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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 pressed (swaged) into slotted bearing bars without welding. Delivers flush faces and 92–95% of welded load 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: Corrosion-resistant grating made from fiberglass rovings set in polyester, vinyl-ester, or phenolic resin. 25–30 year life in chemical exposure.
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 2 to 2-1/2 in (50–65 mm) checker-plate strip welded across the front edge of a stair tread for slip resistance and visual contrast, satisfying IBC 1011 and OSHA 1910.25.
Stair tread: Grating panel fabricated with bolt-on carrier plates and checker-plate nosing, sized to fit a specific stair rise/run. Must carry 300 lb mid-span + 100 psf uniform per OSHA 1910.25.
Trench cover: Grating or solid panel set into a frame above an open channel or pit. Classified by load per EN 124: A15 (walkway), B125 (light vehicle), C250, D400 (truck), E600, F900 (heavy industrial).
Toe plate (kick plate): A 100 mm (4 in) vertical plate along the edge of an elevated walkway that prevents tools and debris from falling. Required by OSHA 1910.29 and IBC.
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 any mechanical fastener securing panel to support: saddle, J-clip, M-clip, or welded lug. Spacing rule of thumb: every 600–900 mm, minimum 4 per panel.

Materials and finishes

Hot-dip galvanizing: Corrosion protection by dipping fabricated steel in molten zinc (~450 °C) per ASTM A123 / ISO 1461. Produces 80–100 µm zinc coating with 20–40 year outdoor life.
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, such as a 4"×4" forklift wheel footprint. A 300 lb concentrated load is equivalent to roughly 500–700 psf uniform on a typical walkway panel.

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 execution standard for structural steelwork including bar grating panels treated as structural components. Specify execution class EXC1–EXC4 per project.
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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