How is steel grating designated and what do the numbers mean?

Steel bar grating is designated by bearing bar spacing, type, and bar size. Example 19-W4: '19' = bearing bar spacing of 19/16 inch (1-3/16") center-to-center; 'W' = welded construction (R = riveted, L = pressure-locked, SW = swaged); '4' = bearing bar size code indicating 1-1/4" depth × 3/16" thickness. Common spacing designations: 19-W4 (1-3/16" c-c, most common for pedestrian/light industrial), 15-W4 (15/16" c-c, heavier loads, forklift traffic), 30-W2 (1-7/8" c-c, primarily for catwalks and light pedestrian). Bearing bar size codes: Code 1 = 1" × 1/8" (3.0 lb/ft²), Code 2 = 1" × 3/16" (4.4), Code 3 = 1" × 1/4" (5.9), Code 4 = 1-1/4" × 3/16" (5.5), Code 5 = 1-1/4" × 1/4" (7.3), Code 6 = 1-1/2" × 3/16" (6.6), Code 7 = 1-1/2" × 1/4" (8.7), Code 8 = 1-1/2" × 5/16" (10.8), Code 9 = 2" × 1/4" (11.5), Code 10 = 2" × 3/8" (17.3), Code 11 = 2-1/2" × 1/4" (14.4). Cross bars (twisted or rectangular) connect the bearing bars at 4" o.c. for welded grating. Weight per square foot increases approximately 65% per code number increment. The grating designation is stamped on the grating panel banding bar for traceability per NAAMM MBG-531.

What are the load limits for 19-W4 grating at various spans?

19-W4 grating (1-3/16" bearing bar spacing) load limits vary by bearing bar size and span per NAAMM MBG-531: For Code 4 (1-1/4" × 3/16", 5.5 lb/ft²): 24" span — uniform load 1,200 psf, concentrated load 2,000 lb/ft width; 36" span — uniform 533 psf, concentrated 983 lb/ft; 48" span — uniform 300 psf, concentrated 587 lb/ft; 60" span — uniform 192 psf, concentrated 383 lb/ft. For Code 7 (1-1/2" × 1/4", 8.7 lb/ft²): 24" span — uniform 2,133 psf, concentrated 3,500 lb/ft; 36" — uniform 948 psf, concentrated 1,750 lb/ft; 48" — uniform 533 psf, concentrated 1,050 lb/ft; 60" — uniform 341 psf, concentrated 680 lb/ft. Deflection is typically limited to L/240 for pedestrian areas and L/300 where machinery vibration or sensitive operations exist. For a given bar size, doubling the span reduces capacity by approximately 75% (governed by strength at short spans, deflection at long spans). For spans over 60", deeper bearing bars (Codes 6-11) are typically required. Concentrated loads assume load distributed over 12" width of grating. All values are for ASTM A1011 steel bearing bars with Fy = 36 ksi. Aluminum grating (not covered here) has significantly different properties — approximately 1/3 the weight but 1/3 the stiffness.

What are the common ASTM specifications for steel grating?

Steel grating is manufactured to the following ASTM specifications: ASTM A1011 SS Grade 36 — standard carbon steel for bearing bars and cross bars (Fy = 36 ksi, Fu = 53 ksi), used for 90%+ of industrial grating. ASTM A1011 HSLAS Grade 50 — high-strength low-alloy for higher capacity or weight-optimized grating (Fy = 50 ksi). ASTM A36 — used for heavier bearing bars (Codes 9-11). ASTM A123/A123M — hot-dip galvanizing after fabrication (minimum 2.6 oz/ft² = 3.9 mils), required for exterior grating and most industrial applications. ASTM A653 G90 — pre-galvanized sheet for lighter grating applications, though post-fabrication HDG per A123 is preferred for durability. ASTM A510 — carbon steel wire for cross bars. The grating is fabricated per NAAMM MBG-531 (Metal Bar Grating Manual) and ANSI/NAAMM MBG-532 for heavy-duty grating. The finish is typically: mill finish (bare steel, interior dry only), painted (shop primer + field paint, interior), or hot-dip galvanized (exterior, wet/corrosive environments). Galvanizing adds approximately 3-5% to grating cost and 0.4-0.7 lb/ft² to weight. Stainless steel grating (Type 304 or 316 per ASTM A240) is available for food processing, chemical plants, and marine environments at 4-6× the material cost of carbon steel.

