The parts of a staircase: a homeowner’s anatomy guide

If you’ve ever stood at the bottom of your stairs trying to describe a problem to a contractor, you’ve probably said something like “the part where my hand goes” or “that wood thing on the side.” You’re not wrong, but there are real names for all of it. Knowing the words saves you money. Quotes get more accurate. The contractor stops nodding politely and starts actually answering your question.

This guide walks through every piece of a residential staircase the way I’d explain it to a customer standing in their own house. Treads, risers, stringers, balusters, newels, handrails, the whole thing. I’ll tell you what each piece does, the building code dimensions that govern it, and the spots where homeowners and remodelers most often run into trouble. Code citations are tagged inline so you can pull the source if you want to read it yourself.

Most of what we build at our shop in Arlington Heights is the metal half of this anatomy: railings, handrails, and the structural metal underneath custom wrought iron staircases. Knowing where those pieces meet the carpentry pieces is half the battle when you’re planning a remodel.

Key takeaways

• A staircase has roughly 15 named parts. Treads, risers, nosing, stringers, balusters, newel posts, handrails, guards, rail caps, fillets, brackets, landings, winders, rosettes, and bullnose. Most homeowners know two or three by name.
• The code numbers you actually need are short. Maximum 7-3/4 inch riser, minimum 10 inch tread depth, minimum 36 inch stair width, 34 to 38 inch handrail height, 4-inch sphere rule for guard openings, 4-3/8 inch sphere on stair guards, 6-inch sphere at the triangle. Cite these correctly and a contractor takes you seriously.^[1]
• Riser height variation is the #1 trip hazard. Code allows no more than 3/8 inch difference between the largest and smallest riser in the same flight. The CDC reports more than 1 million stair-related injuries treated in U.S. emergency departments each year, and falls are the leading cause of injury death for adults 65 and older.^{[1] [2]}
• Stringers do the structural work, treads and risers ride on top. If the stairs feel bouncy or out-of-square, the stringer is almost always the answer. We template every old-Chicago-three-flat install on site for that reason.
• Guards and handrails are not the same thing. A guard is the protective barrier on the open side. A handrail is the gripping rail your hand actually wraps around. Most residential stairs have both, doing different jobs.
• The 4-inch sphere rule has a stair-specific exception. On the open side of a stair flight, the maximum opening relaxes to a 4-3/8 inch sphere, and the triangular gap formed by tread, riser, and the bottom rail of the guard can pass a 6-inch sphere.^[1]
• Custom staircases live or die on the connection details. How the stringer meets the floor, how the newel anchors, how the handrail returns to the wall. Those joints are where 90 percent of the calls we get on older stairs come from.

The two halves of a staircase: structure and railing

Every staircase splits into two systems. The structure is what you walk on. The railing is what you hold onto. They meet at the edges, but they’re engineered separately, governed by different code sections, and (in our world) often built by different trades. Carpenters do treads and stringers. Metal shops like ours do guards, balusters, and handrails. Knowing which half you’re asking about makes every conversation cleaner.

Builders sometimes lump the railing in with the “stair package,” but the truth is that the railing is its own animal. The 2024 International Residential Code has separate sections for stair construction (R311.7) and for guards and handrails (R311.7.8 and R312).^[1] The code separation reflects the trade separation. When something is wrong with your stairs, figuring out which half is the problem narrows the fix fast.

The structural parts: what you walk on

Treads

The tread is the horizontal surface you step on. Per the 2024 IRC R311.7.5.2, residential treads must be at least 10 inches deep, measured from the front of one nosing to the next.^[1] Commercial stairs governed by the 2021 IBC require a minimum tread depth of 11 inches per IBC 1011.5.2.^[3] The depth has to be consistent. Code allows no more than a 3/8-inch difference between the largest and smallest tread in a single flight.^[1]

Tread material is whatever you want it to be. Hardwood is most common in residential. Concrete is common on commercial and exterior. We do a lot of metal-pan stairs where we fab the steel structure and the GC pours concrete or sets stone into the pan. Diamond plate steel is its own option, common in commercial and industrial settings, and we have a project page for stainless steel diamond plate stair treads if that look interests you.

