The Lexington restaurant in St. Paul long has provided a cozy setting for Capitol-level strategizing, anniversary dinners and visits with Grandma — at least when the weather turns cool.

But many of today’s diners like to go outside during the summer, the owners say. So they want to add a rooftop patio with a bar to draw more business during warm weather, and recently got a green light from the City Council.

Their plans are at the heart of a rare neighborhood dust-up between several residents, many of whom frequent the Lex, and the 78-year-old Grand Avenue landmark.

Neighbors are worried that the nightly noise generated by business atop the restaurant will ruin their summer evenings and drive down the value of their homes.

“We’ve lived with a certain amount of noise and traffic for years because we enjoy that urban environment,” said Alice Medley, whose home backs onto the alley behind the Lex.

“What is different about this is the alcohol part, which equates to a certain level of noise. It’s coming into our back yard.”

General manager Michelle Hickey, who owns the Lex with her husband, John, and with Ed and Jenni Ryan, said outdoor dining in the summer is vital to the restaurant’s future success.

In one document, the owners say that the Lex “will likely be forced to close its doors” without outdoor dining.

“You need it to make things viable for a restaurant in this state,” Hickey said. “Our summers are very slow and we need to be competitive. We thought this would be great for the avenue [Grand] and the community.”

The City Council last month approved the Lexington’s license application to serve liquor on an outside rooftop patio, subject to conditions proposed by a hearing officer. Sundays through Thursdays, food and beverage service would end at 9:30 p.m. and the rooftop patio would close at 10 p.m.; for the weekend, food and beverage service would end at 11:30 p.m. and the rooftop would close at midnight.

The Lex will have to hire an acoustic engineer to do a noise impact analysis, and must also hang signs reminding patrons that they’re in a residential area.

Hickey said it’s too late to get the rooftop space ready for service this year. They must submit engineering and architectural plans to the city before getting final approval to build, and construction will take time, as well. “We have to wait another summer for this to happen,” she said.

Medley, for one, can wait. “I’m hoping there will be some middle ground,” she said.

The Hickeys and Ryans have owned the Lexington since 2011, when they purchased it, along with a third couple, from Minneapolis businessman Thomas Scallen. Theirs is only the third ownership group since the restaurant opened in 1935.

It has long been one of the city’s favorite places for family celebrations, political schmoozing, corporate parties and college formals. A hallway is lined with portraits of the St. Paul movers and shakers who have visited over the years, from mayors to bishops and business titans.

The new owners immediately started on the delicate task of injecting some new life into the Lex while preserving its Old World air. They hired a new chef, who introduced fresh dishes and rejuvenated some old ones. They got a sidewalk cafe license, and last year they applied to serve liquor outside.

Maureen Flahaven, who lives down the alley from the Lex, said that last year the owners invited neighbors over to share their plans and show them the rooftop, which faces the back parking lot rather than Grand Avenue. Flahaven said that owners estimated there was room for 40 diners, didn’t mention a rooftop bar and said that rooftop service would end at 9 p.m.

She signed the petition required by the city. “Our understanding was that this was not going to be very intrusive,” she said.

When Flahaven later discovered a conceptual drawing showing room for 70 diners — plus 10 seats at a bar — and learned that Hickey wanted to close the rooftop no sooner than midnight, she felt she had been misled.

“People are just discouraged that the process did not work, and I think it does set a precedent,” she said. “People along Lincoln [Avenue] have to think about what this means if they can open a patio on the second level and look down into your back yard.”

Not everyone is opposed to the Lex’s plans. Some neighbors say they have no objections, and the owners have the support of both the Summit Hill Association district council and the Grand Avenue Business Association.

“We’ve had this idea ever since we bought the Lex, and it’s taken us two years to get through all the process and discussions,” Hickey said. “This opens up a lot of ideas for us to move forward.”