The IBC (International Building Code) and the IPC (International Plumbing Code) provide prescriptive requirements to calculating the minimum number of plumbing facilities needed in a building, including toilets, sinks, & drinking fountains.

**Calculate Occupant Load**

First you need to calculate the number of occupants for a space. The occupant load table in chapter 10 of the building code show the square feet per occupant based on the function of the space. Please see the table below:

So, let go through an example of a bar/ tasting room that is 1,000 SF.

If there is loose, non-fixed furniture, we would use the occupant load factor above of 15 net sf.

The difference between net & gross is that net sf does not include unusable areas such as wall depths, hallways, etc…whereas gross sf includes all areas of the building. If you have a fixed bar in your tasting room, that area can be discounted from the net sf.

1,000 / 15 = 67 occupants. Simple as that! Of course, these calculations can get much more involved when you begin to have multiple functions of space, etc. Hint… the back of the bar where customers do not go can actually be counted as a business occupancy, which is a different factor of 100 sf per person!

**Calculate Minimum Number of Plumbing Fixtures**

**Now we have determined that we have 67 people. **Lets figure out how many bathrooms that equates to.

We go to Table 2902.1 in the IBC (or Table 403.1 in the IPC) to resolve the minimum plumbing fixtures required. The table takes into consideration the occupancy, and a more descriptive use of the space for these purposes. Check out the chart below:

For a bar, we would simply go with the A-2, Bar category. The Water Closets (Toilets) are required to be 1 fixture per 40 people, of each sex. So, We have 33.5 Males, and 33.5 Females. 33.5/40 is .84, so we are required to have 1 toilet for each sex. In most cases, you are required to have separate facilities for each sex (i.e. a separate mens room and womens room), but there are a few exceptions. If there are less than 15 occupants, a shared bathroom can be used.

The lavatories (sinks) would be 33.5/75= .45, which would also just round up to 1 sink for each sex.

The occupant loads and bathrooms can be a critical consideration when designing or remodeling a facility. If you are on the cusp of going over 1 toilet for each sex, that could mean totally different and larger bathrooms. About 80 occupants (40 male and 40 female) would be the threshold to stay under to keep it at 1 toilet for each sex. That translates to approximately 12oo sf for a tasting room area.

Written By:

Matthew Taylor-Rennert

Meghan Anderson says

Hi there,

The 2018 IBC 2902.2 Separate Facilities has added section “4: Separate facilities shall not be required in business occupancies in which the maximum occupant load is 25 or fewer.”

Does this mean that a business of 2500 sq ft only needs 1 bathroom (for both sexes and for employees and the public)? I’m confused by the new code exception. Thank you, Meghan

Matthew Taylor-Rennert says

Hi Meghan,

Thanks for your comment, and interesting to see the changes to the newly adopted 2018 codes.

To answer your question, in short, YES: according to 2018 IBC 2902.2, Exception 4, if you have a business occupancy with an occupant load of 25 or fewer, then you can have just (1) single user / unisex bathroom.

I’m assuming you got to 2,500 sf by using the calculated occupant loads from IBC 1004.5. So, 2,500 sf divided by 100 sf/pp is 25 people. BUT, I just noticed the 2018 codes changed this rate. It is now 150 sf/ pp for business uses. So, under the new code, you could have up to a 3,750 sf office and have 25 occupants/ 1 unisex bathroom (3750/ 150 =25 people).

It’s important to note also that you can have a business OCCUPANCY, but then if you have, say a 500 sf conference room within the space that is really assembly FUNCTION per Table 1004.5 (15 sf per person), then that area would be 500/15 = 34 people. In that case, you would not be able to use the 1 bathroom exception.

Thanks,

Matthew Taylor-Rennert

Dan says

Please show an example with a M use. The toilet count is not divided nicely like the example above. Why is that?

