A question that comes up on many projects is how to correctly determine the occupant load and the total number of required plumbing fixtures for spaces in new buildings. In this post we will walk through the process of how to determine the occupant load and plumbing fixture count, as well as the options and processes available to possibly reduce the number of required fixtures.
Per the Chicago Plumbing Code (CPC 14P and Chapter 18-29 of the Chicago Municipal Code), plumbing fixtures must be provided for all occupied spaces, including amenity spaces. The occupants for each space are calculated based on the requirements of the Chicago Building Code, Section 1004.
Once you have determined the total number of occupants based on the building code, the occupant load is then split by gender, assuming an even split between the genders. If there are any partial occupants, per section 18-29-403.1.1, the number of male occupants is to be rounded down, and the number of female occupants is to be rounded up. Note that exceptions are provided, including if statistical data can be provided to the Department of Buildings documenting that the gender ratio is different, or in certain specific occupancies.
After the total number of occupants per gender is calculated, then the total number of required fixtures is determined per table 18-29-403.1. The number of required fixtures is based on the use of each space, rather than the overall occupancy of the building. The use of the spaces in this table is different from the occupancy classification in the building code, and should be carefully reviewed to determine the most accurate classification of the space. Note that amenity spaces are typically viewed as most similar to the assembly use for restaurants, bars,taverns, or other facilities with a similar use. In a residential use building, plumbing fixtures are still required to be provided for the amenity spaces in the building, as the use of those spaces is separate from the residential use of the dwelling units. Note that this section specifically includes both indoor and outdoor amenity spaces.
As noted in our previous blog post, linked here, non-gendered/non-separated toilet rooms are now permitted to be provided per 18-29-403.2.1, however this does not reduce the total number of required fixtures, only allows for them to be located in a single location.
It is our understanding that DOB is no longer permitting reductions based on meeting and exceeding the Illinois Plumbing Code, which has much lower occupancy and fixture calculations. The code notes that the number of occupants can only be reduced on the basis of access controls or non-simultaneous occupancy.
Some spaces have been previously allowed to be reduced based on access control, such as amenity spaces being only available to residents, or for spaces such as movie theaters that are designed, with fixed seating and furniture, to only accommodate a specific number of persons. Non-simultaneous uses can also be used to reduce the number of occupants, such as pre-function spaces in theaters, where occupants of one space move into another, rather than having both being fully occupied at the same time.
If a reduction is desired, the request should be submitted to DOB through the Alternative Code Approval Request process (ACAR). MAPS is happy to assist with this process, but if you are submitting the request yourself, the documentation should indicate how many fixtures are required, how many fixtures you are providing, and the basis for the reduction request.
While only two options are available to reduce plumbing fixtures per the letter of the code, MAPS has also had some success with requesting reductions based on the experience of the building/space operator, and what their experience is with what the necessary number of fixtures for the intended use, however this approval is on a case by case basis, and is not always approved. Typically, these requests will require some additional supporting information, documenting how the requested number of fixtures was determined.
Note that no matter how the reduction is being determined, generally the total number of fixtures can only be reduced by a maximum of 20%.
Please feel free to reach out if you have any questions regarding the required plumbing fixture calculations.