2021 IPC Chapter 4
Chapter 4 answers a question every commercial project asks early: how many water closets, lavatories, drinking fountains and service sinks must this building have? The answer comes from Section 403 and Table 403.1, plus a handful of rules about who may use the rooms and how far away they can be. It is arithmetic plus judgment, and it is where a plans reviewer catches an undersized restroom before anything is built. Houston enforces the UPC rather than the IPC (Lesson 1), so treat the ratios here as the method, and check the adopted code's own fixture table for the actual count.
Fixtures are provided in the minimum number shown in Table 403.1, based on the actual use of the building or space. Uses the table does not list are decided one at a time by the code official, and the number of occupants comes from the International Building Code (403.1). For a restaurant, the IBC's floor-area factors do the work: 15 square feet net per occupant for assembly space with tables and chairs, 200 gross for a commercial kitchen, and 150 gross for business areas (2021 IBC Table 1004.5). Each ratio in Table 403.1 gives one fixture for the number of persons shown or any fraction of that number (footnote a), and seasonal outdoor seating counts toward the occupant load (footnote d).
Here are the rows GCHS meets most often, rebuilt in our own layout. Ratios are per sex unless a single number applies to both.
| Use | Water closets | Lavatories | Drinking fountain |
|---|---|---|---|
| Restaurants, banquet halls, food courts | 1 per 75 | 1 per 200 | 1 per 500 |
| Places of worship | 1 per 150 men, 1 per 75 women | 1 per 200 | 1 per 1,000 |
| Business (offices, banks, ambulatory care) | 1 per 25 for the first 50, then 1 per 50 | 1 per 40 for the first 80, then 1 per 80 | 1 per 100 |
| Educational | 1 per 50 | 1 per 50 | 1 per 100 |
| Mercantile | 1 per 500 | 1 per 750 | 1 per 1,000 |
| Storage, low and moderate hazard | 1 per 100 | 1 per 100 | 1 per 1,000 |
| Adult and child day care | 1 per 15 | 1 per 15 | 1 per 100 |
Nearly every row also calls for one service sink, though business and mercantile spaces with an occupant load of 15 or fewer do not need one (footnote e). An apartment house works differently: one water closet, lavatory and bathtub or shower per dwelling unit, a kitchen sink in each unit, and one clothes washer connection for every 20 units.
To find the fixtures for each sex, divide the total occupant load in half, apply each ratio to that half, and round every fraction up to the next whole number (403.1.1). When a building holds more than one occupancy, sum the fractions for each fixture across all the occupancies first, then round the total up. Three exceptions matter. Approved statistical data can justify a split other than 50-50. Multiple-user rooms designed for all genders are counted at 100 percent of the total load, with each fixture type meeting the A117.1 accessibility standard and each urinal placed in a stall. And single-user rooms need no sex distribution at all (403.1.1 exceptions).
Where fixtures are required, separate facilities go in for each sex (403.2), with several exceptions. None is needed for dwelling units and sleeping units, or in a structure or tenant space with a total occupant load of 15 or fewer, customers and employees together. Mercantile occupancies with a maximum load of 100 or fewer and business occupancies with a maximum load of 25 or fewer are also excused. Single-user rooms need no sex designation, and a room containing both water closets and lavatories can serve both sexes if privacy for the water closets is provided under 405.3.4 and urinals sit in a visually separated area or in stalls.
Fixtures in single-user toilet and bathing rooms, including the family or assisted-use rooms the IBC requires, count toward the building's total, and those rooms are identified as open to everyone regardless of sex (403.1.2). The total can be met with separate facilities, with single-user rooms, or with any mix. Where separate facilities are required and each needs just one water closet, two family or assisted-use rooms may serve as the two separate facilities (403.2.1). Signs designate the sex where 403.2 requires it, and directional signs must be visible from the main entrance (403.4, 403.4.1).
Customers and visitors must be given public toilet facilities, and employees must have facilities too, either separate or combined with the public ones (403.3). Public facilities are not required in an unattended parking garage or in a takeout or pickup space with a public access area of 300 square feet or less. The route to public toilets must not pass through kitchens, storage rooms or closets, and the public must have access whenever the building is occupied (403.3.1). A toilet room may not open directly into a room where food is prepared for service to the public (403.3.2).