How do you specify grating for forklift traffic?

Grating for forklift and heavy vehicle traffic requires heavier bearing bar sizes and closer spacing. Typical specifications: (1) Bearing bar spacing: 15-W4 (15/16" c-c) minimum — the closer bar spacing distributes wheel loads better than 19-W4. For very heavy forklifts (10,000+ lb capacity), consider 11-W4 (11/16" c-c). (2) Bearing bar size: Code 7 (1-1/2" × 1/4") minimum for spans up to 36"; Code 9 (2" × 1/4") or Code 10 (2" × 3/8") for spans 36-60". The bearing bar must be oriented with the depth vertical — grating spanning the short direction across the traffic lane. (3) Design load: A typical 5,000 lb capacity forklift has a maximum wheel load of approximately 8,000-10,000 lb distributed over a 4" × 6" contact area with pneumatic tires (higher contact stress with solid tires). Apply a 30% impact factor for forklift traffic per ASCE 7. (4) Load transfer: grating bars distribute concentrated wheel loads to adjacent bars through the cross bars. The effective width for a concentrated load is approximately 12" + bar spacing. (5) Banding: all grating panels in traffic areas must have banding bars (flat bars welded to bearing bar ends) on all four sides to prevent individual bar displacement. Banding bar minimum size: 1/4" × 1-1/2". (6) Fastening: grating panels must be fastened to the supporting steel with saddle clips or weld-down tabs at minimum 4 locations per panel to prevent panel lift from vehicle acceleration/braking.

What is the difference between welded, riveted, and swaged grating?

Three fabrication methods for steel bar grating produce different cross bar connections and appearance: (1) Welded grating (Type W) — cross bars are resistance-welded to each bearing bar at every intersection. The electric resistance forge weld fuses the cross bar into the bearing bar under pressure and current. Strongest joint type, most common (90%+ of industrial grating). Joint strength approximately 60-70% of bearing bar tensile strength. (2) Riveted grating (Type R) — cross bars pass through holes punched in the bearing bar web and are riveted over on each side. No welding, so no heat distortion or stress concentration. Preferred for cyclic loading (vibrating screens, shaker decks) where weld fatigue could occur. More expensive than welded (riveting adds ~20-30% to cost). (3) Pressure-locked (dovetail) grating (Type L) — cross bars are press-locked into pre-notched slots in the top of bearing bars under hydraulic pressure, mechanically deforming the bar material to lock the joint. Smooth top surface (no cross bar projection), preferred for architectural applications and ADA-compliant walkways. No welding or rivet heads visible. (4) Swaged grating (Type SW) — similar to locked but the bearing bar is swaged (cold-worked) around the cross bar at each intersection. Used primarily for aluminum grating where welding is difficult. For structural steel applications, welded grating is the default. Riveted is specified only where fatigue or vibration is a concern. Locked/swaged is specified for architectural appearance.

Steel Grating Load Tables — Span & Capacity by Type

Steel bar grating is used for platforms, walkways, stair treads, trench covers, and mezzanine floors in industrial and commercial construction. This page provides load tables, span data, and design guidance for the most common grating types.

Grating Designation System

Bar grating is designated by its bearing bar spacing, type, and bearing bar size.

