Harvard expects to break ground on its new Allston campus within the calendar year, University officials said today as they released the most detailed plan yet for the next half-century of development on the far side of the Charles River.

The expansion will increase the capacity of Harvard’s buildings—already 24 million square feet—by about 20 percent over the next two decades. And the plan includes possible locations for four undergraduate Houses along the south bank of the Charles. But Provost Steven Hyman, speaking by phone from Geneva, Switzerland, said that “the number of undergraduate students will stay the same.” The College’s student body now numbers slightly over 6700.

The three Quad Houses would be converted into graduate-student residences as well as homes for faculty members, the provost said. Four new Houses would be built over the next 20 years on top of what is now the Blodgett Pool, the Briggs Cage basketball arena, the Dillon Field House, and the Palmer Dixon Courts, according to a map released by the University. The Athletics Area would be extended to the south to accommodate the displaced facilities.

Today's announcement marks the most specific explanation to date of the University's plans for future undergraduate dorms.

Harvard also said that its real-estate buying spree in Allston has come to a halt for the time being. After Harvard takes control of the Charlesview apartment complex, the University has “no immediate plans” to add more property to its existing 350 acres in Allston, according to the chief of the Allston Development Group, Christopher M. Gordon.

The full plan, submitted today to the Boston Redevelopment Authority, is available online at a University Web site. Check www.thecrimson.com for updates.

[Click here to view the executive summary published by the University today.]