Not everyone will appreciate the architecture behind a four-story expansion to downtown Bozeman’s Lark Hotel, and that’s just fine, city commissioners said as they unanimously endorsed the project Monday.

“It will be a controversial building because it doesn’t look like anything else that we currently have,” said Mayor Carson Taylor shortly before casting his vote. “I truly appreciate that.”

The expansion will add 28 rooms to the Main Street and Grand hotel complex by building upward on a currently vacant site on the street corner. It’s also slated to include a conference room, ground-floor commercial space and a triangular plaza adjacent to the Victory Taco stand.

“It’s taken some time and planning effort to get to where we are today, but we feel that process has yielded an end result that we’re quite proud of,” said project architect Brian Caldwell of Thinktank Design Group.

The project, he said, will feature a similar aesthetic to the existing Lark building. In a first for Bozeman, he added, it will be framed using cross-laminated timber, or prefabricated solid wood panels.

Commissioners expressed enthusiasm about the project, noting it sits a block outside the formal boundaries of the downtown historic district.

“It’s definitely going to stand out,” said Deputy Mayor Cyndy Andrus. “It’s going to make Bozeman more eclectic.”

“If we’re not going to be building something to make it look historic, let’s make it look intersecting and vibrant,” she added.

“This is not going to be everyone’s cup of tea, but I still get complaints about the Co-op every once in awhile,” said Commissioner Jeff Krauss. “You’re not designing a building for everyone.”

There are people who complain about the building adjacent to the Lark across the street because it’s new construction that tries to emulate a historic feel, Krauss also said.

“I am reminded that people didn’t like the Co-op,” Taylor said. “I don’t hear that any more. It feels right now.”

Commissioners also discussed whether the downtown sewer system will have capacity for the project as it and another major project, the five-story 5 West building underway on Mendenhall Street, come into service.

A stretch of sewer line beneath North Willson Avenue, draining a section of downtown, is nearing capacity with additional development in the area, city engineers said. The construction timeframe for the projects should provide opportunity to physically verify the line’s capacity and expand it if necessary, they said.

The Lark expansion project is set to break ground in October, Caldwell said, with construction taking as long as a year.

Eric Dietrich can be reached at 406-582-2628 or edietrich@dailychronicle.com. He is on Twitter at @eidietrich.