A strike of some 28,000 doormen, maintenance workers, and superintendents was averted early Friday morning, as Local 32BJ of the Service Employees International Union and building owners reached a tentative deal for a four-year contract.

Union and industry representatives announced the decision shortly after 1 a.m. at the Sheraton New York Hotel, staving off what would have been the largest walkout in New York since the 2005 transit strike.

The exact terms of the deal were not immediately made public, but negotiators said that the union had accepted a short-term wage freeze in exchange for building owners dropping their demand that workers pay into their health plan.

"We've achieved what we want to achieve in this agreement, though not everything we wanted. We made compromises, but we feel it's a good agreement for all of us," Michael Fishman, president of the union, said at an early-morning press conference.

The proposed strike had threatened to disrupt garbage disposal and building upkeep at thousands of high-end apartment buildings and co-ops, including 140 Columbia-owned residence halls.

Throughout the week, union representatives were engaged in around-the-clock contract negotiations with the Realty Advisory Board on Labor Relations, which represents the owners of 3,500 buildings throughout the city.

Both parties had indicated in the final hours of talks that a deal was still far off, but at midnight, a Matt Nerzig, a union spokesman, came to the podium and announced that an agreement was expected within a few hours.

"The elements of an agreement seem to be there," Nerzig said. Despite the union's earlier insistence that it would not extend the strike deadline beyond midnight, Nerzig said that the union would hold off pending the deal.

About an hour later, Fishman, and James F. Berg, president of the RAB, appeared at the podium to announce the terms of the agreement.

"This agreement will serve both the employers and the employees and provide us with four years of stability," Berg said.

Union officials had warned for several days that they would initiate a strike on Friday if the board did not drop its demands for workers to accept a 15 percent health care pay-in and a temporary wage freeze. On Tuesday, thousands of union members staged a protest on the Upper East Side, where many of the affected buildings are located.

Industry negotiators had said that skyrocketing health costs made it necessary for workers to contribute to their insurance plans, and that SEIU members who maintain commercial buildings in the city had accepted a wage freeze in 2004. The apartment building workers make an average of $37,300 a year, according to union statistics.

Columbia employs 225 members of Local 32BJ at its off-campus residence halls, which are mostly occupied by faculty and graduate students. The last time New York's apartment building workers held a strike was in 1991 and lasted for 12 days.