Outside malls, required toilet facilities must be no more than one story above or below the space they serve, and the path of travel cannot exceed 500 feet; in malls the limit is 300 feet (403.3.3, 403.3.4). Pay facilities must be extra to the required minimum, and required facilities are free (403.3.5). A multi-occupant toilet room's door cannot be locked from inside, except in a family or assisted-use room (403.3.6). Accessible fixtures follow IBC Chapter 11 and the A117.1 standard (404).
Urinals may stand in for water closets, but only up to a limit. In each toilet room, urinals cannot replace more than 67 percent of the required water closets in assembly and educational occupancies, and not more than 50 percent in all others (424.2). Since you cannot exceed the percentage, round the allowed number of urinals down.
Drinking fountains are not required at an occupant load of 15 or fewer (410.2). Where fountains are provided on a floor, in a secured area or on an exterior site, at least two are needed, one usable by a person in a wheelchair and one for standing users, though one dual-spout unit can serve as both (410.3.1). In tenant spaces, public fountains within 500 feet, and no more than one story away, can serve the space (403.5). Service sinks in mall tenant spaces may be shared if they are within 300 feet on an accessible route (403.6).
The figure works a Group A-2 restaurant with 3,000 square feet of dining and a 1,000-square-foot kitchen: occupant load 205, half for each sex is 102.5, and the result is 2 water closets and 1 lavatory per sex, 1 drinking fountain by the ratio (provided as two fountains or one dual-spout unit under 410.3.1) and 1 service sink. Urinals could replace 1 of the men's 2 water closets. Now a Group B office of 4,500 square feet gross: 4,500 divided by 150 is 30 occupants, or 15 per sex. Water closets: 15 divided by 25 is 0.6, rounded to 1 per sex. Lavatories: 15 divided by 40 is 0.375, rounded to 1 per sex. Drinking fountain: 30 divided by 100 is 0.3, so 1. Because the load of 30 is over 25, the office needs separate facilities, or single-user rooms that count toward the same numbers.
In the field
A community group wants a small cafe in a former retail unit with a 20-seat dining area. On the plan, the only route to the single restroom passes through the kitchen storage room. Before anyone argues fixture counts, check 403.3.1: the route to public toilets cannot pass through kitchens, storage rooms or closets. Even if the count is right, the layout fails. Turning the restroom door to open off the dining area, and keeping it from opening directly onto the food-preparation area under 403.3.2, fixes both problems for far less than a redesign after the rough-in.
1. A Group B office has an occupant load of 60, split evenly by sex. Applying Table 403.1 (1 water closet per 25 for the first 50 persons per sex), how many water closets does the women's room need?
2. A Group A-2 restaurant has an occupant load of 150, divided evenly by sex. Table 403.1 requires 1 water closet per 75 persons for each sex. How many water closets does the men's room need?
3. Under Section 403.1.1, how are fractions handled after applying a fixture ratio to an occupant load?
4. A restaurant's dining room is 3,000 square feet of net floor area with tables and chairs, at 15 square feet net per occupant. What occupant load does that space contribute?
5. A single-tenant Group B space of 4,500 square feet gross is planned at 150 square feet gross per occupant. Under Section 403.2, what does its occupant load of 30 mean for toilet rooms?
6. A small mercantile shop has a maximum occupant load of 90. Under Section 403.2, does it need separate toilet rooms for men and women?
7. A takeout pizza counter has a public access area of 250 square feet. Under Section 403.3, are public toilet facilities required?
8. A floor plan shows the only route to a customer restroom passing through a kitchen storage room. What does Section 403.3.1 say?
9. In a building that is not a mall, what is the maximum path of travel to required toilet facilities under Section 403.3.3?
10. An assembly occupancy men's room requires 4 water closets. Under Section 424.2, what is the greatest number of urinals that may substitute for water closets?
11. Under Section 410.2, drinking fountains are not required when the occupant load is:
12. A new clinic provides two single-user family or assisted-use toilet rooms. Under Section 403.1.2, how do the fixtures in those rooms count?
13. A Group B office needs a drinking fountain at 1 per 100 persons, with an occupant load of 30. How many are required by the ratio, before Section 410.3 is applied?
14. A designer lays out a toilet room door that opens directly into a restaurant kitchen where food is prepared for service to the public. Under Section 403.3.2, this is: