How to Read Load-Span Tables
What a Load-Span Table Actually Shows
A load/span table is a two-way lookup. The rows are the panel options (thickness, mesh or bearing-bar series). The columns are the clear spans you might use. The value in each cell is the allowable load (uniformly distributed load, UDL, in kN/m2 or psf) that the panel carries at a stated deflection limit. A well-formed table states the deflection limit, the safety factor and the support condition on its face - read those first.
| Panel option | Span 0.6 m | Span 0.9 m | Span 1.2 m | Span 1.5 m |
|---|---|---|---|---|
| 25 mm molded | allowable UDL | allowable UDL | allowable UDL | allowable UDL |
| 38 mm molded | allowable UDL | allowable UDL | allowable UDL | allowable UDL |
| 50 mm molded | allowable UDL | allowable UDL | allowable UDL | allowable UDL |
| Pultruded I/T-bar | allowable UDL | allowable UDL | allowable UDL | allowable UDL |
Annotated structure: pick your panel row, move to your span column, and read the allowable UDL. If your required load is below the cell value (at your deflection limit), the panel works.
Two Loads, Two Tables
Uniformly Distributed Load (UDL)
Load spread over the whole area, in kN/m2 or psf. A crowd, a material layer, an equipment mat. Most tables default to UDL at a given deflection limit.
Concentrated Load
A single point load, in kN or lbf - a forklift wheel, a machine foot. Checked on a separate concentrated-load table; a panel fine for UDL can deflect badly under one wheel.
Never compare a UDL table value with a concentrated load. They use different load cases and acceptance criteria; ask for the concentrated-load table if you have wheels or feet.
Deflection Limits and Built-In Safety Factors
| Limit | Deflection Allowed | Typical Use |
|---|---|---|
| L/100 | Span / 100 | General industrial walkways, less sensitive |
| L/150 | Span / 150 | Standard pedestrian platforms, balconies |
| L/200 | Span / 200 | Sensitive areas, machinery decks, high-crowd |
Safety Factor
ZeAllgrate load tables are working-load charts: they already include a safety factor of roughly 4:1 (molded) to 5:1 (pultruded) over ultimate, per ZeAllgrate practice. Do not divide the value again.
Same Panel, Different Limit
A stricter limit (L/200 vs L/100) lowers the allowable load on the same panel. Always read the table at the deflection limit your project specifies - the same number means different things.
Reading Between the Lines
Tables step spans in fixed increments (e.g. 0.6, 0.9, 1.2, 1.5 m). For an in-between span, interpolate linearly between the two adjacent cells on the same row. Because deflection scales with span cubed and strength with span squared, linear interpolation is conservative and acceptable for selection; for a critical design, ask ZeAllgrate engineering to compute the exact value.
| Step | Action |
|---|---|
| 1 | Find your required UDL and your clear span. |
| 2 | Locate the two nearest span columns that bracket your span on the chosen panel row. |
| 3 | Linearly interpolate the allowable load between those two cells. |
| 4 | Compare the interpolated allowable with your required load; require allowable to exceed required. |
| 5 | If close (within 10%), choose the next panel up or request a certified chart. |
Pedestrian Walkway - UDL Selection
| Given | Value |
|---|---|
| Required UDL | 3.0 kN/m2 (approx. 63 psf pedestrian) |
| Clear span | 1.0 m |
| Deflection limit | L/150 (standard pedestrian) |
| Solution | Scan the 38 mm molded row at 0.9 and 1.2 m at L/150; interpolate to 1.0 m. The allowable UDL exceeds 3.0 kN/m2. Select 38 mm molded. |
| Check | Confirm bearing bars across the span, min 50 mm bearing and 4 clips per panel. |
Industrial Platform - Heavier Load, Stricter Limit
| Given | Value |
|---|---|
| Required UDL | 10 kN/m2 (industrial / equipment mat) |
| Clear span | 1.5 m |
| Deflection limit | L/200 (sensitive / machinery deck) |
| Solution | Molded panels at L/200 over 1.5 m cannot carry 10 kN/m2. Move to pultruded I/T-bar at 50 mm class; the pultruded row at 1.5 m, L/200 exceeds 10 kN/m2. Select 50 mm pultruded. |
| Check | Pultruded bars across span, 75 mm bearing, concentrated-load check for any equipment feet. |
Concentrated Load - Check Both Shear and Deflection
| Given | Value |
|---|---|
| Concentrated load | 1.5 kN at midspan (machine foot) |
| Clear span | 0.9 m |
| Step 1 - Deflection | Look up the concentrated-load deflection table; ensure midspan deflection stays within L/150/L/200 under the point load. |
| Step 2 - Shear / bearing | Check end reaction and web crippling at the support (bearing-bar end) against the pultruded web-crippling value and the 150-200 MPa bearing strength. |
| Solution | Choose a panel whose concentrated-load row passes both deflection and shear/bearing at 0.9 m; if UDL alone passes but the point load does not, upgrade the bar series. |
Common Mistakes and Table Limitations
| Mistake | Why It Is Wrong | Correct Approach |
|---|---|---|
| Using the wrong deflection limit | L/100 values look stronger than L/200 | Use the limit the project specifies |
| Ignoring concentrated loads | UDL-fine panels can fail under one wheel | Run the concentrated-load table too |
| Forgetting impact / dynamic load | Forklifts and vibrating equipment amplify load | Apply 1.25-2.0 impact factor before comparing |
| Re-applying the safety factor | Tables already include 4:1-5:1 | Compare required load directly with table value |
| Pultruded bars parallel to span | Panel becomes weak along the wrong axis | Bearing bars MUST cross the clear span |
Table Assumptions
Published values assume simply supported, uniformly distributed load, standard bearing length and room temperature. Continuous spans, cantilevers, impact and high temperature need engineering adjustment.
When to Call an Engineer
Cantilevers, irregular cut-outs, combined UDL plus heavy point loads, temperature above 40 C, or any case close to a table limit - send the load list to ZeAllgrate for a certified chart.
Need Certified Load/Span Tables for Your Project?
Send clear span, UDL, any point load and deflection limit - ZeAllgrate returns the exact panel and chart reference.
Source: ZeAllgrate (Fiberglass Grating Manufacturers Council / ACMA) design guidelines; ASTM International; ISO 14122; OSHA 29 CFR 1910. Indicative data for specification guidance only — final design verified by ZeAllgrate engineering against certified load/span charts.