Published by pultrx, the export trading company of Henan Zhongsheng. This is a buyer planning guide; the manufacturer confirms project specifications in writing.
For panel types, bar spacings and the purchase scope, start with molded and pultruded fiberglass grating
What the rows and columns mean
Every grating load table has three dimensions: a product (depth, bar spacing and bar shape), a clear span between supports, and a load. The cells give deflection. Two load cases are shown. A uniform load is spread over the whole panel and is written in kN/m² or psf. A concentrated load is applied across a strip of grating at mid-span and is written per unit width, in kN per metre of width or pounds per 12-inch strip. The two cases produce different deflections at the same nominal load, so the table carries two rows per span, usually marked u for uniform and c for concentrated.
Pultruded grating tables are read along the bearing bars only. Molded grating is bidirectional and is tabulated for the panel as a whole. Mixing the two kinds of table is the most common reading error.
Worked example from a published table
Strongwell's metric table for its I-2000 pultruded grating at 25 mm depth gives the section properties per metre of width (area 1.056 × 10⁴ mm²/m, second moment of area 8.956 × 10⁵ mm⁴/m) and a weight of 22.0 kg/m². The rows below are copied from the 600 mm span line of that table. They show how deflection scales with load and how the two load cases differ.
| Load (kN/m² uniform, kN/m width concentrated) | 3 | 5 | 8 | 10 | 15 | 20 |
|---|---|---|---|---|---|---|
| Uniform load, deflection u (mm) | 0.19 | 0.31 | 0.50 | 0.62 | 0.93 | 1.24 |
| Concentrated load, deflection c (mm) | 0.50 | 0.83 | 1.32 | 1.65 | 2.48 | 3.31 |
Three things to notice. Deflection is linear with load in the tested range, so you can interpolate between columns. The concentrated case deflects about 2.7 times as much as the uniform case at the same number, because the whole load sits on one strip. And the same table lists a safe load for each span at a 2 to 1 safety factor; at 600 mm the uniform safe load is far above the pedestrian loads a walkway sees, which is why span, not strength, usually governs grating selection.
Safety factor and basis differ between suppliers
A recommended maximum load is only comparable when the basis is the same. Strongwell's metric tables state a 2 to 1 safety factor on the safe load. The SpanTrak data sheet states that its maximum recommended load represents a 5 to 1 factor on ultimate capacity. Both are legitimate; they are not the same number. Some catalogs mark values as theoretical, calculated from section properties, while others cite tests to the ANSI-approved FRP composites grating manual published through ACMA. When you compare two quotations, ask each supplier three questions: is the value tested or calculated, what factor of safety is applied, and to which bar spacing and resin system does it apply.
| Question | Why it matters | Acceptable answer |
|---|---|---|
| Tested or calculated? | Calculated tables assume ideal bars and supports | Test method named, or calculation basis stated |
| What safety factor? | 2:1 and 5:1 recommended loads differ by 2.5 times | Factor stated on the table |
| Which product exactly? | Depth, bar spacing, bar shape and resin change stiffness | Full product code on the table |
| Which support condition? | Simple span versus continuous changes deflection | Support condition stated |
| Units? | kN/m² versus psf, kN/m versus lb per 12 in strip | Units on every column |
Deflection limits that specifications impose
Strength rarely governs a walkway. Deflection does, because a springy panel feels unsafe and lets a grating edge lift under a wheel. Owner specifications therefore cap deflection. The New York State OGS master specification for fiberglass reinforced gratings limits deflection under a uniform load to the smaller of 3/8 inch (9.5 mm) or L/120, where L is the clear span. Pedestrian comfort checks are often made at a uniform load of 100 psf (4.8 kN/m²) with deflection held to 1/4 inch (6.4 mm). Pick the limit from the project specification, then find the span at which the chosen panel still meets it in the table. That span, not the ultimate load, is the number to put on the drawing.
From table to purchase order
- Write the design load as the specification gives it: uniform in kN/m² or psf, concentrated in kN per metre or pounds per strip, and the deflection limit.
- Fix the support layout: clear span, continuous or simple, and whether bearing bars run across the short or long side of the opening.
- Read the manufacturer's table for the candidate panel at that span. If the deflection exceeds the limit, go to the next depth or shorten the span with an intermediate support.
- Ask for the table with the quotation and check the product code, units, safety basis and support condition against the four questions above.
- Put the panel code, span, load case and deflection limit on the order, and ask the supplier to confirm them in writing.
If you have not yet chosen between a molded panel and a pultruded one, read the molded vs pultruded grating guide
What pultrx supplies with a grating quotation
pultrx quotes molded and pultruded fiberglass grating from the Henan Zhongsheng factory with the panel code, depth, bar spacing, resin system and the load data the factory holds for that product. Where a span or load case is outside the factory's test record, the quotation says so and proposes a test or a thicker panel rather than quoting a value from another manufacturer's table. Third-party tables such as the ones cited in this guide are shown for method only; they do not describe pultrx products.
Sources and further reading
- Strongwell: Pultruded fiberglass grating load tables (metric)
Loads in kN/m² (uniform) or kN per m of width (concentrated); u and c are deflections in mm; tables state a safe load with a 2 to 1 safety factor and list section properties per metre of width.
- SpanTrak FRP grating data sheet (ARCAT)
States that the maximum recommended load represents a 5:1 factor of safety on ultimate capacity, an example of a different safety basis.
- New York State OGS master specification 067413: Fiberglass reinforced gratings
Example of a public owner specification that limits grating deflection under a uniform load to the smaller of 3/8 inch or L/120.
Questions buyers ask
- How much weight can fiberglass grating hold?
- It depends on panel depth, bar spacing, span and whether the load is uniform or concentrated. Read the manufacturer's table at your span and check the deflection limit; the recommended maximum load usually includes a stated safety factor of 2 to 1 or higher.
- What is the difference between a uniform and a concentrated load in a grating table?
- A uniform load is spread over the whole panel, in kN/m² or psf. A concentrated load sits on one strip at mid-span, per unit width. At the same number the concentrated case deflects more.
- What deflection limit should I use for a walkway?
- Use the project specification. Common public-owner limits are L/120 or 3/8 inch under uniform load, and 1/4 inch at 100 psf for pedestrian comfort.
- Why do two manufacturers give different maximum loads for the same depth?
- Different safety factors, different bar spacings, different resin systems and tested versus calculated values. Ask each supplier to state the basis before comparing.
- Can pultruded grating tables be used across the bearing bars?
- No. Pultruded grating carries load along the bearing bars only. The table applies in that direction, with cross rods providing spacing, not span.
Ready to move from reading to a scoped quotation?
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