Choosing the Right Stair Nosing Profile: SM vs RC

The Decision You're Making

Three things drive every stair nosing decision: the construction stage (new build vs retrofit), the substrate and traffic (indoor dry vs outdoor wet; pedestrian vs wheeled vs industrial), and the finish intent (flush architectural vs visible applied strip). Line those up against the four Korb nosing families (Aalto®, Venturi®, Tadao®, and Carbtech®) and the right profile picks itself.

This guide works through the two installation formats, the material options, and the compliance envelope, then maps to the Korb range.

What AS 1428.1:2021 Actually Requires

Every stairway on an accessible path of travel must have a compliant nosing strip on every tread. The non-negotiables from clause 11:

• 30% minimum luminance contrast against the adjacent tread, via the Bowman-Sapolinski equation C = 125×(Y2−Y1)/(Y1+Y2+25).
• Strip 50-75mm deep on the tread, full width of the path of travel.
• Single continuous strip only: multistripe nosings (multiple bands of colour in one nosing, e.g. the Aalto® 4 profile which Korb doesn't stock for this reason) and "ladder" patterns are non-compliant. Surface texture (ribbed, corrugated, carborundum) is allowed; colour must be a single continuous band.
• Setback: maximum 15mm from the leading edge; if not set back, any contrast carried onto the riser is limited to 10mm vertical.
• Nose profile: sharp, or radius up to 5mm, or chamfer up to 5×5mm. Bullnose >5mm radius is non-compliant.
• Slip resistance classified to AS 4586:2013. HB 198:2014 recommends P3 internal/dry and P4 external/wet as deemed-to-satisfy minimums for stairs; P5 for uncovered external steps.

The same rules apply to every tread in the flight, including the top tread and the bottom tread. Landings do not need a nosing strip, but the last tread before a landing does.

Surface Mount (SM): The Retrofit and New-Build Workhorse

Surface-mount nosings sit on top of the finished tread, mechanically fixed with countersunk stainless screws into plugged anchors (concrete), self-tappers (steel), or screws (timber). The compliant profile chamfers the leading edge to 5×5mm or less, keeping the transition within AS 1428.1 geometry and avoiding the "shark-fin" trip hazard that full-wrap 90° nosings produce.

When SM Is the Right Call

• Retrofit of completed stairs: the flight is finished and no rebate is possible.
• Concrete, stone, or timber substrates that accept mechanical fixings.
• Fast-track projects where the nosing goes in after the main floor finish.
• Fire-isolated egress stairs and heritage upgrades where the tread must be preserved.

SM Failure Modes

• Screw pull-out on friable concrete or perished mortar: use chemical anchors, not plastic plugs, in soft substrates.
• Voids under the profile on cupped or worn treads: the bridge flex cracks screws within 12-24 months. Level the tread with a thixotropic repair mortar before fixing.
• Adjacent finish damage during installation: mask before drilling.

Recessed (RC): New-Build Architectural Standard

Recessed nosings sit in a channel cut into the tread edge: diamond blade on concrete, wet-saw on stone and porcelain, router on timber. The top surface of the nosing finishes flush or near-flush with the surrounding tread, eliminating the applied-strip shoulder and the micro-trip edge that SM always introduces. For high-end commercial, airports, transit hubs, and clean architectural finishes, RC is the spec that reads as integrated design rather than applied safety.

When RC Is the Right Call

• New construction where the tread formwork or tiling accommodates a rebate.
• Stone, porcelain or polished-concrete finishes where a clean leading edge is part of the brief.
• High-traffic commercial (airport, retail, transport) where an applied SM shoulder reads as wear-prone.

RC Limitations

• Must be coordinated at construction: missed at shop drawing stage, RC becomes an expensive angle-grinder retrofit.
• Not suitable for thin porcelain (<10mm) where rebating undermines the tile, or timber <25mm where rebating compromises structural depth.
• Mortar shrinkage around the profile can loosen a rigid-bedded RC: use polymer-modified bedding or structural epoxy caulk.

The Material Choice

Across both SM and RC formats, Korb carries four material families. Each targets a different combination of environment, traffic, and finish intent.

Brass: Patina Aesthetic

Solid brass nosings anchor heritage and civic specifications where the finish is expected to develop a warm bronze patina over 2-5 years. Extruded brass is mechanically sound for interior and sheltered external; LRV starts around 55-65 and drops to 35-45 as patina establishes. On light stone treads brass holds 30% contrast comfortably even after patina; on dark treads contrast can drift, so pair brass with a polymer or carborundum infill to do the contrast work.

