A group of landscape architects and designers is scheduled to meet with the Greenbelt City Council tonight to talk about plans to rehabilitate parts of the 48-year-old city.

Some old buildings, including the shopping center, need reconstruction. The City Council is scheduled to decide tonight what other projects, including city and commercial buildings, might be needed. If approved, funding for the rehabilitation must come from public and private sources.

The group proposes to stage a "charette," an old French design school technique involving an intensive study of an area under a strict time limit. Designers present their ideas to a jury, which picks a plan.

J.L. Sibley Jennings, head of a District architectural firm involved in the project, said the charette in Greenbelt will probably be completed in one day. The "jury" will be composed of architectural professionals, city officials and community members, he said.

The group will work with existing buildings in the city and devise "sympathetic" design plans that will retain much of the art deco style of the city, Jennings said.

Jennings said the group is donating its services because of the historical interest in Greenbelt, which was completed in 1937 by the Roosevelt administration.

Greenbelt, precursor of today's "new towns," was built from one design plan. That technique has been employed in such local new towns as Columbia, Md., and Reston.

"In terms of urban planning and new-town planning, Greenbelt is world-famous," Jennings said.

"The charette is a chance for design professionals to work with an extraordinary community like Greenbelt and get hands-on experience. And we have fun with it -- it's like a party," Jennings said.

He said that since the charette was announced last week, the number of designers wanting to participate has doubled from about 15 to 30. He said several historical societies have also expressed interest.

Once the charette is complete, the city and building owners will be responsible for financing the development, Jennings said. But he estimated that the volunteer design group will save the city will save about $200,000 "and a lot of time."

". . . It eliminates a lot of hit-and-miss piecemeal development and alteration," he said.

Mayor Gill Weidenfeld said he is "terribly excited" about the project and thinks the city will be able to implement the design plans, "hopefully before 1987, our 50th birthday."