Asbuilt Industry News

How big is a square foot? It all depends on your audience

Friday, May 28, 2004

Measuring square footage is not always an exact science. There are a number of rentable square footage measurement standards commonly used in the commercial real estate market. Each method, if used on the same space, would result in a different rentable square foot number.

The key difference: Some methods benefit the tenant, and some benefit the landlord.

The ANSI/BOMA standard, otherwise known as the BOMA standard, is the prevalent standard for measuring leased office space in the United States. (ANSI is short for the American National Standards Institute and BOMA for the Building Owners and Managers Association.)

BOMA starts with the gross measured area, which is the dominant inside line of the building, which may be the glass line or an inside solid wall of the building. This number is sometimes used as the rentable area of the building for a full building user. For multi-tenant buildings, you start with the inside gross measured area of the building, which is taken from the inside dominant perimeter of the building, usually the inside of the glass wall or the inside of the solid perimeter wall of the building.

To arrive at the floor rentable figure, the major, vertical penetrations -- such as fire stairs, elevators and pipe shafts -- are then subtracted from the gross measured area. The square footage of the building common areas support areas that serve the whole building -- such as the building lobby, elevator lobby, fire pump room, electrical room, the loading dock, fire command room and rear exit corridors -- are prorated throughout the building to the tenants.

Using the BOMA method of measurement, full-floor users would take the total rentable area for the floor, which in their case is the same as the total usable area for the floor, and add their prorated building common area to arrive at their total rentable figure.

Multi-tenant-floor tenants would take their total usable square feet and add in their prorated floor common area, or floor rentable-usable (R/U) ratio, which consists of the rentable areas of their floor's building core, elevator lobby and shared common corridor, to arrive at their floor rentable figure. They would then add their prorated building common area, or building R/U ratio, to arrive at a total rentable square footage number.

BOMA certainly isn't the only game in town. Over the past four years, the General Services Administration has adopted what it deems a more "market-friendly" definition of square feet and has adopted a modified BOMA method of measurement. The term "modified" is ambiguous and should always be qualified, since that can make a huge difference in what is considered rentable.

The International Facilities Management Association has developed its own definition of rentable square feet. This method is widely used by facility managers for use in square footage charge-backs to their departments and strategic facility planning as well as to track assignable square footage (the space actually occupied by offices and workstations).

Having two architects measure the same building and coming up with the same rentable square footage number is virtually impossible. There are, however, a number of quality-control measures that should be implemented to ensure that the resulting number is as accurate as possible:

Understand which method of measurement you are using and the definition of what is included, what is excluded and where the measurements are taken from.
Don't scale off old drawings. Get a set of the base building, architectural drawings and also physically measure the space in the field using a laser tape measure for the long dimensions. Sagging tape measures do not result in accurate measurements.
Using computer-aided drafting, input the outside boundaries of the building, based on the field measurements. CAD-input the interior exclusions, such as pipe chases, and major vertical penetrations, such as elevators and stairs, and their surrounding walls.
For multi-tenant floors, determine the shared, floor common area to be measured.
Determine the building common areas, and prorate that number throughout each floor of the building and to each tenant in the building, according to their percentage of the total usable square feet in the building.