D.C. Public Library trustees abandoned a plan for the MLK Library that called for a two- or three-story addition, opting instead for a simpler one-floor addition such as the one shown in this architect's rendering. ( The DC Public Library)

A plan three years in the making to pay for a renovation of the District’s central library by adding floors on top and renting them out has unraveled amid concerns about financing, practicality and historic preservation.

Instead, D.C. Public Library trustees voted last week to pursue a more modest, publicly financed renovation that they say could transform the Martin Luther King Jr. Memorial Library into a world-class urban center of learning in as little as four years.

“What the decision allows us to do is to begin generating excitement about the phenomenal destination of learning that we’re going to be building here,” said Richard Reyes-Gavilan, the library system’s executive director. “We have the opportunity now to really build the most spectacular destination for innovation, creativity and culture that this city, perhaps this country, has ever seen. And my fear was that this obsession with the top of the building, this distraction, was keeping us away from important milestones.”

The trustees’ vote abandons a proposal to build a two- or three-story addition atop the library at Ninth and G streets NW. The building was designed by famed modernist architect Ludwig Mies van der Rohe and opened in 1972.

Initial renderings envisioned a barlike addition placed at an angle atop the rectilinear steel-and-glass structure, to be occupied by commercial or residential tenants whose rent payments would in theory subsidize the renovation of the library.

However, an appraisal completed for the library board found that even the most lucrative use for the space — as offices — would generate little revenue and seriously complicate the project.

Meanwhile, library advocates and members of the public questioned why the public-private partnership — which was put forth in 2011 by a panel of architects and real estate experts as a way to refresh the aging library without straining the city budget — was necessary.

The decision to abandon the private addition comes as vindication for activists including Robin Diener, president of the Friends of the MLK Library, who raised early concerns that the plan would leave too little space for the library and represent an unwise privatization of public space.

“This is something that the public just understands instinctively: These public-private partnerships are just fraught with peril,” she said. “That’s what I think they were hearing across the city.”

Reyes-Gavilan — who was recruited last year from the library system in Brooklyn, in part for his experience in renovating its central facility — acknowledged that the financing scheme had created a distraction. “That was an increasingly difficult conversation to have,” he said.

Under the mixed-use plan, the library space would have been reduced from about 400,000 square feet to about 250,000 square feet. The new plan approved by the library trustees Wednesday would add one story to the four-story building, expanding the library’s current space.

“We not only need all the space we have now, but a little more,” said Gregory McCarthy, president of the D.C. Public Library’s board of trustees. A draft proposal for the library’s needs, for instance, contemplates more than tripling the library’s event and meeting space.

A year ago, the trustees selected a team of architects consisting of the Dutch firm Mecanoo and local outfit Martinez & Johnson to hone the renovation. Their initial renderings showed a more open, more vibrant interior in addition to the three-story roof addition.

Those conceptual schemes encountered skepticism among District historic renovation officials, who have significant power to shape the renovation because of the architectural significance of the building.

In December, preservation officials objected outright before the National Capital Planning Commission to the multi-story addition. A more recent review called plans involving the more modest one-story addition “an excellent starting point” but cited “significant rehabilitation questions” and questioned the wisdom of altering the current balance of brick, steel and glass inside and outside the building.

The officials also warned that if the multi-story addition returned, they “would have to evaluate whether such a prominent addition would be appropriate for a memorial building that is the work of an internationally celebrated architect.”

McCarthy said the architectural team will embark on a new set of schematic designs that could be ready for public review by spring.

“This is going to be something that is, if you will, almost like a bookend to the Verizon Center in terms of being an attraction where people from all across the city can go to — whether they want to take their child to a reading or practice for the GED or grab a coffee and go to a lecture,” he said. “This is going to be the hub for it, and right now the building just does not lend itself to that.”

The design phase could be well underway this year, but funding for construction remains a question. Cost estimates won’t be firmed up until design work is further along, both McCarthy and Reyes-Gavilan said, but they said they think the new plan can be completed with $220 million in public funding anticipated in the District’s budget for capital improvements.

Most of the money is not scheduled to start flowing until 2019, meaning the city would have to shift projects around to build the library sooner.

Library officials say construction could start within two years, and they are preparing to proceed on that timeline. In November, for instance, the system awarded a contract to an architectural firm to design a temporary-space library downtown that will be open during the renovations.

But shifting the funds forward for the library will involve asking Mayor Muriel E. Bowser (D) and D.C. Council members to move other projects back — including schools, parks and public safety facilities.

Reyes-Gavilan said he was in “ongoing conversations” with elected officials about the funding. He is confident that library officials can build support for the new plan. “We’re going to start building those elements of excitement — renderings, fly-throughs, partnerships with city agencies and nonprofits,” he said. “Then I hope the fun can start.”

Correction: An earlier version of this story misstated the square footage of the library and how much would have been left if a now-defunct renovation plan had been carried out. This version has been corrected.