Composite vs cast iron manhole covers

The honest comparison — including the two situations where cast iron is still the right answer.

The short answer: composite is lighter, will not corrode, has no resale value so nobody steals it, passes radio signals and needs no maintenance. Cast iron still wins above E600 wheel loads and wherever an existing municipal specification fixes the material. First cost is comparable at the same load class.

Property	Cast iron	Composite (SMC / FRP)
Weight, 600 mm cover	≈ 70 kg	≈ 18 kg
Corrosion in salt air	Severe, from the rim	None
Theft risk for resale	High	None
Seizing in frame	Common	Does not occur
Noise under traffic	High — rings	Low — absorbs
Signal transmission	Blocks	Passes (5G, IoT, meters)
Repainting / maintenance	Every few years	None
Installation crew	Two men, lifting gear	One man, T-key
Surface branding	Cast, limited detail	Moulded, full logo
Resale value at end of life	Scrap price	None — but nobody takes it

Where cast iron still wins

Wheel loads beyond E600 — docks, container yards, aircraft pavements.
Projects where the specification is fixed by an existing municipal standard and cannot be varied.

Where composite wins outright

Coastal cities — salt air and sulphate soils destroy iron from the rim inward.
Utilities with recurring theft losses — no resale value means the theft simply stops.
Smart-city pilots — sensors and meters under the cover can still transmit.
Sites where installation labour is expensive or scarce — one man, no crane.

Cost, realistically

First cost is comparable to ductile iron at the same load class. The saving is downstream: no crane or lifting gear, no repainting, no replacement for corrosion. Composite is rarely replaced for corrosion — it is replaced when the road is rebuilt.

Load classes are explained on the EN 124 page. Send us your size and class and we will quote — get a quote.

Send us your opening

Give us the clear opening, the load class and the annual quantity. You get a price, a drawing and a delivery date — usually within two working days.

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