It was not a pretty picture that International Trade Commission Chairman Alfred E. Eckes Jr. painted for the senators: falling plaster, leaking roofs, inadequate plumbing and even "exploding rats" as big as cats in the graceful, mid-19th century ITC building.

Even worse, Eckes told the Senate Finance Committee, the government's General Services Administration doesn't seem to care about restoring the building, situated on the site where Congress met after the British burned the Capitol during the War of 1812--but instead would rather turn it over to the Smithsonian Institution.

Eckes' description of the "deplorable condition" of the ITC's building, on E Street NW between 7th and 8th streets, drew the response he wanted from the committee.

"I think it's outrageous," said Sen. Lloyd Bentsen (D-Tex.).

"It occurs to me," added Sen. Russell Long (D-La.), that since Congress once met on that spot . . . that maybe we could just put that back under the Architect of the Capitol and let Congress assume the responsibility for keeping the building up."

Sen. John Danforth (R-Mo.), who had toured the building the day before the committee hearing, said, "It truly is ridiculous. I mean, the windows are falling out and stuffing is put between the window panes, and the plaster is falling out. It is just obviously a ridiculous situation. And it's demeaning."

The ITC building was designed in the 1830s by Robert Mills and Thomas Ustick Walter, the architects for the Treasury and the Washington Monument. Built in the Roman Corinthian style with two U-shaped sections enclosing an open court, it cost just $2 million and is made entirely of marble. When Charles Dickens visited Washington in the 1840s, he described the building as "very compact and very beautiful."

Eckes, an economic historian who said, "I love the old building," asked the Senate to appropriate the $10 million to $20 million that he estimates full renovation would cost. The GSA, however, opposes any basic renovation for five to six years, which the chairman found unacceptable. Critical defects, such as roof leaks, will be repaired by August, however.

Eckes told the committee GSA spent only $1.2 million of the $5.8 million Congress appropriated in 1974 for the building.

Now the building is in such had shape that plaster walls painted last week already are peeling. Librarian Janet R. Damon said there haven't been any leaks "for a while" in the library, though plaster was peeling near the windows and exposed brickwork marred the beauty of the skylight dome. David Spencer, who calls himself "the man who gets the baling wire and chewing gum to hold the building together," said during winter storms, wind whips snow in through the skylight.

Maintenance people found three dead rats in the building yesterday morning, and Commissioner Veronica Haggart found a dead mouse in her office earlier this month.

Eckes said GSA is using a poison that is supposed to drive the rats out of the building because it gives them an unquenchable thirst that makes them drink so much water that their insides burst. The problem, though, is the ITC building leaks so much that rats can drink from standing water without leaving the premises.