Molded vs Pultruded FRP Grating: Pick the Right Fabric
Two FRP constructions, two stiffness philosophies. Match the cross-section geometry to your load path and your maintenance window.
Why the split matters
Buyers often treat FRP grating as a single product. In reality, molded and pultruded panels are different mechanical systems molded into the same material. Molded is a woven lattice; pultruded is a built-up beam grid. If you pick the wrong construction, you either over-pay for depth you do not need, or you undershoot the deflection limit on a long span. The table below separates the two on the geometry and service axes that actually change the spec.
Side-by-side comparison
| Dimension | Molded FRP grating | Pultruded FRP grating | Best-fit scenario |
|---|---|---|---|
| Cross-section geometry | Bi-directional woven lattice; continuous roving runs in both axes and is wet-out in a closed mould. Openings are integral to the panel. | Assembled from separate I-, T- or rectangular load bars connected by cross rods or woven ties. Depth comes from the bar, not the lattice. | Molded for bi-directional loads; pultruded for unidirectional beam action. |
| Stiffness source | Distributed across the lattice; each opening contributes. Thickness 25, 30, 38, 40, 50 mm. | Concentrated in deep unidirectional bars; heavy I-bar sections reach 50 to 100 mm effective depth. | Pultruded wins on long spans and point loads; molded wins on uniform footfall. |
| Standard meshes | 19×19 mini, 12×12 heel-safe, 25×100, 38×38, 50×50 in concave, grit-top or covered surface. | 25×100 and 38×38 are the common rectangular grids; heavy I-bar runs at wider spacing. | Fine mesh (19×19, 12×12) only exists in molded. |
| Corrosion direction | Resin-rich surface covers fibres on both axes, so splash hits resin regardless of direction. | Web and flange faces are protected, but a damaged gel coat on a load bar can expose unidirectional fibres to wicking. | Molded wins for random splash; pultruded wins for submerged, single-direction flow. |
| Electrical insulation | Same non-conductive laminate, same resin families. | Same non-conductive laminate; the built-up geometry leaves open air between bars. | Tie on either; the difference is ventilation, not insulation. |
| Fire & smoke | Tested to ASTM E-84 on polyester and vinyl ester; phenolic available for low-smoke interiors. | Same resin options, same E-84 basis; deeper bars can trap more air between flanges. | Pick by resin, not by construction, for fire. |
| Fatigue & impact | Lattice distributes a dropped tool or caster across multiple bars; bi-directional damage tolerance. | A hard point load lands on one or two bars; repeated impact can fatigue the cross-connection. | Molded wins on footfall and tool drop; pultruded wins on slow, heavy wheel loads. |
| Installation & field work | Cuts cleanly; cut edge remains structurally bonded. Clips M/C/L/Z in SS304, SS316 or HDG. | Cuts cleanly, but the end of a cut load bar loses its bearing; clip positions must be planned. | Molded for retrofit around pipes; pultruded for engineered layouts. |
| Lifecycle cost drivers | Depth and mesh drive cost; fine mesh (12×12) costs more per m² than 38×38. | Bar depth and cross-connection hardware drive cost; heavy I-bar is the premium tier. | Molded wins on walkway area; pultruded wins on long-span platforms. |
How stiffness actually gets there
This is the axis buyers most often miss. In a molded panel, stiffness is a property of the whole plate: the woven lattice shares load between axes, so a 38 mm panel behaves like a shallow orthotropic plate. In a pultruded panel, stiffness is a property of individual bars: each I-bar is a miniature beam, and the cross-rods only keep them aligned. That is why the load table at /frp-grating-load-table/ publishes molded deflection cells on a 300 to 1200 mm span axis (for example 25 mm depth at 450 mm span under 1000 kg/m² prints 1.53 mm), while pultruded load tables are organised by bar depth and clear span rather than by mesh square. If your load path runs clearly one direction, pultruded uses material more efficiently; if traffic runs both ways, molded distributes it for free.
Decision summary
Choose molded FRP when: the walkway carries foot traffic, casters or pallet trucks in both directions; you need a heel-safe mesh (12×12 or 19×19 mini); chemical splash lands from random directions; or the site is a retrofit around pipes and equipment where on-site cutting is expected. Browse 38×38, 19×19 mini, 25×100 and 50×50.
Choose pultruded FRP when: the clear span is long and the load path runs along one axis; you need heavy I-bar depth for equipment platforms; or the panel sits under slow, heavy wheels where unidirectional bars carry the line load efficiently. Browse pultruded 25×100, pultruded 38×38 and heavy I-bar.
Do not choose our molded panel when: the span exceeds what the molded deflection cells on the load table cover and the load is concentrated on one axis; molded would force an over-deep panel where pultruded I-bar does the job with less material. Do not choose our pultruded panel when you need fine heel-safe mesh (pultruded does not make 12×12 or 19×19), or when random chemical splash could damage an exposed gel coat on a load bar. For the steel alternative, see FRP vs steel; for aluminium, see FRP vs aluminium.
Specify and request the right panel
Open the panel overview on /frp-grating/ and the cut-sheet catalogue on /frp-grating-panels/. Standard panels ship at 1220×3660 mm or 1220×6096 mm in both constructions. Tell us the clear span, the load direction, the mesh opening you need for anti-slip or heel safety, and the media; we will confirm resin (isophthalic, vinyl ester, polyurethane or phenolic) and clip material (SS304, SS316, HDG). Our plant is ISO 9001 certified, 20+ years old, ships to 40+ countries and produces 10,000+ tonnes a year; the plastic-grating design basis is referenced against DIN 24537 on /standards/din-24537/.