The degree of conformity of a measured or calculated quantity to its actual, absolute value.
In building area measurement it is the degree of conformity of a floor area measurement to
the actual floor area. See also Precision, Tolerance and Variance.
A measure of area most often applied to land equal to 43,560 square feet or 4,046.86 square
meters. A square mile contains 640 acres.
Acre Add-on Factor
Another term for the BOMA R/U Ratio, not defined in the BOMA Standard.
A change to construction documents made after they are issued for bidding but prior to award
of the construction contract, often in response to questions by bidders. Changes made by
addenda may be reflected in record drawings.
The American Institute of Architects, with URL
Methods of Calculating Areas and Volumes of Buildings, AIA Document #D101-1995
(current version) published by the AIA.
The American Industrial Real Estate Association, with URL
The AIR Industrial Building Standards, a set of five standards for floor area measurements
of industrial buildings, published in March, 1993 by SIOR and used as a basis for the BOMA
Industrial Measurement Standard which supplanted it in October of 2004.
The American National Standards Institute, the major standards organization in the United
States and publisher of the BOMA Standards, the NAHB Residential Standard, and ISO 9836
International Standard, with URL www.ansi.org.
A level of accuracy that is inexact or incorrect. Unless a Tolerance is explicitly indicated,
"approximate" can mean anything from "as accurate as possible with professional application
of normal measuring technology" to "wild-ass-guess from pacing the area". FYI: In parts of
Canada this level of accuracy is statutorily defined as plus-or-minus 25%.
A term used and defined in the AIA Standard primarily for the purposes of construction cost
estimating. Many of the standard estimating references employ this measure of floor area.
As used in building area measurement, the quantitative measure of a horizontal two-dimensional
plane expressed in Square Feet or Square Meters, bounded by lines relating to building walls or
classes of space as determined by measurement standards or practices.
See Building Area.
Graphic depictions of a building on paper or CAD that, in theory, reflect precisely the actual
construction of every part and system of a building. A perfect set of as-built drawings is generally
infeasible due to the cost of documentation. See Record Drawings.
A term used in the IFMA Standard to measure space assigned to tenant personnel, furniture,
equipment support areas and common support areas, not including secondary circulation within
tenant's Usable Area.
The American Society for Testing and Materials, a U.S. standards organization that publishes
the IFMA Standard, with URL www.astm.org.
See PBS Business Assignment Guide below.
Basic Rentable Area
A BOMA term signifying the result of multiplying the Floor Usable Area of a floor, suite or Building
Common Area, by the Floor R/U Ratio. An intermediary figure not directly used in leasing.
(1.) A systematic measurement error representing the difference
between the average or expected value of a measurement sample and the true value of the
measurement. Ways to introduce bias into field measurements include not measuring horizontally
and allowing measuring tapes to sag excessively.
(2.) A departure from objectivity. Those who are focused on the
interests of a landlord or tenant can be biased in their application of a measurement standard,
which can lead to a measurement dispute.
A term used by the US General Services Administration Public Building Service and defined as
the area bounded by the inside face of surrounding walls, minus the area bounded by the outside
faces of any contained full height columns. See the
GSA BIM Guide.
Building Information Modeling, an enhancement to CAD that allows the construction of a virtual
building in a computer. When complete, the computer is aware of the characteristics of the
virtual building including its Usable and Rentable Areas.
The Building Owners and Managers Association, publishers of and secretariat for the BOMA
Office and Industrial Standards. Their URL is www.boma.org.
Either the Standard Method for Measuring Floor Area in Office Buildings or the
Standard Methods for Measuring Floor Area in Industrial Buildings, depending on the
occupancy of a property. It is clearer to refer to the BOMA Office Standard or the BOMA Industrial
Standard, and clearer yet to specify the publication year. The Office Standard in particular has
been modified and re-published many times and is likely that the Industrial Standard will be also.
Section 502.1 of the International Building Code defines this term as the area included within
surrounding exterior walls (or exterior and fire walls) exclusive of vent shafts and courts. Areas
of the building not provided with surrounding walls shall be included in the building area if such
areas are included within the horizontal projection of the roof or floor above.
A local statute that governs the design and construction of buildings. In most jurisdictions,
building codes require a Certificate of Occupancy, or CO, before a building can be legally occupied.
Although one would think that all rented space meets the requirements of building codes for
occupancy, there are no such requirements in any current major measurement standard.
Building Common Area
Fully enclosed space within a building that benefits all occupants of that building but which does
not accommodate a tenant's personnel, furniture, fixtures or equipment. The usual example is the
first floor building entry lobby. It may include additionally spaces like the building engineer's office,
building HVAC areas and loading docks. See individual measurement standards for definitions.
Building Core and Service Area
Term used in the IFMA Standard to describe Floor Common Area excluding corridors on
multi-tenant floors. See also Core Space.
(1.) Actual: A horizontal line forming a perimeter that
encompasses all the constructed elements of a given floor of a building and other areas covered
by a roof. Non-structural protrusions, including eaves, cornices, canopies, awnings, sills, ledges,
casing, wainscoting, gutters, downspouts, signs, shutters, attached electrical or mechanical
systems or decorative projections, are ignored.
(2.) Statutory: A line or plane established by zoning or
building codes as a limit to buildable area or volume of a building.
Computer Aided Drafting - Software enabling the execution of drawings on a computer to a
much higher degree of accuracy than it is possible to build in the field while still fudging
dimensions critical to a metrologist, like the location of the inside face of exterior glass. In real
estate, it is also an acronym that stands for Cash Available for Distribution.
Computer Aided Facility Management - Software that can contain some features of CAD
that automate aspects of facility management. Most CAFM packages focus more on
non-graphic aspects of facility management.
To check and adjust the accuracy of a measuring instrument relative to a reliable standard.
A measuring tape that has been used a lot or damaged should be calibrated against a new
one or by a laboratory that is certified by the NIST. Lasers and other DME come with
manufacturer's instructions for calibration that should be followed, with records maintained in
case a question arises.
Campus Common Area
Fully enclosed space in a group of buildings that benefits all the occupants of that group of
buildings without being used exclusively by any one occupant. An example might be a HVAC plant
that heats and cools all buildings, or a cafeteria or auditorium shared by occupants of a group of
Campus R/U Ratio
When multiple buildings share common elements (see Campus Common Area) the Campus
R/U Ratio is used to allocate the floor area of those common elements to the Rentable Area of
each tenant. It is also referred to as a Site R/U Ratio or Multi-building R/U Ratio.