Matthew Taylor-Rennert says

Hi Dan,

Mercantile has a very minimal toilet count. Only 1 required per every 500 occupants. So, say you had 1,000 sf M use, divide that by the occupant load factor of 60 people per sf and you get 17 occupants. So, since you only need 1 toilet and 1 lavatory per 500 occupants you only need 1 of each. In most other occupancies you would need 1 toilet and 1 lavatory for each gender. But, per IBC 2902.2, exception 3, you do not need separate facilities in M occupancies under 100 occcupants. So, in this example, you would only need just 1 toilet and 1 lavatory total for the entire 1,000 sf M occupancy.

Jeff Porter says

What if you have a restaurant with a dining room and a bar room with dining tables also, do you have take the net square footage of the bar at 1:40 and the dining room at 1:75 or can I take the whole net s.f. at 1:75?

Matthew Taylor-Rennert says

Hi Jeff,

Thanks for commenting. I would use the two separate rates for each area, 1:40 for the bar area, and 1:75 for the restaurant. That would be the prudent way to go. Keep in mind that rate is based on the occupants for each area, not the square feet. So first you must calculate the occupant loads, and then use those rates on the number of occupants.

You mention the bar room has dining tables also. So, you could make an argument to use the 1:75 for that area too if you needed to. For instance, if it meant the difference of an extra toilet, and more area that you maybe don’t have, then it might be worth pushing for that determination with your AHJ (Authority Having Jurisdiction)…. maybe explaining that the area is not a crowded bar or something like that. Ultimately, its up to the AHJ.

Hope that helps! Thanks, Matt Taylor-Rennert

faesavoirfaire says

How can you calculate the number of universal and/or ada plumbing fixtures required per occupants?

Matthew Taylor-Rennert says

There must be at least 1 accessible toilet/ sink in a public restroom, per IBC 1109.2. ADAAG 213.3.1 also simply requires 1 toilet compartment to be accessible in a multi-compartment bathroom. Note that if 6 or more toilet compartments are required, one other compartment must meet the requirements of 604.8.2, which is a 60″x35-37″ wide compartment.

So, in summary the number of accessible stalls within a bathroom is not dependent on number of occupants. If you have a single user restroom, then it must be completely accessible. If you have a bathroom with multiple compartments, just 1 stall has to be accessible, along with a single accessible lavatory, soap, towel, etc.

Stu Smith says

For a detoxification I-2 condition 2 use. Table 403 lists 1/25 toilets (male & female combined) for employees and 1/75 (male & female combined) for visitors. The occupant load of the building is 74. How do I divide the occupant load for visitor to employee.

Thank you

Matthew Taylor-Rennert says

Hi Stu,

Sorry for the very delayed response on this. So, you would need to take your total occupant load, and figure out how many is visitors and how many employees. You probably know how many employees there are during a shift, so I would use that. For instance, if there are 20 employees, then there would be 54 visitors. Then you’ll take 20 x 1/25 = 0.8 toilets. = 0.4 male and 0.4 female. And for visitors 54 x 1/75 = 0.72 =0.36 male, 0.36 female. So, having 2 single user restrooms for each gender would suffice.

Steven Platt says

Thank you for the simple and easy to follow article and comment responses. I’m doing a project with business areas, mercantile areas, and assembly (workout and locker) areas. There is one mens room and one womens room to supply facilites to all three. Do I need to calculate stalls separately? Say 2 for business, one for assembly, and one for mercantile? Or do I merge them all together into one – but if so then which occupancy do I use?

Matthew Taylor-Rennert says

Hi Steven,

Glad it has helped! Assuming all three occupancies have access to these bathrooms- You essentially merge them. So, say you have a fractions, you add them together first and then round up.

For instance, making up the resultant numbers here.

Mercantile Male = 0.4 toilets

Business Male = 0.5 toilets

Assembly Male = 0.6 toilets

Total Male = 1.5 Toilets= Round up to 2 …. this could be a bathroom with a single ADA toilet stall and a urinal/

Mercantile Female= 0.4 toilets

Business Female= 0.5 toilets

Assembly Female= 0.6 toilets

Total Female = 1.5 Toilets= Round up to 2 …. this could be a bathroom with a single ADA toilet stall and a another smaller stall.