When the General Services Administration, which maintains federal government offices, decided in 1975 to have some painting done in its own headquarters building at 18th and F streets NW, it hired Levcon Construction Co. of Washington to do the job.

It appeared to be a routine job. GSA does most of its building repair and painting work through private companies. Levcon had submitted the lowest bid per square foot of surface to be painted. And a GSA contracting officer certified afterward that the work had been properly done.

But an investigation of Levcon's work by the Washington Post shows:

Levcon' was paid $5,141 for painting 21,400 sq. ft. in two GSA building stairways that contain only 2,896 sq. ft. of surface area.

Levcon was paid $3,134 for painting 197,000 sq. ft. in sixth-floor offices that contain 108,000 sq. ft. of area.

Levcon was paid $24,375 for painting 187,000 sq. ft. in six elevator penthouses that contain 14,316 sq. ft. of area.

Levcon was paid $30,046 for repairing 122,000 sq. ft. of plaster in corridors that contain 79,000 sq. ft. of space.

Asked for comment on Levcon's square-foot figures, Elwood D. Broughton, the Levcon foreman in charge of the project, said, "I guess they're accurate." Michael O'Connor, the principal owner of Levcon, said he would stand by Broughton's comment.

Levcon is one of a number of firms whose work is being reviewed by the FBI and GSA in a broad investigation of allegedly fraudulent repair and alteration work on government buildings here.

Overall, investigators have found more than $2 million in contracts that were awarded for work never completed, jobs smaller than what the government paid for, and even contracts to nonexistent companies. A federal grand jury here has subpoenaed documents in the case, and the FBI has spread its investigation to other cities.

Each year, GSA spends $4.5 billion to provide government workers with office space and supplies. Of this sum, the agency spends nearly $250 million to repair, alter and operate government buildings in the Washington area.

To check on GSA's contracts for the painting of its headquarters building, The Washington Post hired the firm of Robert G. Scharf & Associates - which estimates construction costs for federal agencies, architects, and builders - to determine the wall and ceiling surface areas in the GSA building.

The estimates were made on the assumption all ceilings and wall were painted, even though most of the offices in the building have accoustic tile ceilings that are not painted, as well as windows.

When Levcon did the work in 1975, it painted only about half the GSA buildings's offices. Yet the contracts show that Levcon was paid to paint 2.4 million sq. ft. (excluding the basement level) in a building that has only 1.9 million sq. ft. of surface area.

For its work, which generally entailed repairing plaster and applying two coats of paint, Levcon was paid $781,000, including the basement level.

Levcon's contracts show it was paid $16,454 for painting 62,830 sq. ft. and repairing 5,500 sq. ft. of plaster in stairwells in corridor No. 1. However, the stairwells contain only 18,144 sq. ft. of space, the Scharf firm determined.

Levcon was paid $32,000 for repairing 128,000 sq. ft. of plaster in two basement stairwells in corridor No. 2. These stairwells contain only 2,016 sq. ft. of area.

In addition, Levcon was paid $25,000 for repairing the plaster in all stairwells in the building. Although the stairwells have a surface area of only 63,504 sq. ft., Levcon was paid GSA paid firm for two-coat painting of this windowsill in 1975 contract. for repairing 100,000 sq. ft. of plaster in them.

The contracts listing these areas were signed by Daniel F. J Field, who was then GSA's manager in charge of a number of buildings, including the GSA headquarters building Field, who died last year, lived at 3331 Military Dr., Falls Church.

Field pointed out that no effort had been made to conceal the fact that Field Painting operated out of his father's house. "I wasn't doing anything crooked," he said.

Field said he set up Field Painting because Michael O'Connor, Levcon's principal owner, said he would subcontract work to Field's company. His company "just did work for Levcon," said Field, who added he knew nothing about the square-foot figures in Levcon's contracts.