Ceiling Tile Count
A method of roughly measuring floor area by counting ceiling tiles and multiplying by the area of
each tile. This can be a more accurate way of measuring area than by Pacing but generally
not accurate enough to be used for leasing or appraisal.
To guarantee as true. A measurement or area calculation that is certified is presumably more
reliable than one that is not, depending on the credentials of the entity that provides the certification.
For design professionals, certification gives rise to contractual liability that is not covered by
standard E&O insurance policies.
A change in construction dimensions or materials issued after the contract for construction has
been awarded but before construction has been completed. Change orders may have an impact
on floor area measurements and are sometimes reflected in record drawings when the contractor
See Common Interest Community
See Common Interest Ownership Act.
Used in conjunction with a Space Requirements Projection, this factor is the result of dividing is
Secondary Circulation by Usable Area. It is applied to Assignable Area to calculate required
Usable Area. Care must be taken in application of a Circulation Factor. For example, if the
Circulation Factor is 25%, do not multiply Assignable Area by 1.25. Instead, divide it by 0.75
(Rule: divide by the compliment).
Corridors, aisles and other similar space required for occupants to access means of egress
and all other functions in and serving their space. Circulation may be classified as either primary,
secondary or tertiary, and it may be fully enclosed as in a corridor, or unenclosed, as in a phantom
corridor (a term coined by Willie Pena).
A system for allocating total occupancy costs to individual company departments, divisions or
other groups based upon the square footage they occupy and their actual costs.
The actual surface areas of floors, walls, windows, sills, furniture, fixtures and equipment
that require cleaning in order to maintain sanitary conditions and good appearance. May or may
not have any relationship to other measures of floor area used in leasing.
Coefficient of Expansion (Thermal)
The rate of change in the size or length of a building component or a measuring tape caused
by a given change in temperature. A steel building 200' long without expansion joints will be 5/8
inch bigger at 75 degrees Fahrenheit than it is at 35 degrees. A steel measuring tape likewise
changes length with temperature change, but distance measured by a LDM does not.
In commercial properties, fully enclosed space in a building that benefits others in the building
but does not accommodate tenant's personnel, furniture, fixtures or equipment. It is usually
classified as either Building Common Area or Floor Common Area. Limited Common area is also
seen in certain building designs, and Campus Common area can exist within a group of related
buildings. Appraisers and attorneys may apply this term to parking lots, exterior plazas, sidewalks,
and the like, but its use in the context of building measurement applies only to fully enclosed space.
A space cannot be counted as both Common Area and Usable Area.
In Common Interest Communities, any elements that are not part of the Units. This may include
exterior elements in addition to enclosed spaces, and encompasses both General Common
Elements and Limited Common elements.
Common Area Factor
Another term for the BOMA R/U Ratio, not defined by the BOMA Standard.
Common Interest Community
A form of real property ownership that includes condominiums, cooperatives and planned
communities that may be regulated by state statutes such as condominium acts or common
interest ownership acts, some of which contain explicit definitions of unit boundaries that are
relevant to the measurement of their floor areas.
Common Interest Ownership Act (CIOA)
Common Interest Ownership Acts are state statutes that govern Common Interest Communities
and may contain explicit definitions of unit boundaries that are relevant to the measurement of their
floor areas. See also Declaration.
A form of property ownership in buildings with multiple occupants wherein each occupant owns
a defined unit along with an undivided interest in the common elements, which include building
structure, enclosing and demising walls, hallways, lobbies, mechanical rooms and the like.
Condominium ownership can apply to both residential and non-residential uses. Unit boundaries
in residential condos are often defined by state statute. See also Common Interest Community.
A term used in the 1980 BOMA Standard and not well defined therein. It was replaced in the
1996 BOMA Standard by the term Gross Building Area. See also Architectural Area.
Collectively, the working drawings, specifications, general conditions, addenda and instructions
to bidders that for the basis of a construction contract. They are sometimes referred to as CDs,
but so are Construction Drawings. Does not include RFIs or Change Orders.
See Working Drawings.
Liability that arises out of certain written statements by design professionals, such as certification
of area calculations, which may be excluded from coverage under professional Errors and
Omissions (E&O) insurance. Separate contractual liability coverage is often required to cover
certification of area calculations.
A term used in ANSI/BOMA Z65.1-1980 to describe the relationships between the Rentable
Area of a floor, its Usable Area and its R/U Ratio. The term was discontinued in
Another term for R/U Ratio or Loss Factor, used by the GWCAR Standard.
Collectively, the spaces which serve the usable areas of a floor but which generally are not
themselves usable area. Core space includes fire stairs, elevator shafts, toilets, janitor's closets,
machine rooms, HVAC shafts, electrical and telephone closets. Core space may be
aggregated in a "center-core" or "side-core" building layouts, or dispersed in "multi-core" layouts.
Buildings with defined core areas may have space within the core area that is usable for tenant
storage, communications equipment, work rooms and the like. Elevator lobbies are generally
considered usable area for full-floor tenants.
A volumetric measure of space equal to the volume contained in a cube measuring 12 inches
in length, width and height. Cubic footage is important in HVAC system design and warehouse
buildings but is generally not used in real estate. However, it has recently been seen along with
price per cubic foot in listings for some high-end residential condos in New York and London.
A unit of length, about 17.7 inches, used in construction of The Pyramids, not generally used in
commercial real estate today.
A device use in CAD and BIM systems to display data about a building element like a delimited
portion of floor space. A data tag might include the space ID (SPID), square footage, space type
and occupant information.
See GWCAR Standard.
Also called Covenants, Conditions and Restrictions, it is a set of private documents used in
Common Interest Communities that includes the Map that documents the boundaries (including
lower and upper horizontal planes in the case of a multi-story building) of each unit and all
common elements. The Map must be stamped by a licensed land surveyor in most states, although
some states permit a map to be stamped by a licensed architect.
A legal term derived from the French word demise (to give away) describing a boundary line
encompassing floor area (demised area) within which tenants or condominium owners possess
certain rights to the use or possession of space.
