The owners of the building that houses the Brattle Street Theater have agreed to give city officials a say in renovations of the popular landmark.

Brattle Square Associates, which owns the site at 40 Brattle Street, will need the city's approval to proceed with its planned renovations.

The owners are seeking a historical facade easement. If granted by the Cambridge Historical Commission, the city will have the power to approve any changes made to the outside of the 100--year--old structure.

The city was planning to make the site a Cambridge landmark, said Cambridge Historical Commission official Sally Zimmerman. Such a move would have given the city the same right to approve changes, but the building's owners asked for the easement before the city acted.

Although the easement would restrict changes to the building's facade, the owners could still remodel the inside.

Running Arts, the company that runs the 32--year--old movie theater, could be forced to vacate the site because of the work. The company's lease expires in 1990, and Running Arts co--owner Connie White said she fears the building's owners may raise rents after the improvements are made.

But Sam Plympton, a partner in Brattle Square Associates, called the theater a "gem," and said it would continue to operate. He added that the group undertook the work to "make [the theater's] operation better."

White said the building's owners sought an easement to forestall its declaration as a landmark, which would have given Cambridge the same amount of control over the building. And the commission's executive director, Charles M. Sullivan, said the owners could get a tax benefit from the easement that landmark status would not confer.

"There could potentially be a tax break," Plympton said. But he said the group's main motive in seeking the easement agreement is to "preserve a building that we think is an important part of Brattle Street."

Although Internal Revenue Service staff said a tax break was only possible if the property was sold, Plympton said the group had no plans to sell the site.

Sally Zimmerman, also from the Commission, said, "The standard motive for [seeking] a protective easement is to protect the building after you sell it." But, she said, the owners sought the easement, "I presume because they want the building to be preserved," adding that she doubted that they would sell.

The renovations will probably include a general clean--up of the building's brick facade, a ramp for the handicapped and improved waiting and ticket areas, Plympton said.

Marianne Lampke, a co--owner of Running Arts, said she was pleased by the developer's efforts, but added, "It is important to understand that the future of the theater...depends on the developer's willingness to offer reasonable lease terms...and on community support and responsive press coverage."

The Brattle Square Associates said they are coordinating renovations with nearby Mifflin Place to convert space between the buildings into a shopping area. They said they will also tear down the Casablanca part of the building to create more space. Plympton said that the bar would be moved into unused space in the basement.

Several other buildings in Harvard Square are already covered by easements, including four final clubs.