Checker plate and bar grating are the walking surfaces of industrial work: mezzanines, catwalks, equipment platforms, trench covers, stair treads, and pit covers. Both get bought and priced by the square foot, both get weighed for freight and erection, and both are easy to get slightly wrong because the published weight isn't what the plain-plate formula gives you.
This page covers both, with sources for every number.
Checker plate (diamond floor plate) weight per square foot
Checker plate, diamond plate, tread plate and floor plate are all names for the same product: hot-rolled plate with a raised lug pattern on one face. In the US it's made to ASTM A786.
The part that trips people up is the thickness. The nominal thickness of floor plate is measured at the base of the plate, not over the raised pattern. The lugs are extra steel on top. So a 1/4" floor plate weighs more than a 1/4" plain plate.
Plain plate first
Plain steel plate at 490 lb/ft³ weighs 490 ÷ 12 = 40.83 lb/ft² per inch of thickness. A 1/4" plate is 0.25 × 40.83 = 10.21 lb/ft². (Our flat bar chart uses the same density assumption.)
Floor plate weights
The table below compares computed plain plate with the diamond floor plate weights published in Coyote Steel's No. 1 Handbook of Steel Sizes & Weights. The handbook notes that the thickness it lists is exclusive of the projecting lugs, and that 1/8" plate uses a small pattern while 3/16" and heavier use the large pattern. Upstate Steel's floor plate table lists the same values (6.16 lb/ft² at 1/8", 8.71 at 3/16", 11.26 at 1/4").
| Nominal thickness (in) | Plain plate, computed (lb/ft²) | Floor plate, Coyote Steel (lb/ft²) | Pattern allowance (lb/ft²) | 48" × 96" sheet (lb) | 60" × 120" sheet (lb) |
|---|---|---|---|---|---|
| 1/8 | 5.10 | 6.15 | 1.05 | 197 | 308 |
| 3/16 | 7.66 | 8.71 | 1.05 | 279 | 436 |
| 1/4 | 10.21 | 11.26 | 1.05 | 360 | 563 |
| 5/16 | 12.76 | 13.81 | 1.05 | 442 | 690 |
| 3/8 | 15.31 | 16.37 | 1.06 | 524 | 818 |
| 1/2 | 20.42 | 21.47 | 1.05 | 687 | 1074 |
The pattern allowance is a steady 1.05 lb/ft² at every thickness. That's the weight of the raised lugs, and it doesn't change with plate thickness because the lug pattern is the same height whether the plate under it is 3/16" or 1/2".
So the working rule is:
Floor plate (lb/ft²) ≈ nominal thickness (in) × 40.83 + 1.05
Sheet weights in the last two columns are the handbook's per-square-foot weight times sheet area (32 ft² for 48" × 96", 50 ft² for 60" × 120"). Those two sizes are among the stock sheet sizes both suppliers list.
Where estimators get this wrong
- Pricing floor plate as plain plate. At 1/4" you're about 9% light on weight. At 1/8" you're about 17% light.
- Measuring thickness over the pattern. If someone calipers a sample over the lugs and calls it 5/16", you'll order the wrong plate.
- Ignoring the pattern direction on long runs. Floor plate has a direction. On a long platform, find out whether the architect cares about pattern alignment across seams, because it affects how you nest the sheets.
Bar grating: how the designation works
Rectangular bar grating is described with a three-part code set by NAAMM (the National Association of Architectural Metal Manufacturers) in its Metal Bar Grating Manual, ANSI/NAAMM MBG 531:
19-W-4, 1 × 3/16
- 19 is the bearing bar spacing in sixteenths of an inch, centre to centre. 19/16 = 1-3/16".
- W is the construction type: W for welded, P for pressure-locked, R for riveted.
- 4 is the cross bar spacing in inches, centre to centre.
- 1 × 3/16 is the bearing bar depth by thickness, in inches.
19-W-4 is the standard industrial grating in North America. 15-W-4 (15/16" bearing bar spacing) and 19-W-2 are the common variations, usually specified where a smaller opening is wanted.
19-W-4 bar grating weight per square foot
The weights below come from Grating Pacific's 19-space steel grating load table, which lists approximate weight per square foot for 19-W-4. Grating Pacific's note says to add 0.60 lb/ft² for cross bars at 2" on centre, which is how the 19-W-2 column is built. The NAAMM column is the nominal weight printed in the MBG 531-17 steel grating load table, which NAAMM rounds to the nearest pound and describes as approximate and varying between manufacturers.
The "bearing bars only" column is a physics check: at 1-3/16" spacing there are 12 ÷ 1.1875 = 10.1 bearing bars per foot of width, each weighing depth × thickness × 3.4028 lb/ft. The gap between that and the published weight is the cross bars.