A wall that contains a Demising Line. The demising line may be located on either face, the centerline,
or in some other location (like Dominant Portion) within the wall, depending upon wall location,
measurement methodology or standard cited.
A metric for office space utilization measured in square feet per person. The measure of square
footage is usually Usable Square Feet, but is occasionally Rentable Square Feet. You don't know
unless you ask.
Design Gross Area
A term used by the General Services Administration Public Building Service in their Business
Assignment Guide and defined as the total constructed area of a building measured to the
outside dominant finished surface and including all enclosed floors of a building including
sub-grade levels, mechanical floors, penthouses, structured parking and crawl space.
The act of creating openings in walls by boring or sawing holes to permit inspection of hidden
surfaces or enclosed spaces for the purposes of classifying space and determining field dimensions
to space class boundaries.
Acronym for Deutsches Institut für Normung, the German supra-national standards organization
with an English URL at www2.din.de/en. They publish a floor
measurement standard DIN 277 used in Germany.
Distance Measuring Equipment, usually laser-based, such as the Leica Disto or Hilti Handheld
Range Meter, suitable for the accurate field measurement of buildings if used by a trained
Metrologist. See also LDM.
A term used differently by various standards to identify the surface of a wall that constitutes
the boundary of a floor area for measurement purposes. See individual standards for
Drip Line Method
A method of measuring Industrial Space defined in the BOMA Industrial Standard as Method B.
(1.) Rental efficiency of a building is its Rentable Area divided
by its Gross Area. Rental efficiencies of tall office buildings have increased over time from 69%
for the Empire State Building, (New York City, 1931) to 85% for Republic Plaza, (Denver, 1980).
(2.) Industrial and retail buildings often have rental efficiencies
of 100%, meaning that they are leased using their Gross area.
(3.) Planning Efficiency of a building or floor is its Usable (or
Plannable) Area divided by its Rentable Area, the inverse of the R/U Ratio. Planning efficiencies
vary depending on whether a floor is constructed for a single or multiple occupants.
(4.) Programming Efficiency is the Assignable Area of a tenant
or occupant divided by the Gross area (or Usable or Rentable Area). See definition of Tare Area.
Errors and Omissions Insurance
Insurance carried by design professionals covering malpractice, including making mistakes in
building area measurements and area calculations. It is often referred to as E&O insurance,
professional liability or malpractice insurance and is highly recommended for design professionals
who do floor area measurements that are the basis for commercial transactions.
A base building element that is part of the usable area of a floor but inhibits its use for furniture
and equipment. Examples include window sills, columns, wall-mounted heating & cooling
units and low headroom conditions under pipes, ducts or structure. Encroachments are not
measured by some property management standards (BOMA, REBNY) but may be under facility
management standards (like IFMA).
A web-based distance learning tool that contains a learning module on the BOMA Standard.
The URL is
Facility Usable Area
From the IFMA Standard, fully enclosed space, excluding encroachments, that is available for
the exclusive use of a building occupant for occupant's personnel, materials, furniture, fixtures,
and equipment. This term may be changed in the future to Plannable Area. See also Usable Area.
Dimensions determined on-site in a building using a measuring tape or LDM. Field dimensions are
usually made to apparent building elements and often require adjustment to determine the boundaries
of classes of space for the purpose of doing lease area calculations.
A class of computer software that assists in development of floor plans on portable computers
with CAD software, often connected directly to laser distance meters, without the necessity of
bringing the work back to an office for additional processing.
As used in the NAHB Residential Standard, an enclosed area in a house that is suitable for
year-round use, embodying walls, floors and ceilings that are similar to the rest of the house.
In the BOMA Standard, it is the surface of a wall, floor or ceiling as prepared for tenant use but
excluding the thickness of any special tenant finishes such as paneling or carpeting. Naked
studs without gypsum wall board applied are not a finished surface, but concrete or masonry
units might be.
Space with attributes suitable for occupancy either by offices or light industrial/warehouse
operations. Such space might be measured for leasing employing either a office or industrial
measurement standard at the option of the owner/landlord.
An enclosed horizontal division of a building characterized by a structural surface capable of
supporting loads imposed upon it by occupants. It is sometimes referred to as a "story". See
also "Interstitial Space".
Floor Area, Gross
Section 1002.1 of the International Building Code defines this term as being "The floor area
within the inside perimeter of the exterior walls of the building under consideration, exclusive of
vent shafts and courts, without deduction for corridors, stairways, closets, the thickness of interior
walls, columns or other features. The floor area of a building, or portion thereof, not provided with
surrounding exterior walls shall be the usable area under the horizontal projection of the roof or floor
above. The gross floor area shall not include shafts with no openings or interior courts."
NPFA-101 has a different definition and some local building codes also depart from this
measure in some respects.
Floor Area, Net
A term used in building codes to describe the actual occupied area of a floor, not including
accessory unoccupied areas (stairs, elevator & HVAC shafts, mechanical rooms, etc.) or the
thickness of walls. See NPFA-101 page 17, the International Building Code section 1002.1, or your
local building code.
Floor Area Ratio (FAR)
The floor area of a building expressed as a ratio of the area of the site. Zoning codes often establish
a maximum FAR for buildings in certain locations. Some jurisdictions grant bonus FAR in return
for certain amenities provided by a building to its neighborhood. Floor area for this purpose is
sometimes called Zoning Floor Area (see definition). See also Transferable Development Rights.
Floor Common Area
Fully enclosed space on a floor that benefits all occupants of that floor but does not accommodate
the tenant's personnel, furniture, fixtures and equipment. The usual examples are toilets, janitor's
closets, electrical closets and HVAC equipment rooms serving only the floor upon which they are
located. See individual standards for detailed descriptions.
A scaled graphic representation of a horizontal section looking down through a building customarily
taken at an elevation of three feet above the finished floor unless noted otherwise. Can be part of the
working drawings, record drawings, space plan, or "core and shell" background drawings either on
paper or in a CAD file.
A floor of a building, as depicted by a floor plan, encompassing the major building elements on
the floor like the exterior enclosing walls, columns, core walls, elevators, stairs, and the like.
Usually refers only to core and shell building elements without tenant or occupant fit-up.
