Mayor Bill de Blasio announced a series of measures Wednesday aimed at preserving the affordability of more than 3,000 rent-regulated lofts throughout New York City.

De Blasio, speaking at a news conference in Brooklyn, billed the proposals as an effort to protect thousands of artists and residents who occupy the open-space dwellings that often serve as both work studios and residences. The plan must be approved by the city’s Loft Board.

“I hear all the time from folks . . . in the entire cultural field that it’s harder and harder to live here and they have to think about whether they can hang on or not,” de Blasio said speaking from a ninth-floor loft in Williamsburg with views of the Manhattan skyline. “We don’t want to lose one of the most essential parts of New York City.”

The mayor said the number of buildings with rent-regulated lofts has dropped by nearly 30 percent since 2004. There are currently 342 buildings with rent-regulated lofts, down from 479 in 2004, according to figures provided by the city’s building department.

Under the mayor’s proposal, once a loft tenant accepts a buyout from their landlord, the city would make sure that future rent increases on the loft would be subject to rent regulations. Currently, once a buyout occurs, a landlord can immediately charge the next tenant market rate rent, city housing officials said.

The proposal also would expand tenant protections to all occupants of a loft, whether or not they are the loft’s primary leaseholder. De Blasio’s aides said such a move would give legal cover to family members living in the loft, allowing them to remain living in the unit once a primary leaseholder dies.

The plans must first be approved by the New York City Loft Board, a regulatory panel that includes two de Blasio appointees, two holdover appointees from the administration of former Mayor Michael Bloomberg, and two vacant seats. De Blasio said he expected the board to vote on the proposals by the end of the year.