A construction expert believes a market study into building materials will have little value

The Commerce Commission study will investigate competition issues around key building materials, and suggest ways to fix them.

It's the third such study, after one into the retail fuel market a couple of years ago, and the current one into supermarkets.

AUT Construction Professor John Tookey doubts it'll achieve much, arguing the outcome is already obvious.

He says the reason why so few building material companies compete in New Zealand, is because the market is very small.