IBC 2018 2902.2 Separate facilities - Mixed B and M Occupancy with Low Occupant Loads

[jbrownARCH77]

I have a mixed use project in which the owner wants a single unisex restroom. The occupant loads are as follows:
Business = 11 Occupants
Mercantile = 17 Occupants
Total Occupant Load = 28

Per 2902.2, Exception 4, a Business occupancy can forego having separate facilities if the occupant load is 25 or less.
Per 2902.2, Exception 3, a Mercantile occupancy can forego having separate facilities if the occupant load is 100 or less.

What I BELIEVE needs to happen: Take total occupant load and apply the most stringent requirement of the two occupancies. In this case, the business requirement is the most stringent. We have 28 occupants total. This is greater than 25, therefore we're required to have 2 bathroom facilities.

What I'm questioning: Considering the B occupancy on its own meets 2902.2, Exception 4, AND the Mercantile occupant load meets the requirements of 2902.2, Exception 3, each occupancy on its own is allowed a single unisex restroom. Because of this, I can theoretically provide a single restroom and meet the requirements of both occupancies.

Thank you for any interpretations you can provide.

 

[Paul Sweet]

How about trying
B = 11/25 = .44
M = 17/100 = .17
.44+.17 = .61 <1

 

[JPohling]

Paul has the correct method for a mixed use minimum plumbing fixture calculation

 

[Sifu]

Yes but that doesn't eliminate the separate facilities requirement.

Are these mixed uses completely, physically separate? Under different ownership or lease? Have separate entrances? Or are they the same occupant with the same access? Does one use support the other? If so I would see which is the predominate use is and go with that. So if retail with supporting business use spaces then it would be M. But if mostly internet or wholesale business use with a small display area, I would think it a B. This is really a perception issue. If they are truly independent, then each one gets a single facility based on it's own independent use. If they are supportive of each other and can't be restricted from each other, then I would see if it can't be said to be one or the other and code applied to whichever it ends up being.

If it is the internet/wholesale scenario it seems likely the areas could be revised enough to get the B use under the 25. If it is the retail scenario, it wouldn't matter.

FWIW if supportive, I would have a really hard time requiring two.