Vehicle load
Passenger cars are Class B. SUVs and light trucks push you to Class C. Heavy trucks, fire apparatus, and forklifts are Class D or higher. Under-classing is the fastest way to crack a grate and damage the channel under it.
Grate Selection Guide
Picking the right trench drain grate — load class, material, and pattern.
Load class decides whether the grate survives the wheel that rolls over it. Material decides how long it survives salt and wash-down. Pattern decides whether water drops through cleanly and whether heels stay out of the slots.
- Load classes 6 (A15 to F900)
- Materials we install Ductile, galvanized, stainless, composite
- Typical residential spec Class B or C ductile iron
Short Answer
Match the grate to the traffic first, the environment second, and the look third.
Pick the load class for the heaviest thing that will drive over it, with margin. For a GTA residential driveway that is Class B or C. Commercial parking is usually C or D. Warehouse forklifts are E or higher. Pedestrian-only spaces are Class A.
Pick the material for the corrosive environment it will live in. Plain driveways are fine with ductile iron or galvanized steel. Salt-exposed, pool-deck, and food-service installs last longer in stainless or polymer composite. Heelsafe patterns are non-negotiable on any commercial pedestrian surface near walkers, strollers, and heels.
- A grate one class under-spec for the traffic cracks within the first hard winter.
- Plain steel in salt turns to rust in two to three winters. Stainless or composite costs more up front and less over the life of the drain.
- Pattern matters as much as material in public spaces — heelsafe grates are code on commercial pool decks, food-service zones, and pedestrian walkways.
Selection Factors
Five things that decide which grate goes where
These are the five variables we check on every site visit. Getting any one of them wrong leaves you replacing the grate — or the drain body — within a few seasons.
Corrosive exposure
Salt, chlorine, cleaning chemicals, and food-service wash-down all eat untreated steel. Pick a material that is rated for what the drain will actually live through, not the average.
Pedestrian safety
Walkers, strollers, wheelchairs, canes, and high heels all catch on wide slots. Heelsafe or mesh patterns keep that traffic moving safely and keep you out of a liability conversation.
Water flow rate
Short slots flow less water than long ones or mesh. A driveway that sees cloudbursts needs more open inlet area than a patio that sees irrigation overspray. Get the math wrong and the drain backs up before it drains.
Finish context
A decorative patio asks for a different visual than a loading dock. Cast iron reads industrial. Stainless reads modern. Composite can mimic stone or take any powder-coat colour. None of this matters unless the first four variables are already solved.
Load Classes
What each EN 1433 class actually covers
The same six classes used across Europe and North America. Pick by the heaviest real traffic the surface will see, not the average day.
Pedestrian areas only
Patios, garden walkways, pool surrounds with no vehicle access. Not rated for anything with wheels beyond a hand cart or wheelbarrow.
Residential driveways
Passenger cars, SUVs, and light pickup trucks. The standard residential spec across the GTA for driveway and garage-entrance drains.
Commercial driveways, parking lots
Light commercial traffic, delivery vans, small trucks. The common spec for gas stations, restaurant parking, and residential driveways that regularly see heavier vehicles.
Roadways, loading docks
Heavy trucks, garbage trucks, fire apparatus, paved loading zones. Used on commercial entrances, major loading docks, and public roads with trench drainage.
Industrial yards, freight
Forklifts, industrial equipment, heavy freight operations. Required on warehouse floors and loading areas that see constant forklift traffic or heavy goods handling.
Airports, ports, heavy industry
Aircraft aprons, dock cranes, mining operations. Specified by engineers for the most demanding installations — and almost never relevant to a residential or light-commercial GTA job.
Not sure which class your site actually needs?
We spec this on the site visit — we check the actual vehicles that will cross it, not the ones the homeowner mentions first.
Material Choice
Which grate material lasts in which conditions
Ductile iron is the default for residential and commercial driveways. It is strong, reasonably priced, holds a Class B or C rating without issue, and lasts 15–25 years with normal salt exposure if the coating is maintained.
Galvanized steel is the budget option for low-traffic installs. It is lighter and cheaper than ductile iron but does not handle heavy vehicles. The galvanizing holds up for 8–15 years before rust starts at edges where the coating thins.
Stainless steel is the premium option — the 316 marine grade in particular. It shrugs off salt, chlorine, food-service wash-down, and industrial cleaning chemicals indefinitely. We spec it for pool decks, commercial kitchens, car-wash bays, and any install close to Lake Ontario.
Polymer composite is the newest option and the most flexible aesthetically. It will not rust, takes colour and texture well, and carries lower load classes (A or B). We use it for patios, pool decks, and residential spaces where the grate is visible and the load is light.
