The breakup of some of Washington's oldest and grandest estates has catapulted Elinor R. Brady and her home on Foxhall Road to the top of one of the city's most exclusive lists: single-family, residential properties valued at over $1 million.

A decade ago, the 16-acre Brady estate was a mere No. 6 on the list of Washington's 10 most valuable family-owned properties, eclipsed by such estates as Hillandale, a 42-acre expanse on Reservoir Road owned by the family of oil magnate John D. Archbold, and by Hillwood, the 25-acre estate of cereal fortune heiress Marjorie Merriweather Post.

The mansion at Hillwood now has been turned into a museum, and the Archbold property and several other estates that used to head the list have been sold to developers who have turned them into exclusive subdivisions.

This makes the Brady family's European-style manor house and grounds the highest assessed this year of all D.C. properties that are still family-owned residences, according to city assessment records. The city's proposed 1984 value of the estate is $5.3 million. Elinor Brady is the widow of Rear Adm. Parke H. Brady, former headmaster of the Sheridan School.

The next-highest assessed private estate is the Foxhall Road home of Gwendolyn D. Cafritz, matriarch of a real estate empire. That property is valued at $3.7 million.

The list continues with the estates, also on Foxhall Road, of the family of the late Duncan Phillips, who founded Washington's Phillips Collection with the help of a fortune made in steel, and of insurance tycoon and art patron David Lloyd Kreeger.

The next two are Georgetown neighbors. Evermay, home of heirs of F. Lammot Belin on 28th Street NW, and the Herman Hollerith residence on 29th Street NW are both valued at more than $1.8 million. The Paul Mellon home on Whitehaven Street NW was assessed at $1.67 million.

The Rocks, home of Mona B. Gaillard in Crestwood, is a newcomer to the top 10 and is the only one east of Rock Creek Park.

Finishing off the top-10 list are Tudor Place in Georgetown, passed down from Martha Washington's family and now owned by Armistead Peter III, and the home built by Wayne and Frances Knight Parrish on 30th Street NW.

In all, the city shows 26 residential properties valued at more than $1 million. Eight of these are owned by corporations or foreign countries. The government of France owns property worth $1.8 million on Reservoir Road, for example, and the Sultanate of Oman owns property valued at $1.26 million on 24th Street NW.

In the category of commercial properties, the city has valued International Square at 18th and K streets NW as the highest assessed property in the city at $111.3 million, an increase of 14 percent from a year ago, according to a listing compiled by Rufus S. Lusk and Son.

The Washington Sheraton Hotel was the next-highest commercial property at $82.6 million, a decrease of 14 percent from an assessment the year before that the hotel appealed.

Government-owned property goes off the charts, with the Mall valued at $2.7 billion. East Potomac Park is valued at $762 million, and the Ellipse at $456 million. The Capitol is valued at $310.2 million, while the White House, at $223.85 million, barely made the top-10 listing of government-owned property. The only D.C.-owned property to make the top 10, according to the Lusk list, was D.C. Village in Southwest, at $258.88 million.

Lusk also listed the top 10 tax-exempt properties in the city, starting with the International Monetary Fund property at 19th and H streets NW, assessed at $126.87 million. The other highest valued properties were those owned by the universities in the city, the World Bank, Washington Cathedral and the National Geographic Society.

Among the other highest assessed commercial properties in the city are National Place at 1331 Pennsylvania Ave., Washington Square at Connecticut Avenue and L Street NW, the Washington Hilton Hotel, L'Enfant Plaza, Metropolitan Square, The Washington Post building, and the Watergate.

Lusk also did its own listing of the top 10 residential properties but only included the home and one lot in computing the properties' assessments. By this ranking, the home of developer Lawrence N. Brandt at 2510 Rock Creek Dr. NW would be No. 10 at a value of $1.2 million, and the Mellon home would not be among the top 10.