Technical guide

Choosing the right manhole cover

EN 124 load classes explained, and why we cast in ductile iron. Share it with your site team or save it as a PDF.

BS EN 124-2

Six load classes, from parks to airports

The number in each class is its test load in kilonewtons. If vehicles could ever drive over the cover, choose the higher class.

Where each class goes on a typical road. The C250 zone runs up to 0.5 m into the carriageway and 0.2 m into the footway.

A15 Group 1

15 kN test load

Pedestrians & cyclists

Areas used only by pedestrians and pedal cyclists.
B125 Group 2

125 kN test load

Footways & car parks

Footways, pedestrian areas, car parks and areas open to light vehicles.
C250 Group 3

250 kN test load

Kerb-side channels

Kerb-side channels of roads, up to 0.5 m into the carriageway and 0.2 m into the footway.
D400 Group 4

400 kN test load

Roads & hard shoulders

Carriageways, hard shoulders and parking areas for all types of road vehicles.
E600 Group 5

600 kN test load

Docks & heavy yards

Areas with very high wheel loads such as docks, loading yards and forklift routes.
F900 Group 6

900 kN test load

Airports

Particularly high wheel loads, such as aircraft pavements.

Material

A ductile iron cover bends under impact instead of cracking, and carries the same load at a lower weight.

Grey cast iron compared with ductile iron
Property	Grey cast iron	Ductile iron
Graphite structure	Flakes that act as stress raisers	Spheroids that act as crack arrestors
Under severe impact	Breaks	Bends
Tensile strength	350 N/mm² min (ISO 185 Grade 350)	500 N/mm² min (ISO 1083 Grade 500/7)
Elongation	Nil — no ductility	7% min — moderate ductility
Weight for the same load class	Heavier	About ⅓ lighter
Transport & installation	Harder to handle	Easier to transport, install and inspect
Vibration absorption	Poor	High

Send us the location or drawing and our engineers will recommend the right cover.