Q: What is the difference between a guardrail and a handrail on a set of stairs, and how do the building code requirements for them differ? When can a guardrail and a handrail be the same component?
A: Glenn Mathewson, a building inspector in Westminster, Colo., and a former deck builder, responds: The International Residential Code defines a guard as "a building component or a system of building components located near the open sides of elevated walking surfaces that minimizes the possibility of a fall from the walking surface to the lower level"; and a handrail as "a horizontal or sloping rail intended for grasping by the hand for guidance or support."
Note there is no requirement for a "guardrail," but simply for a guard — which can be any building component that provides the required level of protection, such as a wall, a half-wall, a planter box, a bench, or more typically, a railing.
A handrail, however, is specifically defined as a "rail." Its purpose is to give you something to hold; the purpose of the guard, on the other hand, is to keep you from falling over the edge. Thus, the IRC requirements relating to them are different.
Guards are referred to in Section R312.1 in the IRC: "Open sides of stairs with a total rise of more than 30 inches above the floor or grade below shall have guards not less than 34 inches in height measured vertically from the nosing of the treads." It's important to highlight that this requirement is based on the height of a fall, not the number of rises in the stairs. For example, a set of stairs with four rises — each 7.75 inches high for a total rise of 31 inches — would require a guard on both sides. On the other hand, a set of stairs with 10 rises, each 3 inches high for a total rise of 30 inches, would not require a guard.
Infill — balusters, pickets, solid wall, and the like — between the 34-inch minimum height and the nose of the stairs is considered part of the guard assembly, and is required only when guards are required. (Remember that guards on level areas such as decks, when required, must be a minimum of 36 inches high.)
Unlike the requirement for guards, the one for handrails (IRC Section R311.5.6) considers the number of rises: "Handrails shall be provided on at least one side of each continuous run of treads or flight with four or more rises." This is because the need for handrails is based solely on the movement of the human body, not on the height of the stairs. The more times you must lift your legs and place your feet squarely on a tread, without an intervening landing, the more likely you are to trip or become tired. Also note that unlike guards, a handrail is required on only one side of the stairs.
Consider the two examples given earlier: The stair with four rises of 7.75 inches would require guards on both sides because the overall rise exceeds 30 inches, and it would require a handrail on one side because it has four rises.
Although the second stair, with ten 3-inch rises, wouldn't require guards (total rise doesn't exceed 30 inches), it would need a handrail on one side because of the number of rises. And since guards aren't required, there's no requirement for infill beneath the handrail.
Where both guards and handrails are required, as in the first stair, the top of guard can be constructed to also function as the handrail. The three subsections of section R311.5.6 detail the height, continuity, and grip size that regulates the construction of handrails. The Stairbuilders and Manufacturers Association provides excellent details and visual examples of these sections in its Visual Interpretation of the International Residential Code, available at www.stairways.org.
As always, consult the building department in the jurisdiction where the work is being performed. Some jurisdictions have adopted amended versions of the IRC or published their own code, or they may interpret these sections differently.