Steel grating is installed by setting panels on level steel supports with the bearing bars spanning between them, then fastening each panel with clips or welds and banding the edges around cut-outs and removable sections. The two decisions that matter most come before installation: the grating has to be the right type and depth for the span and load, and the support framing has to be detailed so the panels sit flat at the right elevation. Get those right and installation is quick; get them wrong and no amount of clipping fixes it.
This guide covers how bar grating is made, how it is sized, how it is fastened and what the support steel needs. For grating as a stair tread, see types of steel stair treads.
Types of steel grating
All bar grating has the same two parts: bearing bars (flat bars on edge that carry the load) and cross bars (lighter bars at right angles that hold the bearing bars upright and spaced). The type is named for how the two are joined.
| Type | How it's made | Typical uses |
|---|---|---|
| Welded | Cross bars, usually twisted square bar, forge-welded to the top of the bearing bars | Industrial platforms, walkways, stair treads, trench covers; the economical standard |
| Press-locked (pressure-locked) | Cross bars pressed into notched bearing bars, leaving a flush top | Architectural screens, sunshades, visible floors and treads |
| Swage-locked | Cross bars swaged into punched holes in the bearing bars | Light platforms, walkways and architectural uses |
| Riveted | Bent connecting bars riveted to the bearing bars | Impact loads and repeated heavy traffic |
| Heavy duty | Deep, thick bearing bars, usually welded | Truck and forklift traffic, loading areas, drainage covers |
| Plank (safety) grating | Formed perforated channels with raised slip-resistant openings | Catwalks, ladder platforms, treads where a finer surface is wanted |
Surfaces come plain or serrated. Serrated bearing bars have small notches along the top edge for grip, which helps on exterior, oily and icy surfaces. Serrations take a little depth off the bar, so manufacturers adjust their load tables for serrated grating.
Grating is available in carbon steel (bare, painted or hot-dip galvanized), stainless steel and aluminum. In Ontario, exterior steel grating is almost always galvanized. For finish choices on the rest of the steel, see galvanized vs painted structural steel.
How grating is sized
Bar size and spacing
Grating is described by the size of its bearing bars (depth and thickness), the spacing between them, the spacing of the cross bars, and how it is made. Standard welded steel grating has bearing bars at 1-3/16 in (about 30 mm) centres with cross bars at 4 in (about 100 mm) centres, and a close-mesh version uses bearing bars at 15/16 in (about 24 mm) for heavier foot traffic or where smaller openings are needed. Cross bars at 2 in (about 50 mm) are available where smaller openings are wanted.
Many catalogues abbreviate this in a short code. A designation such as 19-W-4 counts the bearing bar spacing in sixteenths of an inch (19/16 in, or 1-3/16 in), gives the type (W for welded), and gives the cross bar spacing in inches. A full specification adds the bearing bar size, for example 1-1/4 in by 3/16 in, plus the surface, material and finish.
Grating is still made and specified mostly in imperial sizes in North America, even on metric drawings. Make sure the drawings and the supplier are using the same bar size.
Span and load
The span is the clear distance the bearing bars run between supports. Grating is selected from the manufacturer's load tables, which give the safe uniform load, the safe concentrated load and the deflection for each bar size at each span. Three inputs drive the choice:
- Clear span between supports
- Load: pedestrian, equipment, carts, forklifts or trucks
- Deflection limit: manufacturers commonly use 1/4 in (about 6 mm) as the comfort limit for pedestrian grating, because grating that flexes noticeably feels unsafe even when it is strong enough
For vehicle and heavy-duty grating, an engineer should check the selection against the actual wheel loads; load tables for those cases use tighter deflection limits and assume load banding.
Steel grating calculation in practice usually runs backwards: the platform framing sets the span, the use sets the load, and you pick the lightest bar that meets both from the table. Shortening the span with an extra support beam can be cheaper than going to a deeper bar across a whole floor.
Panel layout
Grating is manufactured in large mats and cut to panels. Panel length is measured along the bearing bars (the span direction) and panel width across them. Removable panels are usually sized so one or two people can lift them, which limits width and weight. The panel layout drawing shows each panel's size, mark, span direction, cut-outs and fastening.
