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BCC Ruling No. 97-29-571

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BUILDING CODE COMMISSION DECISION ON B.C.C. #97-29-571

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

AND IN THE MATTER OF Clause 3.1.10.3.(2)(a) of "the Building Code" (Ontario Regulation 419/89 as amended by Ont. Reg. 183/88, 581/88, 11/89 and 115/89).

AND IN THE MATTER OF an application by Mr. Rupert Bronsdon, President, Lighthouse Point Yacht and Tennis Club Inc., 28 Glenwood Avenue, City of Toronto, Ontario, for the resolution of a dispute with Mr. Bill Plewes, Chief Building Official, Town of Collingwood, concerning whether the proposed termination of a 2 hour firewall on the underside of a reinforced concrete roof slab on one side only provides sufficiency of compliance with Clause 3.1.10.3.(2)(a) of the Ontario Building Code (OBC) and whether the wood trusses in an assembly with drywall applied to each side contributes 5 minutes to the fire-resistance rating at Lighthouse Point Yacht and Tennis Club Inc., Highway # 26 West, Town of Collingwood, Ontario.

APPLICANT

Mr. Rupert Bronsdon, President
Lighthouse Point Yacht and Tennis Club Inc.
28 Glenwood Avenue
Toronto, Ontario

RESPONDENT

Mr. Bill Plewes
Chief Building Official
Town of Collingwood

PANEL

Mr. Roy Philippe, Chair
Mr. Demir Delen
Mr. Michael Steele

PLACE
Toronto, Ontario

DATE OF RULING
Wednesday, July 9th, 1997

APPEARANCES
Mr. Rupert Bronsdon
President
Lighthouse Point Yacht & Tennis Club Inc.
For the Applicant

Mr. Bill Plewes
Chief Building Official
Town of Collingwood
For the Respondent

RULING

  1. The Applicant

Mr. Rupert Bronsdon, President, Lighthouse Point Yacht and Tennis Club Inc., is a person who has applied for a permit under the Building Code Act, 1992 to construct a new residential structure, known as Phase Three, at the Lighthouse Point Yacht and Tennis Club Inc., Highway # 26 West, Town of Collingwood, Ontario.

  1. Description of Construction

The proposed Phase Three project at the Lighthouse Point Yacht and Tennis Club is a three storey structure which will be separated into two buildings by a 2 h firewall. One building will be 753 m2 (8 110 ft2) and the other will be 659 m2 (7 094 ft2), for a total area of 1 412 m2 (15 204 ft2). The Phase Three structure will be made of combustible construction and is classified as having a Group C (residential) major occupancy. The structure does not have a standpipe and hose system nor a sprinkler system. It is equipped with a fire alarm system.

The Applicant proposes to terminate the 2 h firewall between the two buildings of Phase Three on the underside of the concrete roof slab. The roof slab, however, is present on one side of the firewall only. They do not propose to construct a parapet extending above the roof.

The Applicant is also proposing to construct wood and drywall truss assemblies for the attic, in which the drywall is applied to the sides of the wood trusses.

  1. Dispute

The issue under dispute between the Applicant and the Respondent is whether the proposed termination of the firewall on the underside of the concrete roof slab can occur on one side only of the subject firewall. (The municipality is regarding the Phase Three project as Part 9 building, however, Article 9.10.11.3 refers to Subsection 3.1.10. for the requirements for firewalls.) Sentence 3.1.10.3.(2) allows firewalls to terminate on the underside of reinforced concrete roof slabs provided that the same roof slab has a fire-resistance rating of 1 h on both sides of the firewall. The Applicant believes that the firewall and roof slab assembly as designed provides sufficiency of compliance with this provision. As well, both the Applicant and Respondent request clarification whether the wood trusses themselves contribute 5 minutes to the fire-resistance rating of the wood and drywall truss assembly provided in the attic of the Phase Three building.

  1. Provisions of the Building Code

3.1.10.3. Continuity of Firewalls

(2) A firewall is permitted to terminate on the underside of a reinforced concrete roof slab provided

(a) the roof slab on both sides of the firewall has a

(i) fire-resistance rating of not less than 1 h if the firewall is required to have a fire-resistance rating of not less than 2 h, or

(ii) fire-resistance rating of not less than 2 h if the firewall is required to have a fire-resistance rating of not less than 4 h, and

(b) there are no concealed spaces within the roof slab in that portion immediately above the firewall.

  1. Applicant's Position

The Applicant submitted that both the proposed firewall and roof truss assemblies provide sufficiency of compliance. Regarding the firewall and roof slab assembly, the Applicant argued that the combination of the 2 h firewall (8 inch semi-solid concrete block) and the 10 inch thick precast concrete roof slab would provide adequate containment and prevent the spread of fire between one building of Phase Three and the other. It is their contention that the proposed design obviates the need for both the concrete roof slab on the other side of the firewall and a parapet extending above the roof line. The Applicant is concerned with drainage problems if the sloped portion of the roof terminates at a parapet.

The fire-resistance ratings of roof truss assembly are set out in OBC Article 3.1.7.1. (Determination of Ratings), which refers to Chapter 2, "Fire Performance Ratings" of the Supplement to the National Building Code 1990. Subsection 2.3 of the Supplement, in particular Table 2.3.C., indicates that a wood truss assembly has a 5 minute rating. The Applicant believes that this provision supports their assertion regarding the contribution of the wood truss itself to the overall fire-resistance rating of the assembly. When combined with 40 minute rated drywall applied on both sides of the wood truss, they argue that the overall fire-resistance rating of the subject truss assembly is 45 minutes.

  1. Chief Building Official's Position

The Respondent submitted that the proposed firewall and roof slab design does not provide sufficiency of compliance with the Building Code. In their view, the firewall is allowed to terminate on the underside of a concrete roof slab, but as per 3.1.10.3.(2)(a) this must be done on both sides of the firewall. In addition, because Phase Three is separated by a 2 h firewall, the OBC requires that the concrete roof slab must have a fire-resistance rating of at least 1 h on both sides. Alternatively, the Respondent notes that with a concrete roof slab on one side only, and therefore no possibility to terminate the firewall on both sides, the Applicant must provide a parapet. Such a parapet should extend 150 mm above the roof line in accordance with Clause 3.1.10.4.(1)(a) and would provide the necessary continuity of the firewall.

As the municipality is also seeking clarification on the fire-resistance rating of the roof truss, they did not offer any arguments regarding this issue.

  1. Commission Ruling

It is the decision of the Building Code Commission that the firewall provides sufficiency of compliance with 3.1.10.3.(2)(a) of the building Code provided that:

a) the cores or the cellular concrete slabs terminating at the firewall are filled with noncombustible materials, and

b) the combustible insulation on the roof of the concrete slab is replaced with noncombustible insulation, the width of the firewall.

It is also the decision of the Building Code Commission that the roof truss detailed protected with 5/8 inch fire-rated drywall does not provide adequate support for the drywall and consequently does not provide sufficiency of compliance with the Building Code, for a 3/4 h fire-rated wall assembly.

  1. Reasons:

Insufficient evidence was provided for the truss configuration to ensure the fire-rated drywall is mounted in accordance with fire performance ratings found in the NBC Supplement for wall assemblies.

Dated at Toronto this 9th day in the month of July in the year 1997 for application number 1997-29.

Roy Philippe, Chair

Demir Delen

Michael Steele