Navigating the Building Code – Part 3 (Required Plumbing Fixtures)

This installment of Navigating the Building Code examines pluming fixtures and the role they play in planning and space layouts.  Required plumbing fixture counts are the number of each fixture that the code prescribes as necessary.  The number of fixtures directly relates to the size and square footage allocated to restrooms and the plumbing systems.  In the code there is a chart that gives the plumbing fixture calculation factors to determine the number of required fixtures.

“Why can’t we just remove that restroom to save space and make the circulation better?”  More often than you would think this question is posed by a client (typically in a commercial design situation), if there are more than two restrooms (one male and one female), clients tend to think of them as “extra.”  The typical answer is that the code requires it, and the architect tries to move the conversation along.  But, it is important to know what the code actually states and the options available to meet code in the most efficient and cost effective way possible and not view those required restrooms as “extra.”

Residential Applications

Residential fixture counts are more straight forward in their calculations.  Typically, fixtures for residential projects are calculated on the number of units in a facility.  In most cases, only 1 water closet (toilet), 1 lavatory (restroom sink), 1 bathtub or shower, 1 kitchen sink, and 1 washing machine are required per dwelling unit.  The fixture count requirements for residences is a way to prescribe and define that a home needs to have a restroom.  It is important to verify the requirements with the building department and/or authorities having jurisdiction for the project.

Minimum Number of Required Plumbing Fixtures

While the code doesn’t prescribe the number of restrooms in a facility it does state the required number of fixtures (water closets, lavatories, bathtubs and/or showers, drinking fountains, or other fixtures).  How the number of required fixtures are incorporated into the building is up to the architect and client to determine.

The required number of fixtures is based on the occupant load of the building (see Navigating the Building Code – Part 4 – Occupant Load).  Once the occupant load is known, the Plumbing Systems section of the code explains how to calculate the number restroom fixtures required.  In general the larger the occupant load, the more restroom fixtures the client will need in their facility.  When calculating fixture counts, any fractional amounts must be rounded up to the next whole number.  So if the calculation determines that 5.2 lavatories are required, then the facility would need 6 lavatories.  Each occupant classification (see Navigating the Building Code – Part 1 (Use and Occupancy)), will have different requirements for the load factors to calculate the total number of fixtures.

For example, if a facility is a restaurant (occupant classification – Assembly A-2), and the occupant load is determined to be 300 occupants, then the required amount of fixtures (based on IBC 2018 table 2902.1), would be 4 water closets, 2 lavatories, 2 drinking fountains, and 1 service sink.  In this case the client and architect could choose have 2 restrooms, each with 2 water closets, 1 lavatory, and 1 drinking fountain directly adjacent to each restroom (figure 1.1).  A second option would to be 4 single use restrooms, each with 1 water closet, 1 lavatory, and the drinking fountains located as best fits (figure 1.2).  In this second situation, 2 of the lavatories would be in excess of the required amount, but that might serve the functions of the spaces better.  Again, there are options available for the allocation of fixtures to best suit the project.

Restrooms Example 1Figure 1.1Restrooms Example 2.jpgFigure 1.2

Women’s and Men’s Fixture Counts

One major (and sometimes overlooked in the preliminary stages) factor in determining the number of fixture counts is that their needs to be designated water closets for men and women.  The code requires that half the water closets are designated for women and half are designated for men.

In the restaurant example above, 2 water closets and 1 lavatory would be required to be designated for women, and 2 water closets and 1 lavatory would be required to be designated for men.   The two allocations explained above would meet this requirement because of the equal distribution of fixtures.  The example would no meet code if the women’s restroom had 3 water closets and the men’s restroom had 1 water closet.  Even though the total number of water closets would be met (4), the distribution of women’s and men’s does not meet the code (figure 1.3).

Restrooms Example 3.jpgFigure 1.3

Restroom Locations

Another factor set forth in the code, that can play a major role in the space design and layout of a facility, is the need for access to restrooms.  Generally, the general public must be able to access the required restroom designated for the public.  So, a customer or visitor to a structure must be able to follow a safe path of travel to get to a restroom without passing through spaces such as kitchens, closets, storage rooms, and even private offices.  The code contains a few other rules regarding locations, for example restrooms are not permitted to open directly into a room used for food preparation, that are described in the Plumbing Systems section of the code that your architect needs to be familiar with from the onset of the project.

Exceptions and Variances

There are some instances where a project qualifies for exceptions from the required number of fixtures, or a variance can be requested.  Urinals in lieu of water closets for men’s restrooms is a typical exception.  In our restaurant example, a variance can be requested to not have the drinking fountain requirement.  The rationale behind that variance is that the restaurant would have clean, drinkable water available to serve as requested.  The variance would still need to be approved by the authority having jurisdiction.

You are more than welcome to contact us regarding any questions you may have regarding plumbing fixture counts or if you would like Gustin Design Services to do a plumbing fixture count analysis for you project –

Leave a Reply

%d bloggers like this: