The mobile-home industry and builders of conventional on-site houses are traditional rivals, but a housing expert says that together they hold the key to solving the nation's housing shortage.

That is one of the findings of Arthur Bernhardt, a veteran housing-industry consultant who led a team of more than 100 other experts in a seven-year study of factory-built housing. The study was based at the Massachusetts Institute of Technology and supported by the U.S. Department of Housing and Urban Development.

Bernhardt's report, "Building Tomorrow: The Mobile-Manufactured Housing Industry," was recently published by MIT Press. It identifies the manufactured-home industry as "the most efficient building industry in the world" and suggests that firms in other sectors of home building can make a lot of money and provide a lot of affordable housing simply by sharing expertise in a joint effort.

Bernhardt estimates, for example, that wider use of manufacturing techniques in building houses can reduce the price of a single-family home by 2 percent and greatly increase the output of single-family and multifamily housing in this decade.

Bernhardt runs a consulting firm in Cambridge, Mass., that employs some of the engineers, political scientists, lawyers and other professionals who participated in the study.

"We found that the mobile home industry's labor productivity is at least twice that of the on-site industry," Bernhardt said. "The finished mobile home, in place and exclusive of foundation, requires 200 manhours per 1,000 square feet of net floor area, as opposed to 700 to 1,100-plus man hours for the on-site builder.

"You give them (individual companies) the marketing strategy to crack the new markets and if you do that with several companies, you get the ball rolling throughout the entire industry. The bottom line is, you've got to rely on the profit incentive."

Bernhardt stresses that the manufactured homes he envisions bears little if any resemblance to the old "trailer" concept associated with mobile homes. Manufactured homes, he points out, can be built to look like any other type of homes.

It's impossible to say what effect, if any, the MIT report will have on the building industry but the chances seem to be improving that the next home you own could come from a factory.