BOMA published it's first Office Standard in 1915 as a way for building owners, managers, and other stakeholders, to measure commercial office space using a repeatable and systematic methodology. Since then, the standard has been revised and reissued several times, most recently in March 2024. To take advantage of the latest features, BOMA always recommends using the latest Standard, however it is not unusual to encounter older versions - 2017, 2010, 1996, and even 1980, during the course of business. The BOMA Office Standard is the de facto method of measurement for transacting commercial real estate in many American, Canadian, and international real estate markets.

The main purpose of the BOMA Office Standard is to determine the Rentable Area of occupant spaces. Rentable Area is a calculated figure comprising the occupant area itself, plus a proportionate share of common service and amenity areas on the floor and across the building (think washrooms, corridors, lobbies, and mechanical rooms etc). Rentable Area is a key metric when it comes to leasing and transacting commercial office space.

The most recent office standards prescribe two distinct options for determining Rentable Area called Method A and Method B, which both produce the identical Total Rentable Area for the whole building. The main difference between Method A and Method B comes down to the way in which common areas are allocated to tenants, meaning the choice to use Method A or Method B is largely strategic in nature.

Method A is called The Legacy Method because of its similarity to past BOMA Standards. Method A applies successive pro rata load factors to tenants, based on the common areas they share and benefit from. Method A is a time-tested approach to distributing common area that promotes fairness and transparency for tenants. Some tenants may struggle to understand why their load factors are different from other tenants, however this is a natural outcome of Method A's approach.

Method B is called The Base Building Circulation Method because fixed circulation corridors are to be measured on every tenanted floor, whether such corridors actually exist or not. The purpose of this is to stabilize common area configurations on every floor and across the, so they can be amalgamated into a single load factor that can be applied to all of the tenants equally.

Extreme Measures is the editor and illustrator of the BOMA 2017 and BOMA 2024 Office Standards.

Standard Method for Measuring Floor Area in Office Buildings (ANSI Z65.1-1980)

The BOMA 1980 office standard is still used in some markets for determining usable and rentable areas in commercial office buildings. The BOMA 1980 Standard measures buildings on a floor-by-floor basis. It can be a simple and effective approach for measuring the Usable and Rentable Area of a single typical floor and its occupying tenants. Unfortunately, BOMA 1980 can be over-simplistic in its allocation of common area. This can result in punishing gross-up factors for floors with large portions of common area (usually ground floors and basements). The BOMA Z65.1-1980 Standard is no longer ANSI approved or supported by BOMA.

Key Terms

USABLE AREA means the actual occupiable area of a floor or tenant

RENTABLE AREA means the floor or tenant's USABLE AREA and its proportionate share of FLOOR COMMON AREA

FLOOR COMMON AREA refers to areas common to all the tenants of a floor, such as corridors, elevator lobbies, washrooms, janitor closets, telecommunications and utility areas. Floor Common Area is often found in and around a building core

MAJOR VERTICAL PENETRATION refers to stairs, elevator shafts, flues, pipe shafts, vertical ducts and the like, and their enclosing walls, which serve more than one floor of a building. Major Vertical Penetrations are excluded from Usable and Rentable Area

What About BOMA 1989?

There is a common misperception that BOMA 1989 is a distinct standard unto itself, however this is not the case. In 1989, BOMA republished the BOMA 1980 Standard to include a French translation and a supplementary question and answer document called "Answers to 20 Questions Frequently Asked about the BOMA Standard Method of Floor Measurement." The text is otherwise identical to the previous publication.

Standard Method for Measuring Floor Area in Office Buildings (ANSI/BOMA Z65.1-1996)

The BOMA 1996 office standard is still widely used in commercial office buildings today. The BOMA 1996 Standard measures buildings on a building-wide basis. It introduces the concept of Building Common Area (areas common to all of the tenants in a building). Due to the inclusion of Building Common Area, a building measured according to BOMA 1996 almost always yields higher Rentable Areas than the same building measured according to BOMA 1980.

Key Terms

USABLE AREA means the actual occupiable area of a floor or tenant

BASIC RENTABLE AREA means the tenant's USABLE AREA and its proportionate share of FLOOR COMMON AREA. Note: Basic Rentable Area is conceptually similar to BOMA 1980's Rentable Area.

RENTABLE AREA means the tenant's USABLE AREA and its proportionate share of FLOOR COMMON AREA and BUILDING COMMON AREA.

FLOOR COMMON AREA refers to areas common to all the tenants of a floor, such as corridors, elevator lobbies, washrooms, janitor closets, telecommunications and utility areas. Floor Common Area is often found in and around a building core.