Grate By Application
Which grate goes over which surface
A cheat sheet, not a specification. We spec against the actual site conditions, but these are the defaults we reach for on each application.
| Application | Load class | Material | Pattern |
|---|---|---|---|
| Residential driveway | Class B or C | Ductile iron or galvanized | Slotted, longitudinal |
| Garage entrance | Class B | Ductile iron | Slotted, longitudinal |
| Patio / walkway | Class A | Composite or galvanized | Heelsafe |
| Pool deck | Class A | Stainless 316 or composite | Heelsafe |
| Commercial parking lot | Class C or D | Ductile or cast iron | Slotted or mesh |
| Restaurant / food service | Class A or B | Stainless 304 | Slotted |
| Gas station / fueling area | Class D | Stainless or epoxy-coated iron | Slotted |
| Warehouse floor | Class D or E | Cast iron | Mesh or perforated |
| Auto repair service bay | Class C | Ductile iron, coated | Mesh |
Heelsafe means no slot opening wider than 8 mm in at least one dimension. It is required on any commercial surface that carries pedestrian traffic.
Where People Go Wrong
Four ways people pick the wrong grate
We see these patterns often enough that they are worth warning about. Two get handed to us by a DIYer. Two get handed to us by a contractor who should have known.
Under-classing the load
Class A grate on a driveway is the classic mistake. The grate cracks the first time a full-size pickup truck parks on it. Class B is the minimum for any driveway that sees a vehicle.
Plain steel in salt
Galvanized steel on a Toronto driveway rusts at edges within two to three winters. Budget choice at install; replacement bill at year four or five. Ductile iron with a good coating or stainless lasts the life of the slab.
Ignoring heelsafe on public surfaces
A standard slotted grate on a commercial patio, hotel entrance, or pool deck will catch heels, cane tips, and stroller wheels. Ontario building code requires heelsafe on commercial pedestrian surfaces for a reason.
Picking the grate before the channel
Grates are sized to specific channel widths. An Amazon-purchased grate almost never fits the channel you already own. Match the system from the start — channel plus grate from the same manufacturer.
Why The Spec Matters
A $300 mistake at install becomes a $3,000 mistake at replacement.
Grate selection is one of the smallest-dollar decisions on a trench drain install. On a $3,000 residential job, moving from Class B to Class C is maybe $150. Moving from galvanized steel to stainless is another $300. Fifteen percent premium on the entire install for a grate that does not crack or rust for 25 years.
The cost of replacing a grate later is never the $300 you saved. It is pulling the existing grate — damaged concrete often follows — sourcing a compatible replacement (the original supplier may be out of stock or out of business), and paying a return visit. Two hours of crew time on site to swap a grate that should have been right the first time.
This is why the grate question is usually the easiest question to answer on a site visit, and usually the one contractors rush through fastest. If your installer hands you a grate choice without asking about load, environment, and heel safety, the grate is probably wrong.
Grate FAQ
Common trench drain grate questions
The questions we usually field after someone sees the load-class guide and wants to know if a particular grate fits their site.
What load class do I need for a residential driveway in the GTA?
Class B is the minimum. Class C if you park an SUV, truck, trailer, or RV on it. Never Class A — that is pedestrian-only and will crack under any vehicle, including a compact car.
Can I use a stainless steel grate on a regular driveway?
Yes, it will outlast ductile iron by decades and never rust. The trade-off is cost — stainless usually adds $300–$600 to a typical residential install. Most GTA driveways do not need it, but if the drain sits close to the lake, on a road that is heavily salted, or you want a permanent spec, it is worth the money.
What is the difference between a slotted and heelsafe grate?
A slotted grate has long, narrow openings running along the channel length. A heelsafe grate has smaller openings — usually no more than 8 mm wide in any direction — so high heels, cane tips, stroller wheels, and wheelchair casters cannot drop in. Slotted flows more water; heelsafe is required on any commercial pedestrian surface.
How long does a ductile iron grate last?
15–25 years with normal GTA salt exposure and a properly maintained coating. The channel body underneath typically outlasts the grate, so a swap at year 15–20 is a grate-only job, not a whole drain rebuild.
Are composite grates strong enough for a driveway?
The Class B composite grates we install are rated for passenger vehicles and light trucks. They are not a good choice for anything heavier — no Class C or higher composite exists that is worth specifying. For a standard residential driveway with passenger cars and SUVs they work, and they never rust.
Does the grate pattern affect how much water the drain can handle?
Yes. Mesh and wide-slot grates have the most open inlet area per square foot; heelsafe and narrow-slot patterns have the least. On a site that sees sudden heavy rainfall, the pattern choice matters. We check the peak rainfall for your area against the grate's rated flow before finalizing the spec.
Can I buy the grate separately from the channel?
You can, but we do not recommend it. Grates are sized to specific channel widths and lockdown mechanisms, and the fit tolerance is tight. Mixing brands or series usually means the grate does not lock down properly — which makes it a safety issue and a theft issue. Buy the system matched.
How do I know if my existing grate is the wrong spec?
Obvious signs: cracked or chipped corners, rust eating through the metal, the grate rocks under foot or vehicle, water backs up in heavy rain, or heels and stroller wheels catch in the slots. Any of those mean the original grate was wrong for the application — and replacing it with the same thing will get you the same result.