He spoke at an event in Gowanus, Brooklyn, to reveal the details of his Block by Block plan, which includes three planks: Building new homes, tenant protections and overhauling NYCHA.
Under plank one, the city will build 200,000 new, affordable and rent-stabilized homes and preserve and stabilize another 200,000 homes.
This will involve a $22 billion investment throughout the next five years.
And there will be zoning code changes to help make it easier to build and buy a home.
The rental ripoff hearings Mamdani held earlier this year inspired plank number two.
It creates a legislative task force to overhaul the city's maintenance code and improve how 311 investigates complains.
When heat season begins on Oct. 1, every single complaint will be investigated. And when necessary, the city will take legal action to remove negligent landlords.
As for NYCHA, the city plans to spend $5.6 billion in the next five years to make much-needed renovations and do it quickly so people don't have to wait years for basic repairs.
The mayor oversees NYCHA, with money coming from federal, state and city coffers.
NYCHA has more than 170,000 apartments throughout 335 developments and many of them were built decades ago.
Mamdani also discussed that landlords can implement a one-time rent increase on empty units, even if a rent freeze is approved later this month.
He said while this is not new, they are emphasizing it as part of the housing plan announcement.
The percentage increases will be determined on a case-by-case basis, but could amount to hundreds of dollars a month in some cases.
As the Rent Guidelines Board votes in June to set the new limit, possibly 0%, for how much landlords of rent-stabilized units increase rent, the administration has been searching for ways to offer landlords relief, while keeping housing affordable.
"At a moment when working people are being pushed out of the city they built, New York cannot afford half-measures or delays," Mamdani said. "This plan meets the housing crisis with the urgency it demands. We are setting the most ambitious housing production and preservation targets in the city's modern history - and backing them up with investments to match - while also protecting tenants and homeowners, investing in public housing and ensuring the workers building that housing have good-paying, safe jobs. We must fight for both the tenants of today and the tenants of tomorrow. Block by Block shows how New York City can do exactly that."
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