Floor Rentable Area
A term used by the BOMA Standards to describe the result of subtracting Major Vertical
Penetrations from Gross Measured Area on a floor. This is different than the Rentable Area of
the floor, which includes a pro-rata portion of Building Common Area.
Floor Service Area
A term used by the Washington Standard to describe the Floor Common Areas in the BOMA
Standard except for corridors on multi-tenant floors. Examples include toilets, janitor, phone
and electrical closets and mechanical rooms and their enclosing walls.
Floor Usable Area
A term used by the BOMA Office Standard connoting the sum of Office, Store and Building Common
Areas on a floor.
A unit of length used in the Imperial System equal to 12 inches. Since 1959 the International Foot
(where the inch is defined as exactly 2.54 centimeters) is the legal foot in most states. However, the
Survey Foot (set in 1893 by the relationship that one meter equals 39.37 inches), is slightly longer
(by about 1 foot in 100 miles) is still the legal standard in some states.
The area enclosed by the Building Perimeter at the ground level of a building. If the building were
cut horizontally at grade level and removed, this would be the area of the remaining scar upon
An athletic field for American football having official NFL measurements of 360 feet by
157 feet, or 56,520 square feet. This measure is used to visualize the approximate size of large
floor areas like the Pentagon since 117 football fields is easier for some to visualize than its
gross area of 6,636,360 square feet.
Strips of wood or metal attached to a wall or other surface to provide a fair and even surface for
the attachment of another finished material such as wood paneling. If furring is attached to a
finished surface, it encroaches into a tenant's usable area, requiring adjustment to apparent
Acronym for Global Positioning System, a system that employs satellites and ground-based
equipment for locating points on the surface of the earth. The best surveying GPS systems have
sub-centimeter accuracy that approaches the accuracy needed for building area measurements,
but they are very expensive and have reception problems indoors. Inexpensive hand-held GPS units
have the same reception problem and they do not have sufficient accuracy for building area
measurement, although they can locate a building well enough to find it.
(1.) The slope of a surface. For instance, a 2% grade indicates
a change in elevation of 2 feet vertically for each 100 feet of horizontal distance.
(2.) The surface of the ground at the outside face of the exterior
enclosing wall. An interior floor that is within 2 feet of grade is usually deemed to be "at grade." See
The total of all areas of a building. The term is commonly used but its measure is defined
differently by different stakeholders, which include designers, developers, cost estimators,
appraisers, property tax officials, real estate brokers, financial institutions, insurance companies,
building code & zoning officials, property managers and facility managers. There is no single
accepted method of measuring Gross Area.
Gross Building Area (GBA)
A term used by federal agencies to measure multi-family properties and industrial buildings, and
by the 1996 BOMA Standard. It is similar to Gross Area.
Gross External Area (GEA)
A term used in the United Kingdom, defined in the RICS Standard, for the area of a building
measured externally at each floor level.
Gross Floor Area (GFA)
See "Floor Area, Gross", "Gross Area", Zoning Floor Area".
Gross Internal Area (GIA)
A term used in the United Kingdom, defined in the RICS Standard, for the area of a building
measured to the internal face of perimeter walls at each floor level. See also Net Internal Area.
Gross Leasable Area (GLA)
Used in retail leasing. Generally the floor area available for the exclusive use of a retail tenant
measured to the outside face of exterior walls and the centerline of demising walls separating
tenants. It includes basements and mezzanines. In Australia, GLA stands for Gross
Lettable Area and is well defined in the Property Council's Method of
Gross Living Area (GLA)
A term used by residential appraisers to describe finished, above-grade residential space,
measured to the outside face of exterior enclosing walls. Also referred to as Residential Living
Area in the 1995 version of the AIA D-101 Standard, the measurement method is not defined
in any major published measurement standard.
Gross Measured Area
From the BOMA Office Standard, the total of all fully enclosed floor areas of a building,
measured to the Dominant Portion of the Finished Surface of exterior enclosing walls, including
basements and penthouses. See the BOMA Standard.
Gross Rentable Area
Another term for Rentable Area, not defined by the BOMA Standard.
A Canadian term for applying an R/U Ratio to Usable Area to determine Rentable Area. It is not
defined by the BOMA Standard and is not to be confused with the Grossing Up of variable operating
expenses as defined by the BOMA Escalation Handbook for Office Buildings.
The Greater Washington Commercial Association of Realtors, with
The Standard Method of Measurement, A Formula for Calculating Rentable Office and Retail
Space, published by the GWCAR and used only in the District of Columbia and nearby areas
of Virginia and Maryland. It is sometimes referred to as the "DC Standard" or the "Washington
A common unit of area in the metric system equal to 10,000 square meters, or about 2.471 acres
in the imperial system. It is the principal unit for expressing land area in most of the world but is
generally not employed to express floor areas in buildings.
In multi-story common interest communities, a plane of elevation relative to an established
benchmark that defines either an upper or a lower boundary of a unit.
Acronym for Industry Foundation Class, a classification system for building components
(including floor area classifications) being developed by the International Alliance for
Interoperability (IAI) for use in CAD and BIM software.
The International Facility Manager's Association, with URL
The Standard Classification for Building Floor Area Measurements for Facility Management,
designated ASTM Standard E 1836-01 (current version).
The system of measurement units commonly used in the United States which includes units of
length like miles, yards, feet and inches with fractions to the base 2 (1/2, 1/4, 1/8, etc.) and that
infamous unit of area known as the Square Foot.. The legal system of measurement in the US
and nearly everywhere else in the world is the Metric System.
Pertaining to the gainful activity of producing, distributing and changing the form of raw
materials, or of assembling components and parts, packaging, warehousing, and transporting
Space suitable for industrial use, characterized by ceilings higher than 12 feet and interior
finishes, HVAC, lighting and power unsuitable for office, institutional or retail occupancy.
A term used in the GWCAR Standard for the same purpose as Gross Measured Area in the
Inter-floor Common Area
See Limited Common Area. This is not the same as Interstitial Space.
Interior Gross Area
A term used by the IFMA Standard that expresses the full area of a floor measured to the
finished surface of the inside face of the exterior wall where it meets the floor.
Load-bearing platforms between floors suitable for equipment and mechanical use but not for
occupancy by personnel except for maintenance purposes. Defined in the IFMA Standard
and found most frequently in laboratory and medical building types. This is not the same as
A measure of floor area under the ISO Standard that excludes the area taken up by exterior
enclosing walls, similar to Interior Gross Area.
