In the Dance Studio Case Study

How many occupants can the client expect to have on the proposed additional level? Assume that the proposed additional level will be built with the same footprint as the building below, and round up to the nearest occupant.

Incorrect - the answer is 72

Based on the 2018 IBC, exercise rooms are allotted an occupant factor of 50 (gross). See Table 1004.5.

The case study scenario notes that the proposed additional level will be the same gross square footage as the building below (4,200 sf) and will be 85% efficient. Therefore, the size of the proposed exercise room will be:

4,200 sf x 0.85 = 3,570 sf

To find the number of occupants that are permissable in this space, divide the square footage by the occupancy factor found earlier:

3,570 sf / 50 occupants per gross square foot = 71.4 occupants, which rounds up to 72 occupants. (Note that the question requires rounding up.)

I don’t understand why did we take the net area not the gross?

Thank you

@coachchrishopstock can you please take a look into this question?


Hi @ylouka - I can totally understand the confusion here, let me try to explain.
We’re at the schematic design phase in this example, so floor plans are not yet fully developed. It’s common to estimate the efficiency of the floor plate at this stage - by saying it’s 85% efficient, we’re noting that corridors, stairs, elevators, etc. will take up 15% of the floor plate. These spaces do not contribute to occupant load, so we must multiply the gross area of the floor by 85% to estimate the size of the dance studio.
After doing that, we use this number and multiply by the occupant load factor (50) to arrive at the number of occupants.

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Thanks for explaining.

Hi @coachchrishopstock @coachdarionziegler–asking this here so the dance studio questions can stay together! When I did the calculations for the additional level, I subtracted 3500 SF from the 4200 GSF to account for the double-heighted dance studio listed in the program. Did I miss something in the question that should have led me to use the full 4200 GSF as my starting point?


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