Risers

The riser is the vertical face between two treads. Per 2024 IRC R311.7.5.1, the maximum riser height in residential is 7-3/4 inches.^[1] Commercial maximum under 2021 IBC 1011.5.2 is 7 inches.^[3] Same consistency rule as treads, no more than 3/8 inch variation across a single flight. That sounds picky until you’ve tripped on the one stair that’s a quarter-inch taller than the rest. The CDC says more than 1 million Americans go to the emergency department each year for stair-related injuries, and inconsistent risers are one of the top causes.^[2]

If the riser is left out entirely, you have an open-riser stair. We’ve done a few of those, including a minimalist open-riser stair in Lakeview. Open risers are legal in residential as long as the opening between treads doesn’t allow a 4-inch sphere to pass through (per 2024 IRC R311.7.5.1).^[1] That rule trips up a lot of designers who didn’t plan for it.

Nosing

The nosing is the front edge of the tread, the part that overhangs the riser below. Code requires a nosing projection of 3/4 inch to 1-1/4 inch on stairs with solid risers (2024 IRC R311.7.5.3).^[1] The nosing is also where you measure handrail height from. Not the back of the tread, not the average, the leading edge of the nosing.^[1] That’s the most-missed dimension on amateur stair builds.

Stringers

Stringers are the diagonal structural members that carry the load of every tread and riser. They run from the floor to the upper landing and they’re what makes a staircase a staircase instead of a stack of boards. Most residential stringers are 2×12 dimensional lumber, dadoed (housed) for the treads or with cleats supporting them. On metal stairs we use steel C-channel, tube steel, or formed plate, depending on the look.

Stringers are the answer to almost every old-stair complaint. Bouncy? Probably the stringer. Out of square? Almost certainly the stringer. Stairs that look fine but feel wrong when you walk them? Stringer. We template every install in pre-1950 Chicago buildings on site because the original stringers have settled, twisted, or sagged just enough that the “drawings” bear no resemblance to the actual stairs anymore.

Landing

A landing is a flat platform that interrupts a flight of stairs. Code requires a landing at the top and bottom of every stair (2024 IRC R311.7.6), and intermediate landings are required when a single flight rises more than 12 feet vertically (2021 IBC 1011.8 for commercial).^{[1] [3]} The minimum landing dimension in the direction of travel must equal or exceed the width of the stair. So a 36-inch-wide stair needs at least a 36-inch-deep landing.^[1]

Winder

A winder is a wedge-shaped tread used in place of a square landing to turn a stair. Common in tight residential layouts, especially in older Chicago two-flats and three-flats with stair towers tucked into a corner of the floor plan. Per 2024 IRC R311.7.5.2.1, winder treads must be at least 10 inches deep at a point 12 inches from the inside (narrow) end.^[1] That dimension is what keeps the inside of the curve from becoming a slip hazard.

The railing parts: what you hold and what holds you in

This is the half of the staircase we build at the shop. Custom railings are most of what we do, and most of those are stair railings. It’s also the half that does the most safety work, statistically speaking. The CDC reports that falls are the leading cause of injury death for adults 65 and older, with 38,742 fall-related deaths in 2021, and that fall mortality has been rising over the last two decades.^[2] Code dimensions on this stuff aren’t arbitrary. They’re the result of decades of injury data.

Guards

A guard is the protective barrier on the open side of a stair, balcony, deck, or any walking surface elevated more than 30 inches above what’s below it (2024 IRC R312.1).^[1] In residential, the guard at a balcony or landing must be at least 36 inches tall. There’s an exception for the open side of a stair flight: that section of guard can drop to 34 inches measured from a line connecting the tread nosings (2024 IRC R312.1.2 Exception 1). When the top of the guard also serves as the handrail, the 34 to 38 inch handrail range governs (2024 IRC R312.1.2 Exception 2). In commercial and multi-family, the standard guard height is 42 inches (2021 IBC 1015.3).^{[1] [3]} People call this the “railing” in everyday speech. The code calls it the guard. Both words show up on our site, but if you’re ever talking to a building inspector, use “guard.”

