Glossary of Stairway Terminology

Step Anatomy and Types

Step — A single unit of a stair: one tread plus the vertical rise to the next tread.

Tread — The flat, horizontal surface of a step where you place your foot.

Riser — The vertical face or board that fills the space between adjacent treads.

Closed riser — A stair where the space between treads is fully closed by a riser board. The opposite of an open riser.

Open riser — A stair where the space between the treads — where you lift your foot — is open.

Nosing — The front edge of a tread that projects beyond the riser below it.

Nosing projection — How far the nosing extends past the face of the riser below it. Codes set a minimum and maximum projection.

Tread return (mitered return) — The finished end of a tread and its nosing, wrapped around the open side of the stair so no raw tread end shows.

Tapered tread — A tread that is narrower at one end than the other, used in winders and curved stairs.

Landing tread — The tread or nosing strip at the top of a flight where the stair meets the landing or the upper floor.

Box tread — A hollow tread, usually solid wood, that slips over and fastens to a steel frame or bracket. Used on floating and cantilevered stairs.

Solid block tread — A thick tread cut from solid wood rather than built up as a box.

Tread bracket — A support, decorative or structural, mounted under the front of a tread at the open side of the stair.

Scotia (cove moulding) — The concave trim fitted under the nosing against the riser face, finishing the joint.

Flight — An uninterrupted series of steps extending from one floor or landing to another.

Landing — A flat platform between flights, or at the top or bottom, used to change direction or rest.

Quarter-space landing — A landing where the stair turns 90 degrees.

Half-space landing — A landing where the stair turns 180 degrees, spanning the width of both flights.

Winders — Triangular, pie-shaped steps used to turn a corner without a flat landing.

Kite winder — The central, kite-shaped winder step used in a 90-degree turn.

Bullnose step — A decorative first step with one or both sides rounded.

Curtail step — A decorative, scrolled bottom step with a wider, spiraled footprint at the base.

Commode step — A starting step featuring a curved, convex riser across its entire front width.

Framework and Structural Elements

Stringer (or string) — An inclined structural beam supporting the treads and risers. It may run along the sides or beneath the center of the stair.

Box stair — Any stair with the stringers on the side — open riser or closed riser, the same. Not to be confused with a box tread (a hollow tread that slips over a frame). A type of floating stair.

Housed stringer (routed stringer) — A stringer with grooves cut into its inner face, enclosing the edges of the treads and risers.

Closed stringer — A stringer whose top edge stays straight and uncut, so the tread ends are enclosed between the two stringers rather than visible from the side.

Cut stringer (open stringer) — A stringer cut into a zigzag profile, allowing the tread edges to be visible from the side.

Sawtooth stringer — A stringer cut or folded into a triangular, step-toothed profile — the steel-plate form of a cut stringer.

Folded-plate stringer (zigzag stringer) — A steel plate bent into a continuous zigzag that follows the steps, supporting each tread on its flat.

Hidden (concealed) stringer — A stringer concealed inside a wall or the construction, so no beam is visible on the finished stair.

Tread frame — A steel frame projecting from a stringer or wall that a cantilevered or box tread slides onto and bolts to.

Wall stringer — The stringer next to or anchored against a wall.

Outer stringer — The stringer on the open side of a staircase, visible to the room.

Inner stringer — On a turning or curved stair, the stringer on the inside of the turn, following the shorter radius.

Carriage (rough stringer) — A rough structural timber hidden underneath treads to provide extra support and prevent sagging.

Trimmer — The joist that runs alongside a stairwell opening and carries the header framing.

Soffit — The finished underside of a flight of stairs.

Stairwell — The opening or space through the floors of a building where the staircase is located.

Header — The structural beam framed into a floor opening to support the surrounding framing and, where designed, the upper stair connection.

Skirtboard — A decorative trim board applied against the wall along the stairs, often shaped to match the treads and risers.

Apron — A trim board applied below a landing edge or along the open side of a stairwell, covering the framing.

Railings and Balustrade

Balustrade — The complete railing assembly along the open side of a stair or landing: handrail, balusters or infill, and newel posts together.

Handrail — The rail grasped for support while using the stair, running along the slope of the flight. Distinct from a guard: a handrail is for holding, a guard is for fall protection; one rail can serve both if it meets both requirements.

Guard (guardrail) — A barrier along open sides of stairs, landings, balconies, and decks that prevents falls to a lower level.

Baluster (spindle) — A vertical infill member between the handrail and the tread, landing, or shoe rail. Balusters keep the guard's openings within code limits.

