Plumbing fixture calculation with small assembly spaces

[MAGB]

I am working on an adaptive re-use project converting a retail building into a dance school. Two of the studios will be larger and sometimes have rehearsals with larger groups, they have occupant loads of over 50 and will be considered A3. The remaining studios are smaller and have occupant loads under 50 so are considered B occupancy. My question is when I do the plumbing fixture calculations can I use the assembly type ratio for all the studios, even the ones that fall under type B occupancy? 2902.1 says the plumbing fixtures shall be provided "based on the actual use of the building space" The fixture count when all the small assembly spaces are calculated as business areas seems disproportionately high and the use of the space is not at all like business/office space.

The lobby and reception areas are also assembly type spaces, but with occupant loads of under 50. Would/could these areas also be an assembly spaces for the plumbing fixture counts or business? We are already adding two restrooms for a total of 4.

This project is 2018 IBC/IPC

 

[RLGA]

Good question. A minor change occurred in the 2018 IBC Table 2902.1 (and 2018 IPC Table 403.1) regarding the application of the table. The occupancy classifications were removed from the table. The justification was the confusion created just as you're experiencing. In lieu of breaking the requirements down by occupancy groups, plumbing fixtures should be considered "based on the use of the building or space."

Since your building is a dance school, the most appropriate classification per Table 2901.1 would probably be the "Education," as none of the descriptions for "Assembly" or "Business" match as closely as "Education" does. However, if the school had a dancewear store associated with it, then for that portion of the building the "Mercantile" classification would be appropriate and the building would be treated per the application for multiple occupancies stated in Section 2902.1.1.

I think the confusion is still there in both the IBC and IPC since Section 2902.1.1 (and Section 403.1.1 in the IPC) still refer to "occupancies" and "occupancy" and not "descriptions" as indicated in the Table.

 

[ADAguy]

As usual, it is in the "semantics".

 

[RLGA]

I have to admit that I got sucked into using the occupancy groups and not using the descriptions.

 

[MAGB]

For the fixture count I would like to place all of the dance studios, dressing room and lobby occupants under the description:
"auditoriums without permanent seating, art galleries, exhibition halls, museums, lecture halls, libraries, arcades and gymnasiums" with 1per 125 men and 1 per 65 women.

The gymnasium seems the closest fit to the dance studios and the city has said they would accept the exercise room function for OLF. Although I am using a higher OLF for the larger studios since they are occasionally used for large rehearsals which would never occur in the small ones.

Nothing about this project fits neatly in the IBC boxes, so I am struggling to land on a reasonable approach.

The areas of office and break room(employee work areas) I am using the Business description for restrooms calcs for those occupants.

Then there is a storage area which gets its own count because it is too large to be considered an accessory occupancy.

I always tie the education label to K-12.

I know that a dance studio generally fits in the B occupancy classification with the use designation of "Training and skill development where not group A" but I do have some group A, so I stated breaking out the areas... It is confusing when the same labels don't translate all the way through or diverge along a logical path, at least for this one.

 

[MAGB]

I received a preliminary opinion from the city that the whole building can/should be considered A3