He said that only 18 consents had been issued for secondary flats in the past five years.
"A lot of it went underground - that is what happened."
Although the council did not know how many people had failed to declare building alterations, Cr Curach said the minimal number who went through the proper channels showed how much of a deterrent the fees had become.
The only fees left standing were the $4300 to $5600 building impact fee for a one or two bedroom stand-alone granny flat.
It was a contribution towards the cost of city-wide infrastructure.
Gone were the more expensive subdivision impact fees that paid for everything local that the developer did not provide, including neighbourhood reserves and main roads.
This represented savings of between $3520 and $21,370.
Home builders in the city's other greenfield growth areas that want a self-contained flat will save $13,000 in Pyes Pa, $15,000 in Welcome Bay, $15,700 in Papamoa, $17,600 in Ohauiti and $19,200 in Bethlehem.