GRP Anti-Slip Stair Nosings & Treads

Description

GRP — glass reinforced plastic, also sold as fibreglass or FRP — is the specification for stairs that get wet, salted or washed down. It is the only common nosing material that carries its slip resistance right through the product rather than on the surface, so grip survives as the material wears instead of disappearing with a coating.

Why GRP rather than aluminium

• Highest wet grip of the common materials. Published UK supplier data puts GRP nosings around 65–69 PTV wet, with some silicon-carbide products above 80 — roughly double the HSE threshold.
• Unaffected by salt. Coastal and marine exposure is the fastest route to aluminium failure. GRP is not attacked by it.
• Chemically resistant. Survives acids, alkalis, oils and aggressive cleaning regimes that pit metal.
• Non-conductive. Which matters on stairs near live plant.
• No coating to maintain. No painting, sealing or protective treatment, and the colour runs through the material.

Where none of that applies — a dry internal office stair — aluminium is usually better looking and cheaper. GRP is a performance material, not a default.

Which GRP product you need

"GRP nosing" covers four distinct products, and picking the wrong one is the most common specification error:

• Nosing covers protect the step edge only. The default retrofit and the cheapest way to make an existing stair safe.
• Tread covers sheet the whole tread, for stairs where the tread surface itself is worn or slippery, not just the edge.
• Replacement treads rebuild the step entirely, for structural damage or poor original construction.
• Landing covers and strips continue the same surface across landings and walkways, so grip does not change underfoot at the top of a flight — a commonly overlooked failure point.

Profiles, grit and colour

Two profiles do most of the work, and both are industry standard across UK suppliers. 55 × 55mm gives equal coverage on tread and riser, matching the contrasting band described in Approved Document M, which makes it the usual choice for public and non-domestic buildings. 70 × 30mm puts more width on the tread and less down the riser, so it covers the zone where foot traffic concentrates and accommodates existing edge damage without substrate levelling — the retrofit workhorse.

Typical thickness is 3–6mm. Look for a chamfered leading edge, which resists chipping, and factory pre-drilled countersunk holes at around 150mm centres. Stock lengths run from 400mm to 3m, with bespoke lengths on project quantities.

Grit grade matters more than people expect. Fine, around 0.5mm aggregate, is for barefoot areas: pools, changing rooms, spa. Medium, around 1mm, is general purpose and the right default for most stairs. Coarse is for heavy industrial and oil-contaminated steps — maximum grip, rough underfoot, and unsuitable anywhere people may fall onto it.

Black, yellow, white, grey, green and red are standard, with RAL matching on volume orders. Yellow is the usual hazard-area specification; black hides dirt and contrasts well against pale concrete; white suits healthcare and food production.

Slip resistance, measured properly

In the UK, slip resistance is measured by the pendulum test to BS 7976, now BS EN 16165, giving a Pendulum Test Value. The HSE benchmark is PTV 36 or above in the wet, and 65 or above where oil, grease or food waste is likely.

R ratings from DIN 51130 are also quoted, and R11 or above is the usual industrial shorthand. The two scales do not convert — a single R10 rating spans pendulum results from 20 to 60 — so ask for both figures. Because PTV can be measured in situ, a periodic pendulum test on the installed surface is how you evidence that a stair still performs.

What the rules require

• Workplace (Health, Safety and Welfare) Regulations 1992, regulation 12 — law. Floors and traffic routes must not be slippery so as to expose anyone to risk.
• Approved Document K — stair geometry: going, rise and nosing projection, 25mm being the figure to work to.
• Approved Document M — access, and the source of the 55mm × 55mm contrasting band for buildings other than dwellings.
• BS 8300-2:2018 — a standard referenced by Part M, not law. Recommends at least 30 points of Light Reflectance Value difference between nosing and tread. Check a combination with our LRV contrast calculator.
• Fire — GRP is available in grades certified to BS 476 Part 7 Class 1 or 2 where flame spread is specified.

Installation and service life

Mechanical fixing is the default: stainless countersunk screws, A4 grade in coastal and marine work. One difference from aluminium worth knowing before ordering — GRP is rigid and cannot be bent or eased to fit on site, so measure each step properly. Cut with an angle grinder or fine-tooth saw, wearing a mask, as GRP throws glass fibre dust. Full method in our installation guide, and deeper specification detail in the GRP guide.

Guaranteed life is ten years across our GRP nosings and tread covers, and installations routinely run beyond that in sheltered and internal locations. Coastal, chemical and heavy industrial settings sit at the shorter end.

Frequently asked questions

What PTV should I specify for an external stair?
At least 36 in the wet, the HSE benchmark for low slip potential. Quality GRP typically measures 65 or above wet, clearing the threshold with margin — useful, because surfaces lose some performance as they wear and soil.

Which grit should I choose?
Medium, around 1mm, for most stairs. Fine, around 0.5mm, where people are barefoot. Coarse only for heavy industrial or oil-contaminated steps; it is uncomfortable underfoot and abrasive in a fall.

How long do GRP nosings last?
Guaranteed ten years, and commonly longer in sheltered or internal locations. Because the anti-slip aggregate runs through the surface rather than sitting on it, grip is retained as the material wears.

Can GRP be used on metal stairs?
Yes, and it is a common pairing on outdoor and industrial steel stairs where the metal is already corroding. Use stainless self-tapping screws. The non-conductive surface is an added benefit near electrical plant.

Can GRP nosings be painted?
They can, with a two-part epoxy system, but it is a poor idea — paint fills the grit texture and reduces slip resistance. The colour runs through the material, so order the colour you want.

Nosing cover or tread cover?
If only the step edge is worn or slippery, a nosing cover is enough and cheaper. If the whole tread surface has gone, a tread cover sheets the full depth. Fitting a nosing to a failed tread only moves the problem back a few inches.

All GRP products are UK stock. Volume pricing, custom lengths and RAL colour matching are available on project quantities, along with material data sheets and test certificates for tender submissions. Call 01282 270 010 for specification advice.