| Bearing bar (depth × thickness, in) | Bearing bars only, computed (lb/ft²) | 19-W-4, Grating Pacific (lb/ft²) | NAAMM MBG 531 nominal (lb/ft²) | 19-W-2 est. (+0.60, lb/ft²) |
|---|---|---|---|---|
| 3/4 × 1/8 | 3.2 | 3.9 | 4 | 4.5 |
| 3/4 × 3/16 | 4.8 | 5.6 | 6 | 6.2 |
| 1 × 1/8 | 4.3 | 5.0 | 6 | 5.6 |
| 1 × 3/16 | 6.4 | 7.2 | 8 | 7.8 |
| 1-1/4 × 1/8 | 5.4 | 6.1 | 7 | 6.7 |
| 1-1/4 × 3/16 | 8.1 | 8.9 | 9 | 9.5 |
| 1-1/2 × 1/8 | 6.4 | 7.2 | 8 | 7.8 |
| 1-1/2 × 3/16 | 9.7 | 10.7 | 11 | 11.3 |
| 1-3/4 × 3/16 | 11.3 | 12.3 | 13 | 12.9 |
| 2 × 3/16 | 12.9 | 13.9 | 14 | 14.5 |
| 2-1/4 × 3/16 | 14.5 | 15.6 | 16 | 16.2 |
| 2-1/2 × 3/16 | 16.1 | 17.2 | 18 | 17.8 |
The computed bearing bar weight lands 0.7 to 1.1 lb/ft² under the published figure in every row, which is about what a row of cross bars every 4 inches adds. The published numbers hold up.
Use the manufacturer's number for your quote, not the NAAMM nominal, and get it from the supplier you're actually buying from. Weights vary a little by manufacturer because cross bar size isn't fixed across the industry.
A note on selection: bearing bar size is picked from span and load by the engineer of record or the grating supplier using their load tables. The weights here are for estimating and budgeting only. Don't use this page to choose a grating size.
What changes the weight
- Galvanizing. Most industrial grating ships hot-dip galvanized. Zinc adds weight, and galvanizers bill on the galvanized weight. See galvanizing cost per ton.
- Serrated bars. Serrated grating has notched bearing bars for slip resistance. NAAMM notes that serrated grating needs a bearing bar 1/4" deeper than plain grating to carry the same load, so the weight goes up by the next size.
- Banding. Flat bar welded around the panel edges and cutouts. Price it by the linear foot, and use our flat bar chart for the weight.
- Toe plate. Flat bar standing up above the walking surface at open edges. Also linear feet.
Misc-metals estimating notes for platforms
Grating and floor plate rarely get priced by the pound alone. A platform line item usually breaks into:
- Area of grating or plate, in square feet, by type. Measure to the outside of the support steel, not the clear opening.
- Cutouts. Every pipe penetration, column notch, and equipment opening is a cut plus banding around it. Count them separately; they drive labor far more than weight.
- Banding and toe plate, in linear feet.
- Fasteners. Saddle clips or weld lugs, commonly four per panel. Count panels first, then multiply.
- Panel layout. Grating Pacific lists stock panel widths of nominal 24", 36" and 48". Laying out the platform in stock widths reduces fabrication and waste; odd widths get custom panels with side banding.
- Support steel. The angles, channels and beams under the grating are a separate takeoff. The mezzanine steel takeoff guide covers framing.
For stair treads, grating treads come as a manufactured item with nosing and carrier plates, and are usually priced each, not by area. The stairs and railings takeoff guide covers that.
Most of this falls in Division 5, and the Division 5 metals estimating guide covers how shops break out the scope. For turning the weight into a price, see fabricated steel cost per pound.
Worked example: a small equipment platform
An 8' × 12' platform with 19-W-4 1-1/4 × 3/16 galvanized grating, two pipe penetrations, and toe plate on three open sides:
| Item | Quantity | Unit weight | Weight |
|---|---|---|---|
| Grating, 1-1/4 × 3/16 19-W-4 | 96 ft² | 8.9 lb/ft² | 854 lb |
| Toe plate, 1/4" × 4" flat bar | 28 ft | 3.40 lb/ft | 95 lb |
| Cutout banding, 1/4" × 1-1/4" flat bar | 12 ft | 1.06 lb/ft | 13 lb |
About 960 lb of grating and trim before galvanizing, plus two cutouts, four panels (at 36" × 8' layout), and at least 16 clips. The weight tells you about crane and freight. The cutouts and panel count tell you about shop hours.
If you get platform drawings as PDFs, Steelflo reads the structural sizes off the sheets and builds the takeoff for the framing, so you can spend your time on the grating layout. See how it works.
Frequently Asked Questions
How much does 1/4 inch diamond plate weigh per square foot?
Standard 1/4" steel diamond floor plate weighs about 11.26 lb/ft² according to published supplier tables. That's about 1.05 lb/ft² more than 1/4" plain plate, because the nominal thickness is measured at the base and the raised pattern is extra.
Why does checker plate weigh more than plain plate of the same thickness?
Floor plate thickness is measured at the base of the plate, excluding the raised lugs. The lugs add roughly 1.05 lb/ft² on top of the plain plate weight at every standard thickness.
What does 19-W-4 mean on bar grating?
19 is the bearing bar spacing in sixteenths of an inch (1-3/16" centre to centre), W means welded construction, and 4 is the cross bar spacing in inches. The bearing bar size, such as 1 × 3/16, is listed after it.
How much does 19-W-4 grating weigh?
It depends on the bearing bar size. One manufacturer's table lists about 7.2 lb/ft² for 1 × 3/16 bars, 8.9 lb/ft² for 1-1/4 × 3/16, and 10.7 lb/ft² for 1-1/2 × 3/16, before galvanizing. Check your supplier's table, because weights vary slightly by manufacturer.
How do you estimate bar grating for a platform?
Measure the area in square feet by grating type, then count cutouts, panels, clips, and linear feet of banding and toe plate separately. The area gives you material and weight, but cutouts and panel count drive most of the fabrication labor.