BUILDING COMMON AREA refers to areas common to all the tenants of a building, such as ground floor lobbies, public corridors, concierge areas and fully enclosed mechanical or equipment rooms. Building Common Area is often found on Ground Floors, Basement Levels and Mechanical Penthouses.

MAJOR VERTICAL PENETRATION refers to stairs, elevator shafts, flues, pipe shafts, vertical ducts and the like, and their enclosing walls, which serve more than one floor of a building. Major Vertical Penetrations are excluded from Usable, Basic Rentable and Rentable Areas.

Office Buildings: Standard Methods of Measurement (2010) (ANSI/BOMA Z65.1-2010)

The BOMA 2010 office is very popular in real estate markets throughout North America and around the world. Like the BOMA 1996 Standard, the BOMA 2010 Standard measures buildings on a building-wide basis and therefore it is necessary to have complete building CAD data in order to determine rentable areas. The BOMA 2010 standard introduced many new concepts and definitions and renamed well known industry terms. For example, Floor Common Area became Floor Service and Amenity Areas and Tenant Usable Area became Occupant Area. Another notable difference is the exclusion of a Gross Building Area (or Construction Area) calculation. Instead, BOMA developed a separate standard for Gross Building Areas titled "The Gross Areas of a Building: Methods of Measurement". The biggest change however is that BOMA 2010 provides the option of selecting two distinct measuring methods; each of which will yield significantly different results. The two methods are known as Method A (Legacy Method) and Method B (Single Load Factor Method), summarized below. Furthermore, the standard allows real estate professionals the option of applying their own Capped Load Factor which is not to exceed the Load Factor(s) determined by Method A and/or Method B.

Method A (Legacy Method)

Calculates areas similarly to the BOMA 1996 ANSI/BOMA Z65.1-1996 Standard. An inherent conceptual weakness of BOMA 1996 is that like Tenant Usable Areas, Floor Common Area is applied to all Building Common Areas, but many Building Common Areas (although necessary to the operation of the building) are not directly used by tenants and therefore should not be grossed-up by Floor Common Area. For example, it has been questioned as to why a building mechanical room (Building Common Area) proportionately shares the washrooms (Floor Common Area) with the tenants who occupy space on the same floor. Clearly, only tenants should proportionately share washrooms. Method A of the BOMA 2010 standard attempts to mitigate this problem by segregating Building Common Area into Building Amenity Areas and Building Service Areas. The key difference being that only Building Amenity Areas (and of course Tenant Areas) are grossed-up by Floor Service and Amenity Areas (previously known as Floor Common Area). Building Amenity Areas are defined as areas in a building that provide a convenience to all tenants of a building and may include areas such as conference rooms, day care facilities, lounges, fitness centers and vending areas. Building Service Areas are defined as areas that are necessary for the building to operate and may include areas such as building mechanical and equipment rooms, building egress corridors and main and auxiliary lobbies.

Method B (Single Load Factor Method)

Many property managers and building owners have expressed a desire to apply a single gross-up factor to all the tenants in a building. Method B of the BOMA 2010 standard provides this option and in doing so, introduces several new approaches and concepts to building measurement. The most controversial is the allocation of Base Building Circulation, which is basically the minimum path (based on the architectural features and local regulations) on a multi-occupant floor which is necessary for access and egress to tenant areas. The process of applying this new concept could be viewed as interpretive to some extent since a "hypothetical" corridor needs to be established on each floor regardless of occupancy or physical conditions. Building Amenity Area, Building Service Area and Floor Service Area, are also introduced (defined below) but are all incorporated into a single new common area type known as Service & Amenity Areas. Under BOMA 2010, Method B, Base Building Circulation and Service & Amenity Areas are represented as separate and distinct areas, but in the calculations, they are combined on a building-wide basis and proportionately distributed to all tenants of the building, establishing the single load factor.

Key Terms

AMENITY AREA is space within a building that adds a convenience to more than one tenant. Amenity Area can either benefit the occupants of a specific floor (Floor Amenity Area) or the entire building (Building Amenity Area).

BASE BUILDING CIRCULATION (Method B Only) is the minimum, necessary path required (based on architectural features, local codes and other requirements) on a multi-occupant floor for access and egress.

BUILDING SERVICE AREA is an area of a building that provides services that are necessary for building occupancy.

EXTENDED CIRCULATION is a portion (usually within a corridor) of a tenant's area that is located outside of its physical boundaries.

