How to Specify Custom Metal Grates

A grate looks simple on a drawing: a hatched rectangle with a callout. But the gap between a clean callout and a panel that actually fits the frame, carries the design load, drains properly, and passes inspection is where most projects lose time. If you have ever received a shop drawing back that bears no resemblance to what you intended, or worse, a delivered panel that rocks in its frame, you already know the value of a tight specification.

This guide walks through exactly how to specify metal grates so the part that arrives on site matches the part you drew, covering load class, material, finish, bearing bar geometry, open area, panel size and weight, banding, frames and anchorage, pedestrian compliance, slip resistance, and corrosion environment.

It is written for the people who actually own the detail: engineers, architects, specifiers, and the general contractors who have to make it all coordinate in the field. We fabricate custom metal grates in-shop and ship across Canada, supply-only or supply-and-install, so the checklist below reflects what we see come across the bench every week, including the ambiguities that cause RFIs.

Why a Complete Grate Specification Matters

An incomplete grate spec does not stop a project, it just defers the decisions to someone else. When the bearing bar height is left off, the fabricator picks one. When the frame detail is missing, the GC improvises an embed. When slip resistance is unstated, you find out at occupancy. Every one of those silent decisions is a risk you have handed off. A grate that is under-specified for its load class can deflect, rattle, or fail; one that is over-specified wastes steel and weight.

The goal is not maximum detail for its own sake, it is removing every assumption that could go the wrong way.

The Custom Grate Specification Checklist

Use this as a section-by-section template. If your drawing or spec section answers all of these, we can detail it without a single clarifying question.

1. Load Class and Loading Condition

• Application loading: pedestrian, light vehicular, forklift, fire truck, or specific wheel/axle loads. State the governing load, not just "heavy duty."
• Design load and deflection limit: uniform load (kPa) and/or concentrated load (kN), plus the maximum allowable deflection (e.g. L/240 or an absolute value).
• Clear span: the unsupported distance the grate bridges, this drives bearing bar depth more than anything else.

If you are unsure where your application falls, our load classes explained post and the load class guide map common scenarios to bar sizing. For demanding applications, see heavy-duty grates.

2. Material

• Base metal: carbon steel, aluminum, or stainless (304 vs 316 matters in corrosive or washdown areas).
• Product type: welded bar grating, press-locked, swage-locked, or plate/perforated, each behaves differently structurally and visually.
• Environment: interior dry, exterior, coastal, chemical exposure, or hygienic. For clean and washdown spaces, stainless steel floor grates are usually the right call.

3. Finish

• Finish type: hot-dip galvanized, mill, powder coat, or passivated stainless. Our metal and finish guide and the galvanized vs stainless vs powder-coated breakdown cover the trade-offs.
• Colour / coating spec: RAL number, coating thickness, and any architectural appearance requirements.
• For exterior steel that will not be stainless, default to galvanized grates and state the coating standard.

4. Bearing Bar Size, Spacing and Cross Bar

• Bearing bar depth × thickness (the structural members running across the span).
• Bearing bar spacing / pitch (centre-to-centre), this sets open area and small-object retention.
• Cross bar type and spacing (the transverse bars that lock the panel together).

5. Open Area and Aperture

• Required open area for drainage or airflow (often a percentage minimum).
• Maximum aperture for safety, heel-proof, bicycle-tire-safe, or small-object retention. State the clear opening dimension; do not leave it to the spacing default.

6. Panel Size, Layout and Weight

• Overall panel dimensions and how the run is divided into liftable panels.
• Maximum panel weight for safe manual handling, or note that lifting points / mechanical handling are required.
• Cutouts and penetrations for pipes, columns, drains, or fixtures, dimensioned and located.

7. Banding, Frames and Anchorage

• Banding: end banding and any cutout banding (toe-plate height where required).
• Frame type: angle frame, embedded frame, or recessed seat, and who supplies it.
• Anchorage and fasteners: clip type, saddle clips, bolt-down, or welded; plus an anti-theft/anti-displacement requirement if the grate is removable.

8. Pedestrian Compliance and Slip Resistance

• Accessibility: heel-proof and barrier-free aperture limits where the grate is on an accessible route.
• Slip resistance: serrated bars or an applied anti-slip surface for wet, sloped, or high-traffic areas.
• Bicycle safety: orientation and aperture for grates in bike-route surfaces.

How to Write a Clean Grate Spec

The cleanest specs we receive share three habits. First, they put the governing constraint first, usually load class and span, and let bar sizing follow from it, rather than specifying a bar size in a vacuum. Second, they separate performance requirements (open area, deflection, slip class) from prescriptive details (bar depth, finish), so we can propose an efficient section that still meets intent.

Third, they name the interfaces: who supplies the frame, who casts the embed, what the adjacent finished floor level is. Most grate RFIs are not about the grate at all, they are about the edge condition where the grate meets concrete, drain, or structure.

Specifying a drainage product? Pair the grate spec with the channel: our trench drain grates, catch basin grates, and tree grates each carry their own frame and load considerations, all under drainage solutions.

Common Grate Specification Mistakes

• Stating "heavy duty" with no load number. It means different things to different people; give us the wheel load or kPa.
• Specifying spacing but not aperture. Banding and serration change the clear opening, the safety dimension is what matters.
• Forgetting panel weight. A structurally perfect grate that two people cannot lift becomes a maintenance problem on day one.
• Mismatched finish and environment. Powder coat over a washdown floor, or bare steel near salt, fails early. Reuse our finish guide before locking it in.
• Leaving the frame and anchorage to "by others." Coordinate it now, or absorb an RFI later.
• No detail for cutouts and terminations. Penetrations and odd panel ends need banding and support that should be shown, not assumed.

Drawings, Detailing and Stamping Coordination

This is where The Grate Guys does the work most catalogue suppliers push back to you. We work directly alongside engineers and architects from concept through delivery, and we produce full structural and shop/fabrication drawings for every grate and fabricated assembly we build, bar layouts, frame and anchorage details, panel divisions, weights, and connection details. You give us intent and constraints; we return detailed drawings you can mark up, not a vague quote.

To be clear about roles: we are the fabricator and detailer, not the engineer of record. We do not stamp drawings ourselves and we make no claim to certifications we do not hold. What we do is prepare drawings to a standard that supports the stamping process and coordinate directly with the engineer of record so the structural review goes smoothly, resolving section sizing, anchorage, and connection questions before they become field problems.

If you are detailing a complex condition, our engineers' resource explains how we slot into your workflow, and the architects' resource covers the appearance and coordination side. General contractors managing the trade interface can start at for general contractors.

The same detailing capability extends across the wider catalogue, structural steel fabrication, metal stairs, railings and handrails, and access platforms, so a grated walkway, its supporting steel, and its guarding can be drawn and built as one coordinated package rather than three disconnected orders.