The Ontario Building Code | Area of Exposing Building Face
3.2.3.2. Area of Exposing building Face
(1) Except as permitted by Sentences (2), and (3), the area of an exposing building face shall be calculated as the total area of exterior wall facing in one direction on any side of a building measured from the finished ground level to the uppermost ceiling.
(2) If a building is divided by fire separations into fire compartments, the area of exposing building faceis permitted to be calculated for each fire compartmentprovided the fire separations have a fire-resistance rating not less than 45 min.
(3) In a building that contains an interconnected floor space, the area of the exposing building face for the interconnected floor space is permitted to be determined by considering each storey as a separate fire compartment notwithstanding openings through the floor assemblies.
In Plain Language
This clause explains how to calculate limiting distance, the distance from an exterior wall to the property line, centreline of a street, or an imaginary line between two buildings on the same property, which then determines how much unprotected opening area that wall is allowed to have.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.