Plans for a new library building are moving forward more than two years after the New Canaan Library hired an architect firm to kick off the project.

Library officials now know how much money they need to raise to replace the existing facility -- $25 million.

The preliminary estimate provided two years ago by Centerbrook Architects and Planners called for about $37 million.

"It was a considerable change between the drawings that were given to us and what we can actually raise," Chris Le Bris, president of the library's board of trustees, told the Town Council several weeks ago.

The next step, he said, is to ask the architects to design "the best building that we can get on our existing footprint for $25 million."

The building will be smaller than library leaders had initially envisioned, but Le Bris said it would have the same quality.

The original design, according to Le Bris, called for a 55,000-square-foot building -- 15,000 square feet more than what the library has today. The design, he said, would be similar to the libraries in Darien and Greenwich.

Problems with the existing building include limited space and 100-year-old infrastructure. The library has seen, for instance, an increasing demand for more meeting rooms beyond the three it now has. The library does have, however, a large area that has to be re-purposed.

"There's a tremendous amount of wasted space, not functional or well-designed space," Le Bris said of the building.

The library has been at 151 Main St. since 1913. It underwent major expansions in 1937, 1952 and 1979, according to the library website.

The building and grounds at the library are owned by an association and not the town of New Canaan. Therefore, the group must raise the majority of funds from private donations for design and construction of the new building.

CCS, a New York-based fundraising consulting firm, interviewed 111 members of the New Canaan community over the spring to determine the library's fundraising capabilities in town.

Last year, the library's revenue, which included a $1.94 million town grant, was $2.6 million. Though it's called a grant, the money given by the town is taken from the general fund every year.

Another large portion of the revenue comes from the library's annual fundraising. During the current fiscal year, library officials are expecting to raise about $415,000.

Executive Director Lisa Oldham said the construction would be staged so that the library won't shut its doors at any point. In terms of parking, she said she's confident the library would be able to maintain the same number of spaces, but she's not sure it would be able to add any.

Le Bris also said that the main building, which faces Main Street, would be saved.

"We want to keep that," he said. "It's a symbol of the town. It's a symbol of the library."

As soon as the new design is complete, the board of trustees will officially launch its capital campaign to raise the $25 million.

"We have to build a building that not only functions today," Le Bris said, "but that gives us functionality 50 years from now."

noliveira@bcnnew.com, 203-330-6582, @olivnelson