BCAB #1368 - Venting for Balconies with a Fire Resistance Rating, Article

November 16, 1994

BCAB #1368

Re: Venting for Balconies with a Fire Resistance Rating, Article

Project Description

The project in question is a wood frame apartment building with exterior balconies.

Reason for Appeal

Article requires exterior balconies to be constructed with the same fire resistance rating as the floor assembly to which they are attached. This is accomplished with a fire resistant membrane on the underside of the balcony floor joists. Good construction practice is to ventilate the joist spaces in the balcony in a manner similar to unheated roof spaces and this is frequently accomplished by strip vents on the underside of the balcony.

Appellant's Position

The appellant contends that a two inch wide vent strip along the outer edge of balconies which are at least four feet deep will not compromise fire resistance of the assembly. The vent strip accounts for about four percent of the area of the balcony soffit and can be equated to other allowable openings in fire rated assemblies such as combustible outlet boxes ( and openings into sheet steel ducts (Chapter 2 of the Supplement to the NBC).

Building Official's Position

The building official maintains that the vent strip does compromise the fire resistance rating of the balcony floor assembly and although venting is desirable the vent strip is not an acceptable method.

Appeal Board Decision #1368

The Board considers Article intends that the wood frame balcony floor assembly be provided with a fire resistance rating which is usually achieved with a fire resistant membrane on the underside. Any unprotected openings in this membrane, such as a strip vent, would defeat the fire resistance rating. However, the Board recognizes that venting of balcony floor assemblies is essential to prevent structural deterioration due to condensation. In order to accommodate both fire resistance and ventilation will require the application of Section 2.5, Equivalents.

George R. Humphrey, Chair