasons this issue persists is that BOMA standards—specifically BOMA Office 2017 and earlier iterations—give landlords considerable latitude. The term “gross measured area” allows for flexibility that often benefits the landlord far more than the tenant.

Some landlords measure to the exterior face of the building rather than the centerline of demising walls. Others include basement storage areas or upper-floor mechanical rooms in the building’s total rentable space calculations, despite those areas offering little or no benefit to tenants. And because landlords often control the measurement reports and rarely make the source documentation available, most tenants never audit what they're paying for.

Sophisticated tenants insist on measurement transparency and sometimes commission their own space verification through certified space planners. That cost pays for itself if it uncovers RSF inflation or improperly allocated common areas.

Base Rent Isn't the Whole Story

Even if the PSF rate looks competitive, tenants must model the real cost per usable foot. A $28 RSF rate in a building with a 20% load factor equates to $33.60 per usable square foot. Compare that to a $30 RSF rate with a 12% load—$33.75 per USF—and the delta disappears. But the landlord pushing the lower RSF rate may seem more competitive on the surface.

This is exactly why savvy occupiers don’t compare RSF rates in isolation. They model annual occupancy cost per USF and factor in everything from load factors to escalation structures, parking ratios, and even utility passthroughs. If you don’t normalize for USF, you’re comparing apples to inflated oranges.

Negotiating Power Hides in the Details

Commercial leases are often touted as non-negotiable when it comes to space measurement. That’s false. While landlords rarely budge on their published RSF numbers, they can and do offer financial concessions that effectively lower your cost per usable foot. These concessions can take the form of higher tenant improvement allowances, additional rent abatement, or fixed operating expense caps that protect against bloated annual reconciliations.

Another negotiation lever: capped load factors. A few institutional landlords allow anchor or long-term tenants to lock in a maximum load factor in the lease. It doesn’t change the RSF figure, but it creates a contractual backstop that limits future increases if common areas are expanded or remodeled later.

Tenants taking 15,000+ RSF or representing a national brand often get these concessions quietly. But they’re not exclusive to Fortune 500 names. Regional firms and even boutique operators have pulled similar terms by positioning themselves as long-term, low-risk tenants and aligning with lease-up goals during a landlord’s marketing window.

Suburban Market Quirks Make This Even More Relevant

In suburban real estate, buildings often have more generous spacing and larger common areas than downtown towers. Surface parking lots, wide lobbies, shared kitchens, and lounge spaces aren’t always proportionally useful to smaller tenants, but the RSF charges still apply.

Single-story flex properties, in particular, often advertise low RSF rates to attract industrial or tech hybrid users, but their load factors vary wildly depending on the layout. In some flex buildings, tenants may be paying RSF on hallways and utility areas they don’t even access.

Medical tenants face their own challenges. MOBs (medical office buildings) typically have more non-rentable space due to specialized HVAC, lead-lined imaging suites, or compliance-driven infrastructure. Yet the RSF calculations may still mirror a standard office building’s load factor, effectively increasing rent without justification.

This is where brokers familiar with suburban footprints can add value. It’s not about quoting a lower rate. It’s about understanding which buildings offer the most usable space for the rent being charged and negotiating leases that reflect the tenant’s actual occupancy footprint.

Lease Audits and Space Recalibrations Aren’t Just for Expansions

Tenants often assume they’re stuck with whatever RSF number they signed for until they expand or renew. That’s a costly assumption. Mid-lease audits, especially for tenants in multi-phase developments or older suburban campuses, can reveal mismatches between recorded RSF and actual occupied space.

Some leases even include re-measurement clauses tied to building renovations or expansions. If a landlord adds shared conference facilities or reconfigures common corridors, your share of the load may increase—even if your physical suite remains unchanged. Without protections in the lease, you could end up paying more for less.

In markets where large tenants have exited or downsized, landlords sometimes increase the load on remaining occupants to maintain their rent roll. Catching that shift early allows for proactive renegotiation or early termination strategies.

Final Thought: Treat RSF as a Negotiation Variable, Not a Given

No tenant should view RSF as a fixed, immutable metric. It’s a financial model constructed by landlords to allocate building costs—and like any model, it’s subject to challenge, adjustment, and leverage. Experienced occupiers don’t just ask “What’s the RSF?”—they ask, “What does that include, who measured it, and when?”

Controlling occupancy cost starts with understanding what you’re actually paying for. When usable square footage gets buried under vague RSF calculations, that’s where overpayment hides.

Push for transparency, compare USF-adjusted costs across buildings, and use measurement as a negotiation tool. Whether you're a multi-site operator looking at suburban campuses or a local firm evaluating space in a Class B office park, clarity on USF vs RSF can lead to smarter leasing decisions—and significant savings.