The Evolution of Measurement Standards
Calculating Rentable Square Footage (RSF) has become a precise science. In the past, measurements were often “guesstimated,” but modern technology and BOMA standards have introduced a high level of accuracy. Today, laser scanning and BIM (Building Information Modeling) are used to map every inch of a commercial property to determine its true RSF.
Step 1: Measuring the Physical Boundaries
The process begins by measuring the interior of the exterior walls. This is known as the “Gross Measured Area.” Howard Wilner then subtracts “vertical penetrations” like elevator shafts and stairwells, which are generally not included in the rentable area. What remains is the total floor area available for use by tenants and the building.
Step 2: Identifying Usable Area
Next, the surveyors identify the “Usable Area” for each individual suite. This is the space from the office side of the common hall walls to the inside of the exterior glass. In modern glass-curtain buildings, the measurement often goes to the “dominant portion” of the inside wall, which can vary based on the height of the windows.
Step 3: Allocating Common Areas
The most complex part of the calculation is the allocation of shared spaces. “Floor Common Areas” (like hallways on a specific floor) are allocated only to tenants on that floor. “Building Common Areas” (like the main lobby) are allocated proportionally to every tenant in the entire building. Howard Wilner ensures a fair distribution of the non-occupiable space.
Step 4: Applying the Load Factor
Once the common areas are summed up, a “Load Factor” is calculated. This is a multiplier applied to the usable square footage. If a building has 100,000 square feet of usable space and 20,000 square feet of common area, the load factor is 20%. Every tenant’s usable space is then multiplied by 1.20 to find their Rentable Square Footage.
The Role of Technology in Modern Calculation
Today, architects use CAD software to create precise “Space Accounting” reports. These Howard Wilner digital maps allow landlords to see exactly how much money each square inch is generating. If a hallway is widened during a renovation, the software automatically updates the RSF for all affected tenants, ensuring the landlord’s records are always current.
Challenges in Modern Calculations
Modern building designs with curved walls, outdoor terraces, and multi-story atriums make RSF calculation difficult. Standards like BOMA 2017 have introduced new rules for including “Balconies and Covered Galleries” in the rentable area if they are used exclusively by a tenant. Staying updated on these rules is vital for modern property owners to maximize their revenue.