One out of four residences sold in the District during the first half of this year was a condominium, a new survey shows. The average price of homes sold in the city during that period -- $70,000 -- was up sharply from prior years.

Data compiled this week by George B. Altoft, senior property assessor for the District, documents the rapid escalation of condos out of the moderate-price market and into the luxury class.

At a fourth of all active condominium projects in the city -- including conversions, new buildings and resales -- units sold for an average of more than $100,000 during the first six months. Roughly 40 percent of all condominum projects had average sales prices in excess of $80,000.

In Kalorama Square, a town house condominium complex near Northwest's embassy area, the average price among the six units sold in 1979 was $360,000. In a Foggy Bottom mid-rise building, the Plaza, the average was $217,000 for five sales.

Six resales at Foxhall East, south of American University, averaged $194,000. At Beekman Place at Florida Avenue and 16th Street NW, the average for 35 new and resale units sold from January through June was $94,780.

Altoft's data comes from the city's property recordation tax filings, and represents the only authoritative statistical summjry of the District's burgeoning condominium market. Sales are strong in the condo sector, the assessor said, and should continue at a brisk pace for the rest of the year, despite the City Council's two successive 90-day moratoriums on conversions.

Hundreds of units approved for conversion before the City Council acted are due to hit the market in the next four months, Altoft estimates, and hundreds of existing units are likely to go up for resale.

Although the number of high-cost condos is eye-opening -- especially for resales -- the mid-year condo statistics also confirm the presence of a large number of moderately priced units on the market. Many of these are in newly converted apartment buildings where tenants and others have bought units at discount prices set by the developer to hasten sales.

Of the 20 condominium projects that went on the market since January, for example, only four posted prices in the luxury class. More typical were prices in the $50,000s or below, such as the 70 units sold at Fairfax Village in Southeast for an average of $37,560, or the 59 units at Webster House, 1718 P St. NW, that went for an averge of $39,985.

If the pattern of the past three years holds true for these converted units, however, their resale prices may reflect larger annual percentage increases than other condos, in part because of their below-market starting prices. As conversions slow down here, the market values of existing units could rise even faster than the 15 to 20 percent annual gains reported for many condos between 1977 and 1979.

Here are some representative statistics for condominium sales around the city, taken from the mid-year assessment study:

Woodley Park Towers, 2737 Devonshire Pl. Nw, nine sales; average price: $117,555.

Altamount Manor, 2400 Good Hope Rd. Se, three sales at an average of $20,965.

Palladium, 1325 18th St. NW, 11 sales; average, $79,545.

Ft. Dupont Park Condominium, Massachusetts Avenue and 42nd Street SE, nine sales; average, $53,420.

4710 Connecticut Ave. NW, eight sales; average, $109,560.

Sutton Place, 3200 block Sutton Pl. NW, 27 sales; average, $114,000.

The Papermill, Grace, Potomac and K streets NW, 20 sales; average, $104,000.

The Davmar, 18 9th St. NE, 37 sales; average, $52380.

2029 Connecticut Ave. NW, two sales; average, $170,000.

The Worland, 2828 Wisconsin Ave. N.W, five sales; average, $148,600.

Town Square Towers, 700 7th St. SW, eight units sold; average, $60,000.

The Colonnade, 2801 New Mexico Ave. NW, nine units; average, $141,000. CAPTION: Picture 1, Average 1979 sales price at the Worland on Wisconsin Avenue was $148,6000. By Larry Morris -- The Washington Post; Picture 2, Average price at the Davmar in Northeast: $52,380. By Jack Hayes for The Washington Post