BCAB #1439 - Percentage of Openings in Exposing Building Face, Article 220.127.116.11.
May 15, 1997
Re: Percentage of Openings in Exposing Building Face, Article 18.104.22.168.
The project in question is a single family dwelling with an irregular exposing building face which is not parallel to the property line.
Reason for Appeal
The application of Article 22.214.171.124. determines the fire resistance rating and type of exterior cladding required for a building and the allowable percentage of unprotected openings in the exposing building face. The limiting distance and the area of the exposing building face must be determined to apply Article 126.96.36.199.
The appellant contends that, in accordance with the definitions of limiting distance and exposing building face in Article 188.8.131.52. the limiting distance is measured at right angles to the exposing building face which is that portion of the exterior wall which faces in one direction. Therefore, wall faces A, C and E form one exposing building face and wall faces B, D and F form another exposing building face. The limiting distance to the property line is measured at right angles to these exposing building faces.
Building Official's Position
The building official maintains that the definition of exposing building face should be read as "... the exterior wall or walls of a building which faces one direction." Therefore, wall faces A to F would combine into a single exposing building face the area of which would be as projected onto a plane parallel to the property line with the limiting distance measured at right angles to the property line. This has been a standard procedure for this building department for some time and is reinforced by Appeal #185 which stated that "... where an exposing building face is at an angle to the datum (property line) we would not consider it unrealistic for the line (limiting distance) to be at right angles to the datum rather than to the building face."
Appeal Board Decision #1439
There are a number of acceptable methods of determining the allowable percentage of unprotected openings in an irregular exposing building face that is not parallel to the property line. One common method has been used by the building official and is mentioned in the Board's ruling in Appeal #185. However, it is the determination of the Board that the method employed by the appellant also complies with the requirements of the code. It also conforms with the science behind the spatial separation requirements which is based on heat radiating away from the building, primarily at right angles to the building face. This is reflected in the definition of limiting distance.
George R. Humphrey, Chair