International Organization for Standardization with URL
www.iso.ch located in Geneva, Switzerland. The US is represented at the ISO by ANSI,
and ANSI distributes ISO standards in the US.
ISO 9836, Performance Standards in Buildings - Definition and Calculation of Area and Space
Indicators, a widely used measurement standard in Europe, published by the ISO and available
Acronym for Laser Detection and Ranging. Very accurate
technology that uses lasers to generate point clouds in space to depict visible 3-D surfaces. It
is possibly the future of building area measurement but currently used only in scientific, industrial
and military context because of high cost.
Acronym for "Light Amplification by Simulated Emission of
Radiation". Lasers are used in some electronic distance measuring equipment like the
Leica Disto and Total Stations to accurately measure distance between specific points on the
measuring unit and visible surfaces up to 100 meters or more away, making it an ideal technology
for building area measurement.
Short for Laser Distance Meter, any of a class of laser based measuring tools
such as the Leica Disto or the Hilti Hand Held Range Meter that have generally made measuring tapes
obsolete for the purpose of measuring interior space in buildings.
The agreement between a landlord (Lessor) and a tenant (Lessee) detailing the terms
of occupancy, rent payments and the like. Because it also defines the Premises, their rentable
area, and often their measurement method, it is the most important document for a metrologist
to read and understand before doing any floor area measurements.
Areas available for leasing to, and the use of, a tenant. Measurement method is not defined by
any published measurement standard and could be anything, including Gross Area, Rentable
Area, or Usable Area. In Great Britain, Australia and many other members of the former British
Commonwealth, this is referred to as Lettable Area.
A review of a landlord's accounting practices, expense pass-throughs and rentable area
calculations under the terms of the lease by a lease auditor, an expert agent of the tenant.
Lease audits can lead to rent abatement paid by the landlord to the tenant, of which the lease
auditor generally keeps 30 to 50 percent as his fee.
Used in retail leasing (shopping malls and the like), this term describes a boundary of a
demised retail premises that may or may not be associated with a wall. It can be located
from a lease exhibit or a leasing plan maintained by the landlord but often cannot be
determined from field observation.
The distance from a core wall of a building to the inside face of an exterior wall or the inside
face of the exterior glass. If there is no central building core, it is half the distance between the
exterior building walls.
As used in the NAHB Residential Standard, areas of the house that are vertically within
2 feet of the same horizontal plane.
Limited Common Area
Fully enclosed space that serves more than one floor (and not accommodating occupant's
personnel, furniture or equipment) but less than the entire building. A common example is a fan
room that serves the floor it is on and the floor immediately below it.
See Gross Living Area.
A term similar to the BOMA R/U Ratio but not defined in the BOMA Standard. A 20% load
factor means that 20% of a tenant's usable area is added to that usable area in order to
calculate rentable area. Compare to Loss Factor below.
A term used correctly only in conjunction with the New York Standard to mark-up usable area
to rentable area, allocating common areas of the building to each floor and tenant. A 20% loss
factor means that 20% of a tenant's rentable area (R) is common area, 80% is usable
area (U). To calculate rentable area from a given usable area, you must solve the equation R
times 0.8 equals U, or U divided by 0.8 = R. Since 1 divided by 0.8 equals 1.25, this is equivalent
to a 25% load factor, making loss factors seem lower than load factors, a fact use to advantage
by some brokers.
Major Vertical Penetration (MVP)
Major openings in a floor to accommodate vertical building elements such as stairs, elevators,
HVAC shafts and the like, including their enclosing walls. They are distinguished from minor
vertical penetrations by various rules of thumb ranging from 64 square inches to 144 square
inches (1 square foot). See BOMA Standards.
A term from the BOMA Industrial Standard that is similar in use to the Dominant Portion as
defined by the BOMA Office Standard.
The mapping of empirical objects to numerical objects by a homomorphism (mathematician
Fred S. Roberts). In building area measurement, the empirical objects are building floor areas
and classes of space as determined by published measurement standards and local
measurement practices. The numerical objects are floor areas used in leasing, management
and valuation of real properties.
(1.) A hand-held field measuring device that utilizes a wheel
linked to a meter that displays distance when rolled over a surface. Generally used for
construction quantity-take-offs (carpet, paint, etc.) and approximate distances. Not an
appropriate measuring tool for accurate building area measurement.
(2.) A hand-held desk-top measuring devise utilizing a small
wheel linked to a digital display showing the distance that the wheel is rolled over a floor plan, often
to the scale of the plan when correctly configured. Used for approximate distances and
construction quantity take-offs for cost estimating. Not an appropriate tool for accurate
building area measurement.
A measure of length used in the Metric System equal to the length of the path traveled by light
in a vacuum during a time interval of 1/299,792,458 second. A centimeter is 1/100th of a meter.
An International Foot equals exactly 0.3048 meters. A square meter is approximately equal to
10.76 square feet.
The International System of Units, also known by the French abbreviation SI (Systeme
International d'Unites), used for measurement by the entire world with the only significant
exception being the United States of America. For real estate purposes, the USA uses the
One who professionally engages in metrology.
The scientific study of measurement and the application of measurement standards.
A floor structure within the exterior walls of a building and between two floors, capable of
supporting personnel, equipment, storage or manufacturing. The area of a mezzanine is limited
by some codes in some occupancies to some fraction (like 1/3) of the area of the floor immediately
below. See the BOMA Industrial Standard.
A property that accommodates different uses. Living over a store was an early form combining
retail and residential uses. Discourage by many zoning codes, it has become a popular
tool for urban revitalization that presents measurement challenges because of a lack of published
A floor on which the Usable Area is or can be leased to more than one tenant. On a floor with
two tenants, its Usable Area gets subdivided three ways - two tenant suites and a common
corridor that then becomes Floor Common Area.
The National Association of Home Builders, publisher of the NAHB Residential Standard
through their wholly-owned subsidiary, the NAHB Research Center, with
NAHB Residential Standard
The American National Standard for Single-Family Residential Buildings / Square Footage
- Method of Calculating, published by the NAHB Research Center and carrying the
designation ANSI Z765-2003 (current version).
