Guide
Bearing Bar Spacing Guide
By DONGFU GRATING Engineering Team · Published 2026-06-24 · Updated 2026-07-17
Bearing bar spacing — the center-to-center distance between load-bearing bars — shapes load capacity, opening size, weight and price. The common metric spacings are 30, 40 and 60 mm; the imperial NAAMM series express the same idea as 19-space (about 1-3/16 inch), 15-space (about 15/16 inch) and tighter close-mesh series, with W-4 or W-2 indicating 4-inch or 2-inch cross bar spacing. Thirty millimeters is the industrial default, balancing strength, material use and an opening size acceptable for most platforms. Forty millimeters saves steel where loads are moderate and openings are not safety-critical. Sixty millimeters suits light duty and covers. Close-mesh spacings keep heels, canes and small wheels out of the openings and are specified for public access; whether a spacing meets accessibility rules such as ADA depends on opening size, orientation and the governing project standard. State your traffic and opening requirements when inquiring — spacing, bar size and span are then confirmed together.
What spacing actually controls
Spacing sets how many bearing bars share the load across a panel, how large the openings are, how much the panel weighs and what it costs. Halving the spacing roughly doubles the number of bars per meter, which adds capacity and shrinks openings but also adds weight and price. Spacing never acts alone: capacity is always confirmed together with bar depth, thickness, span and load type.
Common spacings compared
| Metric pitch | Imperial / NAAMM series | Opening character | Typical applications |
|---|---|---|---|
| 30 mm | 19-space ≈ 1-3/16 in (19-W-4) | Standard industrial opening | Platforms, walkways, stair treads — the default |
| 40 mm | — | Larger opening, less steel | Moderate loads where economy matters |
| 60 mm | — | Open grid | Light duty, screens, covers not walked on |
| ≈ 24 mm | 15-space ≈ 15/16 in (15-W-4) | Close mesh | Public access, heavy pedestrian duty |
| ≈ 17 mm | 11-space ≈ 11/16 in | Tighter close mesh | Heel-conscious commercial areas |
| ≈ 12–13 mm | 8-space ≈ 1/2 in; 7-space ≈ 7/16 in | Very tight mesh | Entrances, public platforms, small-wheel traffic |
Reading designations like 19-W-4
The first number is the bearing bar spacing series, the letter is the construction — W welded, SL swage locked, DT dovetail pressure locked — and the last number is the cross bar spacing in inches. So 19-W-4 means bearing bars at about 1-3/16 inch on center, welded, with cross bars at 4 inches; 15-W-2 closes both directions up. Metric specifications are written as pitch pairs, for example 30 × 100 mm, bearing bar pitch first, cross bar pitch second.
Cross bar spacing matters too: 100 mm (≈ 4 in) is the economical standard, while 50 mm (≈ 2 in) adds lateral stability and stops smaller objects from dropping through — common under platforms above work areas.
Close mesh, heels and accessibility
Public areas change the question from how strong to how small an opening. Close-mesh grating keeps heels, canes, crutches and small caster wheels out of the grid. Whether a given opening satisfies accessibility requirements such as ADA depends on the opening dimensions, their orientation to the direction of travel and the governing project standard — accessibility compliance is confirmed per project, not assumed from a spacing name. If your project must be ADA-friendly, say so at inquiry stage and we will propose close-mesh options with opening data.
Choosing a spacing for your project
- Industrial platforms and walkways: 30 mm / 19-W-4 unless loads or openings say otherwise
- Economy with moderate loads: 40 mm
- Public access, retail, stations: 15-space or tighter close mesh
- Heavy wheel loads: spacing chosen with bar size from load data — see the heavy duty load guide
- Not sure: describe the traffic — shoes, heels, carts, wheelchairs, forklifts — and we will propose a spacing
Common Mistakes to Avoid
- Choosing spacing for strength alone and forgetting what can fall through or catch in the openings
- Assuming close mesh automatically means ADA compliant — compliance depends on opening size, orientation and the project standard
- Misreading designations: 19-W-4 is an imperial series near 30 mm, not 19 mm anything
- Specifying 60 mm spacing in pedestrian areas where dropped tools or heels are a risk