For 10 years here, the Fox & Jacobs construction firm has been building low-price, one-story tract houses designed to lure first-time buyers out of apartments. Built on slabs - a technique Washington builders have shied away from in recent years - the $33,000-and-under houses have met with some success.

Fox & Jacobs has put up 30,000 houses in the Dallas area since 1947 and has expanded its market to include nearby Fort Worth and Houston, which is more than 200 miles to the south.

F&J, as the firm is known here, built 6,000 houses last year, with an average price of $40,000. This year, with most of the first-half production already committed to buyers, the firm expects to complete about 8,000.

True, the Dallas and Houston housing markets now are among the hottest in the nation. But F&J, an independently operated subsidiary of Centex Corp., a national conglomerate with another home-building division, is generally credited with making nearly 90 percent of the new home sales under $50,000 in the Dallas area.

"I've never seen a builder so dominate a major market," said Alan K. Trellis, director of technical services for the National Association of Home Builders.

Essentially, Fox & Jacobs has evolved into the Levitt & Sons of this major Texas market, buying large tracts of undeveloped land and using mass production methods to produce moderate-priced houses on small lots. No options are available, however, the buyer accepts a choice of models and price ranges.

Unlike the old Levitt approach, F&J has moved much of its basic construction off-site to a component plant, where millwork and panels are manufactured and packaged with other home ingredients to be shipped to the construction site.

If Fox & Jacobs can do it in Dallas and Houston, why can't builders do it in Washington?

For one, land prices are much higher in the D.C. area, and builders tend to agree that the cost of land determines the price of the house.

In both Houston and Dallas, the Columbia-based Ryland Group has been competing against Fox & Jacobs and others in the low-price field and doing well. James P. Ryan, chairman of the Ryland Group, calls F&J "really tough competition. So far, we are able to compete in only one line of houses. . . .

"As we do in our plants in Columbia and Fredericksburg, Va., we preassemble components (in Houston) and build on a slab in Texas, where basements are a construction problem," he said.

Ryland prices average nearly $10,000 more in the Washington area.

D.C. area builder Milton E. Kettler, a friend of Fox & Jacobs President David G. Fox, pointed out in an interview in Washington that it's cheaper to build in volume on flat land with few trees. Then there's the milder weather and longer building season in Texas, where labor costs are also lower. Fuel is cheaper, so houses are not insulated as much.

"It's a multitude of little things, from advertising costs to double glazing, but basically it's still the land and development costs," Kettler said. "By the time you did that kind of F&J house in this area, it would be above $60,000, even with no basement. And most buyers want basements here."

By way of example, Kettler said that he was once part of a small group that decided to build $40,000, houses on $20,000 lots near Annapolis.

"In truth, it was a good house in a good neighborhood. But the house was skimpy," he recalled. "In Texas, they can build on a finished lot that costs $5,000; hereabouts it's more like $20,000. Even if we got the land free, the development costs would be $11,000 a house. We need local governments to take a stand to foster home building.

Fox & Jacob's parent corporation since 1972, Centex, is building at a number of sites in the Washington area and completed more than 650 houses last year. Prices range from the low $50,000s to more than $150,000 for a luxury model in McLean.

Centex's regional marketing manager in the D.C. area, Harry Glickman, maintains that the basic Fox and Jacobs house would not be as acceptable in there.

"The rambler turned out to be the least-wanted model at Langley Oaks," he said. "Two-story houses are 60 percent of our sales, because you get 15 percent more space per dollar than is available in a one-story house."

Buyers in Dallas are probably less demanding than those in this area. The upper range of the market goes into custom houses, from the $60,000s into hundreds of thousands of dollars.

The economies and shortcomings of tract building can be observed in the Fox & Jacobs development here called Colony, a sprawling place that recently became incorporated as a town. Although there are dozens of different "fronts" or elevations, the house tend to be snug on lots about 60-by-110 feet. But only a severe critic would fault the general appearance, even in winter when Texas looks browner than usual.

The houses have foyers, even in the lowest-priced models, and firecplaces as well: Two years ago, F&J went on the "affordable house" kick and found that even the lowest-price buyers wanted the latter. CAPTION: Picture, Dallas firm of Fox & Jocobs prices this one-story house in the mid-$40,000s.; Illustration, Floor plan of Fox & Jacobs' cheapest house, priced in low $30,000s.