"We're still recovering in confidence from homeowners, particularly as a result of the watertight crisis ... and something like this, if it turns out to be true, will not look good."
Registered Master Builders Federation chief executive Warwick Quinn condemned the behaviour, and said he hoped it would not reflect badly on the wider industry.
"The past five years for the industry have been tough - prices have been sharp, builders have cut their margins and things like that so this is a one-off event that was done foolishly and hopefully it is the only one."
Mr Quinn and Mr Florence said they doubted the case would affect Auckland house prices as it involved commercial clients and did not appear to be on a large scale.
The commission said CHH and Dodds had co-operated with its investigation, and both had entered settlements admitting their conduct breached the Commerce Act.
"Fletcher Distribution discovered its involvement in the understanding this year, made the commission aware of the situation, and co-operated with the commission's investigation," the commission said.
A penalty hearing before the High Court will take place "in due course".
Price-fixing deals between competitors are illegal under Section 30 of the Commerce Act and carry a penalty of up to $10 million.
Fletcher Building said the "price-fixing" activity involved some people at PlaceMakers in Cook St and Mt Wellington.
Fletcher Building said a review found the arrangements benefited PlaceMakers' pre-tax earnings by just under $100,000. "PlaceMakers is compensating affected customers."