Grating capacity lives in three numbers: bearing bar height, bar thickness and span. Taller bars and shorter spans both raise allowable load steeply. 50×5 or 60×5 bars at 30–40 mm pitch cover most heavy platform and vehicular trench-cover duties; pedestrian walkways run lighter sections at wider pitch. Galvanize to EN ISO 1461 / ASTM A123 for outdoor service.
Four duty classes cover almost every project.
Start by placing the application in one of four classes — this determines the conversation about bar size and pitch:
1. Light pedestrian (walkways between equipment, catwalks): 25×3 to 30×5 bars at 30–40 mm pitch, spans typically up to 1 m. 2. General industrial (maintenance platforms, plant floors): 32×5 to 40×5 bars at 30 mm pitch. 3. Heavy plant (equipment platforms, forklift aisles): 50×5 bars at 30–40 mm pitch. 4. Vehicular (trench covers, road drainage): 60×5 and above at 30 mm pitch, with checked span and wheel-load calculations.
Load capacity is governed by the bar height-to-span ratio: halving the span roughly quadruples the allowable uniform load for a given bar. When a design is marginal, shortening the span (adding a support) often beats upsizing the bar.
Construction type and surface profile are independent choices.
| Type | Construction | Strengths | Typical application |
|---|---|---|---|
| Welded | Cross bars resistance-welded to bearing bars at every intersection | Highest strength-to-weight; standard for load-bearing duty | Industrial flooring, platforms, trench covers |
| Press-locked | Slotted bars joined under high pressure, no welding | Flush, clean two-way appearance; precise bar spacing | Architectural, pedestrian, facades and sunscreens |
| Serrated (surface option) | Serrated bearing bar teeth | Slip resistance in wet, oily or icy conditions | Outdoor walkways, oil & gas, food wash-down areas |
| I-bar / S-bar variants | I-shaped or twisted cross bars | Weight and cost optimization at lighter loads | Light walkways, cable trays |
Bearing bars run in the span direction; cross bars hold spacing and distribute loads. Bar spacing options: 30 mm pitch (heavy), 40 mm (general), wider for pedestrian-light duty.
Citing standards correctly avoids tender disputes.
ANSI/NAAMM MBG 531 (Metal Bar Grating Manual) is the North American load-table and practices reference — most buyers quoting "MBG 531 load tables" mean the uniform and concentrated load rating method. BS 4592 is the British counterpart for industrial type metal grating panels, fixings and treads.
EN ISO 1461 (equivalent ASTM A123) governs the hot-dip galvanized coating: minimum zinc thickness by steel section thickness — typically 70–85 µm on grating sections — plus adhesion and appearance. Material is commonly ASTM A36 / equivalent carbon steel; EN ISO 14122-2 adds safety requirements for permanent means of access (walkways, platforms) on machinery.
Full dimension tables and the complete standards list with official links are on the steel grating specifications page.
Where most installation-day surprises come from.
Stair treads arrive as prefabricated panels: serrated or checker-plate nosing for slip resistance, pre-welded end plates (with or without bolt holes) for direct fixing to stringers, optional yellow warning nosing. Order them cut to the required going width and stringer spacing — retrofitting on site is slow and ugly.
Fixings. Grating clips (saddle or G-clamps) at roughly one per corner of each panel, minimum four per panel; welded hold-downs where panels are permanently positioned; bolted clamps where panels must be removable for maintenance access. Confirm panel orientation against the span direction before cutting — bearing bars must run perpendicular to the supports.
For heavy plant platforms and vehicular trench covers, 50×5 mm or 60×5 mm bearing bars at 30 mm or 40 mm pitch are common starting points. Load capacity is governed by the bar height-to-span ratio: a taller, thicker bar or a shorter support span both increase allowable load. Confirm the final specification against the actual span and load requirement.
Hot-dip galvanizing for steel grating follows EN ISO 1461 (equivalent to ASTM A123). The standard specifies minimum zinc coating thickness by steel thickness — typically 70–85 µm on grating sections — plus coating adhesion and appearance requirements, delivering long-term corrosion protection for outdoor and industrial environments.
Welded grating has cross bars fusion-welded to bearing bars at every intersection — the strongest, most common type for industrial flooring and trench covers. Press-locked grating joins slotted bearing and cross bars under high pressure without welding, giving a flush, clean appearance preferred for architectural and pedestrian applications. Serrated bearing bars are available in both types for slip resistance in wet or oily areas.
Yes. Stair treads are supplied as prefabricated panels with a serrated or checker-plate nosing for slip resistance, pre-welded end plates (with or without bolt holes) for direct fixing, and optional yellow warning nosing. They are cut to the required going width and stringer spacing.