Newel post — The substantial post at the start of a stair, at a landing or turn, or at the end of a run, anchoring the handrail and balustrade.

Starting newel — The newel at the bottom of a flight, often larger or decorative.

Landing newel — The newel at a landing or turn where flights change direction or height.

Half newel — A half-profile newel mounted flat against a wall where a railing ends.

Over-the-post — A handrail system where the rail runs continuously over the tops of the newel posts on curved fittings.

Post-to-post — A handrail system where the rail butts into the sides of the newel posts and the posts extend above the rail.

Volute — The spiral scroll fitting at the bottom of an over-the-post handrail, sitting over the starting newel.

Turnout — A handrail starting fitting that curves outward, away from the stair, over the starting newel.

Starting easing — A curved fitting that eases a sloped handrail up over a starting newel.

Over-easing — A curved fitting where a sloped handrail passes over a landing newel and continues into the next flight.

Up-easing — A curved fitting that transitions a sloped handrail to level at a landing or the top of a flight.

Gooseneck — A fitting combining an up-easing and a vertical drop, used where the handrail must step down over a landing newel to a lower flight or a level rail.

Wreath — A handrail section curved in plan, hand-shaped to twist as it follows winders or a curved stair while keeping the rail profile continuous.

Handrail bracket — The bracket that mounts a wall rail to the wall, setting its distance off the wall.

Rosette — A decorative plate behind a handrail bracket or where a wall rail meets the wall.

Wall rail (wall-mounted handrail) — A handrail mounted directly to a wall on brackets, with no balustrade beneath it.

Shoe rail — A grooved rail at the base of the balusters, on the tread or landing, into which the baluster feet sit.

Fillet — The strip that fills the shoe-rail groove between balusters.

Cable railing — A guard system using tensioned horizontal or vertical cables as the infill between posts.

Base shoe — A continuous metal channel at the base of a frameless glass railing that clamps and supports the glass panels.

Standoff — A round fitting mounted to a stringer, wall, or floor through holes in the glass, holding a glass panel off the surface on a pin.

Glass clamp — A fitting that grips the edge of a glass panel from a post or rail without holes through the glass.

Spigot — A short post-like clamp that holds a glass panel from its bottom edge, floor- or core-mounted.

Dimensions, Geometry and Code

Stairway — The complete assembly: one or more flights, landings, and the handrails and guards serving them. The code's word for the whole thing.

Total rise — The vertical height from the finished surface of the lower floor to the finished surface of the upper floor.

Total run — The horizontal travel of a straight stair. For turning stairs, the app distinguishes developed run along the walking path from the overall plan footprint.

Developed run — The length of a turning or curved stair measured along its walking line, as if the path were unrolled flat.

Unit rise — The vertical distance between consecutive finished tread surfaces—the height you lift your foot each step. A common IRC residential limit is 7¾ inches; confirm the locally adopted code and any exceptions.

Unit run — The horizontal distance between consecutive tread nosings, excluding the additional nosing projection. A common IRC residential minimum is 10 inches; confirm the locally adopted code and application.

Going — The trade synonym for unit run.

Tread depth — The full front-to-back size of the tread material, including any nosing overhang. For example, an 11-inch board with a 1-inch nosing can provide a 10-inch unit run. Material depth and code-measured tread depth are different measurements; confirm the required unit run, nosing and stair type with the local building authority.

Pitch (or slope) — The angle of the staircase relative to the horizontal floor plane, determined by unit rise and unit run.

Headroom — The clear vertical distance from the sloped line connecting tread nosings, or from a landing surface, to the ceiling or overhead obstruction. A common IRC residential minimum is 6 feet 8 inches (80 inches); confirm local requirements.

Line of nosing — An imaginary sloped line running along the frontmost tips of the tread nosings in a flight.

Walking line (line of travel) — The imaginary path a person naturally walks on a stair. On winders and curved stairs, tread depth is measured along the walking line; codes commonly fix it 12 inches from the narrow side of the treads.

Staircase width — The side-to-side width of a stair. Overall width, clear width between stringers, and clear width at handrails may differ. The applicable code defines where the required width is measured.

Clear width — The unobstructed width available for passage, measured where the code requires — between walls, stringers, or handrails, depending on the rule.

Riser uniformity — The difference between the tallest and shortest riser in a flight. Codes limit it (commonly ⅜ inch in the IRC) because uneven risers cause trips.

Handrail height — The vertical height of the top of the handrail above the line of nosing, commonly 34 to 38 inches.

