Yale will begin drafting a more detailed plan for the full renovation of Calhoun, Ezra Stiles and Morse colleges by the end of this month, pending the results of a nearly completed study by an outside architectural firm, University Planner Laura Cruickshank said Wednesday.

The study, which began in December, is based on input from students and administrators in the subject colleges as well as on-site visits, and University officials said they will not develop any details on the renovations until they review the firm’s report.

The administration originally planned only partial renovations to the colleges, but is now committed to a full overhaul, Cruickshank said. The University recruited Philadelphia-based KieranTimberlake Associates, a firm that designed other renovated colleges, to identify exactly how the three remaining colleges should be changed.

“We asked them to go in, look at the existing buildings, and tell us what we have and what we don’t have in Calhoun, Morse and Stiles,” she said. “It’s definite that we’ll do it. It’s the extent of what we need that we’re trying to determine.”

Construction will not begin at least until after work is completed on Jonathan Edwards College, the last building originally slated for a full renovation to be completed in 2008. But planners do not yet know the order of the remaining renovations or whether they will require yearlong closures, Cruickshank said.

The administration will review the study internally before moving to the next step in planning, Yale President Richard Levin said, though it will be three or four years before the details are finalized.

“For the exact details that will be involved, we will await the findings of the study and we will make a decision as to what elements will be included in the renovation plan,” he said.

Students and college administrators said they were pleased that the administration chose to reconsider its plans for the three colleges. But the unique architecture of Morse and Stiles will probably pose a challenge to planners, Stiles Master Stuart Schwartz said.

“These really are architectural monuments,” he said. “Whenever you have a building like that, there’s always a need to balance the comfort of the present inhabitants with the desire to preserve the integrity of the buildings.”

Cruickshank said architects are examining ways to apply improved features in the other colleges to the three in question. But the goal of the study is to tailor the changes to the characteristics of individual buildings, she said.

“The residential parts are very different in Morse and Stiles from what you see in Calhoun and Trumbull,” she said. “No one college looks like another college, and we don’t want them to.”

Rather than focusing on the dormitories, officials said they hope to make major changes to the basement and common spaces of Morse and Stiles. In a presentation to administration officials a few months ago, Schwartz said, he and Ezra Stiles students suggested that their common room, theater area, gymnasium, buttery, and library receive more space and better lighting.

Calhoun students said they are especially interested in improvements to the college’s utilities and infrastructure, which officials have described as adequate but not up to par with its peers. Though the college was the first to be partially renovated several years ago, many rooms lack overhead lighting, and often suffer from flooding or damaged floors and walls, Khang Nguyen ’08 said.

“It’s showing signs of wear,” he said. “I won’t be around to appreciate it, to live in it and enjoy it, but Calhoun is long overdue for a full renovation.”

But Morse Master Frank Keil said those clamoring for specific changes should wait for the results of the architects’ report before jumping to conclusions.

“We’re very grateful that the administration has shown this kind of commitment to a full renovation, but it is premature to be talking about particular changes we’re going to bring about,” he said. “This requires careful study.”

The Yale Corporation, the University’s highest decision-making body, must ultimately approve renovation plans.