Mezzanines

Mezzanines that are essentially open to view, so that a fire on the mezzanines would be visible from the room below and vice versa, do not have to be counted as a storey if their aggregate area does not exceed 40% of the open area of the room (Figure 9.1.-6) (NBC Sentence 9.10.4.1.(2)).

If, however, the condition for visual communication is not met from above or below the mezzanines, the mezzanines are only permitted to not be counted as a storey if their aggregate area does not exceed 10% of the floor area of the building in which they are located and if the area of each mezzanine does not exceed 10% of the area of the suite in which it is located.

Quoted from Illustrated User's Guide - NBC2015

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