Ronez enjoys a monopoly but the competition regular says its prices reflect costs and are not exploitative.
Ronez operates the only ready mix concrete plant in Guernsey under a monopoly, as the market is too small for two operators.
An investigation into concrete and aggregate products by the Guernsey Competition and Regulatory Authority shows Ronez's concrete prices reflect the high cost of imports and the local labour market.
This is despite them sometimes being 100% higher than an equivalent lorry load of ready mix in the UK.
The regulator found Ronez does not aggressively increase prices, they reflect cost pressures at the time and are not 'excessive and unfair.'
"Ronez’s position is not the result of exclusionary behaviour — it is the result of geography, scale, and economics."
There is a choice of supplier for concrete blocks and pre cast concrete, but it was found many builders use Ronez for everything.
The investigation was carried out for Economic Development and showed the market had not changed since a similar exercise 20 years ago.
The regulator says although it did not find unfair pricing, with increase mirroring UK rises, the current market has:
"Outcomes that are bad for consumers. Expensive building materials could mean higher housing costs, public projects costing more, with a knock-on effect for taxpayers, and even developments getting delayed or cancelled."
It suggests change would have to come from States intervention.
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