Banding, cut-outs and toe plates
Banding is a flat bar welded across the cut ends of the bearing bars.
- Trim banding tidies the edge and stops the bar ends from catching feet. It is not a structural element.
- Load banding is welded to every bearing bar so a load on one bar is shared with its neighbours. It is used at cut-outs, at removable panels and under vehicle loads.
Manufacturers recommend banding whenever panels are designed to be removable and where grating carries vehicle loads.
Cut-outs for pipes, columns and equipment are cut in the shop where possible and banded. Every cut bearing bar loses its support at that end, so large cut-outs may need added framing below.
Toe plates (kick plates) are flat bars welded along panel edges or around openings so tools and parts can't roll off. On platforms in workplaces, toe boards are part of the guardrail requirements; see steel mezzanines for platform guard points.
Steel grating installation procedure
In outline, a grating installation runs like this:
- Check the supports. Beams, channels or seat angles must be at the right elevation, level and in line. Grating will follow whatever it sits on, so a high support makes a rocking panel.
- Check bearing. Each panel end needs enough bearing on its support; the manufacturer or designer sets the minimum. Where grating sits in a recessed frame or embedded angle, leave the clearance shown on the drawings so the panel drops in.
- Set panels by mark, with the bearing bars spanning between supports. Press-locked grating goes flush side up.
- Align the bars from panel to panel so the openings line up, which looks right and avoids a trip edge.
- Fasten. Common methods:
- Saddle clips: a bent clip over the bearing bars, bolted to the support. Used for removable panels.
- G-clips: a friction clip that hooks the bearing bar and clamps under the support flange, so no drilling or welding is needed.
- Anchor blocks or weld lugs: small plates shop-welded into the grating for bolting to the support.
- Field welding: tack welds between bearing bars and supports at the spacing and size the manufacturer or designer specifies. Permanent panels only.
- Touch up. Field cuts and welds on galvanized grating need a zinc-rich repair coating.
On a site in use, temporary covers and guards stay in place until each area is fully fastened. Loose grating is a fall hazard.
The support steel underneath
Most grating problems start in the framing, not in the grating. The support steel should be detailed with:
- Top of steel elevations that put the top of grating at the finished floor level, allowing for the grating depth
- Seat angles or embedded angles at concrete edges, trenches and pits, set to the grating depth
- Support spacing that matches the span chosen from the load table
- Framing at cut-outs large enough to cut several bearing bars
- Toe plates and guard posts coordinated with the grating layout, so posts don't land in the middle of a panel
Grating, framing and stairs are often supplied as one package for platforms and mezzanines. For checker plate as an alternative deck, see steel checker plate, which includes a plate vs grating comparison.
Getting grating framing and platforms fabricated
We supply and fabricate steel grating, cut and banded to fit, along with the steel it sits on: platform and mezzanine framing, stair stringers, seat angles and embed angles, with CWB certified welding and shop drawings prepared in-house. We can prime or galvanize to suit the location. Installation is by your installer or contractor.
Send your drawings or platform layout for a free quote, and see our steel products for the sections we supply.
Frequently asked questions
How is steel grating installed?
Grating panels are set on level steel supports (beams, channels or seat angles) with the bearing bars spanning between supports, then fastened with saddle clips, G-clips or welds as specified. Cut-outs and removable panels are banded, and any field cuts on galvanized grating are touched up.
Which way does grating span?
The bearing bars, the deep flat bars on edge, are the ones that carry load, so they must span from support to support. The cross bars only hold the bearing bars in position. Installing a panel turned 90 degrees leaves it unsupported.
How do you calculate the size of steel grating needed?
Grating is selected from the manufacturer's load tables using the clear span between supports, the load (uniform, concentrated or vehicle), and the deflection limit. Manufacturers commonly use a deflection of 1/4 in (about 6 mm) as the comfort limit for pedestrian grating. An engineer should confirm grating for vehicle or heavy equipment loads.
What is the difference between welded and press-locked grating?
Welded grating has cross bars forge-welded to the tops of the bearing bars and is the economical industrial standard. Press-locked grating has cross bars pressed into notched bearing bars so the top surface is flush, giving a neater look for architectural work.