Balusters (also called pickets or spindles)

Balusters are the vertical pieces that fill the space between the top rail and the bottom rail or the floor. Three names for one part: baluster, picket, spindle. The metal industry usually says baluster or picket. Wood-stair carpenters often say spindle. Same thing. On our work, we use a couple of canonical baluster styles: classic vertical pickets for traditional looks, and cleaner vertical bar elements (often square tube) for Urban Modern designs.

Spacing matters. Per 2024 IRC R312.1.3, the openings between balusters in a guard cannot allow a 4-inch sphere to pass through, anywhere.^[1] That’s the famous “4-inch rule.” The threshold is set to keep a small child’s head and body from passing through the opening, and it traces back to decades of consumer-product-safety research on child entrapment hazards in railings, balconies, and similar fixed structures. The 4-inch sphere is a code test, not a free-form measurement: an inspector or contractor literally tries to push a 4-inch ball through every opening in the guard, and any opening that admits the ball fails. On stair guards specifically, the rule loosens to a 4-3/8 inch maximum sphere because of the geometry of an angled rail (2024 IRC R312.1.3).^[1] The triangular opening at the bottom (formed by the tread, riser, and bottom rail of the guard) gets even more leeway: a 6-inch sphere is the limit there.^[1]

Cable railings are subject to the same 4-inch rule, but with a twist. Cables flex under pressure, so manufacturers like Feeney typically space them at 3 inches or less so a deflected cable still passes the test.^[4] That tighter spacing is one of the reasons cable rail tends to cost more per linear foot than picket rail.

Top rail

The top rail is the horizontal piece running across the top of the guard. It has two structural jobs. First, it ties the balusters together so they share load. Second, it provides the surface that has to withstand the code-required loads: per 2024 IRC R301.5 and 2021 IBC 1607.9, top rails on guards must withstand a 200-pound concentrated load applied in any direction at any point. Commercial guards must also withstand a 50-pound-per-linear-foot distributed load.^{[1] [3]}

Bottom rail

The bottom rail (sometimes called the foot rail or shoe rail) is the lower horizontal piece, running parallel to the top rail. Its job is to anchor the bottoms of the balusters and prevent them from being kicked or pushed inward. On a metal stair guard, the bottom rail also closes off the bottom of the picket field so the 4-inch rule isn’t violated by the gap between the lowest baluster and the floor or stair.

Handrail

The handrail is the part you actually grab when you walk up or down. Different from a guard, even though the two are often combined into one piece. Per 2024 IRC R311.7.8, a handrail is required on at least one side of any flight of stairs with four or more risers. In commercial under 2021 IBC 1014.1, handrails are required on both sides of stairways.^{[1] [3]} Chicago’s prior code (Title 13) allowed a single-side handrail on stairs less than 44 inches wide. The city now follows the 2019 Chicago Building Code (Title 14B), based on the 2018 IBC, for permits filed on or after August 1, 2020. The IBC has its own narrow-stair exception (1014.9), but the wording differs. Confirm the current allowance with the Chicago Department of Buildings before specifying a one-side handrail for a Chicago project.^[5]

Handrail height is 34 to 38 inches above the stair nosing line, residential or commercial (2024 IRC R311.7.8.1, 2021 IBC 1014.2).^{[1] [3]} Grippability is also coded. A circular handrail must have an outside diameter between 1-1/4 and 2 inches (per the grip-size provisions in 2024 IRC R311.7.8).^[1] Non-circular handrails must have a perimeter between 4 and 6-1/4 inches with a maximum cross-section of 2-1/4 inches.^[1] The reason for those numbers: a hand needs to wrap around the rail to actually catch you in a fall. A 2×4 nailed flat on top of the guard isn’t a handrail. It’s decorative.

ADA-compliant handrails (commercial only, but applicable to a lot of multi-family work) follow the same 34 to 38 inch height range and 1-1/4 to 2 inch diameter range, plus a few additional requirements. Clearance from the wall must be at least 1-1/2 inches (ADA Standards 505.5).^[6] The handrail must extend horizontally at least 12 inches above the landing beyond the top riser nosing (ADA Standards 505.10.2).^[6] At the bottom of the flight, the handrail must continue at the slope of the stair for a horizontal distance of at least one tread depth beyond the last riser nosing (ADA Standards 505.10.3).^[6] That last detail is what trips up a lot of commercial remodels. It’s also what we offer custom wrought iron handrails for: hand-fit, code-compliant returns and extensions in the finish you actually want.

