Add-on Factor
Another term for the BOMA R/U Ratio, not defined in the BOMA Standard. Often referred to as the Loss Factor or Rentable/Usable (R/U) Factor, it represents the tenant’s pro-rata share of the Building Common Areas, such as lobbies, public corridors and restrooms. It is usually expressed as a percentage which can then be applied to the usable square footage to determine the rentable square footage upon which the tenant will pay rent.


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

AIA Standard
Methods of Calculating Areas and Volumes of Buildings, AIA Document #D101-1995 (current version) published by the AIA.

The American Industrial Real Estate Association.

AIR Standard
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.

Architectural Area
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.

As-built Drawings
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.

Assignable Area
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.

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.


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.

BOMA Standard
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.

Building Area
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.

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.

Building Rentable Area
The BOMA Standard defines it as the sum of all the Floor Rentable Areas.

Building Rentable/Usable (R/U) Ratio
The BOMA Standard defines it as the the conversion factor that distributes the Building Common Area 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.

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 buildings.

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.

Circulation Factor
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).

Circulation Space
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).

Chargeback System
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.

Cleanable Area
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.

Common Area
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.

Common Elements
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
A substitute term for the BOMA R/U Ratio (not defined by the BOMA Standard).

Construction Area
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.

Conversion Formula
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 ANSI/BOMA Z65.1-1996.

Core Factor
A term used by the GWCAR Standard which relates to the BOMA R/U Ratio or Loss Factor, .

Core Space
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.

Cubic Foot
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.

Demising Line
A legal term which describes a boundary line encompassing floor area (demised area) within which tenants or condominium owners possess certain rights to the use or possession of space.

Demising Wall
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 until you ask.

Destructive Measurement
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 national standards organization They publish a floor measurement standard DIN 277 used in Germany.

Dominant Portion
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 detailed definitions.

Drip Line Method
A method of measuring Industrial Space defined in the BOMA Industrial Standard as Method B.

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).

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.

Field Measurement
Dimensions determined on-site in a building using a measuring tape or device. Field dimensions are usually taken from apparent building elements and often require adjustment to determine the boundaries of classes of space for the purpose of doing lease area calculations.

Finished Surface
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.

Flex Space
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).

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.


Floor Plan
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.

Floor Plate
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 Standard 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 R(entable)/U(sable) Ratio
A term used by the BOMA Standard to describe the conversions factor derived as the result of dividing the Floor Rentable Area by the Floor Usable 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.


Gross Area
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 Floor Area (GFA)
See Floor Area (Gross), Gross Area, Zoning Floor 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 Measurement standard.

Gross Measured Area
The BOMA Office Standard defines it as 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.

Gross Rentable Area
Another term for Rentable Area, not defined by the BOMA Standard.

Grossing Up
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 URL

GWCAR Standard
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 Standard".

Acronym for the International Alliance for Interoperability, an organization with URL at that develops the Industry Foundation Classes (IFC).

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

IFMA Standard
The Standard Classification for Building Floor Area Measurements for Facility Management, designated ASTM Standard E 1836-01 (current version).

Inside Gross
A term used in the GWCAR Standard for the same purpose as Gross Measured Area in the BOMA Standard.

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.

Interstitial Space
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 mezzanine space.

Intra-muros Area
AA 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 located in Geneva, Switzerland. The US is represented at the ISO by ANSI, and ANSI distributes ISO standards in the US.

ISO Standard
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 through ANSI.

Leasable Area
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.

Leasing Depth
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.

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.

Load Factor
Another term for the BOMA R/U Ratio, not defined in the BOMA Standard.

Loss Factor
A term used correctly only in conjunction with the REBNY Standard to mark-up Usable Area to Rentable Area, allocating common areas of the building to each floor and tenant. Functions similarly to the BOMA R/U Ratio but expressed differently.

Example: An owner may arbitrarily decide that the rentable area shall be 25% larger than the Usable Area throughout the building. This results in a "Loss Factor" of 20%.


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.

Measure Line
A term from the BOMA Industrial Standard that is similar in use to the Dominant Portion as defined by the BOMA Office Standard.

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.

Multi-tenant Floor
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 URL

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.

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 interior walls.

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.

The National Institute of Standards and Technology (successor to the National Bureau of Standards) with URL at 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.

Occupyable Area
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 measured.

Office Area
Enclosed space usable for personnel, furniture, equipment and office support areas, which has suitable finishes, lighting, environmental controls, power, communications support and ceiling heights.

Partial Floor Factor
Another term for the BOMA R/U Ratio that is not defined in the BOMA Standards.

Primary Circulation
Term used in the IFMA standard to describe corridors on multi-tenant floors or their functional equivalent for full-floor occupants.

Pro Forma
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.

Pro-Rata Share
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 Real Estate Board of New York, with URL

REBNY Standard
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.

Rentable Area
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.

R/U Ratio
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.

Retail Area
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.

Secondary Circulation
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.

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, a organization that collaborated with BOMA in development of the BOMA Industrial Measurement Standard.

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 chargeback systems.

Space Planning
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.

Space Program
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 Program.

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.

Space Standards
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.

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).

Square Footage
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.

Stacking Chart
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.

Storage Area
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.

Store Area
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.

Structural Density
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.

Support Space
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.

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.

Tenant 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.

Tertiary Circulation
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).

Usable Area
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.

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.

Vertical Penetration
see Major Vertical Penetration.

Void Area
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 shafts.

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.

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