On every street, courtyard and car park, manhole covers do the same job: carry the load above and give safe access below. The material you choose — cast iron, composite or plastic — affects safety, theft risk, noise, maintenance and budget. This guide compares the three and adds the shape and type options (round, square, blind, curb, side) that appear in every Georgian BOQ.
Start with the load class (EN 124)
Material comes second. First choose the EN 124 load class for the location:
| Class | Test load | Where |
|---|---|---|
| A15 | 15 kN | Pedestrian and garden areas only |
| B125 | 125 kN | Footpaths, cycle paths, private car parks |
| C250 | 250 kN | Kerb-side channels, road shoulders (within 0.5 m of the kerb) |
| D400 | 400 kN | Carriageways of roads, streets, parking for all vehicles |
| E600 | 600 kN | Docks, heavy industrial yards |
| F900 | 900 kN | Airports and very heavy loads |
Most city streets in Tbilisi and Batumi need D400 in the road and B125 on the pavement.
Material comparison
| Criterion | Cast iron (ductile) | Composite (GRP / polymer) | Plastic (PP/PE) |
|---|---|---|---|
| Load classes available | A15 – F900 | A15 – D400 (some E600) | A15 – B125 (some C250) |
| Weight | Heavy | ~60–70% lighter than iron | Very light |
| Theft risk (scrap value) | High | None — no scrap value | None |
| Noise / rattling | Can rattle without a cushion insert | Quiet | Quiet |
| Corrosion | Coated; surface rust over time | None | None |
| Service life | Very long | Long | Medium |
| Best for | Roads, highways, heavy traffic | Pavements, courtyards, utilities, theft-prone areas | Gardens, landscaping, light private areas |
Ductile cast iron (GGG50) remains the choice for D400 roads and highways. Composite manholes solve theft and weight problems on pavements and in residential courtyards. Plastic manholes are economical for gardens and landscaping.
Shapes and types — what to write in the BOQ
- Round manholes — standard for sewer and storm chambers; they cannot fall into the opening.
- Square / rectangular manholes — for cable pits, valve chambers and paved areas where the joints should line up with tiles.
- Blind (solid) manholes — no openings, so they keep debris out of utility chambers.
- Grated manholes (often written as "manholes replacing a floor drain") — let surface water into the chamber.
- Curb and side-inlet manholes — built into the kerb line to take road runoff.
- Lockable and hinged covers — for security and for safe single-person opening.
Practical installation tips
- Bed the frame on high-strength mortar or a concrete ring, never on loose bricks.
- Set the cover flush with the final pavement surface.
- Use a frame height that suits the class (D400 frames are usually 100 mm or more).
- In roads, align the hinge with the direction of traffic.
What to write in the BOQ
Specify class, material, shape, clear opening and locking: *"Manhole cover and frame, ductile iron EN 124 D400, round, Ø600 clear opening, hinged with locking and cushion insert, frame height 100 mm, set on high-strength bedding mortar flush with finished road level."* For pavements: *"Composite manhole cover EN 124 B125, square 600×600, lockable, no scrap value."*
Quick selector
- City street carriageway → ductile iron D400, round, hinged, with a cushion insert.
- Residential courtyard / pavement → composite B125 or C250 (no theft value).
- Garden or landscaping → plastic A15/B125.
- Telecom or valve chamber in tiles → square, recessed or blind cover.
GON project experience
GON supplied manholes and rain gratings for Tbilisi road works on Akaki Tsereteli Avenue, Tskneti Highway, Kakheti Highway and 9 April Street. We stock cast-iron, composite, plastic and concrete manholes in round and square formats.
Related products: Cast-iron manholes · Composite manholes · Plastic manholes · Rain gullies & gratings
Further reading: EN 124 load classes explained · Telescopic vs fixed frames
Are composite manholes strong enough for cars?
Yes, if they are tested to C250 or D400. Always check the EN 124 marking on the cover.
Why do cast-iron covers rattle?
Usually because the bedding is poor or the cushion insert is missing. A well-seated frame with a cushion insert stays quiet.
Can I mix materials in one project?
Yes. Most projects do: iron in roads, composite on pavements, plastic in gardens.
Get a project quote
Send your manhole schedule (class, size, quantity) to sales@gon.ge or call +995 595 818 800.
GON supplies drainage, water, gas and road-infrastructure products to contractors, utilities and IFI-funded programmes across Georgia.