Use load tables and span calculators based on ASTM D3916 to size FRP grating: pick panel depth and bearing spacing so the allowed load covers your live + dead load with deflection under limit.
- Best for: engineering sizing of FRP grating spans
- Specify when: load class and deflection limit must be proven
- Key spec: ASTM D3916, design load vs bearing span table
1. Engineering Principles & Design Standards
FRP grating design follows ASTM D3916 (pultruded shapes), EUROCOMP design code, and FGMC (Fiberglass Grating Manufacturers Council) guidelines. Key design considerations: allowable stress design (ASD) with safety factors, deflection limits (typically L/200 for floors, L/240 for sensitive areas), creep analysis for long-term loads, thermal effects, and connection design. Unlike steel, FRP is orthotropic (different properties in different directions), so bidirectional molded grating has equal strength in both directions, while pultruded grating is strongest in the bearing bar direction. Safety factors: 2.5-3.0 for ultimate strength, 1.5 for serviceability (deflection).
2. Molded Grating Load Table (38mm, 38×38mm mesh, Isophthalic)
Span 600mm: Uniform load 5.0 kN/m², Point load 1.5 kN, Deflection <3mm, Safety factor 3.0. Span 800mm: Uniform load 4.0 kN/m², Point load 1.2 kN, Deflection <4mm, Safety factor 3.0. Span 1000mm: Uniform load 3.5 kN/m², Point load 1.0 kN, Deflection <5mm, Safety factor 3.0. Span 1200mm: Uniform load 2.5 kN/m², Point load 0.8 kN, Deflection <6mm, Safety factor 2.8. Span 1500mm: Uniform load 1.8 kN/m², Point load 0.5 kN, Deflection <8mm, Safety factor 2.5. Note: Values are for pedestrian/light industrial use. Heavy-duty applications require 50mm grating or pultruded grating. Vinyl ester resin has similar load capacity to isophthalic.
3. Molded Grating by Thickness Comparison (at 1000mm span)
25mm (light duty): Uniform 1.5 kN/m², Point 0.5 kN, Weight 10-12 kg/m², Best for: drainage covers, light walkways. 30mm (medium): Uniform 2.5 kN/m², Point 0.8 kN, Weight 13-15 kg/m², Best for: general walkways, ramps. 38mm (standard): Uniform 3.5 kN/m², Point 1.0 kN, Weight 15-20 kg/m², Best for: industrial platforms, standard applications. 50mm (heavy duty): Uniform 5.0 kN/m², Point 1.5 kN, Weight 22-28 kg/m², Best for: heavy traffic, forklift areas, large spans. Mini mesh (19×19) has approximately 15% higher load capacity than standard 38×38 mesh due to more material per area.
4. Pultruded Grating Load Table (50mm I-bar, 38mm spacing)
Span 1000mm: Uniform 25 kN/m², Point 5.0 kN, Deflection Deflection limits are critical for user comfort and safety. L/200 (e.g., 5mm at 1000mm span): standard for industrial floors, acceptable for most users. L/240 (4mm at 1000mm): recommended for offices, areas with sensitive equipment, or where users perceive deflection as "unstable." L/300 (3.3mm at 1000mm): premium feel, recommended for public areas, retail, or where vibration sensitivity is high. Excessive deflection (>L/150) can cause user discomfort, fatigue, and perception of instability even if structurally safe. For dynamic loads (walking, running), multiply static load by 1.5 for impact factor. Step 1: Determine support spacing (span) — measure distance between support beams. Step 2: Determine required load — pedestrian (3 kN/m²), light industrial (5 kN/m²), heavy industrial (10 kN/m²), forklift (25+ kN/m²). Step 3: Check load table — find thickness that meets or exceeds required load at your span. Step 4: Check deflection — ensure deflection is within acceptable limit (L/200 or L/240). Step 5: Consider environment — select resin based on chemicals, temperature, UV. Step 6: Consider surface — grit top for wet/oily areas, concave for standard, smooth for clean rooms. Step 7: Request engineering calculation for spans >1500mm or loads >10 kN/m². ZEALL provides free structural calculations with every quotation. All load, span and capacity values in this article are typical/indicative, derived from laboratory tests per NAAMM MBG-01 (FRP Grating Design Manual) methodology. Molded grating values apply a 5:1 factor of safety on ultimate