A single point gully works well on a road with a kerb and a camber. In a modern residential complex, the ground is often flat, paved with tiles and stepped with ramps, so water has to be caught along a line instead of at one point. This is where linear drainage channels, also called trench drains or "metric drains" (*метражные трапы*), are essential. They protect building entrances, underground car parks and landscaped courtyards from flooding. These notes help developers, landscape architects and contractors choose the right system.
Where linear drainage is the right answer
- Underground car-park ramps: a channel at the top of the ramp stops street water from running down into the parking level.
- Building entrances and lobbies: level-threshold entrances need a channel in front of the door.
- Large paved courtyards and plazas with very shallow falls.
- Loading bays, fuel stations and logistics yards, where a continuous line of capture is safer than point gullies.
- Sports courts and podium decks.
Load classes for channels (EN 1433)
Channels follow EN 1433 and use the same class letters as EN 124:
| Class | Typical location |
|---|---|
| A15 | Gardens, terraces, pedestrian-only paving |
| B125 | Footpaths, private driveways, car parks for cars |
| C250 | Kerb-side areas, service roads, light commercial yards |
| D400 | Roads, car-park ramps used by trucks, fire-access routes |
| E600 / F900 | Logistics yards, ports, airports |
Fire-access routes through a residential complex must be designed for fire-engine loads. Specify at least D400 on those routes, even in a "pedestrian" courtyard.
Choosing channel size and material
| Choice | Guidance |
|---|---|
| Nominal width | 100 mm for terraces and entrances; 150–200 mm for car parks and ramps; 300 mm+ for large catchments |
| Body material | Polymer concrete (strong, light, chemical-resistant); HDPE/PP (light, A15–C250); concrete (heavy duty) |
| Grating | Galvanised steel (A15–C250), ductile iron (C250–F900), stainless or slotted for architectural areas |
| Fixing | Bolt-locked or screwless locking gratings in public areas to prevent theft and rattling |
| Outlets | End caps, vertical outlets and a sump unit with silt bucket at the outlet |
Installation basics
- Lay channels on a concrete bed and haunch them with concrete. The class rating depends on this surround.
- Set the grating 3–5 mm below the finished paving so water enters.
- Install a sump/catch-pit unit before the connection to the storm collector.
- Leave space for an expansion joint between the channel and rigid slabs.
What to write in the BOQ
*"Linear drainage channel EN 1433 class D400, nominal width 200 mm, polymer-concrete body with integrated galvanised edge rails, ductile-iron slotted grating with screwless locking, laid on C25/30 concrete bed and haunch, including sump unit with silt bucket and DN 160 outlet to storm collector."* State the class for each zone: entrance, ramp and fire route.
Quick selector
- Entrance threshold, pedestrian → 100 mm, A15/B125, stainless or galvanised grating.
- Car-park ramp top → 200 mm, D400, ductile-iron grating, sump unit.
- Courtyard used as a fire-access route → D400 throughout, with lockable gratings.
- Landscape terrace → HDPE channel A15 with a decorative grating.
Combine with point gullies and pipes
Most developments use both: linear channels at ramps and entrances, gullies and rain gratings in roads, and an HDPE corrugated storm collector underneath. GON supplies all three, together with manholes, so the drainage package arrives as one coordinated delivery.
Related products: Drainage & stormwater · D400 rain gratings 600 mm · Composite manhole cover B125 · HDPE corrugated pipe
Further reading: EN 124 load classes explained
Plastic or polymer-concrete channel?
Plastic is light and cheap for A15–C250. Polymer concrete is stiffer, more durable and suited to D400 and above.
How long can a channel run be?
It depends on flow. Long runs need intermediate outlets or a sloped-invert system, which the designer calculates.
Not sure which class?
Send the landscape or car-park drawing to sales@gon.ge and we'll mark the channel class for each zone. You can also call +995 595 818 800.
GON supplies drainage, water, gas and road-infrastructure products to contractors, utilities and IFI-funded programmes across Georgia.