Example: 19-W4

Position	Meaning
19	Bearing bar spacing: 19/16 inch (1-3/16 in) center-to-center
W	Type: Welded (W=welded, R=riveted, L=locked, SW=swaged)
4	Bearing bar size code (depth × thickness)

Bearing Bar Size Codes

Code	Bearing Bar Size (in)	Weight (lb/ft²)	Common Application
1	1 × 1/8	3.0	Light pedestrian
2	1 × 3/16	4.4	Pedestrian walkways
3	1 × 1/4	5.9	Standard industrial
4	1-1/4 × 3/16	5.5	Standard industrial
5	1-1/4 × 1/4	7.3	Heavy industrial
6	1-1/2 × 3/16	6.6	Medium span industrial
7	1-1/2 × 1/4	8.7	Heavy industrial
8	1-1/2 × 5/16	10.8	Heavy industrial
9	2 × 1/4	11.5	Long span, heavy loads
10	2 × 3/8	17.3	Very heavy loads
11	2-1/2 × 1/4	14.4	Long span
12	2-1/2 × 3/8	21.6	Very heavy loads
13	3 × 1/4	17.3	Extra long span
14	3 × 3/8	25.9	Extra long span, heavy

Weights shown are for 19-W (1-3/16 inch spacing) carbon steel, unpainted.

Common Grating Types

Type	Bearing Bar Spacing	Cross Bar Spacing	% Open Area	Application
19-W	1-3/16 in	4 in or 2 in	~75%	Most common — industrial platforms, walkways
15-W	15/16 in	4 in or 2 in	~70%	Heavy-duty platforms
11-W	11/16 in	4 in or 2 in	~63%	Close mesh — high heels, small objects
38-W	2-3/8 in	4 in	~80%	Light duty — ventilation, screens
30-W	1-7/8 in	4 in	~77%	Medium duty — catwalks

Load Tables — 19-W4 (Most Common)

Bearing bar: 1-1/4 × 3/16 inch. Weight: 5.5 psf.

Allowable Uniform Load (psf)

Span (ft)	Allowable UDL (psf)	Deflection (in) at UDL
2	3,643	0.067
3	1,619	0.151
4	911	0.268
5	583	0.419
6	405	0.604
7	297	0.822
8	228	1.073

Deflection limit: L/240 for pedestrian walkways, L/200 for industrial platforms.

Allowable Concentrated Load (lb) at Midspan

Span (ft)	Allowable CL (lb)	Deflection (in) at CL
2	3,085	0.048
3	2,057	0.108
4	1,543	0.192
5	1,234	0.300
6	1,029	0.432
7	881	0.588
8	771	0.768

Load Tables — 19-W7 (Heavy Duty)

Bearing bar: 1-1/2 × 1/4 inch. Weight: 8.7 psf.

Allowable Uniform Load (psf)

Span (ft)	Allowable UDL (psf)	Deflection (in)
2	5,810	0.062
3	2,582	0.139
4	1,453	0.247
5	930	0.386
6	646	0.556
7	474	0.757
8	363	0.988
9	287	1.250
10	232	1.543

Load Tables — 19-W9 (Extra Heavy)

Bearing bar: 2 × 1/4 inch. Weight: 11.5 psf.

Allowable Uniform Load (psf)

Span (ft)	Allowable UDL (psf)	Deflection (in)
3	4,619	0.107
4	2,598	0.190
5	1,663	0.298
6	1,154	0.429
7	847	0.584
8	649	0.762
9	513	0.965
10	416	1.190
12	289	1.714

Stair Tread Load Data

Standard stair treads are typically 19-W4 with a checkered plate nosing.

Span (in)	Allowable CL at Center (lb)	Max Deflection (in)
24	820	0.050
30	655	0.078
36	546	0.113
42	468	0.154
48	410	0.200

Design Considerations

Loading Conditions

Condition	Typical Load (psf)	Application
Pedestrian	100	Walkways, platforms
Light industrial	200-300	Equipment access
Heavy industrial	300-500	Forklift traffic, heavy equipment
Vehicle traffic	1,000+	Vehicle-rated grating required

Deflection Limits

Application	Recommended Limit	Rationale
Pedestrian walkways	L/240	Comfort and perception
Industrial platforms	L/200	Functional requirement
Stair treads	L/240	Code compliance
Mezzanines	L/360	Vibration and comfort
Aesthetic spans (visible)	L/360	Visual acceptability