capacity; pultruded grating values apply a 3:1 factor of safety, both measured at static ambient conditions. Impact loads are limited to 50% of stated values; long-term loads require creep adjustment per ASCE Structural Plastics Design Manual. Certified load tables, stamped engineering calculations and third-party test reports are available on request. For structural sizing of your specific application, contact our engineering team with your load requirements, span and environmental conditions — we provide free structural calculations within 24 hours. Browse our molded grating and pultruded grating product pages for full specifications and resin options. The table below consolidates typical allowable uniform live loads for molded isophthalic / vinyl-ester grating at a deflection limit of L/200, with a 5:1 factor of safety on ultimate capacity. Values are typical/indicative per NAAMM MBG-01; certified load tables are available on request. Typical/indicative values per NAAMM MBG-01; certified table on request. Ranges reflect resin system, mesh tolerance and fabrication variation. For forklift or truck traffic, use pultruded I-bar grating. Unidirectional strength measured along bearing bars; spans must be taken between supports along the bar direction. Typical/indicative per NAAMM MBG-01; certified table on request. ZEALL molded FRP grating is designated by panel thickness x mesh opening. The standard catalog covers four depths (25 / 30 / 38 / 50 mm) and three mesh sizes (38x38, 19x19, 50x50 mm). A typical designation is "38 mm Molded Grating x 38x38 mm mesh" (model code FG-M3838). Common references: The table below gives typical flexural stiffness ranges for FRP grating profiles. Values are typical per NAAMM MBG-01 and are not a substitute for a certified mill test report. E depends on resin system (isophthalic polyester approx. 10-12 GPa; vinyl ester approx. 12-15 GPa); I and S scale with bar depth and profile shape. Typical values per NAAMM MBG-01; certified values per project-specific mill test report on request. Browse our product pages for full specifications: FRP molded grating · FRP pultruded grating.5. Deflection Limits & User Comfort
6. How to Calculate Required Grating for Your Project
Design Standards & Data Basis
Typical Allowable Uniform Load (kN/m²) - Molded Grating
Model Span 600 mm Span 800 mm Span 1000 mm Span 1200 mm Span 1500 mm FG-M2538 (25 mm x 38x38) 2.5-3.5 1.8-2.5 1.2-1.8 0.8-1.2 0.5-0.8 FG-M3038 (30 mm x 38x38) 4.0-5.0 2.8-3.8 2.0-2.8 1.4-2.0 0.9-1.4 FG-M3838 (38 mm x 38x38) 5.5-7.0 4.0-5.0 3.0-4.0 2.2-3.0 1.5-2.2 FG-M3819 (38 mm x 19x19) 6.5-8.0 4.8-6.0 3.6-4.6 2.6-3.5 1.8-2.6 FG-M5038 (50 mm x 38x38) 9-12 6.5-8.5 5.0-6.5 3.8-5.0 2.6-3.6 Typical Allowable Uniform Load (kN/m²) - Pultruded I-bar Grating
Model Span 1000 mm Span 1500 mm Span 2000 mm Span 2500 mm FG-P5038 (50 mm I-bar x 38 mm spacing) 22-28 10-14 5.5-7.5 3.5-5.0 FG-P6538 (65 mm I-bar x 38 mm spacing) 40-50 20-26 11-15 7-10 Model Naming: Thickness x Mesh Reference
Model code Thickness Mesh Duty class Typical use FG-M2538 25 mm 38x38 mm Light Drainage covers, light walkways FG-M3038 30 mm 38x38 mm Medium General walkways, ramps FG-M3838 38 mm 38x38 mm Standard Industrial platforms, standard service FG-M3819 38 mm 19x19 mm Standard mini-mesh Tool handling, heel-safe walkways FG-M5038 50 mm 38x38 mm Heavy Forklift areas, long spans FG-P5038 50 mm I-bar 38 mm bar spacing Heavy pultruded Heavy-duty platforms, truck traffic Typical Structural Parameters (I / S / E)
Profile E flexural (GPa) I (cm⁴ / m width) S (cm³ / m width) 25 mm molded grid 10-12 2.5-4.0 2.0-3.2 30 mm molded grid 10-12 4.5-7.0 3.2-4.8 38 mm molded grid 11-13 8-13 5.0-7.5 50 mm molded grid 11-14 16-26 8.5-13 50 mm I-bar pultruded 12-15 55-85 22-32
Frequently Asked Questions
FRP (Fiberglass Reinforced Plastic) grating is a molded or pultruded fiberglass composite grid used for corrosion-resistant walkways, platforms and floorings. It combines glass fiber reinforcement with thermoset resin (polyester, vinyl ester, epoxy) for superior strength-to-weight ratio, zero rust and 20+ year service life.