EXTERNAL CIRCULATION is an unenclosed multi-occupant corridor which provides access and egress to tenant spaces. It must provide the only means of access and egress in order to be calculated as part of the rentable area.

FLOOR SERVICE AREA is an area of a floor that provides services that are necessary for occupancy on that floor.

LOAD FACTOR A is the total gross-up applied to tenants of a particular floor when using BOMA 2010, Method A.

LOAD FACTOR B is the single total gross-up ratio applied to all the tenants in a building when using BOMA 2010, Method B.

OCCUPANT AREA is the same as Office Area and Store Area in BOMA 1996. It is the areas of a building occupied by a tenant to house personnel, equipment, fixtures, furniture, supplies, goods and merchandise.

OCCUPANT + ALLOCATED AREAS (Method A Only) is essentially the same as Basic Rentable Area in BOMA 1996.

OCCUPANT STORAGE is space within a building that is used by tenants but does not have the services and finishes (such as HVAC) required to be considered Occupant Area. Occupant Storage is accounted for separately and is not part of the rentable area of a building.

VOID is the absence of a floor where a floor might otherwise be expected. A VOID is different than a Major Vertical Penetration and is not included in Method A or Method B calculations.

Differences from BOMA 1996 to BOMA 2010

BOMA 2010 is similar to BOMA 1996 but there are some key differences. For example, in BOMA 1996, building common area is allocated a proportionate share of floor common area, just like a tenant area. Therefore, a corridor (allocated as floor common area), which leads to tenant spaces and building common spaces is proportionately allocated to both, since it provides access to both. In BOMA 2010 however, building common area is divided between building amenity area and building service area. Building amenity area is included in the proportionate allocation of floor common area along with tenant areas (like building common area in BOMA 1996), but building service area is not. This is designed to help prevent rentable areas from fluctuating in the building when floor common areas change.

In BOMA 1996, occupant storage was included in the rentable area of a building. In BOMA 2010, occupant storage that is not suitable for human occupancy (such as below grade storage) is measured and disclosed but omitted from rentable area. Therefore, the total building rentable area under BOMA 2010 is often lower than BOMA 1996. BOMA 2010 also allows landlords to apply a capped load factor to occupants on a floor-by-floor basis. Landlords were already doing this in BOMA 1996, but the practice was not endorsed by BOMA. This resulted in many “Modified BOMA” area studies which was not good for the standard. This issue was mostly resolved by officially allowing capped load factors in BOMA 2010.

Finally, BOMA 2010 is generally a more fair, precise and flexible standard in its allocation of common areas and the document itself is much more detailed than any BOMA office standard before it, which helps greatly with consistency when applying it.

Standard Method for Measuring Floor Area in Office Buildings (ANSI/BOMA Z65.1-2017)

The BOMA 2017 office standard is similar to BOMA 2010 in many respects in that it shares the same overall framework, but many improvements, enhancements and clarifications to the standard have been made. The document itself is progressive in its physical design but it is also well positioned to reflect the present-day and future trends in real estate. The most significant change to the standard is the inclusion of some exterior areas in the rentable area of the building. Tenant controlled balconies, rooftop patios and covered galleries are included as rentable area along with balconies and rooftop patios enjoyed as a building amenity.

A key objective of BOMA International was to make the standard compatible with the International Property Measurement Standards (IPMS). The BOMA 2017 Office Standard has been tweaked in several areas to be compatible with the area calculations known as IPMS 2 and IPMS 3, which make the office standard even more relevant to markets outside of North America.

Another welcome change is the introduction of Inter-Building Areas. Inter-Building calculations present a methodology for allocating areas common to tenants other than by floor or by building by allowing certain service and amenity areas to be proportionately allocated to specific groups of tenants. In the past this has been called “Limited Area” or “Private Common Area”. The calculations also work perfectly in office complex situations where service and amenity areas might be allocated to tenants across multiple buildings (sometimes referred to as “Complex Common Area”). Inter-Building calculations really allow for a more targeted approach to allocating areas to tenants based on the areas they actually benefit from and; consequently, not allocating areas to tenants that don’t benefit from them, which really helps with the overall fairness of the standard.

BOMA 2017 also allows landlords to apply capped load factors on a tenant-by-tenant basis rather than a floor-by-floor basis. This will help landlords negotiate deals with prospective tenants on an individual basis in a way that reflects the uniqueness of each lease negotiation.

