John C. Walker III is a fourth-generation builder and realty professional who now has the fifth-generation members of his old Washington family working for him.

But Walker and his sons John IV and William are building for today's generation in Montgomery County. They are now doing a group of 12 moderately contemporary, fairly large houses on Angus Place off Tuckerman Lane. The houses, priced at about $160,000, have fir siding and cedar shake roofs.

As a builder on his own since 1958, the 52-year-old Walker has known some rough times in the housing business. But he has survived as a small-volume builder -- 25 to 30 new houses in most years but only 8 this year -- by taking a lower profit and cutting back on overhead in lean years.

"That's the advantage of being a small-volume builder," he said recently. "You can quickly cut back production and your overhead, too. That's because you are most of your own overhead."

In a good year, Walker said that a builder like himself will shoot for a 7 percent profit margin above overhead. In a really good year, the margin might be 10 percent. But this year his net profits is likely to be only one-third of what he made last year. Like others, he hopes 1981 will be better.

Walker said that the small-volume builders in Montgomery County have to make some of their money by developing land. "You find a small tract and hold it until the time seems right for it. Usually the land become more valuable if you've chosen well. Then you take it all the way through zoning and permits and build the houses. You hope they will be right for the market," said Walker.

Right now Walker sees as his potential market young couples buying their first single-family house after owning a condo apartment or a town house. "I'm really building at the low end of the single house market in this lower end of Montgomery Country," he added.

"We're seeing smaller households with two persons working. In fact, the incomes of the contrary today. A buyer needs a $35,000 minimum down payment for one of our houses in Birnam Wood and a total of about $75,000 in annual income to handle the monthly payments."

"Now they are lucky if they can get into a condo apartment for their first home and then move up to a town house and then a single house somewhere. Land development and construction costs have risen sharply and continue to do so, even in the face of the housing downturn in the past year," said Walker.

The Walker business, which is based in an office bulding now far from the family house in Chevy Chase, is smaller than it used to be but Walker still has a superintendent, Thomas Matthews, who has been with the firm for 14 years. There are also several trim carpenters and a few laborers on the regular payroll. Most of the work is "subbed out" to contractors.

In the Walker family operation, John IV is "an assistant learning the business" according to the elder Walker. He graduated a year ago from East Carolina University. And son William works off and on as a laborer while going to Montgomery College -- and playing the guitar. Wife Louise, who has worked with decorators on earlier model houses in Walker subdivisions (Falls Orchard, Glen Park and Iverness North) coordinated all of the furnishing and decorating in the one model house at Birnam Wood.

The Walkers also have five daughters. The oldest, Elizabeth, is married to Thomas Lamond and the couple has a realty firm in nearby Maryland. Luisa is married and lives on a farm in Pennsylvania. Margaret lives at home and studies art "and helps her mom in decorating." Jennifer is in New Orleans working in an art gallery. The youngest daughter Susan is now at the University of S. Carolina.

The family's long association with real estate began with John C. Walker I, who also had seven children and was a contractor in the District. John II also did some building and investing in downtown real estate. "My father, Curtis Walker, was also in real estate and I learned appraising from him," John Walker III recalled.

The 6-foot, 220-pound head of the firm and the Walker household started his career after going to Duke University. He taught school one year and was with Waggaman-Brawner before going on his own. He and his older brother Claxton -- now in the home inspection business -- started out building a few houses together some years ago.

Walker is moderately confident about the future, hoping that restrictive impediments to building homes will be lessened so that the dwellings build in the 1980s will be within the reach of young people who want to buy them. "As a father, I know about that problem first hand," he added.

The Walker firm has 178 lots near Gaithersburg and some other land in the Shady Grove Road area. The product is likely to be smaller houses and town houses within the range of more buyers.