A 29-room, four-story expansion to the Lark Hotel is set to break ground Monday, backers said this week — though much of the building will actually be assembled offsite thanks to cutting-edge building materials.

In contrast to the steel or masonry framing more common with larger buildings in Bozeman, the Lark expansion’s frame will be built from cross-laminated timber, or chemically treated wood panels, backers said.

Truck-sized sections of the building will be assembled in Trier, Germany, and a staging area in Four Corners, then brought onto the expansion site, at the corner of Main Street and Grand Avenue, this winter.

“I like to call it adult Legos,” said Lark partner Brian Caldwell, also an architect with Thinktank Design. “We’re using wood in a much more poetic way."

Staging offsite, he said, will help minimize the disruption to hotel guests and other downtown businesses.

Formerly the site of the vacant Imperial Inn, the 38-room Lark opened in 2015. The expansion project has an expected completion date of spring 2018.

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