The couple who owns one of the few structures atop Munjoy Hill to survive the Great Fire of 1866 is seeking Portland’s landmark status for the house, even as they sell it.

The brick structure at 147 Congress St. is “a particularly high style example of transitional Greek Revival/Italianate architecture,” according to a city report prepared for the Portland City Council, which is to vote on whether to grant the landmark designation Monday night.

Karen Rasmussen and Manuel Pena, the couple who own the house, could not be reached for comment, but the architect who prepared the nomination for the landmark designation said they are moving because an older family member had to move in with them and having a two-story structure presented difficulties.

The architect, Julie Larry of ttl-architects, said the landmark designation will ensure that most exterior changes to the house would have to be approved by Portland’s Historic Preservation Board. Additions, window replacements, masonry repair, wood trim and work on the porches would have to be reviewed, she said.

It would also protect the building from demolition unless the owner can prove an economic hardship.

Interior changes wouldn’t need to be reviewed, Larry said, and she pointed out that the couple had to do a lot of work inside when they first bought the house in 2000.

“I believe Karen said it was a rooming house when she purchase it and they restored it back to a single-family,” Larry said in an email.

Larry said the structure, known as the Ann Freeman house for its first owner, is under contract and the potential new owners are aware of, and support, the landmark designation.

Larry said she didn’t know the sales price on the house. City property records say it’s assessed at $307,400.

The local designation doesn’t provide any tax breaks, Larry said. Owners of buildings on the National Register of Historic Places can get tax credits for restoration work, she said, but the Freeman house isn’t on the list and hasn’t been nominated.

The city report said the house, built in 1857, was one of a handful of buildings on the East end of Congress Street to survive the 1866 fire. One of the others is the Portland Observatory, which sits across the street from the Freeman House.