A proposed land use bylaw has some people worried their Calgary neighbourhoods will soon be overrun with secondary suites in homes.

Rewriting Calgary's land use bylaw has been a four-year project. New rules covering all development — residential, commercial, industrial — are aimed at streamlining the approval process and making it consistent across the city.

But the land use bylaw will also include rules for secondary or basement suites, in homes.

On Monday, people lined up at City Hall to have their say at a public hearing about the changes. The hearings could last three days.

"You run the risk of changing the fabric of that neighbourhood," said Blaine Moen, who lives in Southwood, a neighbourhood where basement suites are not permitted.

People in Southwood worry allowing suites would bring a lot more traffic, a lot more garbage, and decreased property values.

But a lot of the illegal suites are popping up in Calgary's tight rental market. City staff estimate Calgary has as many as 50,000 illegal suites.

On Monday, city planners said the rules include a consultation process to allow the suites in neighbourhoods now zoned single-family.

"They would need to re-designate the property through the public hearing process. They would need then to apply for a development permit and a building permit to ensure they're safe," said Paul Cochrane, a land use manager.

Affordable housing advocates argue the new rules don't go far enough and secondary suites should be mandatory in new developments

"What we need is regulation of these suites to protect the interests of the tenants living there," said Grant Neufeld, spokesman for the Calgary Housing Action Initiative.