By Zoe Gaik,
Architectural Forensic Associate
RGA Design Forensics
What is a compliant stair?
All of the factors that go into making a stair compliant with building codes and fire codes may surprise you. A stair is defined in the Florida Building Code (FBC), but no other architectural codes. The definition of a stair in the FBC states, “a change in elevation, consisting of one or more risers” (§202). A riser is defined in the FBC as well, “the vertical component of a step or stair” (§R202). Meaning… a one-step transition is considered a stair as well. Some of the measurable requirements for stairs are discussed within this article. Would your stair be considered compliant?
First off, there are differences between the requirements for new stairs and for existing stairs. The requirements for new stairs are usually more stringent, so it’s important to know whether a building event (such as a major alteration to the stair, or an alteration to an area that uses this stair as a means of egress) has triggered a more recent code. For example, if you have a restaurant built in 1995, but you reconfigured the space inside in 2015, the 2015 Florida Building Code, Existing (FBC-E) would apply, and the code it was built under, such as the Southern Standard Building Code, would no longer apply. However, the FBC-E makes the exception that if the means of egress complies with the Florida Fire Prevention Code (FFPC), then it need not apply to the FBC-E. So the codes kind of let you choose which one you want to use to stay in compliance.
Further, since most of us are dealing with cases that include existing stairs, and seldom any that include new stairs, I’ll mainly discuss the requirements for existing stairs. One thing that is unanimous with both new and existing stairs is that each step must be readily apparent (FFPC 101-§7.1.7.2.4). Meaning, there needs to be some kind of visual cue, like contrasting surface materials, to aid in perceiving the change in elevation.
Existing stairs must be 36” wide minimum, have risers that do not exceed 8” in height, treads (the horizontal component of a step) that are 9” deep minimum, with a minimum headroom of 6’-8”. This is found in table 7.2.2.2.1.1(b) in the FFPC’s NFPA 101. In addition, section 7.2.2.3.3 (for both new and existing stairs) states that stair treads and landings must be solid, be free of projections that could trip stair users, have consistent surface traction, and have a slope that does not exceed 1:48 (a little over 2%). However, for stairs where the bottom or top riser adjoins a sloping driveway or walkway, the bottom or top riser is permitted to have a variation in height of up to 1:12 (8.33%). This exception is found in §7.2.2.3.6.3.
Dimensional uniformity is another factor to consider. Section 7.2.2.3.6* of the FFPC’s NFPA 101 includes a lot of information about it. Generally, risers that vary in excess of 3/16” is prohibited, but the largest and smallest riser heights can vary by 3/8”. They just can’t be next to one another.
As a fairly exhaustive list, this is what a compliant stair looks like, according to the Florida Fire Prevention Code. If you think you have a code violation, or if you just have a question, give me a call/email and let’s chat about it! I can be reached at 813-226-2220 x206 and zgaik@rga-design.com.