FRP Stair Tread Installation: Nosing & Slip Resistance

Stairs are the highest-risk point on any industrial platform — a slip on a horizontal walkway is a stumble; a slip on a stair is a fall. FRP stair tread grating is chosen for exactly this reason: it does not rust, it does not rot, and its grit-top surface stays slip-resistant when wet. But the tread only performs if it is the right type, properly nosing, positively fixed, and dimensioned to the stair geometry. This guide covers the types, the standards and the fixing procedure for ZeAllgrate FRP stair and ladder systems.

Types of FRP Stair Tread

Three tread forms are common, each suited to a different duty and budget.

Tread Type	Construction	Best Application
Molded grating tread	Cut from standard molded panel (25/30/38/50 mm), grit-top or concave	General industrial stairs, corrosive environments, open drainage
Pultruded FRP stair tread	Load-bar grating or pultruded channels, stiff	Longer tread widths, heavier loads, where stiffness matters
Solid cover tread	Solid or plate surface with grit top	Cleanrooms, food & beverage, where debris must not fall through

Molded grating treads are the most common: they are economical, drain freely and accept an abrasive nosing. Pultruded treads suit wider stair widths where a molded panel would deflect. Solid cover treads are specified where nothing may pass through the step.

Standard Tread Dimensions

ZeAllgrate stair treads are supplied to fit the stringer. Typical proportions:

• Tread depth (going): 200–300 mm measured front-to-back.
• Tread width: up to about 1220 mm in a single panel; wider stairs use two panels on shared stringers.
• Thickness: 25–50 mm depending on span and load; pultruded load-bar depth up to 60 mm for heavy-duty stairs.
• Riser geometry: matched to the stair pitch; consistent riser height across the flight is a code and safety requirement.

Standard stair rises and goes follow OSHA and ISO 14122 practice: a consistent riser height and a tread depth that gives a stable footing. Variable riser heights are a trip-hazard and a common audit finding.

Nosing: Visible, Contrast, Abrasive

The nosing — the leading edge of the tread — is the most safety-critical detail on the stair. Standards including OSHA 29 CFR 1910 and ISO 14122 expect the nosing to be visible and slip-resistant. ZeAllgrate supplies:

• Abrasive grit nosing — a quartz-sand strip bonded along the leading edge for high friction where the foot first lands.
• Contrast color nosing — safety yellow, black or gray edge strip that makes the step line visually obvious, especially in low light.
• FRP angle nosing — a pultruded angle that protects the tread edge from impact and doubles as the visible line.

A bare grated edge without nosing is both less visible and less slip-resistant. On any industrial flight, specify the nosing — it is a small cost with a large safety return.

Slip Resistance on the Walking Surface

FRP tread surfaces are graded for friction. ZeAllgrate grit-top treads deliver a coefficient of friction (COF) in the range of about 0.6–0.8 dry and 0.5–0.7 wet, per ASTM C1028-type test methods. Surface options:

Surface	Friction Profile	Where Used
Grit-top (quartz sand)	Highest friction, wet or dry	Stair treads, ramps, wet zones
Concave / meniscus	Good drainage, comfortable underfoot	General walkway treads
Convex	Self-cleaning	Outdoor, dusty or debris-laden stairs
Smooth	Lowest friction	Architectural, dry interior — not recommended for stairs

For stair nosing zones, grit-top is the default. Smooth-surfaced treads on stairs are a slip risk and should be avoided, particularly where washdown or rain is possible.

Fixing Methods

Treads must be positively fixed to the stringer on every flight. Three methods are standard:

1. FRP stair clips / L-clips — an L-shaped saddle clips the tread edge to the stringer flange. Fast, non-penetrating to the tread bar, and the most common method. Use SS316 hardware on wet or corrosive stairs.
2. Bolt through — drill through the tread and the stringer and bolt with a washered connection. Highest rigidity; used on heavy-duty or vibrating stairs.
3. Integrated FRP stringer systems — ZeAllgrate ladder and stair systems use pultruded channel stringers with a designed tread seat, so the whole flight is FRP and non-corrosive end to end.

Whatever the method, fix both sides of every tread to both stringers, and leave a small expansion gap at the tread ends so the step can move thermally without binding. Do not weld or rigidly bond treads to steel stringers — clips and bolts allow movement and allow a tread to be replaced individually.

