Single Tenant Office Floors–Should Restrooms be Considered Part of the Usable Office Area or Occupant Area?

BOMAbathroomThis question is certainly near the top of our list in the “Frequently Asked” and “Most Misunderstood” categories.  It has come up in numerous discussions we’ve had with our clients and colleagues—whether they are building owners and managers, prospective office tenants, or other architectural and building measurement firms. 

To some, logic would dictate that whatever area of a floor is controlled and accessed exclusively by a particular tenant, that floor area is included as part of the tenant’s area.  Following this, the restrooms on a single tenant office floor could be measured as part of the usable office area (Office96) or occupant area (Office2010).  This measurement practice is actually quite common.  In fact, prior to the publishing of the 2010 Office standard, it had grown to become a central facet of office building measurements in various local and regional real estate markets, mostly driven by a desire to advertise lower add-on factors. Unfortunately, the BOMA office measurement standards clearly assert that this measurement practice is erroneous.

Here’s what BOMA says specifically on the matter:

BOMA 1996 Office Standard:

The following excerpts are from ANSI/BOMA Z65.1-1996 Standard Method for Measuring Floor Area in Office Buildings

  • OFFICE AREA shall mean the area where a tenant normally houses personnel and/or furniture, for which a measurement is to be computed
  • USABLE AREA shall mean the sum of the USABLE AREAs of OFFICE AREAs, STORE AREAs, and BUILDING COMMON AREAs of a floor.
  • FLOOR COMMON AREA shall mean the areas on a floor such as washrooms, janitorial closets, electrical rooms, telephone rooms, mechanical rooms, elevator lobbies, and public corridors which are available primarily for the use of tenants on that floor.

The following excerpts are from “Answers to 26 Key Questions about the ANSI/BOMA Standard Method for Measuring Floor Area in Office Buildings

  • 23. Q: On a single tenant floor, are the elevator lobby and restrooms considered Usable Area?
  • A: The BOMA Standard defines Usable Area as space that tenants can actually occupy and use and may allocate to house personnel and furniture…Restrooms are not considered Usable Area under the Standard, although they are part of Rentable Area.

BOMA 2010 Office Standard: 

The following excerpts are from ANSI/BOMA Z65.1-2010 Office Buildings:  Standard Methods of Measurement

  • Occupant areaa portion of a building where an occupant normally houses personnel, equipment, fixtures, furniture, supplies, goods or merchandise
    Discussion:  In the predecessor standard, occupant area was termed “office area” or “store area” but the distinction between those terms are removed in the 2010 Office Standard. An occupant generally has control over its occupant area (except for extended circulation) and determines use within the pre-established guidelines or rules.  However control over an area does not make it occupant area, with the most common example being restrooms on single occupant floors.

It’s clear from the excerpts above that restrooms were never intended to be part of the usable office area (office 96) or the occupant area (office 2010)—even on a single tenant floor—although they will be part of the calculated rentable area.  Now, if you are familiar with the calculations you may be wondering what difference it makes—since there is only one tenant the entire restroom area will be allocated to that tenant in its rentable area.  In other words, the rentable area that is calculated for the single tenant suite is the same whether I call the restroom usable/occupant area or floor common/floor service area.  This is true, and is a likely reason that the practice became common when applying the BOMA 1996 Office standard (it does make for a more marketable add-on factor after all).  So if it doesn’t affect my rentable area results, is it imperative that I follow the BOMA standard to the letter in these cases?  Yes!  I go back to the purpose of using these measurement standards in the first place.   They are clearly stated in the BOMA 2010 Office standard:

  • To permit clear communication among all participants in the commercial real estate industry
  • To foster consistent, unambiguous measurement of rentable areas
  • To allow comparison of values on the basis of a clearly understood and generally agreed upon method of measurement

Although it may seem negligible to the rentable area results how restrooms are classified and measured on a single tenant floor, it is crucial to clear communication, unambiguous measurements, and to the comparative value attained by using the standard methodology.

To illustrate, I offer a common scenario that we have experienced time and time again.  A prospective tenant would like us to verify the rentable area of the suite they are looking at occupying.  Since we won’t be measuring the entire building, we tell them that we can measure their occupant area (BOMA 2010) per the BOMA standard, and apply the load factor that the landlord has provided via their BOMA calculations.  It is not uncommon in this exercise to come up with several hundred square feet difference in our results when compared with the landlord’s.  After some comparative analysis and conversations with the stakeholders we finally find out that the landlord has included the restrooms in the occupant area, thus understating the load factor.  So, our final word to the tenant is that while the rentable area can be verified as correct based on the given information, the landlord has overstated the size of your Occupant Area and understated the Load Factor (see illustration).


10th Floor Full Floor Suite Summary
Landlord Version Verified Version
Occupant Area 16,588 16,023
Load Factor 1.0851 1.1234
Rentable Area 18,000 18,000

As the two different sets of numbers illustrate, the verified results paint a much different picture of the prospective space than the numbers that were originally provided by the landlord.  The tenant may question just how desirable the space is now that they understand how the landlord’s numbers were derived.  It’s a case of paying the same amount for much less than anticipated.  On the other hand, while the landlord may not have been aware that there were any issues with how their rentable area results were obtained, they may now experience liability concerns after realizing that they cited the BOMA standard although their methodology was not in compliance.  The solution to all of this miscommunication is to simply perform all measurements and calculations in adherence with the BOMA standards.  Doing so will bolster confidence in real estate negotiations and uphold the aim of measurement standards to “permit clear communication among all participants in the commercial real estate industry”.

Do you have questions or need help conducting an area study?
Contact Gensler’s Area Analysis team:
Call 844.412.9251 |

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