Newel post

The newel post is the big vertical post anchoring the handrail at the bottom, top, and any turn or landing. Newels are structural. They have to take that 200-pound concentrated load and transmit it into the floor framing.^[1] A wobbly newel post is the most common service call we get on older stairs. The fix is almost always: open up the floor (or build a steel sleeve), re-anchor properly, close back up.

Newels come in a range of styles. Square boxed newels are common in Traditional and Transitional stairs. Turned and twisted-bar newels show up in French Country and Traditional work. Round metal newels are typical in Urban Modern, Minimalist, and Industrial designs. We keep a tight set of canonical style names in the shop, so when a customer says “I want something modern,” we narrow it down to Urban Modern, Minimalist, or Industrial before we draw anything. The narrowing is the design conversation.

Volute, turnout, and easing

Three names for shaped handrail terminations. A volute is a curved scroll where the handrail spirals inward at the bottom of the stair, common in formal traditional stairs. A turnout is a quarter-turn that flares the handrail out away from the newel. An easing is a vertical or angled transition where the handrail changes direction (typically at landings). All three are decorative and structural, and all three are where a handful of metal shops separate themselves from the field on custom work.

Rail cap, rail bracket, and rosette

The rail cap is the top profile of the handrail, especially on stairs where the handrail also serves as the top of the guard. We sometimes finish a metal top rail with a wood cap so the hand has something warmer to grip.

A rail bracket mounts a wall-mounted handrail to the wall. Per ADA Standards 505.5 (commercial), the bracket must give 1-1/2 inches of clearance between the rail and the wall surface.^[6] Residential is similar in practice but not strictly required by IRC.

A rosette is the decorative round or square plate that finishes the wall side of a handrail termination. Cosmetic, but a missing rosette is the visual equivalent of a hung painting that’s slightly crooked. Easy to overlook, hard to un-see once you have.

Fillet

A fillet is the small filler piece between balusters in a top or bottom rail that has a recessed channel for them. You see fillets on traditional wood stairs more often than on metal ones. Worth knowing the word, because if a stair carpenter mentions “the fillets are loose,” the fix is small but the cause (movement somewhere in the rail system) might not be.

Bullnose

A bullnose is the rounded bottom step that flares wider than the rest of the staircase, often wrapping around the newel post in a quarter-circle. Decorative on traditional stairs, common in older Chicago single-family homes. Bullnose steps are usually solid wood (or covered with a thick veneer) and they’re a giveaway that the staircase was built before about 1950.

The numbers you came here for

If you’re skimming, this is the section to bookmark. Every dimension below is verified against the 2024 IRC, 2021 IBC, the 2010 ADA Standards, and the 2019 Chicago Building Code (Title 14B) as of the time of writing.^{[1] [3] [5] [6]} Local jurisdictions can amend these numbers, so verify with your building department before finalizing a design. Code is the floor, not the ceiling.

Tread and riser

• Maximum riser height (residential): 7-3/4 inches (2024 IRC R311.7.5.1).^[1]
• Maximum riser height (commercial): 7 inches (2021 IBC 1011.5.2).^[3]
• Minimum tread depth (residential): 10 inches measured nosing to nosing (2024 IRC R311.7.5.2).^[1]
• Minimum tread depth (commercial): 11 inches (2021 IBC 1011.5.2).^[3]
• Maximum tread/riser variation in a flight: 3/8 inch (2024 IRC R311.7.5).^[1]
• Nosing projection: 3/4 to 1-1/4 inches on stairs with solid risers (2024 IRC R311.7.5.3).^[1]
• Minimum stair width (residential): 36 inches clear width above the handrail height (2024 IRC R311.7.1). Below the handrail, the clear width can drop to 31-1/2 inches with a handrail on one side, or 27 inches with handrails on both sides.^[1]
• Minimum stair width (commercial): 44 inches in most cases, with an exception allowing 36 inches when the stair serves an occupant load of less than 50 (2021 IBC 1011.2). Required width also has to satisfy egress capacity calculations under IBC 1005.^[3]
• Minimum headroom: 6 feet 8 inches measured vertically from the nosing line (2024 IRC R311.7.2).^[1]
• Maximum vertical rise per flight (commercial): 12 feet between landings (2021 IBC 1011.8).^[3]

