Being aware of how an approving agency defines an opening beneath a building projection can prevent costly delays and re-design caused by unexpected plan check corrections. The building code is clear that the floor area of a building not provided with surrounding exterior walls, is considered the usable area under the horizontal projection of the roof or floor above. However, for areas containing building projections or recessed balconies, the building code does not define what is considered the exterior wall of a building for the purpose of establishing exterior wall construction and opening protection.
When a building has cantilevered floors or recessed balconies, many approving agencies consider the vertical plane at the outer edge of the cantilevered projection or recessed balcony to be considered the virtual exterior wall used to determine allowable exterior wall construction and opening protection based on fire separation distance (i.e., the distance from the exterior wall to the adjacent property line).
For example, a cantilevered floor projecting over a sidewalk below could be interpreted to create a virtual exterior wall with 100 percent unprotected openings. Should the outer edge of the projection/virtual exterior wall be located less than 20 feet away from a lot line, in a sprinkler protected buildings, unlimited openings are not allowed. In this scenario, the approving agency may consider the condition to be non-compliant and require portions of the virtual exterior wall to be infilled with solid exterior wall construction to reduce the percentage of openings under the limit allowed by the building code. Or, an alternate means and methods request may be made to provide an equivalent approach to code compliance (e.g., close-spaced water curtain sprinkler protection).
Being aware of this interpretation early in your design can prevent delays caused by addressing plan check corrections and prevent costly re-design efforts. YCI can help you identify and solve potential code challenges such as this early in the design process.
