You have to go digging on that site a little bit to get to the why: "The building typology of five to six-storey apartment buildings usually involves a single

You have to go digging on that site a little bit to get to the why: "The building typology of five to six-storey apartment buildings usually involves a single shared central stair, accessed directly from the street with typically two to four dwelling units per floor. However, because the Ontario Building Code requires two means of egress, mid-rise buildings in Toronto are designed with two exit stairs connected by a common corridor. The result is that mid-rise construction only proves feasible on larger sites where around ten or more units can fit within a typical floor plan to achieve an efficient floor area ratio. Zeidler explains that “this appears to be a reasonable precaution for life safety. However, the life safety of this single stair type in Europe has been equal to, if not better than ours,” due to the fact that the single stair scheme is shared between fewer units. By changing the code requirement for two exit stairs, apartment buildings of midrise height could be designed around a single common stair. For instance, a point-access block, the dominant housing typology in dense urban contexts like Berlin, Paris, or Barcelona, is currently not permitted in Canada." https://secondegress.ca/A-Wicked-Problem https://secondegress.ca/A-Wicked-Problem