Rex Holland sliced the San Francisco sourdough bread and made hoagies. Neighbors milled about and offered advice. The police even came to keep order and direct traffic on narrow streets for the unusual home delivery.

But rather than being taken to a home, this delivery was a home, a whole house -- all 13,000 pounds of it -- arriving on flatbed trucks, one floor at a time.

"This is more fun than a wedding," said Ellen Moore, 36, as she watched a massive crane swing about, pick up one-fourth of her soon-to-be upstairs and drop it smartly next to the bathroom. The vanity mirror broke, but she didn't worry.

Nor did the builder, Thomas Horne, president of Alexandria Builder, Inc., who decided that building a house in six hours is better than six months. For Horne, who watched Moore's prefabricated duplex rise in the middle of the 300 block of La Verne Avenue, in the low- to moderate-income Del Ray neighborhood west of Jefferson Davis Highway, this was his third venture in his new line of work. "This is it," he said. "This is the new way to go."

Factory-built housing is not in itself new. Prefabricated homes have been on the market for more than 40 years. But Horne said that high-quality housing straight off the assembly line is an innovation. "The [prefabricated] industry started off pretty shabby," he observed. "There was a lot of crap around. We're trying to rebuild the image. . . . This house was built to my specifications, and it's better than a stick-built home."

John Kupferer, executive vice president of the National Association of Home Manufacturers, agrees. He contends that top-quality modular homes are sturdier than the typical house built on site by a construction crew.

"You don't have the quality control with stick-built houses that you have with modular," he said, adding that assembly-line houses are subjected to tougher inspections than on-site construction.

Mat Page, on the other hand, an appraisor for the Alexandria Redevelopment and Housing Authority, still questions the quality of the prefabricated houses. "I don't really think they [prefabricated units] are quite as sound. But it is something that you can put up quick. It's a new concept. But you never know the life span of the structure."

But customer Moore is delighted. "We had a lot of misconceptions" when she and her husband first considered the idea, she said. "But there are no creaks, moans and groans in the floors. I couldn't be happier."

About 41,000 modular homes were built in the United States last year, Kupferer estimated. He said they sell from $35,000 to $100,000 and that most are one-story structures that are usually built in rural areas.

In general, Kupferer said buyers erroneously lump mobile and modular homes into one category.

Modular homes, he said, are errected in accordance with strict local building codes. Mobile homes, on the other hand, are built to the specifications of the more general National Manufactured Housing Construction and Safety Standards Act of 1974.

Home contends that the main advantages of factory-built housing are speed of construction and lower cost. The La Verne Avenue home, for instance, was designed, cut and assembled at a Delaware plant, shipped to Alexandria and put together for $30,000. And in Horne's profit and the cost of a lot, and the price of the La Verne house climbs to more than $90,000. With 2,000 square feet of space, the cost of the La Verne Avenue house is $45 a square foot, Horne said.

Since this home is located in Alexandria, where land prices are substantially higher than in other parts of the country, its per-square-foot cost is higher than the typical modular unit, however.

On a national scale, Kupferer said a typical, conventional 1979 home contains 1,700 square feet and cost $42.11 a square foot, or $72,000. By comparison, a typical modular home put up in 1979 has 1,300 square feet at $34.56 a square foot, making the average price tag $47,000.

Moore, who plans to rent the house, was happy that workers who cleared the land for the house-raising were able to spare several trees within five feet of the structure. "Conventional builders chop every tree in sight," said Horne.

Moore said she and her husband Christopher, a 38-year-old patent researcher, were skeptical when Horne first approached them, but they quickly became believers.

"Now we think this can help a depressed area that's starting to turn around," she said.

If Moore does rent the house, her renters will find a home with wall-to-wall carpeting, vinyl siding and windows that is insulated and has a fenced-in front porch.

And according to Tim White, the owner of White Construction, a Northern Virginia firm that builds new homes and assembles factory-built models, the tenant also will have a sound home.

"These jobs are more stable than stick-built houses," he said. "Manufactured housing is drawing-board perfect. They are all glued and nailed at every point. Some people are afraid of getting things out of the factory. But this is more of what you'll see with interest rates going up for low- and moderate-income owners. This is the wave of the future."