Industrial facility managers replacing corroded steel grating for the third time in a decade share a common frustration: the lifecycle math never works. FRP pultruded decking breaks this cycle — continuous-fiber structural profiles that combine 450-585 MPa tensile strength with permanent corrosion immunity, at 20-30% lower installed weight than equivalent steel decking panels.
This buyer’s guide maps the specifications, supplier qualification criteria, and total-cost-of-ownership calculations procurement teams need to evaluate FRP pultruded decking for industrial flooring, offshore platforms, chemical plant walkways, and marine dock applications.
FRP Pultruded Decking vs Traditional Flooring Materials
The pultrusion process — pulling continuous glass fiber rovings through a resin bath and heated forming die — produces decking profiles with unidirectional fiber alignment achieving fiber volume fractions of 55-65%, roughly double the 25-30% Vf typical of SMC compression-molded panels. This fiber architecture translates directly to structural performance: pultruded decking panels deliver flexural modulus of 20-30 GPa versus 8-12 GPa for SMC panels of equivalent thickness.
Steel bar grating has been the industrial flooring default for decades, but the corrosion math is unforgiving. Carbon steel grating in a coastal chemical plant loses 0.1-0.3mm of section thickness per year to atmospheric corrosion — meaning 6mm bearing bars reach minimum structural thickness in 15-20 years. Hot-dip galvanizing extends this to 25-30 years in moderate environments but fails within 5-8 years in acid fume or salt-spray conditions. FRP pultruded decking has zero corrosion rate in the same environments, giving it an effective service life of 30-50 years limited only by UV degradation of the resin matrix.
Aluminum decking resists atmospheric corrosion but introduces galvanic compatibility problems when mounted on steel structures — the aluminum itself becomes a sacrificial anode. FRP decking is electrically insulating, eliminating galvanic corrosion entirely and removing the need for isolation kits between decking and support steel.
Load Rating & Structural Design
FRP pultruded decking panels are classified by uniform distributed load (UDL) capacity, expressed in kN/m² or psf. Three standard loading classes cover the majority of industrial applications:
Light-duty (2.5-5.0 kN/m² or 50-100 psf): Personnel walkways, inspection platforms, and access decks. Typical panel construction uses 25-30mm thick pultruded profiles with 300-400mm support spacing. These panels weigh 12-18 kg/m² — roughly one-quarter the weight of equivalent steel grating.
Medium-duty (5.0-7.5 kN/m² or 100-150 psf): Maintenance platforms with occasional equipment loads, chemical plant operating decks, and marina floating docks. Panel thickness increases to 35-40mm with 250-350mm support centers. Integrated anti-slip surface (grit-bonded or molded-in texture) achieves slip resistance ratings of R11-R12 per DIN 51130.
Heavy-duty (7.5-12.0 kN/m² or 150-250 psf): Forklift-trafficable decks, helideck platforms, and military bridging. These use 50-65mm thick multi-cavity pultruded profiles, often with bidirectional fiber architecture (0°/90° fabric layers alternating with unidirectional roving) for biaxial stiffness. Support spacing tightens to 200-300mm.
Deflection limits per ASTM D790: maximum allowable deflection under full design load is span/200 for pedestrian decks and span/300 for vehicle-trafficable decks. FRP’s lower modulus versus steel (20-30 GPa vs 200 GPa) means deflection, not strength, governs most FRP deck designs — a 3-meter simply supported span with 5.0 kN/m² UDL typically requires 40mm section depth to limit deflection to 15mm (span/200).
Corrosion Resistance: Chemical Compatibility Guide
The resin system determines chemical resistance. Three resin families cover most industrial environments:
Isophthalic polyester: The workhorse resin, resistant to most acids (HCl, H₂SO₄ at concentrations up to 50%), alkalis (NaOH up to 25%), salt solutions, and organic solvents. Maximum continuous service temperature 80-90°C wet, 110°C dry. Suitable for general chemical plant flooring, water treatment facilities, and marine docks.
Vinyl ester: Upgraded chemical resistance for strong oxidizing acids (nitric, chromic), chlorinated solvents, and bleach solutions. Maintains strength at 100-110°C wet, 130°C dry. Specified for bleach plants, electroplating facilities, and pulp & paper mill decks where isophthalic polyester would soften within 12-24 months.
Phenolic: Maximum fire performance with inherent ASTM E84 Class A flame spread rating (FSI ≤25) and UL 94 V-0 without additive flame retardants. Low smoke evolution (DS ≤50 per ASTM E84) makes phenolic decking mandatory for enclosed occupied spaces and tunnel walkways. Chemical resistance is limited to acids — phenolics are attacked by strong alkalis.
Installation & Support Systems
FRP pultruded decking panels install differently than steel grating. Thermal expansion must be accommodated: FRP’s coefficient of linear thermal expansion (CLTE) of 8-12 × 10⁻⁶/°C is roughly equal to steel (12 × 10⁻⁶/°C) in the longitudinal (fiber) direction but 2-3× higher (20-25 × 10⁻⁶/°C) in the transverse direction. A 6-meter deck length in an environment cycling from -10°C to +40°C undergoes approximately 3mm of longitudinal and 7mm of transverse thermal movement. Panel-to-panel gaps of 6-10mm with elastomeric compression seals accommodate this movement while providing a flush walking surface.
