On sites less than 1200sq m, the council has agreed to one house per 400sq m.
There are concerns that design rules only apply to larger developments requiring a resource consent and developers will be able to construct poor quality housing for housing deemed a "permitted activity" that does not require resource consent.
Regional planning manager Penny Pirrit said "development design controls" were in the planning rulebook, or Unitary Plan, for permitted activities.
Developments requiring a resource consent would have to go through design assessment criteria set out in the Unitary Plan.
Unitary Plan manager John Duguid said officers believed there was an extensive suite of design rules, including a non-statutory urban design manual.
Several councillors, including Sandra Coney, have expressed concern about the lack of urban design controls for permitted activities.
Ms Coney said design controls were one of the biggest issues the council was grappling with.
She said there wasn't a cry against intensification, but against bad intensification from apartments to infill housing.
"What they are looking for is real reassurance. That is not going to happen under the Unitary Plan.
"The rules in the Unitary Plan that apply to people around design that don't require a resource consent are extremely bald and thin and will not deliver good urban design.
"Let's go with lowering the lines to have to get a resource consent," Ms Coney said.
Manurewa Local Board chairwoman Angela Dalton said more than elsewhere, her area with an average family size of 6.5 was going to receive a lot of affordable and low cost housing.
"I'm a bit cynical about how these design criteria will influence design and build in our community.
"It is important we have confidence that the design criteria is going to meet our needs," she said.