Net vs. Gross when calculating occupant loads
When referencing the 2018 IBC table 1004.5 for example, are you supposed to just use both the "net" and "gross" ratios interchangeably if there is no grossing factor provided on a given problem/ scenario?
That messed me up on a practice exam. If they give you the area for a room with occupancy "X" that's 40 net and then occupancy "Y" that's 150 gross, are we just supposed to assume the areas they give you are already accounting for the gross/ net sq. ft.?
Maybe I am thinking too deep into this but I don't want to be tripped up on an exam.
Thx,
RJ
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I can see how that would be confusing, Raymond. We’re trying to allow everyone to get out in the event of a fire and to do that we need to estimate how many people occupy a space. Sometimes we can best estimate the number of people in a space by using net (often, but not always public spaces) and sometimes we can best estimate the number of people in a space using gross (often, but not always, storage spaces). Let’s look at libraries in the table. We’re told that we have to assume that there is one person for every 50sf, net, which has a kind of logic because if we wanted to establish the number of people that needed to get out of the reading room area, we might not include those in storage areas and corridors at the moment of a fire. However we are also told that we need to assume that there is a human for every 100sf, gross, in the stacks…which makes sense because everyone in the stacks is kind of in a corridor or kind of in storage.
For purposes of this table, Net excludes corridors, stairways, closets, etc.
Generally, I’ve found that those who are most comfortable with this kind of positive ambiguity tend to do best on these exams.
—Michael Ermann, Amber Book creator
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