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Fixture Calculations

rgrace

rgrace

Sawhorse
Joined
Feb 18, 2010
Messages
250
Location
Culpeper County, Virginia
(IPC) Assume a three story office building with an occupant load of 100 per floor. If I calculate the required water closets per floor, I would need 2 male and 2 female for each floor, or a total of 6 and 6 for the entire building. If I apply 403.3.3 (and the layout complies), I can put all 12 of the required water closets on the second floor, correct? Now, what says that I cannot combine my occupant loads from all three floors to do my calculation? If my "building" has 300 occupants, and I can comply with 403.3.3, if I calculate water closets for 300 occupants, I would only need a total of 4 and 4 for the entire building, not 6 and 6. What code and code section(s) does or does not permit me to calculate the plumbing fixtures for the total occupant load of this building? Obviously, I would prefer to install 8 water closets instead of 12.
 
You just needed to read a little farther...

403.1.1 Fixture calculations. To determine the occupant
load of each sex, the total occupant load shall be divided in
half. To determine the required number of fixtures, the fixture
ratio or ratios for each fixture type shall be applied to
the occupant load of each sex in accordance with Table
403.1. Fractional numbers resulting from applying the fixture
ratios of Table 403.1 shall be rounded up to the next
whole number. For calculations involving multiple occupancies,
such fractional numbers for each occupancy shall
first be summed and then rounded up to the next whole
number.
 
Sorry, I don't see it here. "For calculations involving multiple occupancies" refers to a space that would have a Group B and a Group A, adding both ratios up to determine the required fixtures. This does not refer to multiple floors, only multiple occupancies. For this example the only occupancy in the building is B.
 
To determine the occupant load of each sex, the total occupant load shall be divided in half.
To determine the required number of fixtures, the fixture ratio or ratios for each fixture type shall be applied to the occupant load of each sex in accordance with Table 403.1.

For fixture count it is based on the total occupant load, not story by story.
 
Agree with JBI....Gets really screwy when you have one service sink or drinking fountain for multiple tenants...And keep in mind that I think you only get 1 floor up or down for accessible fixtures...
 
JBI said:
To determine the occupant load of each sex, the total occupant load shall be divided in half.
To determine the required number of fixtures, the fixture ratio or ratios for each fixture type shall be applied to the occupant load of each sex in accordance with Table 403.1.

For fixture count it is based on the total occupant load, not story by story.
Click to expand...

So, JBI, you agree that in my example, the 4 and 4 is required for the entire building since the occupant load is 300, rather than a requirement of 6 and 6, which would be the result of calculating per floor? Of course, the toilet facilities would have to be in a core area accessible to all occupants for this to work (and compliant with 403.3.3).

What really starts to get "screwy" is when you try to apply this to a 10 or 20 story building. At that point, it would be difficult to show compliance to 403.3.3 unless you broke it down to providing a core facility on floors 2 (serving floors 1, 2, and 3), 5 (serving floors 4, 5, and 6), 8 (serving floors 7, 8, and 9), and so on. And, trying to keep up with this when future alterations are presented would be a nightmare. It would be nice to have something in the code that clearly stated that calcs would be limited to a per floor basis rather than opening up this possible can of worms. I currently have a request to calculate plumbing fixtures based on the scenario provide at the beginning of this string, and I cannot come up with either code language or code intent to deny this request, other than I simply do not like it.
 
With the information provided, yes I agree that the total occupant load drives the fixture count, and that placement could be entirely on the second floor. The plain language of 403.1.1 is clear... use entire OL, divide by 2, apportion accordingly.
Extreme hypotheticals are not worth the energy to conceive - such as applying this logic to a high rise building; and placing all required fixtures on the second floor is probably not the best option.
 
$ ~ $ ~ $


rgrace,

I do not know how you can market this, but from Section 101.3
[ `15 IPC - Intent ] "Reasonable level of safety, health,
property protection and public welfare regarding location, etc... ".

From my own experience, the [ possible ] females that intend to use
the restrooms ain't going to want to travel up or down one story.

For all practical purposes, spend the extra monies and install the
extra number of fixtures \ per floor calcs.......It will be money well
spent in the long run. :eek:


$ ~ $ ~ $
 
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Thanks :) If I were the designer, I would lean toward the per floor calcs. Unfortunately, I am the governmental official that is being asked to accept this. I like to have something solid on my side when I say "no" so that I can back up this decision to the LBBCA if it went that far. And just for clarification, the actual building in this tale is 6 stories, and the calcs in question are for the upper three stories.
 
The IBC commentary below provides an interpretation of intent and for existing buildings request the designer or applicant to provide calculations in accordance with the IEBC Section 810 as applicable.

810.1 Minimum fixtures. Where the occupant load of the story is increased by more than 20 percent, plumbing fixtures for the story shall be provided in quantities specified in the International Plumbing Code based on the increased occupant load.

2902.3.2 Commentary: "A 20-story high-rise office building cannot have all of the required plumbing fixtures located on the 10th floor, as the path of travel must neither exceed a travel distance of 500 ft. nor require travel beyond the adjacent story above or below. While this travel path limitation can result in toilet facilities not being located on every floor of a multistory building, the intent of the code is for a proportional number of fixtures to be available for the intended occupant use. For example, occupants on the 20th, 19th and 18th floors could reasonably be expected to utilize toilet facilities located only on the 19th floor (as long as the 500-ft. travel distance limitation is not exceeded). However, that toilet facility cannot have just one fixture of each type to serve three floors of occupants. The distribution of fixtures must be proportioned according to the number of occupants that will be using the toilet facility. To illustrate, assume that each of the 20 floors in this high-rise business occupancy building has an occupant load of 100. Applying the business occupancy water closet fixture ratio to the occupant load for the entire building results in 40 male water closets required for the building. Three floors of occupants will require (150 floor occupants/1,000 total occupants) x 21 w/c = 3.15 or 4 male water closets on the 19th floor."

Hope this is useful.
 
I have always calculated fixtures based on the total occupants in the building, then tried to distribute them proportionally. Fixture calculations are required to be based on the occupant load for exiting, which is usually far greater then the actual number of occupants usually in the building.
 
A single tenant building should not be an issue if the restrooms are not placed on each floor. However in a multi-tenant building a tenant may require their entire floor to be secured from other tenants and then you will have problems. Perhaps explaining this scenario to the owners will help them re-think the placement of the restrooms.
 
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