In the Bloomberg years, developers were often presented with a choice: they could build a denser building if they agreed to make a certain portion of it affordable. The city program, known as voluntary inclusionary zoning, has received lots of media attention, but its actual impact on creating affordable housing was fairly limited because many developers decided not to take the deal. Now, with Mayor de Blasio at the city’s helm, that option is off the table. In New York City, voluntary inclusionary zoning has become mandatory inclusionary zoning.

Taken alone, this policy change is not surprising; the mayor has publically supported mandatory inclusionary zoning since his days on the campaign trail, and it is a central piece of his plan to build or preserve 200,000 units of affordable housing over the next decade. In that plan, which was released in May, the administration pledges to require affordable development “in rezonings that substantially increase potential housing capacity.”

Speaking just four months after that report was unveiled, the city’s planning commissioner, Carl Weisbrod, took things one step further. He said that inclusionary zoning would not just be mandated at large-scale redevelopments, but at any individual building that requires a zoning change. “You can’t build one unit unless you build your percentage of affordable housing,” he said at a New York Law School breakfast. “You can’t just build market-rate housing. Period.”

What exactly that percentage will be for developers, though, has not yet been decided. But Weisbrod said the city would not simply mandate the across-the-board 80 percent market-rate/20 percent affordable ratio that was seen under Mayor Bloomberg. “What we think we can require in a super hot neighborhood in Manhattan is going to be a lot different from what we think we can require, or should require, in an emerging area,” said Weisbrod.

He added that any changes to inclusionary zoning would have to be decided carefully at the risk of supposedly scaring off developers. “With mandatory, if we get it wrong, we won’t get any housing because if it’s too oppressive a developer won’t build anything,” he said.

The commissioner said the city is currently studying the issue and expects to have a proposal by the end of the year. The New York Times reported that the change could take effect as soon as next fall.

While a lot could change before then, Weisbrod emphasized the administration’s new direction on affordable housing: “It is the beginning of a new era,” he said.