Guards and openings

• Guard required at: any walking surface more than 30 inches above the surface below (2024 IRC R312.1, 2021 IBC 1015).^{[1] [3]}
• Minimum guard height (residential): 36 inches (2024 IRC R312.1.2).^[1]
• Minimum guard height (commercial / multi-family): 42 inches (2021 IBC 1015.3).^[3]
• Maximum sphere through guard openings (general): 4 inches (2024 IRC R312.1.3, 2021 IBC 1015.4).^{[1] [3]}
• Maximum sphere on stair guards: 4-3/8 inches (2024 IRC R312.1.3).^[1]
• Maximum sphere at stair triangle (tread, riser, bottom rail): 6 inches (2024 IRC R312.1.3).^[1]
• Chicago variation: As of August 2020, the City of Chicago has adopted the 2019 Chicago Building Code (Title 14B), which incorporates the 2018 IBC with Chicago amendments. New construction in Chicago generally follows the IBC opening rules above, but some older buildings were built under the prior Chicago Municipal Code (Title 13), which had a 4-inch sphere up to 34 inches and an 8-inch sphere between 34 and 42 inches. Always verify the current rules with the Chicago Department of Buildings before specifying a guard for a Chicago project.^[5]

Handrails

• Required when: the stair has 4 or more risers (2024 IRC R311.7.8). Commercial requires both sides on most stairs (2021 IBC 1014.1).^{[1] [3]}
• Height above nosing: 34 to 38 inches (2024 IRC R311.7.8.1, 2021 IBC 1014.2).^{[1] [3]}
• Circular handrail diameter: 1-1/4 to 2 inches (2024 IRC R311.7.8 grip-size provisions).^[1]
• Non-circular handrail perimeter: 4 to 6-1/4 inches with a maximum cross-section of 2-1/4 inches.^[1]
• ADA wall clearance: 1-1/2 inches minimum (ADA Standards 505.5).^[6]
• ADA top extension: handrail extends horizontally at least 12 inches beyond the top riser nosing (ADA Standards 505.10.2).^[6]
• ADA bottom extension: handrail continues at the slope of the stair for at least one tread depth beyond the last riser nosing (ADA Standards 505.10.3).^[6]

Loads

• Top rail concentrated load: 200 pounds applied in any direction at any point (2024 IRC R301.5, 2021 IBC 1607.9).^{[1] [3]}
• Top rail distributed load (commercial): 50 pounds per linear foot horizontal or vertical (2021 IBC 1607.9). Does not apply to one- and two-family residential.^[3]
• Infill panel load: 50 pounds applied to a 1 square foot area (2024 IRC R301.5, 2021 IBC 1607.9).^{[1] [3]}
• Live load on the stair itself: 40 pounds per square foot residential (2024 IRC Table R301.5), 100 pounds per square foot commercial (2021 IBC Table 1607.1).^{[1] [3]}

Where staircases go wrong (and why)

After 20+ years of fixing other people’s problems, a few patterns repeat. Knowing them up front saves you the call to us, or at least makes the call shorter.

Inconsistent risers

Most often caused by a contractor who divided the total rise by the number of risers, came up with a weird fractional dimension, and shaved the bottom or top step to make the math come out. Code requires no more than 3/8 inch variation.^[1] The CDC reports more than 1 million stair-related injuries treated annually in U.S. emergency departments, and inconsistent rise is one of the top mechanisms.^[2] If your stairs feel “off,” pull a tape measure across the risers from top to bottom. You’ll find the culprit.

Handrail too low or too high

The 34 to 38 inch range is from the nosing of the tread, not from the back.^[1] Older stairs were built to looser standards, and replacements often inherit the wrong height. If your hand naturally rests above the rail (not gripping it), the rail is too low. We see this on probably one in five remodels we touch in older Chicago neighborhoods.

Newel post wobble

A newel that moves more than 1/8 inch under hand pressure has lost its anchor. The fix is to open the floor framing at the base, re-bolt to a structural member (or add a steel sleeve), and close back up. Don’t bandage it with construction adhesive. We’ve had to redo bandaged newels more than once because the fix didn’t hold.

