Ball Proof Load Tables
Load and span data for ball-proof close-mesh grating. For applications requiring small opening sizes.
What is ball-proof grating?
Ball-proof grating is a close-mesh bar grating pattern where the clear opening is small enough to reject a 11/16" (17 mm) diameter sphere — the standard ball test used by NFPA, OSHA 1910.28, and many industrial specifications to prevent tools, hand objects, and small debris from falling through elevated walkways.
Typical pattern is 11-W-4: bearing bars on 11/16" (17 mm) centers, cross bars on 4" (100 mm) centers. For extra protection, a reticuline (serrated-crimp) pattern is used where the cross bars crimp into the bearing bars with near-zero open area.
Design basis
- Material: carbon steel Fy = 36 ksi, optionally hot-dip galvanized per ASTM A123.
- Pattern: welded 11-W-4 (11/16" × 4" opening rejects a 17 mm sphere).
- Bearing bar thickness: 1/8" or 3/16" (3 or 5 mm); 1/8" most common due to tight pitch.
- Allowable bending stress: 0.66 Fy = 24 ksi per AISC ASD.
- Support condition: simple span, banded panel.
Allowable uniform load — welded 11-W-4, 1/8" bearing bar
| Bearing bar depth | 24" (610 mm) | 30" (760 mm) | 36" (915 mm) | 42" (1065 mm) | 48" (1220 mm) |
|---|---|---|---|---|---|
| 1" × 1/8" | 580 | 370 | 260 | 190 | 145 |
| 1-1/4" × 1/8" | 900 | 580 | 400 | 295 | 225 |
| 1-1/2" × 1/8" | 1290 | 820 | 570 | 420 | 320 |
| 1-3/4" × 1/8" | 1760 | 1120 | 780 | 575 | 440 |
| 2" × 1/8" | 2300 | 1470 | 1020 | 750 | 575 |
Values in psf; bending-stress controlled. For applications with water/debris washdown, confirm hole-blocking tolerance with engineering.
Ball-proof vs reticuline patterns
| Feature | Welded 11-W-4 ball-proof | Reticuline (crimped) |
|---|---|---|
| Sphere rejection | 17 mm (11/16") | 9 mm (3/8") |
| Open area | ~68% | ~60% |
| Relative weight | 1.35× standard 19-W-4 | 1.5× standard 19-W-4 |
| Typical use | Elevated walkways near people | Reducing-gear pits, shop floors |
| Load capacity vs 19-W-4 | ∼105% (more bars support load) | ∼95% |
Compliance & standards
- OSHA 1910.28(b)(3) and 1910.29(k) — openings in walking/working surfaces shall reject a 1" sphere (welded 11-W-4 exceeds this).
- NFPA 101 / IBC 1011 — stair and landing openings limited to 4" (100 mm) sphere for safety; ball-proof exceeds both.
- IEC 60529 IP3X — grating protects against solid objects greater than 2.5 mm; ball-proof meets IP3X.
FAQ — ball-proof load tables
- Does ball-proof grating carry less load than standard grating?
- No. Because more bearing bars sit under the same plan area, ball-proof (11-W-4) grating of the same bar size actually delivers ∼5% more allowable uniform load than 19-W-4 — but at roughly 1.35× the weight per square meter.
- Can I get ball-proof in stainless or aluminum?
- Yes. Stainless 304/316 is widely used in food/pharma plants. Aluminum 6061-T6 is available for corrosion-prone rooftops. For stainless, derate uniform load by ~17% (Fy lower); for aluminum, deflection governs.
- What does 11-W-4 actually mean?
- The first number (11) is the bearing-bar center-to-center spacing in 16ths of an inch — 11/16" or 17 mm. The "W" denotes welded construction. The final number (4) is the cross-bar spacing in inches.
- Does ball-proof meet OSHA floor-hole requirements?
- Yes. OSHA defines a floor hole as an opening larger than 1" in its least dimension. Ball-proof 11-W-4 has a maximum opening of 11/16" (17 mm), well under the limit, and also meets IBC/NFPA 4" sphere safety rules.
- Is ball-proof grating drainable?
- Yes. Open area is approximately 68%, which is adequate for most walkway drainage. If you need a solid-feel finish, add checker-plate overlay or a closer 9-W-4 mesh.
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