Abbreviation for Net Assignable Square Footage. See Net Assignable Area.
Acronym for National CAD Standard, with URL at
www.NationalCadStandard.org/ncs6/ that governs naming and content of "layers" used in
application of CAD to buildings, including building area measurements. The AIA CAD Layer
Guidelines are part of the NCS.
A term previously used by the General services Administration Public Building Service but replaced
by the term BIM Area.
Net Assignable Area
This term is used in educational facilities programming and planning to describe functional
areas such as classrooms and laboratories without required building support spaces like circulation,
mechanical and structural areas. See also Assignable Area.
Net Floor Area
A term used in the ISO standard to express the Interior Gross Area less the areas of all
Net Internal Area (NIA)
A term used in the United Kingdom, defined in the RICS Standard, for the usable area of a
building measured to the internal face of the perimeter walls at each floor level. It is used in much
the same way as "Rentable Area" in North America although its calculation is quite different.
Net Leasable Area
Another word for Rentable Area. This term is not defined in the BOMA Standards or any
major published measurement standard. This term should not be used if the BOMA
Standards are being employed.
Net Rentable Area
Another word for Rentable Area. Some people also use this term to refer to Usable Area.
This term is not defined in the BOMA Standards or any major published measurement
standard. This term should not be used if the BOMA Standards are being employed.
Net to Gross Ratio
A term used in facilities programming and planning as a measure of building efficiency, it is a
number less than one, the numerator of which is the Net Assignable Area and the denominator
of which is the Gross Area.
Net Usable Area
A term used in the REBNY Standard to describe the usable area available to a tenant on a
multi-tenant floor, excluding corridors but including the thickness of exterior building walls.
New York Standard
See REBNY Standard. This applies to New York City, not the State of New York.
The National Institute of Standards and Technology (successor to the National Bureau of
Standards) with URL at www.nist.gov that oversees U. S.
measurement science, standards, and technology. If you suspect someone of using a rubber
measuring tape you can have it calibrated at an NIST-certified laboratory, but don't expect any
government agency to certify square footage numbers. All floor area measurement standards
for U. S. commercial property are voluntary.
A simple transaction or task requiring little imagination or intelligence, the opposite of
doing floor area measurements.
Freedom from bias, a desired trait for those applying published measurement standards to
determine floor areas that underlie transactions. Measurement disputes often arise when bias
affects the parties' application of a measurement standard. Objectivity from a qualified neutral
third party can be an important factor in resolving such disputes.
A term used by some government agencies as a measure of usable area and often as the
basis upon which they will pay rent. Can exclude areas included in BOMA Usable Area such
as window sills, wall-mounted HVAC units and the like. Lease language determines how it is
Enclosed space usable for personnel, furniture, equipment and office support areas, which has
suitable finishes, lighting, environmental controls, power, communications support and ceiling
Acronym for Open Standards Consortium for Real Estate, an international group that
promotes standards relating to real estate, including floor area classifications and terminology
for building area measurement.
A method of roughly measuring distances by walking, counting steps and multiplying the
number of steps by the average distance per step. Distances determined thereby can them
by multiplied to determine floor area. This is not an accurate enough way of determining floor
area for leasing or valuation purposes, but it is a useful way of quickly understanding approximate
Partial Floor Factor
Another term for the BOMA R/U Ratio that is not defined in the BOMA Standards.
PBS Business Assignment Guide
A system for classifying, measuring and tracking space based upon a modified version of
the 1996 BOMA Standard. It is employed by the US General Services Administration Public
Building Service in conjunction with its STAR system to manage the square footage that it
owns and leases.
In common interest communities, a vertical or horizontal boundary at the perimeter of a unit.
A desktop device for measuring the area of a planar region. Invented in 1894 by British
mathematician O. Henrici, it was made obsolete by the use of the polyline region in CAD but can
still be useful for approximate measurements of irregular areas delineated on paper.
A 2D element employed in an AutoCad drawing that is capable of determining with extreme
Precision the area of the space it delineates, and also documenting the boundaries of that
area. This is an AutoCad term. Other CAD systems use other terms, like shape or polygon.
The number of digits that are used to express a value. Not to be confused with Accuracy.
CAD commonly expresses areas bounded by polylines with precision of 16 significant digits.
That level of precision is meaningless when the precision of construction is 1/8" or less. Because
of this, the normal precision used in building area measurement is 1/8" or 0.01 feet or 3mm.
The legal word, included in most leases, for the Tenant Area enclosed by Demising Walls. The
best description of a premises is a graphic lease exhibit showing the floor plan with the
boundaries of the Premises and its area in whatever terms are used by the lease.
Term used in the IFMA standard to describe corridors on multi-tenant floors or their functional
equivalent for full-floor occupants.
A financial projection of income and expenses used as a basis for securing financing for a property.
An important basis for a pro forma is the rentable area of the property under the measurement
standard cited in the lease in addition to the projected rent rates and other factors.
A fraction, the numerator of which is the Rentable Area of a tenant and the denominator of which
is the Rentable Area of the building. It is used in allocating certain expenses to tenants under
certain types of leases.
The unit of plane angle adopted under the Metric System as an alternative to the degree. It is equal
to the angle at the center of a circle subtended by an arc equal in length to the radius, approximately
57.2958 degrees. There are 2Pi radians in a circle.
A graphic depiction of a building on paper or CAD that incorporates changes to the working
drawings made during the construction phase of a project. These are different from as-built
drawings in that they do not document all actual construction, but are still a better basis for
calculating floor areas than working drawings.
The Real Estate Board of New York, with URL
The Recommended Method of Floor Measurement for Office Buildings published by
the REBNY. Board member Realtors quoting square footages must use this standard, and it is used
only in New York City and nearby areas of New York, Connecticut and New Jersey.
Rent Abatement (RSF)
(1.) Free rent used as an incentive for prospective tenants.
(from the BOMI Dictionary).
(2.) A rebate of rent by the landlord to a tenant stemming
from mis-measurement of Rentable Area, improper accounting practices or expense pass-throughs
under the terms of a lease. Sometimes called rent restitution.
Also called Rentable Square Footage (RSF), the area of a building, floor or suite used as
the basis for calculating Base Rent. Different measurement standards define this in different
ways. Refer to individual standards for measurement methods and definitions.