Stair guards that pass the 4-inch sphere only when nobody’s pushing

Cable rail systems can deflect enough under sideways pressure to fail the sphere test even when they pass at rest. Manufacturer Feeney recommends spacing cables at 3 inches or less to account for deflection.^[4] Some Chicago commercial inspectors have also raised the “ladder effect” concern with horizontal cables, where a child can climb the cables like rungs. Verify with the AHJ before specifying horizontal cable on commercial work.

The triangular gap at the bottom of the guard

The triangle formed by the bottom of the guard, the riser, and the tread is the one place the 4-inch rule loosens to 6 inches.^[1] That’s a generous allowance, and it’s easy to over-design with a tiny first picket. Most of our pickets just run to within 1/2 inch of the tread, and it works fine. The 6-inch allowance exists for the geometry of bottom rails that float above the tread, not as an excuse for sloppy detailing.

How this all gets enforced in Chicago and the suburbs

Illinois generally adopts the IRC and IBC, but the year of edition adopted varies by municipality.^{[1] [3] [7]} The City of Chicago modernized its building code in 2019, replacing the old Title 13 with the 2019 Chicago Building Code (Title 14B), which is based on the 2018 IBC with Chicago amendments. Title 14B applies to permit applications started on or after August 1, 2020.^[5] Most suburbs adopt one or the other model code, often a few years behind the most current edition. The 2024 IRC is the most current edition as of this writing. The 2021 IBC is the most current.

Practical reality: every project in our 50-mile service area might cite a different code year. We default to the most current edition unless the AHJ tells us otherwise. We pull permits where the GC isn’t pulling them, and we always confirm what edition the inspector is enforcing before we cut metal. If you’re a homeowner planning a stair replacement, ask your contractor what edition the local building department is on. If they don’t know, ask another contractor.

When you need a permit

Generally, a permit is required for new construction, structural additions, and any deck or balcony work elevated more than 30 inches off grade. Like-for-like railing replacements often don’t require a permit in many jurisdictions, though Chicago is stricter than most. Chicago specifically requires permits for nearly all exterior porch and balcony work and follows its own Porch Design and Construction Guidelines for those projects.^[5] Always confirm with the local building department before you assume.

A last word

Knowing the parts of a staircase isn’t about sounding smart. It’s about getting the work right. When a homeowner can say “the newel feels loose” instead of “the bottom thing wobbles,” the contractor can quote the actual fix the first time. When you can ask “what’s the rise on these stairs?” and your builder gives you a real number, you know they know. And when you get a quote that lists the parts you need replaced, you can compare it to a second quote and see which one is honest.

We do this work every day at our shop in Arlington Heights. Most of what we replace is the railing half of the anatomy, plus the structural metal pieces underneath custom stairs. If you’re planning a stair project anywhere in the 50-mile radius of Chicago, including the city, the suburbs, southern Wisconsin, and northwest Indiana, give us a call at 312-912-7405 or stop into the shop at 3027 Malmo Dr in Arlington Heights any weekday between 9 and 5. Bring photos. Bring measurements if you have them. We’ll figure out what you actually need.

Frequently asked questions

What is the difference between a baluster, a picket, and a spindle?

Three names for the same part: the vertical pieces between the top rail and bottom rail of a guard. Metal shops typically say baluster or picket. Wood-stair carpenters often say spindle. Code uses “baluster” throughout the IRC and IBC. Use any of the three and a tradesperson will know what you mean.

Is a guard the same as a railing?

In casual conversation, yes. In code language, no. A guard is the protective barrier on the open side of an elevated walking surface. A railing can mean the same thing colloquially, or it can refer specifically to the handrail (the gripping piece). When you’re reading code, “guard” is the precise term. When you’re talking to a contractor, “railing” usually covers the whole assembly.

How tall does a stair handrail need to be?

34 to 38 inches above the nosing of the tread, residential or commercial, per 2024 IRC R311.7.8.1 and 2021 IBC 1014.2.^{[1] [3]} If the handrail is also serving as the top of the guard, the same 34 to 38 inch range still applies. The guard alone (when separate from a handrail) is 36 inches minimum residential, 42 inches commercial.

Do I need a permit to replace my stair railing?