Support framing is typically hot-dip galvanized steel channels (100-150mm depth) at the specified support spacing. FRP decking panels are secured with 316 stainless steel hold-down clips at 500-600mm centers — the clips engage the panel edge flanges without penetrating the deck surface, preserving the corrosion barrier. Never through-bolt FRP decking to steel supports; the bolt holes create stress concentrations and moisture ingress paths that initiate delamination within 3-5 years.
Total Cost of Ownership: 30-Year Analysis
FRP pultruded decking carries a higher upfront material cost than steel grating — approximately 1.5-2.0× per square meter — but the cost advantage emerges over the service life:
Year 0 (installation): FRP decking panels at $120-180/m² versus galvanized steel grating at $70-100/m². Installation labor is 30-40% lower for FRP due to lighter weight (no crane required for panel handling) and simpler fastening (clips vs welding). Installed cost gap narrows to 1.2-1.5×.
Years 5-10: Steel grating in corrosive environments requires spot-repair of damaged galvanizing (zinc-rich paint touch-up) at approximately $15-25/m² per treatment cycle (every 3-5 years). FRP decking requires zero corrosion maintenance — only periodic washing to remove surface contaminants.
Year 15-20: Steel grating in aggressive environments (coastal, chemical) reaches end of service life and requires full replacement. FRP decking continues service. The single replacement cycle more than offsets FRP’s higher initial cost, putting the 20-year NPV (net present value) of FRP decking at 40-60% below steel in corrosive service.
Year 25-30: UV degradation of the FRP resin matrix may require surface re-coating (UV-resistant polyurethane topcoat, $20-30/m²). The underlying glass fiber structure retains full mechanical properties — FRP does not suffer the section-loss failure mode that terminates steel grating service life.
FRP Decking vs Traditional Flooring: Performance Comparison
| Property | FRP Pultruded Decking | Steel Bar Grating | Aluminum Grating | SMC Molded Grating |
|---|---|---|---|---|
| Tensile strength (MPa) | 450-585 (ASTM D638) | 400-550 | 240-310 | 80-120 |
| Flexural modulus (GPa) | 20-30 | 200 | 69 | 8-12 |
| Density (g/cm³) | 1.7-1.9 | 7.85 | 2.7 | 1.7-1.9 |
| Weight (kg/m², 30mm) | 14-18 | 50-70 | 22-30 | 16-22 |
| Corrosion rate (C5 marine) | Zero (inert) | 0.1-0.3mm/year | Galvanic if steel contact | Zero (inert) |
| Slip rating (DIN 51130) | R11-R12 | R10-R11 | R10-R11 | R10-R12 |
| Thermal expansion (CLTE) | 8-25 × 10⁻⁶/°C | 12 × 10⁻⁶/°C | 24 × 10⁻⁶/°C | 15-25 × 10⁻⁶/°C |
| Installed cost ratio | 1.0 (baseline) | 0.6-0.8 | 0.8-1.1 | 0.7-0.9 |
| Service life (C5 marine) | 30-50 years | 8-15 years | 15-25 years | 20-30 years |
| Best for | Chemical plants, offshore | Dry indoor mezzanines | Non-galvanic roofs | Walkways, trench covers |
What is FRP pultruded decking made of?
FRP pultruded decking is manufactured by pulling continuous E-glass fiber rovings through a thermoset resin bath (typically isophthalic polyester or vinyl ester) and then through a heated steel die that cures the resin and forms the deck profile. The resulting material has 55-65% glass fiber by volume, giving it a flexural modulus of 20-30 GPa and tensile strength of 450-585 MPa per ASTM D638.
How does FRP decking perform in fire?
Standard polyester FRP decking carries a Class B flame spread rating (FSI 26-75 per ASTM E84). For applications requiring Class A (FSI ≤25), phenolic resin FRP decking achieves this without additive flame retardants. All FRP decking is available with UL 94 V-0 rating. Smoke toxicity of FRP is comparable to wood; CO is the primary toxic species, with HCN and HCl absent (no halogenated resin systems).
Can FRP decking replace steel grating directly?
FRP decking can directly replace steel grating on existing support steel, provided the support spacing and panel dimensions are matched. Because FRP has lower modulus than steel (20-30 GPa vs 200 GPa), deflection at equivalent thickness is higher — existing support spacing designed for steel grating may need to be reduced by 20-30% or the FRP panel thickness increased by one profile size to maintain the same deflection limit.
What is the slip resistance of FRP decking?
Standard FRP pultruded decking with molded-in grit surface achieves R11-R12 slip resistance per DIN 51130 (equivalent to a coefficient of friction of 0.55-0.70 dry, 0.45-0.60 wet). For helidecks and offshore platforms requiring maximum slip resistance, retrofit adhesive grit strips or epoxy-bonded aggregate coatings can achieve R13 (CoF >0.75 wet).