A listing of each tenant and vacant suite in a building showing the rentable areas of each suite
as shown on leases and that of the building as a whole, in addition to other pertinent
information like lease expiration dates and the like.
Request for Information (RFI)
(1.) A term used when the contractor requests clarification
of construction documents after the award of contract. This is often cause by conflicts between
different parts of the construction documents and sometimes results in dimensional changes to floor
plans that are significant for those measuring floor areas.
(2.) A request for information from prospective bidders, not including
an actual proposal or bid.
Buildings or portions thereof used for human habitation, including single and multi-family houses,
row houses, rental apartments, residential condominiums and rooming houses, but not hotels or
motels. Only single family units and row houses have a published measurement standard.
See NAHB Residential Standard.
A figure greater than one, the numerator of which is Rentable Area and the denominator of which
is Usable Area, which allocates Common Areas to Usable Areas and Basic Rentable Areas. There
are Floor R/U Ratios, Building R/U Ratios and occasionally Campus R/U Ratios. Refer to specific
standards for detailed definitions. This is often incorrectly called an R/U Factor, and is sometimes
referred to as an Add-on Factor, Common Area Factor, Loss Factor, Load Factor, Gross-up Factor
or Partial Floor Factor.
A term used in the GWCAR Standard to define Store Area, but optionally including certain exterior
areas such as outside dining for restaurants or carry-out food establishments, or a portion of the
main building lobby.
The Royal Institute of Chartered Surveyors with URL
ww.rics.org, a London-based standards and membership organizations for professionals
involved in land, valuation, real estate, construction and environmental issues. They publish the
The Code of Measuring Practice, a Guide for Surveyors and Valuers, published by the
Royal Institute of Chartered Surveyors (RICS), used in the United Kingdom.
To change the value of recorded digits to some other value considered more desirable for the
purpose at hand by dropping or changing certain digits. If your CAD software reports that a
polylined area contains 45.1234 units, you would round that value to 45.12 because the last two
digits are a misleading expression of accuracy for floor area measurement. Incorrect rounding can
lead to errors in floor area measurement. Use the "round-to-even" rule and refer to NIST Handbook 44,
Appendix A, Section 10 for standards and practices of rounding.
This occurs when the sum of a string of correctly rounded numbers is different than the sum of
those same numbers un-rounded. This kind of rounding error can be unavoidable in a short string
if numbers but tends to be minimized in a long string of numbers. To help avoid rounding error, always
use one or two more digits in your calculations than you require in your final result.
When the last digit of a number is a 5, the digit to its immediate left is increased by one if it is
odd. Otherwise, it is left even. This helps eliminate an upward bias caused by always rounding up
when the last digit of a number is 5.
(1.) A graduated instrument that allows a measurer to
determine linear distances from paper floor plans that are drawn to scale for the purposed
of calculating floor areas. Sometimes incorrectly referred to as a "ruler".
(2.) The ratio between a drawing of a floor and the size of the
actual floor it represents. Most commercial buildings are drawn at a scale of 1/8" = 1'-0", called "
eighth scale". Small buildings and houses are most often drawn at "quarter scale".
Used by the IFMA Standard, corridors and walk-ways required within the Usable Area of a tenant
or department, required for access and egress to/from all Assignable Areas.
Detailed, accurate drawings produces by individual trades from which a building is actually
constructed. The most reliable source of dimensional information short of field dimensions.
Square footage that disappears between the pro forma and the rent roll due to lease negotiations,
the dynamics of leasing or inadequacies in the method of accounting for square footage.
Abbreviation for the French term Systeme International d'Unites, the Metric System.
Single Tenant Floor
A floor on which all usable area is completely occupied or leased by a single tenant.
The Society of Office and Industrial Realtors with URL
www.sior.com, a organization that collaborated with BOMA
in development of the BOMA Industrial Measurement Standard.
Swedish Standards Institute with URL www.sis.se that publishes a measurement standard
used in Sweden, Area and volume of buildings - Terminology and Measurement, SS 021053.
Space Management System
A system that determines and tracks space occupancy, density and utilization by department and
division within an organization for the purpose of optimizing space utilization and minimizing
occupancy costs. Square footage figures from these systems drive charge back systems.
The process of translating a space program into a physical layout or floor plan that satisfies an
occupants needs in terms of square footage, adjacencies, circulation, workflow, capacity for
growth and many other criteria.
A document specifying the comprehensive facilities requirements of a user of space. A
significant part of a program is the Space Requirements Projection. Also called a Facilities
Space Requirements Projection
A projection of the Usable Area needed by an occupant at one or more future time horizons. It is
often based upon space standards, a detailed space inventory and circulation factors. When done
for tenants, they usually assume that basic building services (toilets, fan rooms, and the like) are part
of the base building and are therefore excluded from the program.
A documented standard allocation of square footage to each position or function within an
organization. It is used as a basis for doing a space requirements projection as well as a tool to
control actual allocation of space in many organizations.
Spatial Program Validation
A process used by the US General Services Administration Public Building Service to evaluate
proposed building designs for conformance with programmed space requirements. This utilizes
explicit measurement standards and documentation requirements outlined in the PBS Business
Assignment Guide and the GSA BIM Guide.
A written part of the Construction Documents that sets out requirements for materials, equipment,
construction systems, standards and workmanship as well as standards for construction services
required to produce the work. Occasionally there will be information in the "specs" of interest
to a person measuring floor areas of un-built buildings.
Space Identifier, a term used in the PBS Business Assignment Guide representing a
human-assigned number that uniquely identifies every space on all floors of a building. Not to be
confused with a GUID, or Global Unique Identifier, that is used internally by a CAD or BIM
system to track building elements like floor areas.
Square Foot (SF)
A square unit of area measuring twelve inches on each of its four sides that becomes grotesquely
distorted when found in office buildings (attributed to John Windsor, past chair of the
BOMA Method of Measuring Floor Area Committee).
A term used in the BOMA Standard and others in the real estate industry in parts of the world under
the Imperial System to describe a quantity of floor area.
A horizontal bar chart that used a "stacked bar" for each floor of a building to indicate the
square footage occupied by each tenant, department or vacant suite on each floor. Easily
implemented in Excel spreadsheet software and very useful for developing strategy for phased
re-stacking of organizations occupying multiple floors or buildings.
