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Bar Grating Glossary

Concise definitions for industrial bar grating, stair treads, trench covers, FRP, and related standards — the terms used throughout the Wiberg Metal website, RFQs, and engineering documentation.

Grating construction

Bar grating: An open-grid floor built from primary bearing bars and perpendicular cross bars, used for industrial walkways, platforms, trench covers, and stair treads.
Bearing bar: The primary load-carrying bar in a grating panel. Runs across the span and is specified by depth and thickness, e.g. 1" × 3/16" or 30 × 3 mm.
Cross bar: Secondary bar set perpendicular to the bearing bars to transfer loads laterally and lock panel geometry. Typically at 50 or 100 mm (2 or 4 in) centers.
Pitch / mesh / spacing: Center-to-center distance between bearing bars (s1) and cross bars (s2). The designation 19-W-4 means bearing bars on 19/16 in (30 mm) centers, welded, cross bars on 4 in (100 mm) centers.
Banding (end band / side band): Flat bar welded along the panel edge to restrain bearing-bar ends and finish the perimeter. Standard on welded panels per NAAMM MBG 531.
Open area: Plan-view percentage of the panel that is open (not steel). Standard 19-W-4 welded has ~78% open; ball-proof 11-W-4 about 68%; reticuline about 60%.

Types of grating

Welded bar grating: Bearing and cross bars joined by forge (resistance) welding at every intersection. The industrial default for platforms and walkways.
Press-locked (swage-locked) grating: Cross bars are mechanically pressed into slotted bearing bars. Capacity depends on the exact geometry, material, joint and producer data; do not apply a fixed percentage of welded-grating capacity.
Heavy-duty grating: Deeper (50–125 mm) and thicker (≥ 1/4" / 6 mm) bearing bars with tighter cross-bar spacing, engineered for forklift, truck, and H20 wheel loads.
Ball-proof grating: Close-mesh pattern (11-W-4) whose opening rejects a 17 mm (11/16 in) sphere. Used where dropped tools or debris could injure workers below.
Close-mesh grating: Tighter-than-standard bearing or cross-bar spacing to reduce opening size. A step below ball-proof.
Reticuline grating: Crimped pattern where cross bars crimp into bearing bars with near-zero open area, rejecting a 9 mm sphere. Heavier and less drainable than welded.
Serrated bearing bar: Bearing bar with a notched top edge that improves shoe friction under wet, oily, or icy conditions. Used in refineries, food plants, and outdoor stairs.
Composite grating: Bar grating with a solid checker plate welded to its top, producing a non-penetrable surface where nothing may fall through and small wheels must roll.
FRP grating: Grating made from reinforcement and a resin system. Chemical, fire, UV, electrical and structural performance depend on the exact construction and supplier test data.
Molded vs pultruded FRP: Molded FRP is formed in a flat mold with equal strength in both directions; pultruded FRP uses a pulled I-bar profile 2–3× stiffer in the primary direction.

Details and accessories

Checker-plate nosing: A front-edge detail intended to improve visibility or slip resistance. Shape, width, contrast, performance and attachment follow the governing project standard and approved drawing.
Stair tread: Grating panel with carrier plates or another connection, sized for the stair and verified for the project-specific uniform and concentrated loads, footprint, deflection and attachment criteria.
Trench cover: Grating or solid panel set into a frame above an open channel or pit. Specify the clear span, support seat, load footprint, traffic condition and governing standard. Do not assign an EN 124 class to an untested grating panel by vehicle name alone.
Toe plate (kick plate): An edge plate intended to reduce falling-object risk. Height, location and attachment depend on the governing safety code, risk assessment and owner specification.
Saddle clip: Two-piece fastener (top saddle + bottom plate) with a through-bolt that clamps a grating panel to its support beam. Allows later removal for maintenance.
Hold-down clip: Generic term for a mechanical fastener securing panel to support, such as a saddle, J-clip or M-clip. Type, quantity and spacing depend on panel, supports, uplift, vibration, traffic, environment and the approved fixing schedule.

Materials and finishes

Hot-dip galvanizing: Corrosion protection by immersing prepared steel in molten zinc under a specified standard such as ASTM A123 or EN ISO 1461. Coating requirements and inspection depend on the governing standard and steel category.
Stainless steel 304 / 316L: 304 for low-chloride indoor/outdoor service; 316L for coastal, food, pharma, and aggressive chloride. Typical cost premium 2–3× galvanized carbon.
Aluminum 6061-T6: Light-weight, corrosion-resistant alternative to steel. Lower modulus of elasticity (~10,000 ksi) means deflection usually governs; use for architectural, electrical-isolation, or weight-critical installations.
Sherardized coating: Thermal-diffusion zinc coating for small parts and fasteners, useful on clips and hardware where galvanizing bath size is limiting.

Engineering terms

Allowable uniform load: Maximum distributed load (psf or kPa) a panel can carry within its allowable bending stress and deflection limit. Published by bearing-bar geometry and span.
Deflection limit (L/240): Maximum midspan deflection under service load, as a fraction of span L. Common limits: L/240 walkways, L/360 public access, L/800 masonry-supporting.
AISC ASD: American Institute of Steel Construction Allowable Stress Design. Allowable bending stress for compact members: F_b = 0.66 F_y (e.g., 24 ksi for carbon steel F_y=36 ksi).
Clear span: Distance between inside faces of the two primary supports (beam flange, angle, channel). Always larger than nominal structural bay width; tabulated load values are for clear span.
Concentrated (point) load: A load applied over a limited contact patch. It must be checked separately from a uniform load because the two cases are not interchangeable; state magnitude, footprint and position.

Standards and documentation

ANSI / NAAMM MBG 531: North American standard for metal bar grating manufacture: bar sizes, mesh patterns, tolerances, and load tables. The de facto spec in US / Canada projects.
GB / YB/T 4001: Chinese national standards for welded steel bar grating (YB/T 4001) and hot-dip galvanizing (GB/T 13912). Default reference on projects sourced from China.
EN 1090: European standards for execution and conformity assessment of structural steel and aluminium components. Establish applicability, execution class and any regulatory route for the exact product and intended structural use.
ASTM A123 / ISO 1461: Hot-dip galvanizing coating standards: minimum zinc thickness 55–100 µm by steel thickness category, plus adherence and uniformity requirements.
Mill certificate (EN 10204): Material test certificate issued by the steel mill. 3.1 is signed by mill QA; 3.2 is counter-signed by independent inspector. Required for spec compliance.
ITP (Inspection and Test Plan): Document listing every inspection step, hold point, acceptance criterion, and responsible party during fabrication. Standard on large or third-party-inspected projects.

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