information. For planning purposes, GSA converts agency
The ANSI/BOMA Z65.1 standard uses a two-step process
space requirements, expressed as usable area, to gross
to determine rentable area assessed a tenant. The first step
building area through the application of building
allocates common shared space on each floor to the
efficiency factors. For rental charges, GSA converts the
tenants of that floor. The second step allocates common
agency space requirements, expressed as usable area, to
spaces that support the entire building to all tenants
rentable area through the application of ratios that are
within the building. This explains the use of different
unique to each building. Agencies identify the amount of
ratios for each floor.
usable area they require within a building for the GSA and
Basic Rentable Area. Basic rentable area is the usable area
request this space on a Standard Form 81 (SF81).
occupied by a tenant plus their proportion of the floor
GSA provides a tenant improvement allowance for
common areas. It is calculated by:
finishes and features within its rental charge. The A/E
Usable Area X Floor R/U Ratio = Basic Rentable Area
must design within that allowance. The agency may fund
any costs over the tenant improvement allowance directly
Building Common Area. Building common area is usable
through a Reimbursable Work Authorization (RWA).
area allocated to provide services to building tenants but
The GSA uses formalized standards for establishing the
is not included inside a tenant space. Building common
area to be allocated to each tenant agency for the rent
areas include lobbies, atrium floor space, concierge areas,
charge. GSA has adopted the Standard Method for
security desks located in public areas, conference rooms,
Measuring Floor Area in Office Buildings ANSI/BOMA
lounges or vending areas, food service facilities, health or
Z65.1, current edition, issued by the Building Owners and
fitness centers, daycare facilities, locker or shower
Managers Association (BOMA). This standard is a
facilities, mail rooms, fire control rooms, fully enclosed
national standard approved by the American National
courtyards, and building core and service areas such as
Standards Institute. The full standard is available from
mechanical or equipment rooms. Excluded from building
BOMA International.
common areas are floor common areas, parking spaces
and loading dock areas outside the building line.
Certain systems related to security monitoring and
building control may be provided as part of the project by
Building R/U Ratio. Building R/U ratio is the factor used
GSA, or, if specially requested, by the tenant agencies, with
to distribute building common areas to all tenants on a
GSA providing the infrastructure support.
prorated basis. Note that this figure will be constant for
the entire building, but could change over time if portions
Space Measurement for Rental Purposes
of the ground floor are converted from common areas to
store areas.
A Summary. The following are terms and calculation
Building Rentable Area. Building rentable area is the sum
formulas extracted from the ANSI/BOMA Z65.1. They are
of the floor rentable areas. It is also equal to the gross
provided to assist the user in understanding GSA's space
measured area of the building minus vertical penetrations.
accounting. Individuals responsible for performing space
measures must utilize the entire Standard Method for
Measuring Floor Area published by BOMA.
55
ARCHITECTURAL
AND
INTERIOR
DESIGN
3.1
Basic Building Planning Principles
Revised March 2005 PBS-P100
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