Measuring Floor Area in Office Buildings

by Bill Toomey

The purpose of having a “Standard Method For Measuring Floor Area in Office Buildings” is to permit communication and computation on a clear and understandable basis. The Building Owners And Managers Association (BOMA) standard has been the generally accepted method for measuring office space for many years. It should be noted that this standard can and should be used in measuring office space in old as well as new buildings. It is applicable to any architectural design or type of construction.

Usable Area

This method measures the actual occupiable area of a floor or an office suite and is of prime interest to a tenant in evaluating the space offered by a landlord and in allocating the space required to house

personnel and furniture. The amount of Usable Area on a multi-tenant floor can vary over the life of a building as corridors expand and contract and as floors are remodeled. Usable Area can be converted to

Rentable Area by the use of a conversion factor. The Usable Area of an

office shall be computed by measuring to the finished surface side of

the office side of corridor and other permanent walls, to the center of

the partitions that separate the office from adjoining Usable Areas, and

to the inside finished surface of the dominant portions of the permanent

outer building walls. No deduction shall be made for columns and

projections necessary to the building.

The Usable Area of a floor shall be equal to the sum of all Usable Areas

on that floor.

Rentable Area

This method measures the tenant’s pro-rata portion of the entire office

floor, excluding elements of the building that penetrate through the

floor to areas below. The Rentable Area of a building is fixed for the

life of a building and is not affected by changes in corridor sizes and

configuration. This method is therefore recommended for measuring the

total income producing area of a building and for use in computing the

tenant’s pro-rata share of a building for purposes of rent escalation.

The Rentable Area of floor area shall be computed by measuring to the

inside finished surface of the dominant portions of the permanent outer

building walls, excluding any major vertical penetrations of the floor.

No deduction shall be made for columns and projections necessary to the

building. The Rentable Area of an office on the floor shall be computed

by multiplying the Usable Area of that office by the quotient of the

division of the Rentable Area of the floor by the Usable Area of the

floor resulting in the R/U Ratio.

Load Factor

The Load Factor is the percentage of space on a floor that is not

usable, expressed as a percent of Usable Area. It is also known as the

Common Area Factor or the Loss Factor.

Glossary —

Finished Surface:

A wall, ceiling, or floor surface, including glass, as prepared for

tenant use, excluding the thickness of any special surfacing materials

such as paneling, furring strips and carpet.

Dominant Portion:

That portion of the inside finished surface of the permanent outer

building wall which is 50% or more of the vertical floor to ceiling

dimension measured at the dominant portions. If there is no dominant

portion, or if the dominant portion is not vertical, the measurement for

area shall be to the inside finished surface of the permanent outer

building wall where it intersects the finished floor.

Major Vertical Penetrations:

Stairs, elevator shafts, flues, pipe shafts, vertical ducts, and the

like, and their enclosing walls, which serve more than one floor of the

building, but shall not include stairs, dumb-waiters, lifts, and the

like, exclusively serving a tenant occupying offices on more than one

floor.

Bill Toomey is a Commercial Real Estate contractor in San Diego.