Hi @xurubi ,
My understanding is it is always best to round up when dealing with occupants as you can’t have a partial occupant and when it comes to exiting you always need to deal with the ‘worst case scenario’ which means rounding up to the nearest whole occupant.
The reason most jurisdiction require you to round up is this section from IBC 2018.
The 2018 IBC Code Commentary goes on to state, “The worst case scenario should be used to determine the requirements for means of egress elements”.
However, this doesn’t mean that there isn’t some ambiguity in this and it’s always enforced exactly in this manner by the individual AHJ. I’ve read that NFPA actually does allow for traditional rounding (rather than forced rounding up).
So, I wouldn’t let this example of traditional rounding you found in Building Code Illustrated get under your skin. (PS - I’m afraid I had to delete the screenshot as we do not allow posting of any paid content, 3rd party or Black Spectacles). I wouldn’t worry too much about it as I think it’s unlikely the ARE is going to throw you a question where the occupant load could be either 49 or 50 based on rounding. Plus, any questions that require rounding will prompt you to round.
If you encountered this in the real world, likely you would simply adjust the areas in some ways so it was less ambiguous whether the occupancy should be rounded up or down so the AHJ would clearly agree that the occupancy was not over 49.
Here’s an article on Hyperfine you might find helpful:
Hope this helps!
-Darion