Sales of new homes in the Washington area in 1981 were down 5 percent from 1980, and condominiums accounted for a greater share of the market, Housing Data Reports says in its latest publication on local sales.

The local new-home marketing specialists called the 5 percent drop "a surprisingly strong effort, given the state of the housing market." Sales held up well in the first half but declined sharply in the second half, HDR reported. The drop appears to have bottomed out after October, with December's figures higher than for the past two years, the group said.

In other hopeful signs for the housing industry, there were fewer cancellations in December than in the previous three months, and traffic picked up a bit at area subdivisions in the first two weeks in January.

Condominium sales in the Washington area represented 45 percent of the market in 1981, up from 39 percent in 1980.

While the number of new single-family homes and town houses sold in 1981 declined to 13,137 from 15,371 in 1980, condominium sales rose to 10,658 from 9,632 the year before.

The Metropolitan Council of Governments reports that the number of condominium units in the area increased by nearly 14 percent from July 1980 to July 1981, with 11,549 new units added. Of those, 64 percent were converted from rental status.

The previous year, a record number of apartments -- 11,837 -- had been converted, COG said.

Recent residential condominium or cooperative residential sales in Montgomery County include the following, selected at random from information furnished by Rufus S. Lusk & Son Inc.:

Silver Spring

J. F. Parsons and others sold a condo at 14401 Astrodome for $63,000 to Rosemary A. Cardwell. Colonial Mortgage Service Co. placed an FHA mortgage of $62,700 at 15 1/2 percent for 30 years.

Georgian Colonies Development Co. sold a condo at 3505 Banquo Dr. for $111,150 to Mr. and Mrs. Fred A. Natkin. Yorkridge Calvert Savings & Loan Association placed an $88,900 mortgage for 30 years.

Bethesda

H. F. Kimel sold a condo at 7501 Democracy Blvd. for $45,000 to Robin M. Norman. The seller took back a note for $2,000 at 12 1/2 percent for two years.

Investment Group Developers sold a condo at 5101 River Rd. for $106,200 to Mr. and Mrs. Assadollah Fouladi. Home Federal Savings & Loan Association placed a mortgage of $71,500 for 30 years.

Parkside Association sold a condo at 10500 Weymouth St. for $80,600 to Harvey Coustan. Dominion Financial & Investment Corp. placed a mortgage of $72,500 for six years.Germantown

Bresler & Reiner, Inc., sold a condo at 18318 Tinko Ln. for $65,000 to Steven G. Garnand. Citizens Savings & Loan Association placed a mortgage of $54,750 for 30 years.

Recent residential condominium and cooperative residential sales in Northern Virginia included the following, selected at random from information furnished by Rufus S. Lusk & Son Inc.:

Alexandria

Belle View Associates sold a condominium at 6506 Boulevard View for $60,000 to Andre A. L'Heureux. Dominion Bankshares Mortgage Co. placed a $57,000 mortgage for 30 years.

Belle View Associates sold a condo dwelling at 6512 Boulevard View for $62,600 to Rose E. Adami. Washington & Lee Savings and Loan Association placed a $42,600 mortgage for 30 years.

Burke

Burke Cove associates sold a condominium dwelling at 5810 Cover Landing Rd. for $69,850 to Jeffery Nolton. Washington and Lee Savings & Loan Association provided a $66,300 mortgage for 30 years.

Mr. and Mrs C. M. Kohlmeier sold a condo unit at Fesnestra Ct. for $80,000 to Gloria Bakalis. the buyer assumed a trust for $46,896, and the seller took back a note for $13,100 at 12 percent for five years.

Fairfax

S. L. Jess sold a condo at 9487 Arlington Blvd. for $45,000 to David Rowe. The buyer assumed a trust for $20,486, and the seller took back a note for $4,000 at 13 percent for three years.

S. C. Day sold a condo at 9718 Kingsbridge Dr. for $48,250 to Mr. and Mrs. Herbert G. Risse. The buyer assumed a trust for $29,715.

Reston

D. K. Jones sold a condo dwelling at 2315 Freetown Ct. for $40,000 to Virginia J. Yee. The buyer assumed a trust for $26,608.

Lorton

D. L. Coppage sold a unit at 9640 Hagel Cir. Lorton, for $54,500 to Mr. and Mrs. W. L. Kvasnicka. The buyer assumed a trust for $32,192, and the seller took back a note for $10,000 at 12 percent for six years.

Oakton

T. A. West sold a condo unit at 10214 Bushman Dr. for $59,500 to Lee Lilly, trustee. The buyer assumed a trust for $44,748. H. F. Garrett Jr. provided a mortgage of $7,350 at 14 percent for four years.

Recent condominium and cooperative unit sales in the District included the following, selected at random from information furnished by Rufus S. Lusk & Son Inc.:

Northwest

Valley Vista Tenants Association sold a condo dwelling at 2032 Belmont Rd. for $73,616 to Mary A. Kolesar and Charles W. Tuck. American Home Funding provided a $66,250 mortgage for 30 years.

Mr. and Mrs. W. E. Fore and others sold a dwelling at 1604 Belmont Rd. for $90,000 in cash to Lawrence N. Brandt.

Mr. and Mrs. C. C. Lander sold a dwelling at 535 Brummel Ct. for $118,000 to Mr. and Mrs. Eugene A. Harrington. The seller provided an $18,000 mortgage for three years.

C. D. Feske sold a unit at 2123 California St. for $129,500 to Jack Gould. The seller provided a mortgage for $32,500 for seven years.

Mr. and Mrs. C. E. Madavo sold a condo at 2123 California St. for $158,000 to Virginia K. Washburne. The seller provided a $55,500 mortgage for five years.

Mr. and Mrs. D. M. Ifshin sold a condo at 1880 Columbia Rd. for $92,500 to Max M. and Jeffrey Kampelman. The buyer assumed a trust of $67,450.

Carlton Towers Association sold a unit at 2829 Connecticut Ave. for $42,000 to Agnes Palmer and Engin M. and Janice G. Artemel. Perpetual American Federal Savings & Loan Association provided a $31,500 mortgage.

The 4707 Connecticut Avenue NW Tenants Association sold a unit at 4707 Connecticut Ave. for $77,280 to Bernard Choseed. The B. F. Saul Co. placed a $55,000 mortgage for 15 years.