Skip to content
You are here > Home > Your Ministry > Ontario Building Code > Appeals & Approvals > Building Code Commission > Rulings of the Building Code Commission > 1996 > BCC Ruling No. 96-40-523

Follow us

BCC Ruling No. 96-40-523

Email this page


IN THE MATTER OF Subsection 24(1) of the Building Code Act, 1992.

AND IN THE MATTER OF Sentences & (2) of the Revised Regulation of Ontario 1990, Regulation 61, as amended by O.Regs. 400/91, 158/93, 160/93, 383/94 and 20/95 (the "Building Code").

AND IN THE MATTER OF an application by Mr. John Hunt, Project Director, 741501 Ontario Limited, Toronto, for the resolution of a dispute with Mr. Mani Navabi, Chief Building Official, City of Vaughan, concerning whether the bevelled side of a bay window is a wall or exposing building face of a fire compartment and if the portion of the exterior wall between such windows in each suite requires a fire resistance rating at least equal to the rating required for the interior demising wall, as described in Sentences & (2) of the Ontario Building Code at the Emerald Gate Townhomes, 151 Towngate Drive, Thornhill, Ontario


Mr. John Hunt
Project Director
741501 Ontario Limited
Toronto, Ontario


Mr. Mani Navabi
Chief Building Official
City of Vaughan


Mr. Roy Philippe, Chair
Ms. Susan Friedrich
Mr. Michael Lio


Toronto, Ontario


September 11th, 1996


Mr. Allan Larden
Larden Muniak Consulting Inc.
Toronto, Ontario
Agent Representing Applicant

Mr. Mani Navabi, Chief Building Official
Mr. Steve Penna, Plan Review Supervisor
City of Vaughan
The Respondent


  1. The Applicant

The Applicant is a holder of a permit under the Building Code Act, 1992 to construct seven townhouse buildings known as the Emerald Gate Townhomes at 151 Towngate Drive, Thornhill, Ontario,

  1. Description of Constrution

The project consists of 7 separate buildings of which 6 are linked by a single level underground garage. Two of the buildings have a 45 degree angled exterior wall and bay type window assembly on either side of a 2 hour fire separation. One building has this exterior configuration occurring in two locations and the other has it occurring in three locations. A total of ten dwelling units are affected.

The municipality is requiring the exterior wall of each compartment within the calculated distance "Do" to have the same fire resistance rating as the 2 hour fire separation between dwelling units.

  1. Dispute

The dispute between the Applicant and the Respondent concerns sufficiency of compliance with the technical requirements of Sentences & (2) of the Building Code. At issue is whether the bevelled side of a bay window is a wall or exposing building face of a fire compartment and if the portion of the exterior wall between such windows in each suite requires a fire resistance rating at least equal to the rating required for the interior demising wall.

  1. Provision of the Building Code

Sentences & (2) Wall Exposed to Another Wall

  1. Except as provided in Sentences and, where an opening in an exterior wall of a fire compartment is exposed to an opening in the exterior wall of another fire compartment, and the planes of the 2 walls are parallel or at an angle of less than 135?, measured from the exterior of the building, the openings in the 2 fire compartments shall be separated by a distance at least equal to D? where

D? = 2D - (?/90 x D), but in no case less than

1 m (3 ft 3 in)


D = the greater required limiting distance for the exposing building faces of the 2 fire compartments, and

? = the angle made by the intersecting planes of the exposing building faces of the 2 fire compartments, (in the case where the exterior walls are parallel and face each other, ? = 0?).

  1. The exterior wall of each fire compartment in Sentence (1) within the distance, D?, shall have a fire-resistance rating not less than that required for the interior vertical fire separation between the compartment and the remainder of the building.

  1. Applicant's Position

The Applicant submitted the following rationale as to why the bay windows of adjacent suites (not separated by a firewall) may be found acceptable under the Building Code:

The requirements of the Article of the Building Code originally applied only to the exterior walls of fire compartments that met at a firewall. The requirement was extended to walls of separate fire compartments (not necessarily separated by a firewall) in the 1983 Building Code (based on changes made in the 1980 National Building Code).

Depending on the design specifics and variable code interpretation, this change has at times proved problematical for design of multi- unit residential buildings and inquiries have been made through a committee of the Ontario Association of Architects to the Canadian Code Centre (CCC). The CCC has indicated that there is no record of why the requirement was extended to walls of adjacent fire compartments meeting at a fire separation; it is presumed that the rationale implicit in the requirement for firewalls was extended to these other situations.

For the case at hand, the exterior walls of the two dwelling units are in the same plane. The bay windows (which extend as projections of the floor from floor to ceiling) are, in effect, "bumps" in the exterior exposing building face of the two dwelling units. These "bumps" do not extend from the full height of the dwelling unit; they project from the walls of the second and third floors of the dwelling units but not from the first storey or the attic gable. The Applicant regards these "bumps" as minor articulations in the exterior of each dwelling unit.

