The government’s plans did not provide surety such flats would be built to specification, Cr David Benson-Pope said.
Reduced regulation could lead to "leaky homes ... on steroids", he said.
Cr Benson-Pope made the comments at a Dunedin City Council workshop yesterday ahead of the council preparing a submission for government consultation.
The Ministry of Business, Innovation and Employment and the Ministry for the Environment are seeking feedback on options to make it easier to build small, self-contained and detached houses, commonly known as granny flats.
Proposed rules may allow, on a property where an existing home exists, a single-storey standalone house covering up to 60sq m to be built without a resource or building consent.
Work would still need to comply with the New Zealand building code.
The proposed changes are aimed at increasing the supply of affordable homes and meeting demand for small houses.
Dunedin Mayor Jules Radich said it was important to have clarity about where liability should fall if the government’s changes led to problems.
"Will it be made clear local government has no liability?
"Homeowners would like to have a trail of accountability ... some reassurance about what they’re getting."
Cr Christine Garey was one resident who could attest attempting to resolve a past problem could be difficult.
Her experience was "nobody is interested".
It is expected the city council submission will advocate for prevention of problems.
Risks identified for building control included faulty building work, property owners bearing the cost of remediation and city council infrastructure being built over.
A slide for the workshop about the "Dunedin context" highlighted building consents cost less than 2% of full projects and the average processing time across consents was 12 days.
Concerns emerged at the workshop about the proposed system likely leading to confusion and some city planning being overridden by national policy.
Cr Jim O’Malley said there seemed to be no requirement to notify the council of some activity that could be quite damaging.
He imagined a scenario where a lot of granny flats were built in north Dunedin.
The Three Waters network was constrained there and development might put pressure on it, he said.
Council planner Emily McEwan anticipated a potential problem in South Dunedin.
Lack of ground for water to soak in there is a growing issue amid climate change.
"Things like permeable surface are a particular concern," she said.
