Office Area. Office area is the usable area within the
lobby and other building common areas to be prorated to
all tenant spaces in the building measured in m2. Most
tenant space including internal partitions and half of the
common space on main ground levels normally falls
demising wall separating the space from other tenants. It
within building common areas rather than floor common
is measured to the tenant side finished face of all building
areas, so rentable figures for store areas will not normally
common areas.
be significantly impacted by floor common areas.
R/U Ratio. R/U ratio is the factor used to convert usable
Usable Area. Usable area is the actual area the agency
area to rentable area. It is the product of the Floor R/U
occupies in a tenant suite measured in square meters. It is
ratio and the Building R/U ratio. It is derived by the
the office area, store area or building common area. It is
following formula:
calculated by measuring from the dominant portion of
Floor R/U Ratio X Building R/U Ratio = R/U Ratio
the exterior wall to the outside face of major vertical
It accounts for the allocation of floor common areas and
penetrations. It includes all structural elements, openings
building common areas. Note that it will be different for
for vertical cables, and vertical penetrations built for the
each floor.
private use of the tenant.
Rentable Area. This is the figure that will be assessed each
Space Measurement for Planning Purposes
tenant for their space charges. Rentable area includes the
usable area, the prorated share of the floor common area,
Tenant agencies communicate their space requirements
and the prorated share of the building common areas. It is
to GSA on the Standard Form 81 (SF81). This form
calculated by the following formula:
identifies the total area of each space classification
required by the agency within an individual building.
Usable Area X R/U Ratio = Rentable Area
Tabulation of space requirements for planning purposes
It may also be calculated by the following two-step
involves four steps:
formula:
Step 1 Tenant agencies must identify the individual
Step 1)
room areas they require within a facility or tenant suite.
Usable Area X Floor R/U Ratio = Basic Rentable Area
Step 2 To calculate the total usable area within an
then Step 2)
agency's suite, additional area must be added to the
individual room areas to account for internal corridors,
Basic Rentable Area X Building R/U Ratio = Rentable Area
partitions, structural members, and planning
inefficiencies. Traditionally, GSA has instructed the
Store Area. Store area is the usable area of a structure that
tenants to include 50 percent of an aisle space directly
is directly served by permanent public lobbies or has
direct access from outside. BOMA describes these spaces
as suitable for retail occupancies. The term store area was
developed for main ground levels to allow the public
57
ARCHITECTURAL
AND
INTERIOR
DESIGN
3.1
Basic Building Planning Principles
Revised March 2005 PBS-P100
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