Dock & Marina FRP Deck Grating

Dock decks must (1) survive constant salt spray, (2) be anti-slip when wet, (3) be light enough for floating pontoons, (4) not rot. FRP molded #38 in vinylester resin is the standard marina decking. SS316 clips are mandatory (SS304 will pit in 2–3 years). Double carborundum top for wet friction 0.8. Panel size 1220×3660 mm; weight 14 kg/m² vs wood 18 kg/m² vs steel 48 kg/m².

Decking comparison

Marina decking must meet IMO Resolution A.753(18) for surface fire performance, and be resistant to salt spray per ASTM B117 (500 hours). Our vinylester molded #38 passes both. SS316 clips are mandatory — SS304 will pit in marine atmosphere within 2–3 years. Anti-slip surface is double carborundum (top and bottom), giving wet friction 0.8 even when covered by seawater spray.

Floating vs fixed docks

On floating pontoons, weight is critical. FRP at 14 kg/m² is 70% lighter than steel grating, reducing pontoon buoyancy requirements by the same margin. On fixed piers, FRP decking is bolted to steel stringers with SS316 clips. See Marine & Coastal.

Glass-fiber reinforced polymer (GRP / FRP) grating has become the default choice for industrial walkways, platforms and trench covers. The reason is not aesthetics — it is total cost of ownership. Painted steel grating requires scraping and repainting every 3–5 years in chemical and marine environments. Galvanized steel lasts 10–15 years before corrosion attacks the bars. Aluminum corrodes in alkaline washdown areas. Stainless 316 is the only comparable metal, but at 3× the cost of vinylester GRP and still prone to pitting at the waterline.

FRP does not rust, does not need painting, and carries a 25-year design life. It is 70% lighter than steel, which reduces the structural steel subframe, lowers shipping cost, and makes manual installation feasible without heavy equipment. It is non-sparking and non-conductive, which is why it dominates refinery, offshore and substation applications. It also has a lower coefficient of thermal conductivity than aluminum, so barefoot areas stay cool in sunlight.

Total cost of ownership comparison

The numbers tell the story: vinylester GRP is 55% lower total cost than either steel or stainless over a 25-year horizon. Add the safety benefits (non-sparking, non-conductive, anti-slip wet), and the engineering case is clear.

FRP grating is famously low-maintenance. But "low maintenance" does not mean "no maintenance". For a 25-year service life, we recommend the following inspection schedule. Annual visual inspection: walk every 12 months, look for broken bars, missing clips, UV chalk on the top surface. Clips: re-torque every 3 years — thermal cycling loosens bolts slightly. Cleaning: wash with high-pressure water 200 bar; for chemical residue, use pH-neutral detergent. Do not use solvent-based cleaners on the gel coat — they can craze the surface.

UV chalk: after 8–10 years outdoors, the gel coat may show faint surface chalk. This is normal and does not affect structural strength. If appearance matters, apply a coat of UV-stabilized clear gel coat, available from us as a touch-up kit. Repairs: a broken bar can be spliced with a FRP repair kit (resin + mat) in 30 minutes; the panel remains in service. Full panel replacement takes 15 minutes for two workers — no hot work, no welding.

Safety in installation

Cutting FRP generates dust. Wear P100 respirator, eye protection, gloves. Dust is silica-glass, not toxic but irritates lungs. Wet cutting suppresses dust. Do not cut near open flame — resin is combustible, though self-extinguishing per ASTM E84.

When specifying GRP grating for a new project, three variables dominate: panel thickness, resin type, and surface finish. Thickness carries the load. Resin determines chemical and temperature resistance. Surface finish determines slip resistance. Get these three right and the rest follows.

Panel thickness guide

Resin selection

Isophthalic is the default for atmospheric and light chemical service. Vinylester for marine, chemical splash, hot water. Phenolic for high temperature and low-smoke requirements. We provide a chemical resistance chart for 200+ chemicals on request — if your media is not listed, send us the concentration and temperature, and our engineering team will recommend the right resin.

Surface finish

Smooth top for indoor dry areas. Carborundum grit (aluminum oxide F24) for wet and slip-prone areas. Double grit (top and bottom) for marine and washdown. The grit is cast into the gel coat, not glued on — it will not peel.