QUAKE-PROOFING A HOUSE

By EDWARD W. DESMOND/TOKYO

Most houses and commercial structures that went up after 1980, when Japan's building code had its last major revision, are still standing. But more than 80,000 older buildings suffered serious damage. The government has promised tougher standards for new buildings, but the immediate challenge is how to improve existing structures. Says Charles Scawthorn, vice president of EQE International, a San Francisco firm that specializes in quake-resistant engineering: ``This is the real heart of the seismic-hazard problem.''

Scawthorn happened to be in Osaka when the quake hit and spent the next several days surveying the damage in Kobe. What he saw convinced him that relatively simple precautions could have prevented the most common form of damage: the roofs and upper stories of buildings crashing down onto lower floors. Such ``pancake'' collapses accounted for 90% of the 5,090 deaths in Kobe.

Older Japanese homes are often perched a half-meter or so off the ground on wooden frames. ``It's as if the house is standing on stilts,'' says Scawthorn. ``In a quake it collapses, and the house comes down.'' Well-placed plywood braces, combined with steel-expansion bolts anchoring the house in a cement foundation, would keep the base intact.

In the traditional Japanese house, Scawthorn says, the first floor lacks interior walls that could help support the weight of the second floor, as they would for a Western home; in Japan rooms are frequently separated by flimsy, sliding shoji screens. Scawthorn's recommendation: place a few steel braces along the exterior walls, and reinforce one or two interior walls so they can help carry the weight of the second story. ``Last of all,'' he says, ``I would take those heavy tiles off the roof and replace them with the lighter-weight plastic ones available in Japan now.'' All told, the work and materials needed to reinforce a typical Japanese house might cost $20,000.

Many older commercial buildings in central Kobe, mostly constructed with reinforced concrete, suffered pancake collapses. In such cases the prescription is also to add stronger interior reinforcing, often by replacing a few existing room dividers with permanent, weight-bearing walls. Retrofitting buildings to survive another Big One is still rare in Japan, but in the wake of the Kobe tragedy it may catch on. By Edward W. Desmond/Tokyo