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 on a floor can be converted to Rentable Area by the use of a conversion factor.

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 floor is fixed for the life of a building and is not affected by changes in corridor sizes or 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. Lenders, architects and appraisers will use Rentable Area in analyzing the economic potential of a building.

It is recommended that on multi-tenant floors the landlord compute both the Rentable and Usable Area for any specific office suite.

Definitions
"Finished Surface" shall mean 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" shall mean 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 portion. 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 Portion" shall mean 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.

"Office" shall mean the premises leased to a tenant for which a measurement is to be computed.

Conversion Formula
Rentable Area = Rentable/Usable Ratio
Usable Area = 1"R/U Ratio"
Usable Areas R/U Ratio = Rentable Area
Rentable Area = Usable Area
R/U Ratio

The Rentable Area of a floor shall be computed by measuring to the inside finished surface of the dominant portion 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" described herein.

The Usable Area of a floor shall be computed by measuring to the finished surface of the office side or corridor and other permanent walls, to the center of partitions that separate the office from adjoining Usable Areas, and to the inside finished surface of the dominant portion of the permanent outer building walls.

No deductions 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.