Guard height — The minimum height of a guard above the surface it protects — commonly 36 inches residential and 42 inches commercial.

Inner radius — On a curved or circular stair, the radius to the inside (short) edge of the treads.

Outer radius — The radius to the outside (long) edge of the treads — inner radius plus the tread width.

Centerline radius — The radius to the middle of the tread width, often used for layout, stringer mark-out, and handrail bending.

Total turn — The total angle a stair changes direction, in degrees: 90 (quarter), 180 (half), 270 (three-quarter), 360 (full).

Angle per tread — On a circular or winder stair, the total turn divided among the treads; each tread occupies this wedge of the plan.

Arc length — The distance along a curve at a given radius. On a circular stair, arc length at the walking line gives the going of each tread.

Chord — A straight line between two points on a curve, used in layout and for cutting templates.

Maximum vertical rise — The maximum height one flight may climb before a landing is required. The limit depends on the adopted code edition, occupancy, and stair type. Do not assume one limit applies to every project.

Staircase Types

Straight staircase — A linear design with no turns or changes in direction.

Turn stair — Any stair that changes direction, by landing or by winders. Turn stairs are classified by how far they turn: quarter, half, three-quarter, or full.

L-shaped staircase (quarter-turn) — A staircase that makes a 90-degree turn at a landing.

U-shaped staircase (half-turn / switchback) — Two parallel flights joined by a landing that changes travel direction by 180 degrees.

Switchback staircase — Another name for a U-shaped, half-turn stair: the flight doubles back on itself at a landing.

Three-quarter-turn staircase — A staircase that turns 270 degrees between floors, usually around an open well.

Full-turn staircase — A staircase that turns a full 360 degrees and arrives facing the same direction it started.

Dog-leg staircase — A half-turn stair where the two flights sit directly against each other with no open well between them, sharing one half-space landing.

Open-well staircase — A turning stair whose flights are separated by an open vertical space (the well), so you can see between the flights from top to bottom.

Winder staircase — A stair where triangular steps replace a flat landing at a turn.

Winding staircase — A stair that makes its turn entirely on winders, with no flat landing. "Winding" describes the whole stair; a "winder" is one step in it.

Spiral staircase — A design where steps radiate from a central vertical column or post in a tight circle.

Circular staircase — A staircase that follows a circular arc in plan, with treads radiating from a common center point. The center may be a pole, a structure, or open space. Broader than "spiral": a spiral is always circular, but a circular stair need not wind around a pole.

Curved staircase — The umbrella term for any stair following a curved path in plan — circular, elliptical, or free-form.

Helical staircase (curved) — A sweeping curved staircase forming an arc without a central column, often with curved inner and outer stringers.

Elliptical staircase — A curved stair whose plan follows an ellipse, so its radius tightens and relaxes along the curve.

Oval staircase — A curved stair whose plan is an oval: two half-circles joined by straight or gently curved runs.

Geometrical staircase — A traditional continuous stair, usually curved or winder in plan, built with a continuous handrail and no newel posts breaking the rail at the turns.

Floating staircase — The treads show no support: nothing under them coming from below, and no stringer showing along the wall. Types include the single stringer, the box stair, and the hidden stringer. The Radcliffe, its stringer hidden inside the wall, is the ultimate floating stair.

Cantilevered staircase — A stair where each tread is structurally anchored at one end, usually to a wall or concealed beam, with no outer support.

Suspended staircase — A stair whose treads are hung from the structure above by rods or hangers, rather than supported from below.

Central mono-stringer staircase — Has open risers and only one stringer, in the middle. A type of floating stair.

Double stringer staircase — A framework using two parallel stringers on either side of the treads.

Bifurcated staircase (split stairs) — A wide lower flight ascending to a landing and splitting into two narrower flights.

Imperial staircase — Another name for a bifurcated stair, usually a grand centerpiece in a foyer.

Scissor staircase — Two separate flights intertwined in the same stair shaft, climbing in opposite directions without connecting — used mainly in commercial buildings for separate exit paths.

Alternating tread staircase (space-saver / paddle stair) — A steep stair whose treads are cut away alternately left and right, so each foot gets a full tread in half the horizontal run. Restricted or prohibited by many codes.

Ship's stair (ship's ladder) — A steep stair or heavy ladder with handrails both sides, built for tight spaces.

CODE NOTE

Code examples refer to common residential IRC requirements. Local amendments, commercial stairs and spiral stairs may have different requirements.