Last week, New York City welcomed Carmel Place, its first building composed of micro-units. Stocked with kitchens, bathrooms and living spaces, all of the 32 tiny apartments that fill the Kips Bay building are smaller than 400 square feet.

Buildings like Carmel Place aren’t the only way to create more living space in a crowded city. Repurposing basements and other small spaces has been suggested as a solution to New York City’s housing crisis for years. But a lack of regulatory framework for these spaces has stalled their development, said Jerilyn Perine, Executive Director of the Citizens Housing and Planning Council.

“Here’s a stock of housing that’s already been acquired by the homeowner. And if we had a regulatory framework that would support that, we could not only make homes more affordable for a lot of striving families, particularly immigrant families, but we could also put more units out there,” said Perine, speaking on a housing panel at the Crain’s New York Summit in Manhattan on Tuesday.

Housing groups like the Citizens Housing and Planning Council have long advocated on behalf of building small units and repurposing accessory spaces, like basements, into full apartments. And the opening of Carmel Place has been a major success. But there’s still a long way to go. Perine estimates that between 50,000 and 100,000 basements and other spaces could be turned into full units.

She said that, like the discussion around homeless crisis and housing for former prisoners, there was a lack of language surrounding the contentious issue that stalled progress. “Try to bring that up in a political context—see how it ends,” she said.

And this results in a lack of regulation for basement and other accessory units. People who live in small spaces often don’t have leases and can’t turn to the authorities for help when they have problems with their landlords, according to a story published in the New York Daily News earlier this year.

Homeowners who want to make their extra spaces fit for habitation often don’t have any recourse. The Department of Buildings fines landlords $2,500 for violations like the absence of sprinklers and living spaces that are smaller than the minimum of 450 square feet. Housing advocates want to do away with some of these regulations, while still maintaining safe housing for tenants that can’t afford to live anywhere else.

The minimum square foot requirement has also been a hurdle for developers who want to build small units, said Brad Hargreaves, founder and CEO of Common, a company that has built compact, dormitory-style housing in cities around the world. “That’s one layer of several layers that make it difficult to practically build a building full of smaller units,” he said at the Crain’s New York Summit. “What are the things that are preventing people from experimenting, that are preventing new and innovative types of units?” he said.

It’s a battle that still has a long way to go before the city sees another Carmel Place. “We’re seeing a little incremental change, but we’re a city that’s become addicted to incremental change in the regulatory framework, and not big changes. I think it’s because we don’t have a way to speak about these things,” said Jerilyn Perine.