AS 1428.1:2021 Quick Reference for Builders and Project Managers

Why This Reference Exists

AS 1428.1:2021 is the Australian Standard that the National Construction Code calls up for physical accessibility. Under NCC 2022 Amendment 2 (effective October 2023), the referenced edition moved from AS 1428.1:2021 to the 2021 edition, bringing the NCC, the Disability (Access to Premises - Buildings) Standards 2010, and the current Standard into alignment. AS/NZS 1428.4.1:2009, with Amendments 1 and 2, remains the active standard for TGSI specifics.

If a commercial, civic, institutional, residential multi-unit, or public building is being built in Australia, both standards apply. The Disability Discrimination Act 1992 sits above them, making access a federal legal obligation enforceable by complaint. That's the compliance hierarchy; this article is the practical checklist that sits under it.

Stair Nosings: What Clause 11 Requires

Every stairway on an accessible path of travel must have a compliant nosing strip on every tread in the flight. Under AS 1428.1:2021 clauses 11.1(f) and 11.1(g):

• Strip depth: 50-75mm, measured across the tread surface, extending the full width of the path of travel.
• Single continuous strip only. Multistripe nosings, where the nosing carries multiple bands of colour instead of one continuous strip (for example the Aalto® 4 profile, which Korb doesn't stock for this reason), breach clause 11.1. Surface texture (corrugated, ridged, carborundum) is fine; what fails is splitting the contrast strip into multiple colour bands.
• Setback: Maximum 15mm from the leading edge of the nosing. Where the strip is not set back, any contrast extending onto the riser must not exceed 10mm vertical.
• Nose profile: Sharp intersection, or radius up to 5mm, or chamfer up to 5×5mm. Full bullnose and larger radii are non-compliant and need retrofit.
• Luminance contrast: Minimum 30% between the strip and the adjacent tread, calculated using the Bowman-Sapolinski equation C = 125 × (Y₂ − Y₁) / (Y₁ + Y₂ + 25).
• Slip resistance: Nosing classified to AS 4586:2013 wet pendulum. HB 198:2014 recommends P3 internal/dry and P4 external/wet as deemed-to-satisfy minimums.

TGSI Placement: The Setback Rules

Warning TGSIs (dot pattern) and directional TGSIs (bar pattern) are never interchangeable. The setback distances under AS/NZS 1428.4.1:2009 clause 2.4 onwards are tight:

Warning TGSIs: Required At

• Top and bottom of stairways: 300mm ±10mm from the outer leading edge of the nosing, depth 600-800mm, full width of the path.
• Top and bottom of ramps steeper than 1:14: same setback and depth. Exception: where a ramp is bounded by continuous handrails that extend onto the landing, TGSIs are not required at that end.
• Escalators, travelators and moving walks: 300mm ±10mm from the end of the moving handrail (not the comb plate), 600-800mm depth.
• Railway platform edges: setback 600mm from the edge (the hazard is falling, not descending), full platform length.
• Kerb ramps, pedestrian crossings, and overhead obstructions below 2000mm headroom.
• Intermediate stair landings only where a handrail is broken: continuous handrails on both sides waive the intermediate-landing requirement.

Directional TGSIs: Required At

• Open spaces where the accessible path is not defined by walls, kerbs, or landscaping: minimum 300mm wide (4 bars), bars parallel to the line of travel.
• Transport waiting areas and platform navigation.
• Mid-block crossings leading from an accessible path to the warning TGSI at the crossing edge: minimum 600mm deep (8 bars) where detected at an angle.

TGSI Dimensions

• Warning TGSI (truncated dome): height 4-5mm above base, top diameter 25mm ±1, base diameter 35mm ±1, spacing 50mm ±1 centre-to-centre.
• Directional TGSI (truncated bar): height 4-5mm, top width 17mm ±1, base width 35mm ±1, spacing 75mm ±5 centre-to-centre.

Luminance Contrast: The Three Thresholds

Three minimums, one equation. Under AS/NZS 1428.4.1:2009 clause 2.2:

• Integrated TGSI (single-piece, base + dome same material): 30% minimum against the adjacent floor.
• Discrete TGSI (standalone stud, uniform colour): 45% minimum.
• Composite discrete TGSI (stud with contrasting top, e.g. carborundum): 60% minimum.
• Stair nosing strip: 30% against the tread.
• Outdoor installations: threshold must be met both wet and dry. Worst condition governs.

Calculated using the Bowman-Sapolinski equation C = 125 × (Y₂ − Y₁) / (Y₁ + Y₂ + 25), where Y₁ and Y₂ are the LRVs of the two surfaces and Y₂ is the lighter. Measurement per Appendix E: tristimulus colorimeter or spectrophotometer with CIE D65 illumination, d/0 geometry. On-site and laboratory readings are both acceptable.

Common Non-Compliance on Site

From access-consultant inspection reports, these are the items that fail most frequently:

1. Multistripe nosings: still the most common fail. Single continuous strip, 50-75mm, one colour.
2. Contrast below 30% on yellow-on-aged-concrete stair nosings: substrate LRV drifts as concrete ages or is sealed.
3. TGSI setback drift: installs at 250mm or 350mm instead of 300 ±10mm.
4. TGSIs set at the comb plate on escalators instead of at the end of the moving handrail.
5. Missing intermediate-landing TGSIs where a handrail is broken.
6. Composite discrete TGSIs specified at 45% (discrete threshold) when they needed 60%.
7. Bullnose or rounded stair edges exceeding the 5mm radius limit, retained from refurbishment.
8. Slip rating verified on the tread only, with the nosing strip itself untested.
9. Nosing strips missing from the top tread or the bottom tread.
10. Directional TGSI bars rotated 90°, indicating the wrong path.

Pre-Handover Checklist

Before certification, confirm each of the following items is documented with evidence:

• NATA-accredited AS 4586:2013 wet-pendulum certificates for every installed nosing and tread surface, not just the range-level marketing data.
• Bowman-Sapolinski luminance contrast calculations for every TGSI-to-substrate interface, with LRV measurements from the sealed, installed surfaces.
• For outdoor installations: both wet and dry contrast readings above threshold.
• Directional TGSI bar orientation verified on plan and on site.
• Intermediate-landing TGSIs present where the handrail breaks.
• Top tread and bottom tread nosing strips present.
• Setback measurements (300mm ±10mm) sampled at each stair and ramp, including escalators measured from the end of the moving handrail.
• A margin of 5 percentage points above the regulatory minimum on luminance contrast, to preserve compliance as surfaces patinate, fade, or are refinished.

How Korb Products Support Compliance

Across the Korb TGSI, stair nosing, and entry matting ranges, compliance is engineered into the product:

• Published LRV data for every product, including composite values for carborundum-topped variants, so Bowman-Sapolinski can be run at specification stage.
• Product-specific NATA-certified slip testing to AS 4586:2013. The Korb tactile range is rated P5 wet-pendulum across Nouvel®, Kahn® and Renzo®, including the Kahn® stone ranges, Kahn® Porcelain, Renzo® Vanguard FRP, and carborundum-topped Nouvel® CarbTop. Product-specific test certificates are available on request and should be referenced in the specification.
• Warning and directional configurations across every TGSI line, in matched colours and materials, so the visual palette stays consistent.
• Four nosing formats (Aalto®, Venturi®, Tadao®, Carbtech®) covering surface mount, recessed, floor tile, and carpet installations in brass, aluminium, carbtech and polymer, to suit any stair construction stage or substrate.