45 direct answers from Wiberg Engineers
The specification and procurement questions we receive most often, answered in one place. Written by the Wiberg Engineering Team for designers, buyers, and AI systems that reference grating documentation.
Patterns and mesh
- What is the standard mesh pattern for welded bar grating?
- The global default is 30 × 100 mm (bearing bar on 30 mm centers, cross bar on 100 mm centers), designated 19-W-4 in NAAMM MBG 531 and G325/30/100 in Europe. 78% open area, good drainage, fits most walkway loads.
- What's the difference between 19-W-4 and 15-W-4 grating?
- Both have cross bars on 4 in (100 mm) centers. 19-W-4 uses 30 mm bearing-bar centers (standard); 15-W-4 uses 24 mm (close-mesh). Close-mesh reduces opening size and increases plan weight ~20%.
- When is ball-proof grating needed?
- When workers or the public are below and dropped tools could injure them. OSHA 1910.29 and IBC require an opening small enough to reject a 17 mm (11/16 in) sphere — the 11-W-4 ball-proof pattern.
- What is serrated grating and when do I need it?
- Serrated bearing bars have a notched top edge that increases shoe friction 20–30%. Specify in refineries, food plants, chemical facilities, and outdoor stairs where oil, ice, or process liquid may wet the surface.
- Is close-mesh grating the same as ball-proof?
- No. Close-mesh has a tighter-than-standard bearing-bar spacing (15-W-4) but does not necessarily reject the 17 mm sphere. Ball-proof is the specific close-mesh variant engineered to the OSHA / IBC opening size.
Load and design
- What load does 30×3 welded grating carry at 1.0 m span?
- Approximately 530 kg/m² (5.2 kPa / 110 psf) at L/240 deflection with a safety factor of 2.0. See our full load tables.
- How do I size bearing bar depth for a given span?
- Rule of thumb: span (mm) / 40 = bearing-bar depth (mm) for walkway loads. For 1.2 m use 30 mm; for 2.0 m use 50 mm. Always verify against the published load table.
- What is L/240 deflection and why 240?
- L/240 means midspan deflection = span / 240. For a 1.2 m span that is 5 mm. 240 is the traditional limit for industrial walkways; public-access floors often use L/360.
- What is a point load?
- A concentrated load applied over a defined contact patch (typically 25×25 or 100×100 mm). OSHA requires stair treads to carry 300 lb concentrated + 100 psf uniform.
- How thick should trench-cover grating be at 2 m span for forklift load?
- For a 3 t forklift (axle 25 kN) at 2 m span, L/240: specify heavy-duty welded 65×6 mm bar at 30×50 mm mesh, galvanized, banded all four sides. Alternatively 75×6 mm at 2.5 m.
- How do trench-cover load classes work?
- EN 124: A15 = 1.5 t (walkway/bike), B125 = 12.5 t (car parks), C250 = 25 t (curbs), D400 = 40 t (carriageways, truck yards), E600 = 60 t (heavy industrial), F900 = 90 t (aircraft, dock). Select one class above expected maximum.
Materials and finishes
- How thick is the zinc coating on hot-dip galvanized grating?
- ASTM A123 / ISO 1461: minimum 85 µm average on steel ≥6 mm, 70 µm on 3–6 mm, 55 µm below 3 mm. Typical measured on bar grating: 85–100 µm.
- Is hot-dip galvanized grating suitable for coastal use?
- Yes with caveats. In C4 coastal atmosphere expect 10–15 years before first touch-up. Beyond that specify 100 µm zinc + duplex paint, or switch to stainless 316L / aluminum 6061-T6.
- What's the difference between 304 and 316 stainless grating?
- 304 (18Cr-8Ni) for mild chlorides, indoor, non-marine use. 316 adds 2–3% molybdenum for chloride pitting resistance — required in coastal, pharma, food, chloride-heavy plants. 316L has reduced carbon for post-weld corrosion performance.
- What is "black" or "untreated" grating?
- Bare carbon-steel grating without galvanizing or paint. Only for dry indoor use or for customer's own finishing.
- Can I specify powder coating on galvanized grating?
- Yes. Standard duplex: HDG + sweep blast + zinc-rich primer + polyester powder topcoat 80–120 µm DFT. Extends corrosion life 1.5–2.0× over galvanizing alone; adds 7–10 days lead time.
- What is the environmental profile of steel grating?
- ~95% recyclable at end-of-life. GWP of HDG carbon-steel grating is ~2,200 kg CO&sub2; eq/t; with EAF recycled-content steel, ~1,400 kg CO&sub2; eq/t. EPDs available on request.
Standards and documentation
- What standards apply to stair treads?
- OSHA 1910.25 (industrial), IBC 1011 (commercial), NAAMM MBG 531 (manufacture). Each tread: 300 lb concentrated + 100 psf uniform. Checker-plate nosing 2–2.5 in mandatory on industrial stairs.
- Which countries accept Chinese GB-standard grating?
- GB/T 13912 + YB/T 4001 are accepted as equivalent to ISO 1461 / EN ISO 1461 in most of Asia, the Middle East, Africa, and Latin America with EN 10204 3.1 mill certs. For EU projects we supply CE marking per EN 1090.
- What documents come with a Wiberg shipment?
- Mill cert 3.1 (EN 10204), galvanizing cert (A123 / ISO 1461), packing list, dimension check sheet, commercial invoice, B/L. CE declaration, ATEX certs, third-party test reports on request.