It depends on the jurisdiction. In many suburbs, replacing an existing railing with one of similar dimensions and the same type doesn’t require a permit. In Chicago, exterior porch and balcony work almost always does. Always confirm with your local building department before starting. We pull permits where required and where the GC isn’t handling that piece.

What is the maximum spacing between balusters?

The 4-inch sphere rule. No opening can allow a 4-inch sphere to pass through, anywhere on a guard, per 2024 IRC R312.1.3.^[1] On the open side of a stair flight, the rule loosens to a 4-3/8 inch maximum, and the triangular opening at the tread, riser, and bottom-rail corner allows up to a 6-inch sphere. Chicago’s prior code (Title 13) had a different rule that allowed an 8-inch sphere between 34 and 42 inches of guard height, but Chicago modernized to the 2018 IBC base in 2020 (Title 14B). Verify the current rule with the Chicago Department of Buildings before specifying a guard for a Chicago project.^[5]

How much weight does a stair handrail need to support?

A 200-pound concentrated load applied in any direction at any point, residential or commercial, per 2024 IRC R301.5 and 2021 IBC 1607.9.^{[1] [3]} Commercial guards must also withstand a 50-pound-per-linear-foot distributed load. Standard wrought iron and solid metal railings exceed these loads by a wide margin. Cable, glass, and thin-element railings are where the load math actually drives the design.

References

Sources verified at the time of writing.

1. ICC Digital Codes, 2024 International Residential Code (IRC), Chapter 3 Building Planning. Source for residential stair tread and riser dimensions (R311.7.5), nosing projection (R311.7.5.3), stair width and headroom (R311.7.1, R311.7.2), landings (R311.7.6), winders (R311.7.5.2.1), handrail requirements (R311.7.8), guard heights (R312.1.2), opening limitations (R312.1.3), and load criteria (R301.5). https://codes.iccsafe.org/content/IRC2024P2/chapter-3-building-planning
2. U.S. Centers for Disease Control and Prevention (CDC), Older Adult Fall Prevention data and WISQARS Nonfatal Injury Reports. Source for older adult fall mortality (38,742 fall-related deaths in 2021) and the leading-cause-of-injury-death finding for adults 65 and older. The annual stair-injury figure (roughly 1.07 million ED visits per year) comes from Blazewick et al., American Journal of Emergency Medicine 36(4), pages 608 to 614 (2018), based on NEISS data from 1990 to 2012. https://www.cdc.gov/falls/data-research/index.html
3. ICC Digital Codes, 2021 International Building Code (IBC), Chapter 10 Means of Egress and Chapter 16 Structural Design. Source for commercial stair tread and riser dimensions (1011.5), commercial stair width (1011.2), landings and vertical rise (1011.6, 1011.8), commercial handrail requirements (1014), commercial guard requirements (1015), and load criteria (1607.9, Table 1607.1). https://codes.iccsafe.org/content/IBC2021P2
4. Feeney CableRail technical specifications and installation guidelines. Source for recommended cable spacing under deflection. https://www.feeneyinc.com/cablerail
5. City of Chicago, Chicago Construction Codes (2019 Chicago Building Code, Title 14B), incorporating the 2018 IBC with Chicago amendments, effective for permits filed on or after August 1, 2020. Source for current Chicago code adoption status. Note: prior Chicago Municipal Code Title 13 sections referenced in legacy literature (including 13-124-335 on guard openings, 13-160-320 on stairway handrails, and 13-52-100 on handrail loads) were superseded by Title 14B and should not be relied upon for new work without reverifying with the Chicago Department of Buildings. https://www.chicago.gov/city/en/depts/bldgs/provdrs/bldg_code/svcs/chicago_buildingcodeonline.html
6. U.S. Access Board, ADA Standards for Accessible Design (2010), Section 505 Handrails. Source for ADA handrail height (505.4), wall clearance (505.5), cross-section (505.7), top extension at stairs (505.10.2), and bottom extension at stairs (505.10.3). https://www.access-board.gov/ada/#ada-505_handrails
7. Illinois Capital Development Board, building code adoption status. Source for the model codes adopted by the State of Illinois and guidance for local jurisdictional amendments. https://cdb.illinois.gov