Prototype 3
6 storeys / 22 units / 66’ lot
Typology
Six-Storey Apartment Building
Six-Storey Apartment Building
Occupancy
Group C - 22 Dwelling Units
Group C - 22 Dwelling Units
Classification
NBC 3.2.2.51
NBC 3.2.2.51
This scenario proposes a six-storey apartment building on a 66’ (20.2m) wide lot as an assembly of two typical 33’ lots. This lot dimension is common 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 one 4-bedroom, two 3-bedroom and one 2-bedroom dwelling unit on each of the upper floors and two additional 3-bedroom units on the ground floor (total of 22 homes), with a common amenity, garbage, bicycle, storage and mechanical room on the ground floor. Each upper storey has 12 bedrooms such that the SES serves a total of 24 occupants per storey (calculated as 2 persons per bedroom), which is 40% of the 60 person occupant load permitted for floor areas served by a single exit in the National Building Code of Canada. The cumulative occupant load served by the SES on all upper storeys therefore equals 120 persons. A minimum exit facility width of 1500mm is provided for the purposes of illustrating the requirements of the British Columbia Building Code for SES building design. The design provides a direct exit discharge to the exterior on the ground floor and an another path through the residential lobby to the street, located within proximity of the fire access route.
Lot Size
66’ x 122’
Lot Area
748.0m2
(8,052 sq.ft.)
Lot Coverage
57%
Building Area
427.9m2
Building Height
6 storeys
Building Depth
25.0m
Gross Floor Area
2,562.9m2
Floor Space Index
3.43
Residential Unit Mix
22 dwelling units
(5x2-Bed, 12x3-Bed, 5x4-Bed)
Occupant Load (SES)
120 persons
Occupant Load (per storey)
24 persons
Exit Facility Width
1500mm (BCBC)
66’ x 122’
Lot Area
748.0m2
(8,052 sq.ft.)
Lot Coverage
57%
Building Area
427.9m2
Building Height
6 storeys
Building Depth
25.0m
Gross Floor Area
2,562.9m2
Floor Space Index
3.43
Residential Unit Mix
22 dwelling units
(5x2-Bed, 12x3-Bed, 5x4-Bed)
Occupant Load (SES)
120 persons
Occupant Load (per storey)
24 persons
Exit Facility Width
1500mm (BCBC)
Floor Area Efficiency
single stair = 91.5%*
scissor stair = 87.0%
+4.5%
* 92.5% if 1100mm exit width
Construction Cost (Direct Only)
single stair = $7,842,600 ($280/sf)
scissor stair = $7,911,300 ($282/sf)
-0.9% (-$68,700)
Net Operating Income (Rental)
single stair = $675,230 annualized
scissor stair = $632,450 annualized
+6.8% (+$42,780)
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 increases the efficiency of the typical floor plan by 4.5% at an exit facility width of 1500mm and 5.5% at an exit width of 1100mm. The construction costing of the building (with no change in overall building size and accounting for the additional fire and life safety measures) shows a difference attributed to the additional staircase, partitions and doors compared to the cost of the smoke control measure. The impact of changing the design by 10 bedrooms is also captured in terms of rental income.
Appendix (Downloads)
SES Prototype 3 - Class D Construction Costing (2025.02.12)
SES Prototype 3 - Pro Forma Analysis (2025.03.10)
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