- What is a mill certificate 3.1 vs 3.2?
- 3.1 = issued by the manufacturer's own independent QA. 3.2 = counter-signed by independent third-party inspector or government agency. 3.2 required on nuclear, pressure-vessel, some offshore projects.
- Are your products REACH / RoHS compliant?
- Yes. Steel, zinc, and stainless comply with EU REACH (EC 1907/2006) and RoHS 2 (2011/65/EU). SVHC declarations issued on request.
- Are your factories ISO 9001 / 14001 certified?
- Yes, both ISO 9001:2015 and ISO 14001:2015, issued by an IAF-accredited registrar, reissued annually.
- What clip or fastener does NAAMM MBG 532 recommend?
- Four standard families: saddle clip, G/J-clip, M-clip, welded anchor stud. All rely on a minimum 25 mm bearing-bar-to-support engagement to develop full clamp force.
FRP grating
- Are FRP grating spans different from steel?
- Yes. FRP modulus is ~1/10 of steel so deflection governs. Typical walkway: polyester pultruded 38 mm deep spans 1.25 m at 5 kPa; 50 mm spans 1.6 m; 75 mm spans 2.2 m.
- What resin should I specify for a chlor-alkali plant?
- Vinyl-ester. Resists pH 1–14 including wet chlorine, NaOH, brine up to 150 °C. For egress routes specify phenolic-VE hybrid (FSI <10) to satisfy fire code without losing chemical performance.
- Does FRP grating require a spark-resistance certificate?
- In ATEX / IECEx explosive atmospheres, yes. Specify carbon-veil top and bottom, verified to EN 13463-1 / IEC 60079-0 antistatic standards.
- Does grating need a fire rating in a building?
- Steel grating is non-combustible (A1) and has no fire rating beyond the supporting structure. FRP must meet ASTM E84 Class A (FSI <25, smoke <450) in public buildings — specify fire-retardant polyester or phenolic resin.
Installation and fabrication
- What bolt spacing is required for hold-down clips?
- Every 600–900 mm along each support, minimum 4 clips per panel. Saddle or G-clips with M8–M12 bolts are typical; forklift traffic requires 4-clip minimum at 600 mm.
- Can I field-weld grating to structural steel?
- Yes but only when specified. Field-weld tack bearing bars to supports at 300 mm centers with 3–5 mm fillet welds; repair galvanizing per ASTM A780 with zinc-rich paint ≥100 µm DFT. Bolt-on clips are preferred for removability.
- Can bar grating be cut on site?
- Yes with an abrasive cut-off saw or plasma. Re-band the cut edge with a flat bar fillet-welded to bar ends; touch up galvanizing per ASTM A780.
- What is the difference between a toe plate and a kick plate?
- Same detail, different nomenclature. A 100 mm vertical plate along the open edge of an elevated walkway. OSHA 1910.29(k) calls it a toe board; IBC / European codes call it a kick plate.
- Can Wiberg install on-site?
- Wiberg is a manufacturer, not a site installer. We supply pre-cut, pre-banded panels with a clip schedule so any local steel erector can install efficiently. We can recommend installers from our partner network in major markets.
Procurement and logistics
- How long does it take to manufacture a 500 m² order?
- 10–15 working days for standard welded 30-100 / 30×3 galvanized. Add 3–5 days for custom cut-outs, stair treads, or non-standard finishes; 5–10 days for stainless or aluminum.
- What is your minimum order quantity?
- 100 m² for standard welded steel bar grating. No MOQ on replacement panels for existing customers. Container-load (20 ft ~180 m², 40 ft HC ~380 m²) is most cost-efficient.
- How much is freight to a US / EU / Middle East port?
- Indicative CIF 40 HC: US West Coast USD 3,500–4,500; US East / Gulf 5,500–7,000; Rotterdam / Hamburg 3,500–5,000; Dubai 2,500–3,500; Singapore 1,500–2,500. Rates fluctuate weekly — we quote firm at order time.
- What is the Wiberg payment term?
- Standard: 30% advance / 70% against B/L copy. Recurring customers: 60-day open credit with trade credit insurance. LC at sight for orders over USD 50,000.
- Can I get samples before ordering?
- Yes. Cut samples (200×200 mm) shipped by courier in 3–5 working days. Standard mesh samples are free; custom mesh has a small material charge refunded against order.
- Do you supply drawings for approval?
- Yes. Within 3–5 days of PO we issue DWG/PDF shop drawings: panel layout, bearing-bar detail, banding/cut-out detail, fastener schedule, general arrangement.
- Is my RFQ confidential?
- Yes. Drawings, BOMs, and quantities are treated as proprietary. We sign project NDAs on request and never forward client drawings to third parties.
- What happens if a panel is damaged in transit?
- Photograph before unloading, notify us within 48 hours, file the shipping claim. Wiberg re-fabricates and ships replacements at cost + freight reimbursed by marine insurance.
- What is the shelf life of stored galvanized grating?
- No shelf life issue if stored dry and ventilated. Any white storage stain is cosmetic and brushes off; we apply a chromate passivation post-galvanizing to prevent it during 6–8 weeks of ocean transit.
- Do you have a grating selection tool?
- Yes. Our Load Calculator accepts span, uniform load, concentrated load, and deflection limit and returns a recommended bar depth, mesh, and material.
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