To supersede the requirements of Sentence 9.10.9.11.(2) for a residential occupancy with not more than 2 dwelling units that is adjacent to a mercantile occupancy and permit a reduction in the minimum required fire-resistance rating of the fire separation, on the basis that the number of dwelling units is limited and thus the mercantile occupancy does not pose a risk to a large number of persons.
This is to limit the probability that fire will spread from one mercantile occupancy to an adjacent residential occupancy having a different degree of fire risk, which could lead to damage to the building.