Landing, Riser and Handrail Integration

A stair is not just the treads — it works as a system with the landing and the handrail:

• Landing platforms — the top and bottom landings use the same deck grating and clip schedule as the main deck, with the 40 mm minimum support bearing and 3–5 mm expansion gaps.
• Riser gaps — open risers are common on FRP stairs; ensure the opening between treads does not create a fall-through hazard and meets the applicable code.
• Handrail — integrate with the tread/landing structure. OSHA 1910.23 expects top rail strength of 200 lbf, mid-rail 50 lbf/ft, and top-rail height around 1070 mm (42 in); ISO 14122-3 specifies height ≥ 1100 mm. ZeAllgrate FRP handrail systems mount directly to the landing and stringer.

The choice between an open grated tread and a solid cover tread is driven by what lies below the stair. Grated treads drain freely and shed debris, but they drop anything small — tools, water, material — onto whatever or whoever is on the level below. Where the stair sits over equipment, a walkway, or an area where falling objects cannot be tolerated, switch to a solid cover tread or add a metal/FRP under-tray. Conversely, where drainage matters — outdoor stairs, washdown areas, coastal platforms — the open grate is the right choice because standing water on a smooth tread is the number-one slip contributor. Match the tread surface to the zone: grit-top grated treads on outdoor and wet stairs, concave grated treads on general industrial interior stairs, and solid grit-top cover treads where nothing may fall through. ZeAllgrate can supply the same flight with mixed surfaces — grit-top on the exposed outdoor steps and smooth cover on the interior landing transition — so the stair is safe in both zones without a custom engineering job.

Tread Loads, Riser Geometry and Maintenance

A stair tread is a small span, but it sees concentrated impact loads every time a boot lands. Select thickness from the span tables for the tread-to-stringer distance: a molded 30 mm tread suits narrow industrial stairs, while wider spans or trolley traffic call for 38–50 mm molded or pultruded treads up to 60 mm load-bar depth. Riser geometry must be consistent — code expects a uniform rise and going across the flight, and mixing rises by even 10 mm creates a stumble point. Open-riser stairs are common in FRP, but guard against fall-through between treads and against anything rolling through the gap. In service, inspect treads twice a year: check that the grit top is not worn smooth in the centre line (the tell-tale of high foot traffic), that the nosing strip is still bonded along its full length, that clips are snug, and that no bar has cracked or delaminated. Pay special attention to the first and last tread of each flight — that is where boots land hardest and where grit wear appears first. Replace a worn tread as a single unit — the clip-and-bolt fixing lets you lift one step without dismantling the flight. For coastal or wastewater stairs, keep SS316 spare clips on hand so a loosened fitting is fixed the same day it is found, not weeks later.

Conclusion

FRP stair treads earn their place on corrosive, wet or coastal platforms because they outlast steel and stay slip-resistant. Specify the right tread type for the width and load, put a contrasting abrasive nosing on every leading edge, use grit-top where the foot lands, and positively clip or bolt each tread to both stringers with SS316 hardware in corrosive service. Pair the flight with a ZeAllgrate FRP stringer and handrail system and the whole stair is non-corrosive, code-consistent and safe for decades.

Frequently Asked Questions

Q: What is the best FRP stair tread surface for wet stairs?

A: Grit-top (quartz sand) tread with an abrasive nosing. It delivers the highest wet coefficient of friction — roughly 0.5–0.7 per ASTM C1028-type testing — and the nosing protects the leading edge where feet first land.

Q: Can FRP stair treads be cut to fit an existing steel stringer?

A: Yes. Treads are cut to depth and width on site, deburred and edge-sealed, then fixed with L-clips or through-bolts to the stringer. Allow a small expansion gap at the tread ends. For best results, send the stringer dimensions to ZeAllgrate for factory-cut and factory-sealed treads.

Q: Do FRP stairs need a handrail to OSHA 1910.23?

A: Where the stair rise exceeds the code threshold, yes — typically a guard/handrail system with a 1070 mm (42 in) top rail, a mid rail, and 200 lbf top-rail / 50 lbf-per-foot mid-rail load capacity. ZeAllgrate FRP handrail systems are engineered to meet this and ISO 14122-3.