NEWBURYPORT — The former home of Mike's Sub Shop could get a face-lift — growing by a story and expanding by several hundred square feet.

But the Historical Commission, which must approve the changes because of the building's age and where it is located, is opposed to the changes proposed by the building's owner, Robert Finneran.

Linda Smiley, the chairwoman of the committee, said both the materials for the exterior of the expansion — wooden clapboard — and the architectural style — a Cape Cod-like look — do not fit within the downtown district.

"The commission is not happy with the choice of materials and the configuration of what he is proposing," she said, adding that the wooden clapboard, for instance, does not match the downtown's mostly brick facade. "We didn't feel like that was appropriate for the downtown location."

Finneran, a Plum Island attorney who could not be reached for comment, purchased the distinctive, 400-square-foot brick building at 42 Merrimac St. for $329,000 in January, according to Essex County Registry of Deeds records. He said at the time that he bought the property "to invest in and improve it."

Part of the plan to improve the structure is to expand the building in the rear by 396 square feet and build a second story on the present first floor and the proposed expansion, according to plans filed at the city Planning Office. In all, the space would increase by about 1,192 square feet.

In a previous interview, Finneran said it is "too early to say" what he plans to do with what is probably the smallest free-standing commercial building in the downtown, although he said it would lend itself to retail or small office use.

On the plans at City Hall, the first floor space that exists now is marked as an area for an "office/shop."

Smiley said that at a meeting Thursday night, the commission asked Finneran to come back to its Aug. 7 meeting with changes to the material and style of the proposed addition.

She said "it is hard to say" if Finneran seemed cooperative to the commission's suggestions.

The commission isn't the only entity that has problems with the style of the building. In a letter filed at the Planning Office, Kari and Rene Bernard, property owners who abut the property, said they do not object to the expansion, but only to the style.

A letter from the Bernards says the proposal "goes against the style and brick facades that line Merrimac Street."

Much of the land surrounding the small building is owned by billionaire developer Stephen Karp, who owns almost all the property from the Black Cow Restaurant to Michael's Harborside.

Finneran, in a previous article, said he had not had any dealings with Karp.

Karp, along with his local team of developers, is planning to build a mixed-use development of some kind for the area, which is dubbed Waterfront West. The full extent of Karp's plan for the area is not clear, but it will include a hotel as its focal point.

Previous owners Peter and Jane Jensen of Hampton Falls, N.H., had been asking for $495,000 for the building and its 1,620-square-foot lot near Green and Merrimac streets. Judy Fogel, the sub shop's longtime owner, retired and closed the business at the end of September.

The assessed valuation of the property rose this year to $375,300, from $314,400.

The building was built in 1930, according to assessors' records.

In Newburyport, changes to buildings that are at least 100 years old — or at least 75 years old in a historic district — must get approved by the Historical Commission.

Smiley said that during a walk-through of the site, despite city assessor records, "it is clear to us that the building is much older than the 1930s."

"We thought this one being so much in the public eye, we wanted to give any abutters a chance to weigh on about what they thought about the plans," Smiley said.

It is unclear what it was first used for, but old city directories from the 1950s through 1978 list the building as the office for several taxicab companies.

New owner Finneran, a Newburyport native who lives in the Newbury section of Plum Island, has twice run for state representative in the 2nd Essex District as a Republican. He lost to current Rep. Harriett Stanley, D-West Newbury, in 2002 and 2004.