BOMA 2017 has renamed several key terms to be more intuitive and easier to understand. For example, “Interior Gross Area” has become “Boundary Area”, “R/U Ratio” has become “Floor Allocation Ratio” and “R/O Ratio” is now “Building Allocation Ratio”. Best of all, “Occupant + Allocated Area (O)” is now simply “Floor Allocation”. Also, the new Global Summary of Areas has a “Rentable Exclusions” column that includes major vertical penetrations, occupant storage, parking and public covered galleries.

Key Terms

ACTUAL LOAD FACTOR is sometimes referred to as the organic load factor. It is the calculated load factor, representing the entire allocation of common areas to tenants. It is also used as the maximum allowable Capped Load Factor.

ANCILLARY RETAIL is space used by a retail occupant which is outside the physical boundaries of their space, such as a display area.

BOUNDARY AREA is the peripheral extent of all measured areas.

CAPPED LOAD FACTOR is an optional fixed ratio or percentage allocation of common area to tenants that cannot exceed the Actual Load Factor.

DEDICATED RESTROOM is a room with a sink and toilet that a tenant has exclusive use of.

FINISHED ROOFTOP TERRACE is a legally renovated rooftop area that is either tenant controlled or an amenity to the building.

INTER-BUILDING AREA is an area of a building that provides a service or amenity to a specific group of tenants.

RENTABLE EXCLUSIONS are all the areas to be excluded from rentable area (major vertical penetrations, occupant storage, parking and public covered galleries) combined in a single column in the Global Summary of Areas.

TENANT ANCILLARY AREA are those areas outside of the physical boundaries of a tenant that is also included in the occupant area of the tenant, such as interior door setbacks and extended circulation.

Differences from BOMA 2010 to BOMA 2017

The BOMA 2017 Office Standard was released in October 2017 and represents a significant leap forward for the standard. Several of the changes focus on the formatting of the document itself, which is designed to be easily digested. One of the goals was to make this standard more approachable to owners, property managers and brokers who might not need to apply the standard, but do need to understand it on a cursory level. The changes made with the general organization, copy and illustrations lends itself well to achieving this goal. However, the document remains primarily a technical manual, focused on how to apply the office standard accurately, consistently and objectively.

BOMA 2017 removes the Public Pedestrian Thoroughfare Boundary Condition. In previous versions of the standard, ground floor tenants with street frontage were measured to the outer surface of exterior walls, rather than the inside finished surface. The removal of this condition results in slightly reduced rentable areas, but this was a confusing nuance of the standard and BOMA decided for overall consistency, that all tenant spaces should be measured the same.

Major Vertical Penetrations are no longer excluded from rentable area at their lowest level in 2017. Previously, this rule was already applied to vertical service areas, such as pipe and mechanical shafts, but not to vertical circulation areas, such as stairwells and elevator shafts. It was confusing to apply two different rules to Major Vertical Penetrations. This change results in higher rentable areas but there is now one cohesive rule that respects one of the most basic principles of the standard - that floor space is rentable area and openings in the floor are not.

BOMA 2017 also finally includes an official methodology of calculating amenity and service areas that are in use by specific groups of occupants, rather than simply allocating such spaces to an entire floor or to the entire building. BOMA calls this Inter-Building Area and it really allows for a great level of customization to the standard. It helps to ensure that Tenants will not pay for space in the building that they do not derive a benefit from and it can also be applied across buildings in an office complex. This doesn’t have any impact on the total rentable area of a building, but it does distribute proportionately allocated areas more fairly.

Another key change made was to allow capped load factors to be applied on an occupant-by-occupant basis rather than a floor-by-floor basis. This will go a long way in helping landlords and tenants negotiate leases appropriate to the market at any given time, while still adhering to the standard.

Finally, the BOMA Office Standard is now compatible with the International Property Measurement Standards or IPMS. IPMS is an international committee developing a full suite of measurement standards focused on producing a consistent measurement methodology for building valuations across international markets. BOMA’s direct compatibility with IPMS will enhance its usefulness and further position BOMA as the de-facto standard to use internationally.

Making the standard compatible with IPMS had its complications, but there is a certain synergy to its timing. In particular, it really made BOMA reevaluate unenclosed exterior areas and consider the real world changes occurring in the industry. In today’s market, owners and tenants are demanding that their buildings include well-appointed exterior amenities where occupants can work or refresh in a finished outdoor environment. The standard needed to adapt to these changes in the marketplace and so the standard will allow balconies, covered galleries and rooftop patios to be included as rentable area in certain conditions.

Extreme Measures is the editor and illustrator of the BOMA 2017 Office Standard.