What is a Highrise?
WHAT IS A HIGH-RISE?
According to the IBC, a high rise building is any building with an occupied floor located more than 75 feet above the lowest level of fire department vehicle access.
Let's break that definition down further.
The first component of the definition is an occupied floor. While “floor” or “occupied floor” are not defined terms in the code, the phrasing is generally understood to mean any floor area where occupants are normally expected to be.
Through the 2021 edition of the IBC, a roof or a rooftop penthouse would not be considered an occupied floor for the purposes of this measurement, though that point of view has been interpreted differently by some building code officials.
MORE THAN 75 FEET
The next component of the definition is the occupied floor being more than 75 feet above the lowest level of fire department vehicle access. To make this measurement, you need to determine the lowest elevation at which a fire department vehicle can access the building site. Note that this may or may not be the same elevation as the grade plane. If you have a perfectly level site, then the lowest level fire department vehicle access will be the same as the grade plane elevation. However, if you have a sloped site, the lowest level of fire department vehicle access could be at a lower elevation than the average grade plane.
As a side note, the basis for the 75 foot threshold comes from the fact that many fire departments use a 100 foot aerial apparatus. 75 feet was determined to be the maximum building height that could be effectively reached when accounting for the apparatus being parked some distance away from the building due to curbs, parked cars or other obstructions.
So if your building has an occupied floor located more than 75 feet above the lowest level of fire department vehicle access, it is considered a high-rise building and must comply with all of the requirements of IBC Section 403. We’ll get into the specifics of those requirements in a separate video.
As a final note, there is currently a code change proposal for the 2024 edition of the IBC to change the definition of high-rise buildings to include an occupied roof above this 75’ threshold. If this change is adopted into the code, an occupied roof above 75’ would trigger designation as a high-rise building, even if the highest occupied floor is less than 75 feet.
I’m Chris Campbell, this is MeyerFire University.
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Aaron Johnson, CFEI
Al Yakel, SET
Chris Campbell, PE
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Joe Meyer, PE