Material Options

Material	Weight Factor	Corrosion Resistance	Cost Factor
Carbon steel (painted)	1.00	Low	1.0x
Carbon steel (galvanized)	1.05	Moderate	1.3x
Stainless steel 304	1.00	High	3.5x
Stainless steel 316	1.00	Very high (marine)	4.5x
Aluminum 6061-T6	0.35	Good (natural oxide)	2.5x

Surface Options

Surface	Description	Application
Plain	Smooth bearing bars	Dry, indoor environments
Serrated	Notched bearing bars	Wet, oily, or outdoor environments
Serrated + galvanized	Notched + zinc coated	Best overall slip resistance

Grating Support Requirements

Minimum bearing length: 1 inch on each support
Fastening: Grating clamps or weld attachments at each support
Saddle clips: Minimum 2 per panel, one at each end
Welded attachment: 3/16 inch fillet weld, 1 inch long at each end
Maximum unsupported span: Per load tables above

Weight per Square Foot

Type	Code 1 (1×1/8)	Code 3 (1×1/4)	Code 7 (1-1/2×1/4)	Code 9 (2×1/4)	Code 14 (3×3/8)
19-W	3.0	5.9	8.7	11.5	25.9
15-W	3.8	7.5	11.1	14.7	33.1
11-W	5.2	10.2	15.1	20.2	45.4
38-W	1.5	2.9	4.4	5.8	13.0

Frequently Asked Questions

What is the most common steel grating? 19-W4 (welded, 1-3/16 inch bearing bar spacing, 1-1/4 × 3/16 bearing bars) is the most widely used grating for industrial platforms and walkways.

How far can steel grating span? For 19-W4 (the most common type), typical spans range from 3 to 6 feet for pedestrian loads (100 psf). Heavier bearing bars (W7, W9) can span 8-10 feet.

What is the difference between welded and riveted grating? Welded grating (W-series) has cross bars welded to bearing bars — most common and economical. Riveted grating (R-series) has cross bars riveted between bearing bars — provides a more rigid, flat surface for rolling loads.

Do I need serrated grating? Use serrated grating for outdoor applications, wet areas, oil and grease environments, ramps, and anywhere slip resistance is a concern. Plain grating is acceptable for dry, indoor environments.

How much does steel grating weigh? 19-W4 weighs approximately 5.5 lb/ft². 19-W7 weighs 8.7 lb/ft². Weight increases with bearing bar size and closer spacing.

Can vehicles drive on steel grating? Standard grating is designed for pedestrian and light equipment loads. For vehicle traffic, use heavy-duty grating (2 inch or deeper bearing bars, 3/8 inch thick) with appropriate span ratings. Verify with manufacturer load tables.

Beam Calculator — Calculate beam reactions and deflection
Deflection Limits — L/240, L/360 criteria
Steel Weight Calculator — Calculate grating weight
Steel Deck Types — Floor and roof deck profiles
Steel Floor Framing — Floor system design guide

Disclaimer

This is a calculation tool, not a substitute for professional engineering certification. All results must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in construction, fabrication, or permit documents. The user is responsible for the accuracy of all inputs and the verification of all outputs.

Steel Grating Load Tables — Span & Capacity by Type

Grating Designation System

Bearing Bar Size Codes

Common Grating Types

Load Tables — 19-W4 (Most Common)

Allowable Uniform Load (psf)

Allowable Concentrated Load (lb) at Midspan

Load Tables — 19-W7 (Heavy Duty)

Allowable Uniform Load (psf)

Load Tables — 19-W9 (Extra Heavy)

Allowable Uniform Load (psf)

Stair Tread Load Data

Design Considerations

Loading Conditions

Deflection Limits

Material Options

Surface Options

Grating Support Requirements

Weight per Square Foot

Frequently Asked Questions

Related Pages

Disclaimer