It's been almost six weeks since Dan Landry's Falls Church contsruction company has received a call for a job. He's kept his four-man crew busy by lending them to other contractors who have formed a pool to cope with the lean times.

"Everybody's in real bad shape," said Landry. "A lot of contractors have gone out of business completely. Others are just trying to keep their heads above water.

"Next week I might be down to three guys if something doesn't break." Landry said he already has laid off one employe.

Even though business has slowed to a trickle, Landry -- who specialzes in renovation -- said he consides himself better off than his colleagues in the new-home construction business.

"They've all starved," he said.

Northern Virginia home builders have laid off almost 70 percent of their employes in the last 16 months, according to a survey by the Northern Virginia Builders Association.

"Any company that's still in business is laying off all employes except the core of the staff," said Robert Johnson, executive vice president of the Northern Virginia Builders Association.

The layoffs are another sign of a crippled housing industry that has slumped to its lowest levels since World War II, government officials and home builders say.

But now the headaches of the housing industry have spilled over into the two markets that had been booming because of the construction market bust: condominium sales and apartment rentals.

In the last two years, condominium sales in Northern Virginia have gone from their highest mark to their lowest since the conversion rush began a decade ago. Apartments are in an all-time short supply in Fairfax County and vacancies are critically low in neighboring Arlington and Alexandria.

The high interest rates and deepening recession that squeezed many home buyers out of the market and pushed many home builders to the brink of bankruptcy are now pinching the would-be buyers and developers of condominiums.

"Today you have to make at least $60,000 to buy a house and at least $40,000 to be able to afford a condominium," said John T. O'Neill, vice president of the Apartment and Office Building Association of Metropolitan Washington. "Less than 5 percent of the people can afford that."

New housing starts have slowed to a crawl in Alexandria and Arlington as well as Fairfax County, until recently the scene of a flurry of construction activity.

Housing starts in Fairfax County plummeted 44 percent last year, from 6,259 houses in 1980 to 3,486 last year.

Building permits for houses and town houses in Arlington dipped 21 percent, from 355 in 1980 to 280 last year.

House sales in Arlington, Fairfax and Alexandria dropped 22 percent from 1980 to 1981 and have shown little sign of improving this year. In the first three months of 1982, house sales were 39 percent lower than the same time last year, according to the Northern Virginia Board of Realtors.

Despite slow sales and bloated interest rates, the price tag on new houses has continued to rise. Last year the average price of a house in Northern Virginia climbed 8 percent to $104,060--topping $100,000 for the first time.

William L. Berry, whose construction company is involved in four new housing developments in Fairfax County, said, "We've raised prices on every job two or three times in the last six months."

The price increases come at a time when Berry says "profit margins are squeezed."

It was the combination of skyrocketing house prices and escalating interest rates that pushed many first-time owners into the more affordable condominium market. But now, those same conditions are strangling condominium sales and conversions.

Between 1972 and 1980, the condominium market flourished throughout Northern Virginia, especially in apartment-dense Arlington and Alexandria.

In Arlington, apartments were being converted into condominiums at a rate of 607 units a year until 1979, when the market leaped to 1,672 conversions in a single year. In 1980, the number of units converted dropped slightly to 1,300 units. But last year, condominium conversions plunged almost 29 percent to 925 conversions. In the first three months of 1982, 210 units have been converted to condominiums.

The story is much the same in Alexandria. Last year 2,548 units were approved for condominium conversions.

"As of now, 837 have not yet converted due to a decline in sales and the economy," said Mark Looney, landlord-tenant administrator for Alexandria. And in the first three months of 1982, only one apartment complex with 51 units has been approved for conversion.

"The cost of the condominium units has gone up tremendously," said Edward B. Brandt, supervisor of Arlington County's housing services. "Many of the units are twice as high as they were initially."

Developer Allan Hudson received permission last June to convert the 290-unit Whiting Place in Alexandria into condominiums.

"We're up in the air," said Hudson. "We haven't given anybody renters any notice. It all depends on the money market."

But despite all the grim statistics, many county officials and homebuilders remain cautiously optimistic.

"The cataract is healing itself," said Johnson of the builders association, making an analogy to surgery. "It had to get worse before it could get better."

Johnson said he thinks the worst times have passed for the housing market.

Developer John Neill agreed. Bracing for a year of dismal sales, Neill laid off a third of his staff in January. He has since rehired some of them and said he sold 26 houses last month, almost double the 14 he sold last year during the same period.

"But, we're swimming against the tide," he conceded.

Small contractor Dan Landry is skeptical of the predictions of upturns in the market. "Everyone said the market should break this month," he said. "They were saying the same thing last month and the month before that."

But, he added, "I'm staying alive in a very bad time. There's nothing you can do but keep pessimism out of the way and keep on going till you can't hang in there any more."