BOULDER - The city of Boulder's planning board on Thursday will hold a public hearing regarding plans for 1738 Pearl St., a building in downtown Boulder whose owners are proposing a three-story addition.

J Nold Midyette, a partner in the building with majority owner of Unico Properties Inc., filed the plans with the city. Midyette, a prominent property owner in Boulder, last year sold a 56 percent share of his holdings to Seattle-based Unico.

The plans call for adding an additional 17,245 square feet of space to the existing 24,755-square-foot building that houses Frasca Food and Wine on the first floor. The 38-foot-tall addition mainly would be built on what is now a surface parking lot east of the existing two-story, 35-foot building. The first floor is slated for retail or restaurant uses, as well as some parking near the alley at the back of the lot, while the second and third floors would be for offices.

"There is strong demand for office space in downtown and a striking lack of supply," said Jim Rock, Unico senior vice president for leasing. "We have the ability to accommodate our tenants' needs for growth while improving the neighborhood through this investment."

Rock said Unico is nearing 100 percent prelease on the office space, while the retail space has yet to be spoken for.

The building, at the southwest corner of Pearl and 18th streets, is in the Downtown 2 zoning district, which dictates a 38-foot height "by right" - meaning a building specification that requires no extra, more rigorous design review. But because the district allows only two stories by right, the three-story addition must go through the full design-review process before permits can be applied for. In addition to the third-story exception, the plans also call for a 7-foot setback on some parts of the third story, while a 15-foot setback is required "by right." The plans also seek an exception to setback restrictions at the back of the property.

City planning staff last month approved the plans, and the planning board called it up on Oct. 17. Planner Elaine McLaughlin said that all aspects of the plans are up for review before the board, not just those for which by-right exceptions are being sought.

The same ownership group earlier this year added a third story to the building at 1600 Pearl Street, with natural foods company Boulder Brands Inc. recently moving its headquarters to the new space.

"I can't site specific projects but adding square footage to existing buildings is an effective way to accommodate business needs in downtown while maintaining the essence of Boulder," Rock said of whether adding on to downtown buildings rather than redeveloping would become a trend. "Undoubtedly there are other opportunities to do so."