Standard for Measuring Floor Areas of an Office Building

Standard for Measuring Floor Areas of an Office Building

This page describes standard methods of measuring office building Usable Area and Rentable Area, this will give you the general idea on how an office building should be measured for rental purposes. This has been generally accepted by property managers, brokers, and landlords throughout the industry.

Usable Area
This method measures the actual occupiable area of a floor or an office suite. The amount of usable area on a multi-tenanted floor can vary of the life of a building due to hallways and common areas being expanded or contracted and due to floors being remodeled. Usable floor area is then converted to Rentable Area by the use of a “Core Factor”, “Conversion Factor” (Common area factor). The Usable Area of an office is typically computed by measuring the finished surface side of the office side of the corridor and other permanent walls, to the center of the partitions that separate the suite from adjoining Usable Areas, and to the inside finished wall of the primary portions of the permanent outer building walls. The columns and projections necessary to the facility are not deducted.

Rentable Floor Area

This method measures the total pro-rata portion of the entire floor plate, excluding elements of the building that penetrate the floor to areas below. The Rentable Area of the floor is fixed for the life of the building and should not be affected by any changes within the corridor or any other configurations. This method is typically used to measure the total income producing area of the building. It is also used when calculating the tenant’s pro rata share of the building for purposes of rental escalations.
It is recommended that on multi-tenanted floors the landlord compute both the Rentable and Usable Area for any specific office suite, this helps with allowing the tenants know what they are getting vs. what they will be responsible for financially.

Common Areas

The Common Areas typically include the areas of a building that are used to provide services to building tenants, but are not included in the suite of any specific tenant. It should include any associated common areas and is applied to the Floor Rental Area to calculate the Rentable Area.

Gross Rentable Area

When using this calculation this is typically based upon the Gross Rentable Area (GRA) which includes the Floor Rentable Area plus the pro rate share of the Common Areas.

Quick Formula:

Total Building Rentable Area + Pro Rata Common Area = Total Rentable Area

Core Factor – Load Factor

The Core Factor is the percentage of space on a floor that is not usable (I.E. Mechanical Rooms) plus the pro rata share of the Common Area, expressed as a percent of Usable Area. It is also known as a Common Area Factor or the Loss Factor. A Typical Range is from 10% to 18% but is dependent upon the facilities layout.

Quick Formula:

Gross Rentable Area / Usable Area = Core Factor

“Finished Surface” This shall be defined as 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” This shall be defined as the 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” This shall be defined as 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.
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

For More Information please contact:

Bryan E. Cole | Team Leader
NAI Keystone Commercial & Industrial, LLC
direct: 610-370-8502

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NAI Keystone is a full service commercial and industrial real estate firm located in Reading PA; representing buyer, tenant, and landlord representation throughout Pennsylvania.

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