One of the most important designations for tall buildings is whether or not it is considered a high-rise. Once a building is deemed a high-rise structure, there are fire protection, emergency power and smoke removal systems that need to be accounted for and implemented. This classification is also frequently a source of confusion and is a commonly asked question for code experts. The source of confusion is likely due to how it was defined in the 1968 Building Code.
As per the 1968 Building Code, a high-rise was any building or structure at least 75 feet in height. However, the definition of “Building Height” measures that vertical distance to the roof elevation, as described below.
The vertical distance from the curb level to the highest point of the roof beams in the case of flat roofs, or to a point at the average height of the gable in the case of roofs having a pitch of more than one foot in four and one-half feet; except that where the curb level has not been legally established or where every part of the building is set back more than twenty-five feet from a street line, the height shall be measured from the adjoining grade elevation.
As of the introduction of the 2008 Building Code, the high-rise definition has been clarified and simplified. Instead of measuring to the building’s highest point, the distance is now measured to the highest “occupied floor”. The definition is as follows:
A building with an occupied floor located more than 75 feet (22 860 mm) above the lowest level of fire department vehicle access.
Therefore, buildings that would have previously been categorized as a high-rise, may avoid this impactful and costly designation if the roof is not occupiable and the highest occupied floor is less than 75 feet above the lowest level or fire department access (ie – the street).