Fairfax Juvenile and Domestic Relations Court judges are pressuring county officials to let them leave their aged quarters and join the other county judges one block away in the new $18.7 million Judicial Center, due to open in April.

A war of memos has been waged between the judges and county officials for the last several months. At present, county officials are holding firm and intend to remodel the 181-year-old courthouse, keeping all five lower court judges there.

Speaking for the five judges, Arnold B. Kassabian, their chief judge, sent a memorandum to county executive J. Hamilton Lambert asking the county government to rethink its plans to keep the judges and their 100-member staff in the old courthouse, which now holds all of the county's judges.

The lower court judges need a facility "comparable to that which is being provided both General and Circuit Courts in the new Judicial Center," Kassabian wrote.

Under the county's plan, only the 11 Circuit Court judges, seven General District Court judges, the county prosecutor, the sheriff and their staffs are scheduled to move into the Judicial Center that, unlike the old courthouse, will have potted plants, 21 spacious courtrooms and secure passageways to transport prisoners.

In his memorandum, Kassabian said that the $4.6 million bond issue approved by county voters last year to renovate the old courthouse is not sufficient to fix up the old courthouse, with its erratic electrical system and various hazards, such as the slab of plaster that fell from one of the ceilings after a recent snow storm. He said the juvenile judges want a building that conforms to all building codes and "contributes to the dignity of the court."

If the Juvenile and Domestic Relations Court judges are allowed to move into some other facility, Kassabian argued, "the present courthouse could be used entirely for general county office use, greatly reducing the amount of rental space needed by the county . . . ."

But Lambert rejected the request.

"As much as I would like to build a new facility to meet your needs," he responded, "the cost of doing so would exceed the budget significantly. In fact, there are considerable legal questions as to whether the bond funds to remodel the courthouse could be used for any other project but that."

Another memorandum was sent to Lambert last week from the juvenile judges, again asking him to reconsider his decision.

When reached last week, however, Lambert said that he has not changed his mind and added that he has instructed architects to proceed with the renovation plans.