Korb brass nosings: Aalto® Brass (SM · Recessed, black or white infill); Venturi® Brass (four installation formats, striped or corrugated infill); Tadao® Brass (SM · Recessed, corrugated or striped).

Aluminium: Stable, Cost-Effective, Wide Finish Range

Anodised aluminium (typically 6063-T5 architectural alloy) delivers a stable LRV over decades. The anodised finish palette (mill, black, champagne, heritage bronze) gives architects a coordinated material without the patina drift of brass. Aluminium nosings weigh less, fabricate more flexibly, and sit at lower cost.

Korb aluminium nosings: Aalto® Aluminium (SM · Recessed, black/white/yellow infill); Venturi® Aluminium (four formats, silver/black/champagne/heritage); Tadao® Aluminium (SM · Recessed, corrugated or striped).

Carbtech: Heavy-Duty Industrial and External Wet

Carbtech® is a silicon-carbide aggregate in a structural polymer matrix: the abrasive does the slip-resistance work that smooth metal cannot. Silicon carbide has a Mohs hardness of 9.0-9.5 and persists as the binder wears, which is why carbtech nosings return P5 wet pendulum reliably. This is the specification for industrial loading docks, rail platform edges, uncovered external steps, and any environment where the nosing must remain grippy under water.

Luminous (photoluminescent) carbtech variants supplement emergency egress path-marking. AS/NZS 2293 governs emergency escape lighting; photoluminescent nosings are an additional measure, not a substitute, but on projects following US NFPA 101 or ISO 16069 protocols, they are routinely specified for stair legibility in a power-loss event.

Korb carbtech nosings: Carbtech® standalone heavy-duty range (SM, industrial); Venturi® Carbtech (four formats, carborundum infill in black/grey/white/yellow/luminous); Tadao® Carbtech (heavy-duty SM · Recessed).

Polymer: Interior Budget, Colour-Matched

Polymer nosing infill is the option for interior commercial and budget-sensitive projects where the infill needs to colour-match adjacent finishes. Korb's Venturi® Polymer range uses colourways that match the Renzo® Tile and Renzo® Classic tactile palette: useful on projects where tactile and nosing need to read as one specification.

Infill Patterns: Corrugated, Striped, and Carborundum

The infill is the working surface: the part that delivers both the visual contrast and the slip resistance. Three patterns, three different performance envelopes:

• Corrugated: transverse grooves. Interior-rated; P3-P4 wet; acoustically comfortable underfoot.
• Striped: longitudinal ridges. Similar grip envelope to corrugated; slightly less directional feel.
• Carborundum: silicon-carbide aggregate bonded in thermoset polymer. P5 wet capable. The only infill type that extends reliably into external wet and industrial duty.
• Polymer: softer, colour-matched to adjacent tactile or tile finishes. Used where the frame (brass or aluminium) provides contrast and the infill blends.

The Four Venturi Installation Formats

The Venturi® family is the most versatile Korb nosing range, covering four installation formats in each of four materials:

• Surface mount (Venturi® SM): retrofit and fast-track.
• Recessed (Venturi® RC): new-build architectural flush finish.
• Floor Tile: threshold transitions, single-step level changes, doorway thresholds where a riser does not exist. Bonded flush with surrounding floor adhesive.
• Carpet: carpet-clad stair nosings for hospitality, hotels, theatres, heritage buildings. Includes a carpet gripper or tuck-under channel so the adjacent carpet finishes flush against the metal frame.

Aalto®, Tadao®, and standalone Carbtech® cover SM and RC only. Venturi® is the range to specify when the project has mixed conditions across one continuous scope (stair flights, thresholds, carpet-clad treads, and floor-level transitions) and the design needs a single material family across all of them.

Quick Selection Guide

• Existing stair, needs compliance now: Venturi® SM Aluminium (corrugated or polymer infill) or Aalto® SM Brass for a heritage aesthetic.
• New build, stone or porcelain treads, architectural finish: Aalto® RC in brass for a heritage aesthetic, or Venturi® RC Carbtech for compliance-first external or high-traffic.
• Industrial, loading dock, uncovered external: Carbtech® standalone heavy-duty, black or yellow.
• Rail platform, transport hub, 20-year service life: Venturi® RC Carbtech with carborundum infill.
• Heritage civic, brass aesthetic, moderate traffic: Aalto® Brass SM or RC.
• Hospitality carpeted stair: Venturi® Carpet with brass or anodised aluminium body.
• Threshold or single-step transition: Venturi® Floor Tile.
• Egress-critical luminous marking: Venturi® Carbtech or Carbtech® luminous as supplementary to AS/NZS 2293 compliant lighting.