The Wolf Trap Foundation has asked the major contractors involved in the rebuilding of the Filene Center for funds to cover the estimated $1 million repair bill stemming from an eight-foot crack found six weeks ago in a huge beam holding up the center's roof.

The crack, discovered Jan. 24, ran along three sides of a 130-foot-long structural girder and caused the roof to sag visibly at the open-air center for the performing arts, which reopened last summer after being rebuilt following a 1982 fire that destroyed it.

It could not be learned yesterday how much money the private foundation, which stages productions at the center, has asked of each of the contractors. Officials of several firms that helped rebuild the Filene Center said they were studying the foundation's request.

Foundation officials say they are determined to repair the center's roof in time for the 1985 season, scheduled to begin June 8.

"The Wolf Trap Foundation does not have the money to make the immediate repairs, so it is turning to the contractors," said Robert T. Skunda, senior associate at Dewberry & Davis, the Northern Virginia firm that designed the Filene Center.

Officials from the foundation and the contracting firms said they had agreed not to talk yet about who is to blame for the broken structural beam.

Several officials said privately they expect lawsuits will be filed and the questions of liability and payment will ultimately be settled in court.

A preliminary report issued this week by the Wolf Trap Foundation said the crack was caused by a tiny welding flaw inside the beam, as well as by the extremely cold weather in late January, when temperatures dipped below zero.

The report, prepared by John W. Fisher, a professor at Lehigh University in Bethlehem, Pa., also concluded that the material used in the beam and welding was not strong enough.

The beam fabricator was Norfolk-based Globe Iron Construction. The material used in the beam and welding was specified by Dewberry & Davis, the design firm. The firm responsible for testing the welds done by Globe Iron was Materials Testing Laboratories, also of Norfolk. Officials from all three firms either could not be reached or would not comment on the extent of their responsibility for the cracked beam.

Engineers hired by the foundation are now planning repair work for the center, whose roof has been buttressed by towers of scaffolding.

Wolf Trap Farm Park, located near Vienna, is the first national park in the country devoted to the performing arts. The Filene Center still belongs to the Wolf Trap Foundation, but the National Park Service will own it once the building's problems are cleared up.