The Building Owners and Managers Association (BOMA) recently released a new standard for measuring an office building's rentable area. The new standard (ANSI/BOMA Z65.1-2010) includes a number of changes from the prior (1996) standard and additions which reflect the recognition that there are a wide range of space configurations and architectural conditions in contemporary office developments. It also provides an alternative standard for determining the rentable area of an office building. The new standard is available for purchase only in electronic form at

The new standard's most important change is the addition of a standard for calculating a single load factor for an entire building as an alternative to the 1996 standard which only provided for the calculation of load factors on a floor-by-floor basis. Building owners may now choose between a slightly modified version of the 1996 floor-by-floor method (now known as Method A - Legacy Method), which establishes a load factor for each floor of the building which is then applied to the occupant area on that floor to determine rentable area, and the new, building-wide, single-load factor method (known as Method B - Single Load Factor), which is applied consistently throughout the building, regardless of whether a particular floor is subdivided or occupied by a full-floor tenant.

Lease forms should be reviewed to determine that they correctly reference the BOMA standard being used to measure rentable area in an office building. For buildings to which the 2010 standards are applied, it is no longer sufficient to reference the latest version of the BOMA/ANSI standard, it is also necessary to specify which of Method A or Method B applies.

Use of the new Method B avoids the need to re-calculate the rentable area for each floor and for the building as a whole as the use of the floor changes over time. This is accomplished by designating a new class of space, "base building circulation," which is assumed to exist on all floors of the building, even those that are fully occupied by one tenant. Base building circulation is defined as the minimum path on a multi-occupant floor which is assumed to exist in order to provide access to and egress from the areas one would expect to have access to, such as occupant areas, stairs, elevators, rest rooms, janitors' closets, required areas of refuge and building service and amenity areas such as lobbies and building conference rooms. Base building circulation may not represent the actual layout of the floor; in some cases it will be a hypothetical measurement. The building owner has the discretion to determine the extent of the base building circulation but it should reflect applicable legal requirements and also take into consideration the architectural features of the particular building, so that the width of corridors may be more than that required by codes if such is, or would be, the building standard. If and to the extent that a corridor on a multi-occupant floor is longer or wider than base building circulation, then the additional area is included in the occupant area of the occupant(s) served. If an occupant actually occupies some or even all of the base building circulation, as would be the case with a full floor tenant, the occupant area for such occupant ignores the base building circulation area occupied, since the base building circulation is accounted for in the load used to calculate rentable area. Once determined, base building circulation remains fixed over time. Note Method A and Method B are intended to be alternatives, once one is used, the other cannot be, and once applied to a building, the method used should not be changed.

Due to the dearth of new office building development, there have been few opportunities for application of the new method and it is not clear whether it will receive market acceptance.

Other significant changes in the 2010 standard are the use of different terms for certain concepts from those in the 1996 standard and revision of the definition of other terms that are continued in use. For example the term "common area" is no longer used and is replaced by the concepts of "building amenity area," which is the portion of the building that provides an amenity, such as a building conference room or fitness center, intended for use by all building occupants, and "building service area," such as lobbies, enclosed loading docks and mechanical rooms. Building service area is excluded from the calculation of one of the ratios (R/U) used to establish the load. The concept of "gross building area" is replaced with that of "interior gross area" with a somewhat different definition. BOMA recently published another standard, "Gross Areas of a Building: Standard Methods of Measurement (ANSI/BOMA Z65.3 - 2009," for determining gross building area for use in other contexts, such as construction cost benchmarking.

The term "occupant area" replaces "office area" and "store area." As with the prior definition of office area, occupant area is the space where an occupant normally houses its personnel, FF&E and goods. There is now a separate category for "occupant storage area," the area that is not fully finished and is useable for storage only and not usually located on the same floor as occupant areas. Occupant storage areas are also deducted from the interior gross area (formerly, the "gross measured area"), so that the "load" of non-rentable space is not allocated to such areas and so that they therefore do not dilute the load as applied to the other occupant areas.

Among other changes in the new standard are the recognition that unenclosed circulation areas in buildings in warm climates that function in the same manner as enclosed corridors in buildings in temperate climates should be included in building service area, whereas the prior standard excluded them as exterior areas. The discharge corridor from the vertical core to the building perimeter is now clearly a building service area rather than part of the major vertical penetration. Major vertical circulation, which is taken into account in determining the load, now excludes voids, which are now also excluded from interior gross area.