University planners face serious challenges in adding student space to the basements of Ezra Stiles and Morse colleges, according to a preliminary report presented to the administration this week, but officials declined Wednesday night to predict whether the Yale Corporation will approve the 15-month projects that the report suggested would be necessary.

Yale President Richard Levin said last week that the University is now committed to “major renovations” of Morse, Stiles, and Calhoun College, none of which had been scheduled for comprehensive refurbishment on the scale of other dormitories. But architects who produced the new report — a draft of their nearly finished “benchmark study” on the proposed renovations — said it will be difficult to create new space for both student activities and upgraded mechanical equipment, particularly in Morse and Stiles. They also said complete renovations of the three colleges will likely require construction during the academic year and are unlikely to be completed during one or more summers, as some officials had said they hoped.

Deputy Provost Charles Long said that while nothing in the presentation was conclusive, it appears that the existing mechanical rooms in Morse and Stiles are not large enough to accommodate the new heating and air conditioning facilities that officials would like to install. Making room for the equipment while expanding student areas will pose a big challenge, he said.

“Stiles and Morse create significant architectural barriers for the same kind of renovations that went on elsewhere,” Long said. “They are so different that it’s going to take real architectural imagination to make a renovated college fit both better student space and more mechanicals.”

Possible options include finding more efficient uses for existing student space, uncovering space hidden behind walls and excavating to add square footage, Long said. But unlike other renovated colleges that had large unused spaces such as squash courts, Morse in particular has a small basement with less free space.

Still, Long said he has faith in planners’ abilities to improve student facilities.

“Architects have the capacity to take a very small space and make it a very effective and attractive functional space,” he said. “Until you really start digging in with the architectural drawings, you don’t know how much expansion space you have in the current basement.”

The architects are conducting the benchmark study work for KieranTimberlake Associates, an outside firm that has designed other residential college renovations. Administration officials said they expect the study to be finalized by next weekend, when the Yale Corporation will convene to discuss the scope of the project.

Deputy Provost for Graduate and Undergraduate Programs Lloyd Suttle said the architectural firm’s study aims to assess the colleges in question rather than make specific design recommendations. So far, it has provided useful information about how the colleges compare to their renovated peers, he said.

“It will input to a whole series of decisions about how much we do in each college and what we do in each college,” Suttle said. “There’s a lot of work to be done after we get the final version of this report.”

One of the more immediate considerations is the schedule and order of the renovations, Suttle said.

Morse College Council President Larry Wise ’08, who helped organize a presentation to the administration in December suggesting possible improvements, said he expects the renovations to significantly improve the basement facilities despite the architectural challenges.

“When we don’t have common rooms for students, it’s more pressing to have common spaces where people can congregate,” Wise said. “Our expectations are to have as good facilities as there are in other colleges, period.”

Morse College Master Frank Keil said he hopes the administration will commit the time and resources necessary to restore parity among the residential colleges, but he acknowledged that Morse’s unique historical architecture could make it different to conduct a full-scale excavation.

“If they can’t do it within existing space, I very much hope they’ll be able to expand on the space so we can come up to par,” Keil said. “We are an original architectural monument, so we have to be careful of what we do.”

Calhoun was renovated in the summer of 1989, and Morse and Stiles are more modern than the original versions of the other residential colleges. But the report suggested that all three buildings must likely close for a year if optimal renovations are to take place, Long said.

“People had some hope that since two of the colleges were newer and one was renovated 20 years ago, a small-scale renovation would be adequate,” Long said. “But they made it pretty clear that would make the goals much harder to accomplish.”