The Washington area's home construction industry, which ground to a virtual halt last fall under the impact of soaring interest rates and the recession, is coming back to life, according to building officials.

"People are actually buying," said Robert C. Johnson, vice president of the Northern Virginia Builders Association, the largest trade group in the region.

Although precise figures on the extent of the upsurge weren't available yesterday, builders and government officials in several areas where home building has been a majority industry agree that they have detected signs of a recovery. Figures kept by the National Association of Homebuilders for the Washington area indicate that new housing starts in the area for June were running only 15 percent behind June a year ago. Earlier this year those same figures were down as much as 46 percent from the 1979 levels.

"I think it's significant," said Johnson after polling builders in the Virginia suburbs. "Of course when you're working from zero sales, just about anything would be sufficient."

The housing industry in suburban Maryland has not recovered completely, according to Steven R. Eckert, a spokesman for a home builders group there. "There has been a return to life in Montgomery County, but Prince George's County is still in the doldrums."

Builders in both Maryland and Virginia, however, caution that the industry is far from the strength it exhibited in the late 1970s. "It's no boom yet, but it's the first clear streak of sunshine I've seen," Johnson said.

"We were looking at doomsday three months ago," said Bill Detty, president of Woodside Development, which is in the midst of a 204-home development in the $120,000 to $170,000 price range on Old Keene Mill Road in the Burke area of southern Fairfax County. "Now we're seeing light at the end of the tunnel."

"There's no question," Detty said, "that the recovery has been faster than we had expected. Earlier we saw ourselves looking at the bottom of the trough through the rest of the year."

Executives at C. I. Mitchell and Best, a medium-sized company that is building in Potomac and western Fairfax, agree. "I think we've hit a turning point," said vice president Lou Best. "We sold a half a dozen houses the past weekend, three the previous one and five the weekend before that."

But like other builders, Best remains cautious as to whether the industry can sustain the upswing. "We're ever so cautious," he said. "We've been burned before. We're not building huge numbers of houses."

What makes Best and other people in the home-construction industry cautious is the uncertain path taken by interest rates.

After conventional mortgage rates fell to 12 or 13 percent from a high of nearly 20 percent in the spring, they have started to edge upward.

"If they got up to 13 or 14 percent, they will take quite a few buyers out of the market," said William J. Fauver, senior vice president of First American Bank of Virginia in McLean, which makes many loans to homebuyers. a

At Washington-Lee Savings and Loan, another major lender, chairman and president Richard S. Lawton said the steep fallout in interest rates since last spring has brought many new loan applicants. "We had a good month in July from the standpoint of applications," he said. "It was parallel to the previous July. There were 180 applications totaling $12 million with about 40 percent for new homes."

Lawton said he believed the increase in interest rates would be temporary, but builders say they are worried because a house isn't sold until it goes to settlement, which could be six months after the sales contract is signed.

If interest rates jump, say, 2 or 3 percentage points between signing of the sales contract and settlement, the buyer would have to pay the higher rate -- that is, if he qualifies. If he doesn't qualify -- a "kickout" in industry parlace -- the builder can be stuck with a completed house on which he is paying an expensive short-term construction loan.

In Fairfax and Montgomery, where the median price of housing is close to $100,000, most housing customers are what are called "step-up" buyers, people moving to larger homes. Because they don't have to move, they tend to hold back, waiting for interest rates to go down.

The overall drop in rates apparently has induced many such families to look for new housing.

"People looking at model homes are much more serious buyers," said Kenneth L. Crovo, who is in charge of real estate lending for First and Merchants Bank in Fairfax and Loudoun and Prince William counties. "It used to be you would get people coming to get decorating ideas, but gasoline prices have eliminated that."

Some builders aiming at first-home buyers are selling as if they never heard of a recession. Rippon Landing in Prince William near Neabsco Creek east of Rte. 1 offers townhouses in the $54,000-$59,000 range.

"We're a helluva lot better than last year," said general manager Francis X. McCarthy.