FRP stair treads

What it is

FRP stair treads are steps made from fibreglass reinforced plastic – either cut from FRP grating with a bonded nosing, or moulded as solid treads – that replace steel treads where corrosion, chemicals, salt spray or electrical safety make steel a poor choice. They are common on access stairs in water and wastewater plants, chemical plants, wharves and marine structures, cooling towers and switchyards.

World Steel does not manufacture FRP. We supply FRP treads from specialist FRP manufacturers together with the steel stairs we fabricate: we set out the tread size and fixing points in the stair shop drawings, order treads to suit, fit them to the stringers, check them and pack each flight as a set. Where an all-composite stair is needed, the treads can also be used with stringers made from FRP sections.

Types and options

• Nosing: grit-bonded nosing in a contrasting colour (typically yellow) so the step edge stands out.
• Fixing: end plates or angle brackets bolted to the stringer, or stainless clips to carrier angles.
• Resin: polyester for general use, vinyl ester for chemical areas, phenolic where better fire behaviour is required.

Design and compliance

Stair geometry is set by the governing code, not by the tread material. Under OSHA 29 CFR 1910.25 standard stairs have an angle of 30°–50°, riser no more than 9.5 in and tread depth of at least 9.5 in; AS 1657-2018 allows 20°–45°, risers of 130–225 mm and goings of 215–355 mm; EN ISO 14122-3 sets 20°–45° and 600 mm ≤ g + 2h ≤ 660 mm. The tread depth and nosing are chosen so that each flight meets these limits and the overlap rules of the code.

The load per tread is checked against the manufacturer's data for the tread size and span – OSHA requires stairs to carry five times the anticipated live load and not less than a 1,000 lb concentrated load, and AS/NZS 1170.1 or EN 1991-1-1 imposed loads apply elsewhere. Because FRP is much more flexible than steel, deflection under the point load is usually the deciding check. Slip resistance (for example AS 4586 classification) and fire behaviour are product-specific and must be shown in the manufacturer's test reports; World Steel does not test or certify FRP.

Supply and fitting by World Steel

Stringers, landings and stair handrails are fabricated in our plant and finished by hot-dip galvanising or stainless steel. FRP treads are ordered to the shop drawing sizes, cut where needed with every cut edge sealed in compatible resin, and trial-fitted to the stringers when specified. Each flight is labelled and packed with its treads, fixings and touch-up resin for export shipping.

Installation and selecting

• Fix treads with stainless steel bolts and the end plates or clips provided; do not drill extra holes through bearing bars.
• Check that every nosing lines up and the rise is uniform over the flight.
• Seal any site cuts straight away.
• Specify stair width, rise, going, code, type of tread, resin, nosing colour and fire or slip requirement. See also PEB stairs and gratings.