If the Kennedy Center has added a touch of casual elegance to your theater or concert-going, remember it fondly over the next months.

Early this morning workmen began a rush construction job on the first link in a network of covered plywood walkways to protect patrons from the danger of plaster fallout from the water-weakened 60-foot-high ceiling of the Grand Foyer. The plywood walkways - much like those on a construction site - will be there from six months to a year.

Actually, there have been no plaster falls since two square-foot sections of thin decorative plaster broke loose Wednesday afternoon in the Grand Foyer. But inspectors yesterday found to their dismay, severed ceiling damage from water seepage after a rain-pelting electrical storm early this week.

Center officials yesterday assured theater-goers that they don't have to worry about any personal danger or interrupted performance schedules. The Concert Hall, Opera House, and Eisenhower Theater are not underneath the leaking roof terrace and are sheltered under several floor levels below the main roof.

Roger L. Stevens, the Center's chairman, settled on the plywood construction walkways as the easiest, cheapest, and quickest way to protect the public until permanent repairs are made. It won't be until September that construction drawings will be finished and bids let.

Until the network of plywood "canopies" is completed, patrons will be rerouted to side entrances off the Hall of Nations and Hall of States to get to their seats in the theater and opera house.

By Monday night, the wood-covered walks down the two halls and the Grand Foyer should be finished, allowing a return to the regular foyer entrances to the theaters. By tonight's curtain time, workmen should have completed walkways from the three auditoriums for intermission and exit purposes and access to the river terrace overlook.

Until Monday, the Grand Foyer will remain roped off. By Tuesday, Center officials hope to be ready to re-admit tourists, who will be threading labyrinth of wood-covered pathways at their national cultural center.

Center officials did talk about a netting device to hold up the Grand Foyer ceiling, but decided the covered walkways would offer the fastest protection.

As for the bars, which are near where the ceiling fell, they have been moved temporarily to both ends of the two halls.