Aluminium walkway grating is usually ordered by naming a product code from a catalogue, which works until the day something falls through it or water stops draining off it. The properties that actually matter are aperture size, bearing bar depth and pitch, the span it has to cross, the surface treatment and the open area, and each one answers a different question about how the walkway will be used.
Open area is the one clients think about least and notice most. It is the proportion of the deck that is void, and it decides drainage, how much light reaches what is underneath, how snow behaves, and what can pass through the surface.
Open area is a trade-off, not a quality
A high open area drains instantly, sheds debris, lets light through to equipment below and puts less wind load on an elevated structure. It also lets small objects fall through, which above a process line or a public area is a hazard rather than an inconvenience, and it makes some people uncomfortable to walk on because they can see the drop.
A low open area, achieved with a fine mesh, stops dropped tools and fasteners, suits routes above areas where people work, and is the usual answer where heeled footwear is present. The cost is drainage: fine apertures hold water, block with debris and ice over more readily.
The choice therefore follows from what is underneath the walkway rather than from the walkway itself, which is why a plant frequently needs both and specifying one grating type for a whole site is a false economy.
Bar depth, pitch and span go together
Grating is strongly directional. The bearing bars carry the load and the cross bars hold them together, so a panel spanning the right way and the same panel rotated ninety degrees are entirely different structures. Getting this wrong at installation is a recognised failure and it is worth marking the span direction on the drawing.
Bar depth and pitch are then chosen against the span and the design load. Deflection usually governs rather than strength, particularly on aluminium, and a deflection limit should be stated rather than left to the supplier. Span over two hundred is a common criterion for walking surfaces; a tighter figure is appropriate where equipment is wheeled along the route.
| Decision | Driven by |
|---|---|
| Aperture | What is below |
| Bar depth and pitch | Span and load |
| Surface | Slip conditions |
| Fixing type | Access needs |
Point load is the case that catches people out
A uniformly distributed load is the figure quoted in catalogues and it rarely governs. What governs on a walkway is a concentrated load: one person’s weight on a small contact area, a wheel, or a piece of equipment set down. Grating that satisfies a distributed figure comfortably can deflect visibly under a single point load, and the sensation of a deck flexing underfoot is what generates complaints even when nothing is overstressed.
Specifying both cases, with the point load and its contact area stated, is the fix. It costs nothing in an enquiry and it is the difference between a deck that feels solid and one that does not.
Surface and slip
Plain grating relies on the edges of the bars for grip, which works well until the surface is oily. Serrated bars cut into that film and are the normal choice where lubricants, process liquids or ice are present. Perforated plank decking with a raised or gritted surface goes further and is used where the slip requirement is explicit.
The requirement should be stated as a classification with the condition it applies in, wet or dry, rather than as the word anti-slip. Grit-surfaced products give the highest performance and wear, so on a heavily trafficked route the specification should say what performance is required after wear rather than on delivery.
Cleaning decides the answer in some industries
In food, beverage and pharmaceutical environments the governing question is not load at all, it is whether the surface can be cleaned and whether it holds product. Open grating drains and does not trap liquid in the way a closed deck with an upstand does, but the bar intersections themselves are surfaces that need reaching.
Where hygiene governs, smooth plank decking with a drainage fall is often specified in preference to grating, accepting a lower open area for a surface that can be hosed. That is a different product with different span capability, and it should be identified at enquiry stage rather than substituted later.
Fixing, and the panel that has to come up
Grating is either clipped down or welded. Clips allow panels to be lifted for access to services below, which is almost always needed at some point, and they need to be specified as a quantity per panel rather than left to the installer. Welded fixing is more secure and turns every future access operation into a cutting job.
Wherever aluminium grating is clipped to a steel supporting structure, the fastener and the clip material matter, because that interface is exactly the situation where contact between dissimilar metals drives rapid attack. Isolation at the clip is a detail worth showing on a drawing.
What to put in the enquiry
State the aperture or open area and what is underneath the route. Give the span and the support positions. Give both the distributed load and the point load with its contact area, plus the deflection limit. Name the slip classification and the condition. Say whether panels must be removable. State the supporting structure material so the fixing interface can be detailed.
Six lines, and they turn a catalogue code into a specification that can be checked on delivery.
Before the panels are ordered
Grating is the part of a walkway that people actually stand on, and almost every complaint about an access structure is really a complaint about the deck: it flexed, it drained badly, a spanner went through it, or it was slippery in the rain. All four are settled by four lines in an enquiry.
Our engineers will select the deck type by area rather than by site, and the aluminium walkways and access platforms we supply are quoted with the point load case and the deflection limit stated in the offer.