While home sales wane in the Washington area, tje developers of Reston are counting on commercial and industrial growth that may mean more jobs and more residents for the Fairfax County planned community.

In it's first 17 years of life, Reston's outlying residential areas were developed, noted Michael Was, vice president of the Reston Land Corp. Now much of the development emphasis has switched to the business center near the Dulles Airport Access Highway, he said. While current marketing plans center on attracting commercial/industrial buyers, he added, "we haven't turned our back on the residential side."

Despite soaring interest rates, projects representing more than 25 percent of the new town's entire commercial and industrial growth were under construction in 1981, Reston Land reported. More than 900,000 square feet of space was built up in 1981, compared with 3 million square feet in previous years, officials said.

Although the sale of new houses and condominiums in Reston fell nearly 12 percent--to 381 units in 1981 compared with 431 in 1980--six new projects are under construction. Development of North Point Village, Reston's fifth and final residential area, began last month.

Reston Land is a division of Mobil Land Development Corp., the Mobil Corp. subsidiary that bought more than 3,000 acres in Reston when Gulf Oil bailed out of the 7,400-acre new town in 1978. Gulf had purchased the land in 1967 after developer Robert E. Simon ran out of cash when sales failed to meet his projections. When he created Reston in the early 1960s, Simons envisioned a well-built, carefully designed urban complex where residents could work as well as live. It currently has a population of about 35,000; about 5,500 residents work there.

"Probably the key contribution of Mobil has been its decision to continue to develop the master plan" that Simon conceived, said Thomas Burgess, executive director of the Reston Home Owners Association.

Unlike Gulf, which built houses and industrial plants and managed large portions of the commercial property, Mobil has confined its role to land sales and development, Burgess said. While Gulf's view of Reston as "a company town" resulted in some strained relationships between the developers and residents, Burgess said, Mobil's approach has meant fewer problems for everyone in the community.

Mobil has become adept at real estate development since its land subsidiary was established in 1970, said an official of the Community Associations Institute, a nonprofit association of developers, homeowners and property managers. "They're trying, apparently, to do a decent job" in Reston, said Joe West, the organization's membership director. Mobil now holds 14 commercial and residential projects in the United States.

Aside from the decline in residential sales, West said, Reston is considered a success by many industry observers who consider it a "role model" for other planned communities.

Nevertheless, some city planners cite the failure of the town's Lake Anne Plaza as one sign of Reston's weakness. An award-winning commercial and residential complex that for years was the symbol of Reston's early strength, the plaza faltered as the community grew.

Some blame the plaza's decline on Robert Simon for building it too small; others say that Gulf ignored the plaza and allowed it to decay; many residents blame themselves for getting in their cars and taking their dollars to bigger, more conventional shopping malls along the Beltway. The question remains unresolved.

Five companies--Piedmont Airlines, ConTel, NUSAC, ComSearch and Advanced Technology, Inc.--moved into new facilities during the past five weeks, Was said, bringing 750 jobs to the planned community. While unemployment is rising around the country, he added, "we are expanding our job base."

Many new jobs were created by 54 national associations that moved to Reston during the last 10 years, Was noted. Ten years ago there were none.

More than 13,000 people work in Reston now. That figure represents one job for each Reston household, although 58 percent of the work force is currently comprised of commuters. Since approximately 80 percent of the new commercial/industrial space is pre-leased or owner-occupied, Was said, employment figures are expected to rise significantly. Reston officials estimate that 3,500 new jobs will be created over the next three years.

"Our business growth has just taken hold," Was said. "In a time period when the downturn of the economy is hitting many other places, it just keeps popping in this area," he said.

"Certainly we have seen a substantial increase in new industry and new jobs" during the past three years, said the homeowner association's Burgess. "It would be easy to say, 'That's because of Mobil,' " he said, but other factors, like the proposed upgrading of Dulles Airport and the relatively low population density, have attracted many firms. Nevertheless, he added, "Mobil may be the catalyst that made it happen."

Reston is now second to the Tysons Corner area for industrial/commercial square footage under construction in Fairfax County. Two firms--Tandem Computers, Inc., and Sperry Systems Management--account for more than 30 percent of the new growth: Tandem is moving its eastern regional headquarters to a 235,000 square foot low-rise building; Sperry is adding 150,000 square feet to its existing 110,000-square-foot facility.

Tandem's decision to move to Reston was a major victory for the community, said Reston Land general manager James G. Cleveland. He said the California-based computer company will be a "drawing card," attracting other advanced-technology industries to the area.

And James O'Brien, Coldwell Banker vice president, sees Tandem's move to Reston as a sign that planned communities work and that other high-technology companies are likely to move to the area. Businesses could locate down the road for half the cost, but choose Reston despite its higher price, O'Brien said.

Despite the fall in Reston's residential sales last year, Was said, the housing market is holding its own. "As compared to 1980, it's down, but the bottom hasn't fallen out," he said. Because the job market is increasing, "there's still a strong demand for housing," he added.

The development of North Point Village marks the last major phase of Reston's residential expansion. North Point will occupy 1,500 acres--20 percent of Reston's total area--between Rte. 7 and Baron Cameron Avenue. Reston's new visitors center is scheduled to open there this fall. Plans call for 4,500 homes when the village is completed in the late-1990s.

Residential sales in Reston were in line with the rest of Northern Virginia, where the average sales price for homes rose 10 percent, to $100,050, in 1981. Reston posted a 9 percent rise on resales of houses and condominiums, to $85,100, during the same period. Home prices in Reston range from $42,250 for condominiums to more than $200,000 for custom-built houses.

When home sales fell dramatically to approximately three a week last summer, Reston Land spent $200,000 on a "Grand Tour" promotion designed to attract buyers and bolster sales. The six-week scheme featured a $50,000 prize to be used toward the purchase of a Reston home.

The promotion drew 15,000 visitors to 17 model-home sites throughout Reston, Was said, and about 5,000 of them said they had never seen Reston. "That was what we were trying to accomplish," he said. While only 38 houses and condomiums were sold, he said, "we expect excellent, long-term effects."