Prototype 1
4 storeys / 6 units / 33’ lot
Typology
Four-Storey Apartment Building
Four-Storey Apartment Building
Occupancy
Group C - 6 Dwelling Units
Group C - 6 Dwelling Units
Classification
NBC 3.2.2.52
NBC 3.2.2.52
This scenario proposes a four-storey apartment building on a typical 33’ (10.1m) wide residential lot. This is a common lot width in the City of Vancouver and across the lower British Columbia mainland - as a result of metal chainset surveying methods used to establish property divisions in the 19th and early 20th century.
The proposed single exit stair (SES) building design contains two 2-bedroom homes on each of the upper storeys with common amenity, garbage, bicycle and mechanical rooms on the ground floor. The SES serves a total of 24 occupants (calculated as 2 persons per bedroom), which is less than half of the 60 person occupant load permitted for floor areas served by a single exit in the National Building Code of Canada. Given this low occupant load, an exit facility width of 1100mm is proposed. The design provides a direct exit discharge on the ground floor located within proximity of the fire access route.
Lot Size
33’ x 122’
Lot Area
374.0m2
(4,026 sq.ft.)
Lot Coverage
45%
Building Area
166.7m2
Building Height
4 storeys
Building Depth
25.0m
Gross Floor Area
666.8m2
Floor Space Index
1.78
Residential Unit Mix
6 dwelling units
(6x2-Bed)
Occupant Load (SES)
24 persons
Occupant Load (per storey)
8 persons
Exit Facility Width
1100mm
33’ x 122’
Lot Area
374.0m2
(4,026 sq.ft.)
Lot Coverage
45%
Building Area
166.7m2
Building Height
4 storeys
Building Depth
25.0m
Gross Floor Area
666.8m2
Floor Space Index
1.78
Residential Unit Mix
6 dwelling units
(6x2-Bed)
Occupant Load (SES)
24 persons
Occupant Load (per storey)
8 persons
Exit Facility Width
1100mm
Floor Area Efficiency
single stair = 83.9%
scissor stair = 73.4%
+10.5%
Construction Cost (Direct Only)
single stair = $2,551,400 ($336/sf)
scissor stair = $2,639,600 ($347/sf)
-3.4% (-$88,200)
Net Operating Income (Rental)
single stair = $135,570 annualized
scissor stair = $119,120 annualized
+13.8% ($16,450)
The floor plans below compare the single stair building design with an overlay of the prescriptive requirement for two exits. As a measure of leasable floor area, the single stair plan increases the efficiency of the typical floor plan by 10.5%, whereas a scissor stair eliminates one of the bedrooms on each upper storey. A construction costing of the building (with no change in overall building size and accounting for the cost of additional fire and life safety measures) shows a decrease compared to the scissor stair design attributed to the additional staircase, partitions and doors. The impact of changing the design by 3 bedrooms is also captured in terms of rental income.
Appendix (Downloads)
SES Prototype 1 - Class D Construction Costing (2025.02.12)
SES Prototype 1 - Pro Forma Analysis (2025.03.10)
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