How to Read FRP Grating Load Charts & Span Tables
A load chart is the contract between a grating panel and its supports. Read it correctly and your walkway stays within deflection limits for decades; read it loosely and panels flex, clip and fail early.
Two Load Types You Will See
Uniform load (kN/m²) simulates distributed weight — a crowd of people, a layer of product, an equipment mat. Concentrated load (kN) simulates a single heavy point — a forklift wheel, a machine foot, a dropped load. Both must be checked against the chart for your span.
Deflection: The Real Limit
Specifications typically limit deflection to L/100, L/150 or L/200 of the clear span. Longer spans and lighter panels deflect more. If your project specifies L/200, the allowable load is lower than L/100 on the same panel — always verify the deflection criterion before comparing charts.
Span Direction Matters
Pultruded grating carries load along the bearing bars only — orient bars across the short span. Molded grating carries load in both directions. Reversing a pultruded panel is the single most common specification error on site.
ZeAllgrate provides certified load/span charts for every configuration — send your span, load and deflection requirement and we return the exact panel recommendation.
Reading the Chart: A Worked Example
Take a process walkway with a clear span of 1.2 m and a specified uniform load of 4.0 kN/m² at a deflection limit of L/150. On the ZeAllgrate chart for molded grating, locate the 1.2 m span column, read down until the tabulated allowable uniform load reaches or exceeds 4.0 kN/m², and confirm the panel thickness and resin grade printed in that row. If the same walkway were specified at L/200, the allowable load for the identical panel drops — the chart's second block for the same span carries the L/200 values, and a thicker panel or closer supports may be required. Always read the chart at the deflection limit your specification names, not the one printed largest.
Safety Factors and Allowable Loads
Published chart values are allowable loads, not ultimate capacities. The tests establish ultimate strength, and the published values apply a safety margin consistent with the relevant design code and the service factor for the resin and environment. When combining loads — a uniform crowd load plus a concentrated equipment point — check each load case separately against the chart, then verify the combined effect against the deflection limit. In high-temperature chemical service, de-rate the allowable load in line with the resin manufacturer's elevated-temperature factors; a chart generated at 23 °C does not apply unchanged at 70 °C.
Concentrated Load Cases
Forklift wheels, machine feet and dropped loads are checked as concentrated loads in kN. The governing case is the heaviest single wheel or foot, applied at the worst position — usually mid-span — because that is where deflection is greatest. If the concentrated capacity at your span is marginal, the practical fixes are a deeper panel, a shorter span, or pultruded grating whose aligned bars concentrate stiffness where the wheel runs. Note that many codes require both uniform and concentrated cases to pass independently; a panel that passes the uniform case can still fail the point-load case at mid-span.
Common Chart Errors on Site and in Specs
- Wrong span direction — pultruded capacity is valid only with bearing bars across the span; reversing the panel invalidates the chart value.
- Mixing deflection limits — comparing an L/100 value from one vendor with an L/200 value from another overstates the real capacity.
- Ignoring support conditions — charts assume adequate bearing and clipping at every support; a panel resting unclipped on two beams does not develop the tabulated capacity.
- Using room-temperature values for hot service — always apply the elevated-temperature de-rating factor before comparing against the load requirement.
Deflection Limits at a Glance
| Limit | Typical Use |
|---|---|
| L/200 | Walkway default; general foot traffic |
| L/150 | Heavy maintenance platforms; less strict |
| L/100 | Industrial service where small deflections are acceptable |
| Project-specific | Cleanrooms, vibration-sensitive decks; tighter than L/200 |
Unit Discipline
Span tables are published in kN/m² with metre spans or in psf with feet — pick one system and stay in it. A common error is mixing a psf load with a metre span, which shifts the result by the unit factor and can select the wrong panel. Note whether the table is working load (safety factor included) or ultimate (factor to be applied), and confirm the concentrated column is checked alongside the uniform column — the point load governs on many walkways.
Span tables are published in kN/m² with metre spans or in psf with feet — pick one system and stay in it. A common error is mixing a psf load with a metre span, which shifts the result by the unit factor and can select the wrong panel. Note whether the table is working load (safety factor included) or ultimate (factor to be applied), and confirm the concentrated column is checked alongside the uniform column — the point load governs on many walkways.Discuss Your FRP Project
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