The Applicant submitted that the building could be designed with the completed glazed exterior walls of adjacent fire compartments meeting at an angle of 135 degrees. The glazed openings of one fire compartment could be no more than 3 or 4 inches from the glazed opening of the adjacent fire compartment and there would be no restriction on the proximity of the glazing or the amount of glazing. A fire plume emanating from one compartment in the vicinity of the exterior angle between walls would be immediately in front of windows of the adjacent compartment.

The Applicant submitted that the design of the Emerald Gate Townhomes separates the glazing of adjacent units (measured at the point where there is mutual exposure) at least 5 feet. The total projected width of the mutual exposure (glazing to glazing, measured at right angles to the brick face of the building between the window units) is some 13 inches. This is a less hazardous situation than is permitted by the lack of any restriction in the code of the vertical separation of windows, storey to storey, where a fire plume emanating from a window opening in the lower storey may be directly exposed to the upper storey window.

The Applicant submitted that on the basis of the 135 degree angle between the plane of the face brick and each of the bevelled sides of the bay windows, there should be no impact on the rating of the wall behind the face brick between the bay windows.

The Applicant further submitted that if the bevelled sides of the Emerald Gate Townhome bay windows which oppose one another across the end of the demising wall were to be window openings governed by Sentence of the Building Code; the as-built situation would be straight forwardly acceptable.

The scale of the building, the relationship of windows and storeys to grade and the general configuration of the dwelling units of the Emerald Gate Townhome project are entirely consistent with buildings one may evaluate under Part 9 of the Code.

The Applicant submitted that information provided by the City of Vaughan Fire Department demonstrated that in the event of a fire the time for smoke detector activation will be some 92 seconds and that, at most, a 1.5 minute evacuation time would be required for a dwelling unit. Flashover, according to the model used by the Fire Department would occur some 667 seconds (11 minutes) after the start of a fire, which is well beyond the time required for smoke alarm activation and evacuation of the dwelling unit. The Fire Department response time of 4 minutes plus evacuation time would still be expected to be well within the time limit for flash over in a dwelling unit. Occupants of both the unit containing the fire and adjacent units would, therefore, be expected to be evacuated before flashover occurred.

The Applicant submitted that it is most unlikely that there will be any hazard of fire exposure from one bay window to an adjacent bay window prior to flashover.

The Applicant submitted that with automatic detection of fire in a suite, and a 4 minute response time be the Fire Department, it is expected that fire suppression activities could begin in a time frame which would prevent any involvement of a neighbouring dwelling unit due to fire exposure from the bevelled edge of the bay window in an adjacent compartment containing fire.

The Applicant submitted that on this basis, the bay window certainly does not represent a fire hazard to life safety or a significant hazard in respect of potential for property damage of a neighbouring unit.

  1. Chief Building Official's Position

The Respondent submitted that Sentences and (2) of the Building Code requires that the exterior wall of each fire compartment within the calculated distance "Do" have the same fire resistance rating as the 2 hour fire separation between the dwelling units.

The Respondent submitted that the two townhouse buildings in question are classified under Article of the Building Code. The floor assemblies are required to be constructed as fire separations with a fire resistance rating of 45 minutes. Sentence of the Building Code waives this requirement if the distance between the lowest floor and the uppermost floor is not greater than 6 m (19ft 8 in). This height is exceeded in six of the buildings in this development.

The Respondent submitted that he agreed to waive the required 45 minute fire resistance rating of the floors within each dwelling unit, if the units were separated from one another by a concrete block fire separation with a 2 hour fire resistance rating.

The Respondent submitted that an inspection on August 26, 1996 confirmed that the angle of the windows and wall is actually 45 degrees and the distance between the openings is 1.23 m (4 ft 1/2 in).

  1. Commission Ruling:

It is the decision of the Building Code Commission that the bevelled sides of the bay windows in separate fire compartments provide sufficiency of compliance with Sentence of the Building Code provided exterior walls between such windows have a one hour fire resistance rating.

  1. Reasons:

    1. For similar buildings under Part 9 of the Building Code, Article permits window openings in walls that meet at an external angle of less than 135 degrees where the horizontal distance from one opening in one wall to another opening in another wall exceeds 1.2 m (3' 11").

    1. The dwelling units are separated from each other at common walls by masonry partitions having a 2 hour fire resistance rating.

    1. The bay window configuration applies to a limited number of dwelling units within the complex.

    1. The local fire department analysis indicates that the times for detection, evacuation, and fire department response are well below time for flashover to occur.

    1. No evidence was provided by either party of significant incidence of fire spread with this window configuration.

Dated at Toronto, this 11th day, in the month of September, in the year 1996, for application number 1996-44.

Roy Philippe

Susan Friedrich

Michael Lio