American home builders will face problems similar to those of the automobile industry in coping with Japanese imports within the next 10 to 15 years if they don't change their construction methods, according to a building expert.

Daniel Desmond, a special assistant with the Pennsylvania Governor's Energy Council, told members of the National Institute of Building Sciences this week that U.S. home builders must move their operations into factories if they are to compete with Japanese housing firms, which have been studying the American market.

"American consumers won't hesitate to buy Japanese houses any more than they hesitated to buy Toyotas," Desmond said.

He appealed to the group of housing representatives from federal and local government agencies, manufacturing corporations, trade associations and unions to study ways of converting from on-site construction to factories.

He called current manufactured housing in the United States "a glorified staple-gun process" that's "not using any high technology."

By contrast, he said Japan's factory housing industry is highly automated, employing sophisticated robots and advanced computer systems that allow consumers to sit in front of terminals and choose their home's design from more than 2,000 models.

Desmond added that Japanese factories can build 20,000 to 40,000 houses a year compared with about 15,000 from the biggest U.S. home factory. He said the Japanese manufacturing process is producing a surplus of homes, making it "inevitable" that Japanese firms will export houses to the United States.

Harvey Sorum, chairman of the building group that Desmond addressed, said his organization will study whether Japanese-built factory housing could threaten U.S. builders. "It's going to be difficult to convince builders that this will happen to us by the year 2000," Sorum said. "But we have the time now where we can gear up and meet the Japanese challenge."