Software distributed by BOMA that automates some aspects of floor area calculations under the
BOMA Office Standard.
An acronym for System for Tracking and Accounting for Real Property, used by the
US General Services Administration to manage the space that it owns and leases. Square footages
in the STAR system are based upon a modified 1996 BOMA standard described in the
PBS Business Assignment Guide.
Space suitable only for the storage of materials and equipment and not for occupancy by
personnel, by virtue of inadequate lighting, finishes, environmental controls, power, access,
egress, or ceiling height.
Space on the street level of an office building that is suitable for retail occupancy. This is not the
same as retail space in shopping centers and is defined in the BOMA and New York Standards.
Strategic Facilities Planning (SFP)
The process of crafting a facilities plan for an organization that integrates with and supports its
business plan while minimizing occupancy costs. A good space management system is a foundation
for an SFP.
A term used in real estate development, meaning the ratio of the total ground floor area of a building
to the total area of its site. Building area for this purpose is measured to the outside face of exterior
enclosing walls. Average urban structural densities in the U. S. have been declining since 1945,
which is a measure of increased urban sprawl.
In a space requirements projection, space for functions other than workstations occupied by
staff. Includes conference rooms, filing areas, reception spaces and the like but does not
include primary or secondary circulation space.
As a noun, a document that locates the boundaries of a site or parcel of land relative to a public
benchmark or plat, and that may show the location and size of the footprint of improvements
thereon. For a metrologist, a survey can be not only useful but also critical in the case of
buildings that are intersected by property lines or easements.
A term used in architectural programming meaning difference between the Gross Area (or
the Usable or Rentable Area) of a building or portion thereof and the Assignable Area
required by a tenant/occupant. Its use is described in Programming for Design, a book
authored by Edith Cherry, FAIA.
An occupant (Lessee) of space who does not own it but who has tendered legal consideration
to the owner (Lessor) in return for certain rights for the use and "quiet enjoyment" of a defined
demised floor area.
Space that is used exclusively by a tenant for their personnel, furniture, equipment, storage,
support, and processes of any sort. It includes Secondary Circulations and, for a tenant
occupying a full floor, Primary Circulation as well. It may be applied to any type of occupancy
(office, industrial retail, etc.) and so can be measured many different ways.
Space allowing flow of people through assignable spaces. For example a file room may include
an aisle that not only allows for opening of file drawers but also passage of staff through the file
room to other assignable spaces.
The allowable difference between an area calculation made by an individual and the actual
area of a subject space, floor or building. If the Tolerance is 1%, then two individual's area
calculations must always be within 2% of each other (one could be 1% high and the other 1% low).
A sophisticated (and costly) surveying instrument that combines the functions of a transit, a level
and EDM with a computer to enable very accurate measurements of points on land and in
buildings. For distances of over 100 meters, a Total Station is superior for building area
measurements than a hand-held DME. However, a hand-held DME used professionally is more
mobile, faster and sufficiently accurate for most building measurements.
Transferable Development Rights (TDR)
A mechanism allowed by some jurisdictions for increasing the FAR on one site by purchasing rights
to build floor area within the FAR of another site. See definitions for Floor Area Ratio and Zoning
A subset of geometry that deals with triangles and the relationships between their dimensions
and angles. Abbreviated "trig", it employs trigonometric functions like Sine, Cosine and Tangent.
Trig, including the Law of Cosines, and is useful in measuring irregular floor plans.
A physical portion of a Common Interest Community designated for separate ownership or
occupancy, the boundaries of which are described by a Common Interest Ownership Act.
Fully enclosed space that is available for the exclusive use of a building occupant for
occupant's personnel, materials, furniture, fixtures, and equipment. Different standards measure
this in different ways. It is referred to in leases as The Premises.
There are two types of vacancies:
(1.) Floor areas that are not producing rental revenue under
lease to a tenant; and
(2.) Floor areas that are producing rental revenue under a
lease but are not occupied by the tenant.
The former is considered true vacant space whereas the latter is called Shadow Space because of
the likelihood that it will become true vacant space when the lease term expires.
The amount of rentable area that is truly vacant (not including shadow space) divided by the total
rentable area in building or group of buildings.
The difference between two area calculations of a subject suite, floor or building area made by
two individuals. The area calculation of a building owner is deemed accurate if the variance
between their area calculation and that of another party is less than 2% under the BOMA,
GWCAR and NAHB Standards.
A term used to describe space, generally in an urban context, that is an extension of a
basement beyond the Building Line, often under public rights of way such as sidewalks and
plazas. This has nothing to do with bank vaults but derives its name from the masonry vaulting
once used to support the sidewalk, street or alley above.
In common interest communities, any boundary of a unit that is not a horizontal boundary.
See Major Vertical Penetration.
A term used in the IFMA Standard to describe portion of an enclosed floor area that is open to
the floor below. It is sometimes indicated on plans with the abbreviation "OTB" for Open to Below.
Examples are an upper level of a multi-story atrium or a portion of a ramp (sloping floor) whose area
is included in the floor area of a lower level. It is distinguished from Major Vertical Penetrations in
that it does not usually provide inter-floor building services like elevators, stairs and mechanical
Web Site Registration Form:
Web mail form used to register with the Halo Realty Web Site Data Base and receive a free gift for registering.
See GWCAR Standard. This refers to Washington DC, not the State of Washington.
Graphic depictions of a building on paper or CAD, prepared as the basis for a construction
contract. They include floor plans at multiple scales, building and wall sections, details and
schedules, as well as architectural, structural, mechanical and electrical drawings. They do
not reflect changes made during construction unless stamped "As-built" or "Record Drawings".
Sometimes referred to as Construction Drawings or CDs. See also Construction Documents,
also referred to as CDs.
The square footage dedicated to supporting the tasks of a single worker, measured to the
centerline of any normal enclosing walls or panels. In some instance, workstations are designed
to be shared between two or more workers.
Zoning Floor Area (ZFA)
Floor area as measured for purposes of compliance to a zoning code. It is usually defined
as Gross Area measured to the outside face of enclosing walls but is also defined by some
municipal codes (Santa Monica, CA, for instance) as measured to the inside face of exterior walls
and excluding certain spaces like elevator shafts, open balconies, atriums and certain other areas.