Alternate Methods for Building a Secondary Suite
There are non-mandatory alternate methods for altering an existing building to add a secondary suite that do not apply to new additions or buildings. These methods recognize that the standards for new construction, which aims for a higher performance level, may not be practical for existing buildings.
These methods are not meant to be used retroactively on existing units or for new construction where existing structures don’t limit compliance with Division B of the BC Building Code.
Code Requirements in Division B
Ceiling Heights of Rooms or Spaces
Ceiling height shall not be less than 2.1 m over the minimum area required in Table 9.5.3.1 in Division B.
Doorway Opening Sizes
Doorway openings shall be designed to accommodate swing-type and folding doors not less than 1980 mm (Table 9.5.5.1).
Height Over Stairs
The clear height over stairs shall not be less than 1950mm (9.8.2.2(3)).
Openings Near Unenclosed Exterior Exit Stairs and Ramps
Unprotected openings in exterior walls that are within 3m horizontally and less than 10m below or less than 5m above an unenclosed exterior exit stair or ramp of a house with a secondary suite shall be protected where the unenclosed exterior exit stair or ramp provides the only means of egress from a suite and is exposed to fire from unprotected openings in the exterior walls of another dwelling unit, ancillary space or common space (9.9.4.4(1)).
Openings Near Exit Doors
Where an exterior exit door in one fire compartment is within 3m horizontally of an unprotected opening in another fire compartment and the exterior walls of the fire compartments intersect at an exterior angle of less than 135 degrees, the openings shall be protected (9.9.4.6(1)).
Fire-Resistance and Fire-Protection Ratings
In a house with a secondary suite, where a minimum fire-resistance rating of 30 min is permitted, it is permitted to use wood-frame construction where stud and joist spaces are filled with absorptive material, resilient metal channel spaced 400 or 600mm o,c, is on one side and not less than 12.7mm thick gypsum board is installed on ceilings and on both sides of walls (9.10.3.1(3)).
Fire-Resistance Ratings for Walls, Columns, and Arches
Loadbearing walls, columns and arches in the storey immediately below a floor or roof assembly shall have a fire-resistance rating of not less than that required for the supported floor or roof assembly (9.10.8.3(1)).
Sound Transmission
In residential buildings, each dwelling unit must be separated from other spaces where noise can be transmitted. This can be achieved through three methods (9.11.1.1(2)):
- Construction with joist spaces filled with sound-absorbing material of not less than 150 mm nominal thickness, stud spaces also filled with sound-absorbing material, resilient channel on one side of the separation spaced 400 or 600 mm on center (o.c.), and walls and ceilings covered with not less than 12.7 mm thick gypsum board
- Construction that provides a Sound Transmission Class (STC) rating of not less than 43
- A separating assembly and adjoining constructions that together provide an Apparent Sound Transmission Class (ASTC) rating of not less than 40.
Alternate Compliance Method
Ceiling Heights of Rooms or Spaces
Except as required by Sentence 9.9.3.4(3), the minimum ceiling heights in a secondary suite over the required area (Table 9.5.3.1) shall not be less than 1.95m. It shall be possible to travel from the required area of one room to the required areas of all other rooms within the secondary suite without reduction of ceiling height to less than 1.95 m.
Except as required by Sentence 9.9.3.4(3), the minimum clear height under beams and ducting, including where located over stairs, in a secondary suite shall not be less than 1.85m.
Doorway Opening Sizes
Except for exit doors and for doors serving public corridors and exit corridors that serve a house with a secondary suite, doorway openings within a secondary suite shall be designed to accommodate swing-type and folding doors not less than 1890mm high.
Height Over Stairs
Except for stairs in a public corridor or exit corridor that serve a house with a secondary suite, the clear height over stairs that are located under existing beams and existing ducting in a house with a secondary suite shall be not less than 1850mm.
Openings Near Unenclosed Exterior Exit Stairs and Ramps
Protection of the unprotected openings (9.9.4.4(1)) is not required when all smoke alarms within a house with a secondary suite are a photoelectric type and interconnected as described in Clause 9.10.19.5(2)(a).
Openings Near Exit Doors
Protection of the unprotected openings (9.9.4.6 (1)) is not required when all smoke alarms within a house with a secondary suite are of photoelectric type and interconnected as described in Clause 9.10.19.5(2)(a).
Fire-Resistance and Fire-Protection Ratings
Adding resilient metal channel spaced 400mm or 600mm o.c. and an additional layer of not less than 12.7mm gypsum board to one side of an existing finished all assembly that has not less than 12.7mm gypsum on the ceiling side is permitted to be used where a 30 min fire-resistance rating is required.
Fire-Resistance Ratings for Walls, Columns, and Arches
Except for heavy timber elements and those of masonry or concrete construction, light frame walls, columns, arches and beams as well as loadbearing steel elements that support floors between dwelling units in a house with a secondary suite including their commons spaces shall be protected by not less than 12.7 mm thick gypsum board.
Sound Transmission
The assemblies and adjoining constructions that separate the dwelling units in a house with a secondary suite including their common spaces need not comply with Clause 9.11.1.1(2)(a) where resilient metal channel spaced 400 or 600 mm o.c. and an additional layer of not less than 12.7mm gypsum board is added to one side of an existing finished assembly.