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Bracing for the Next One : Southland Homeowners Are Looking at How Homes Can Be Structurally Reinforced to Better Withstand Earthquakes

March 13, 1994|CAROL TICE | SPECIAL TO THE TIMES; Tice is a Los Angeles free-lance writer. and

His name is Billy Martin and he's famous. His Hollywood home is the only one on his block still standing after the Northridge earthquake and even the First Lady has been by to gawk.

Although the retired film production manager says the house was "shaken like a 36-foot boat on the high seas," he survived without a single crack in his 26 stained-glass windows or his living room's mirrored wall.

It wasn't just fate that Martin's 1910 Craftsman bungalow remained intact while his neighbors' homes fell off their foundations. Six months earlier, he had the house structurally reinforced to better withstand earthquakes, a process known as foundation retrofitting.

Martin's home offered such a striking demonstration of the value of retrofitting that Hillary Rodham Clinton has dropped by to check it out, with Federal Emergency Management Agency Director James Lee Witt in tow.

For the Record
Los Angeles Times Sunday March 20, 1994 Home Edition Real Estate Part K Page 7 Column 2 Real Estate Desk 2 inches; 44 words Type of Material: Correction
Retrofitting-- The March 13 article on foundation retrofitting ("Bracing for the Next One") incorrectly reported that Billy Martin's house was the only one left standing on his Hollywood street after the Northridge earthquake. In fact, several other houses on the street survived the quake with only minor damage.

"Everybody wanted to know what I did," Martin said.

Martin is not enjoying his moment as an earthquake celebrity, however. He just wishes he'd been able to persuade his neighbors to retrofit their houses in time. "I feel bad," he said. "My neighbors are living in tents. But you know how people are--they don't think about these things until they get kicked in the head."

Still smarting from their most recent kick, many owners of older homes in Southern California are taking a look under their dwellings, trying to discover whether their foundations are prepared for an even bigger quake.

For homes built after 1973 or on concrete slab foundations, the structure is probably fine.

But hundreds of thousands of older, wood-framed, raised-foundation houses in the Southland lack even the most basic earthquake-safety features.

In addition, older homes built on posts, or with a "tall wall" used to level a hillside lot, are at particular risk of collapse in a quake, experts say. Those with a room over a garage also need special reinforcing.

But strengthening existing foundations is not terribly complicated or expensive, and it greatly increases the house's ability to withstand earthquakes.

Retrofitting secures the house's outer walls to the foundation, so that in an earthquake, the house will move together as a unit and stay intact.

A look under most older houses will reveal a concrete or masonry foundation topped with either the floor's supporting boards or a short supporting wall, called a cripple wall.

There are three basic steps that need to be taken to increase a house's ability to resist ground movement, and all of the work takes place in the usually cramped space beneath the house.

1--Resting on top of the foundation is the house's main support board. Called the "mudsill," this board should be bolted to the foundation. Normally, expansion bolts are used, which have an expanding tip to grip the concrete firmly.

If the crawl space is too small to allow the bolts to be drilled straight into the foundation from above, they are drilled in sideways and L-shaped metal brackets hold the sill to the foundation. If your floor's supporting boards, or joists, are attached directly to the mudsill, this is the only step you need take.

2--If you have a cripple wall between the foundation and the floor, bracing brackets known as hold-downs should be installed to strengthen the right-angle connections between the mudsill and the cripple wall studs.

3--The cripple wall should be further reinforced by creating a shear wall, usually of half-inch plywood, which is nailed onto the wall at close intervals to create more resistance to movement. Fifty percent of the cripple wall's area needs to be covered for one-story buildings, 70% for two-story. To prevent moisture buildup and rot, ventilation holes are drilled in the plywood, and then screened over to keep out rodents.

Although there are more elaborate strengthening measures, they are very expensive. "The most bang for the buck is gotten by bolting to the foundation and shear-paneling the cripple walls," said Shelly Perluss, general manager of Industry-based Cal-Quake Home Improvement. "These are very common failures that are relatively easy to remedy. You can spend a little money--roughly 1%-3% of the value of the house--and get a lot of insurance."

These are the three steps John Given of Ocean Park took last fall to strengthen his 1915 home. "I think it certainly pays," he said recently, having survived the quake in good condition.

Given was inspired to retrofit his house when he inspected its foundation. "If you actually crawl under there and see the entire house is supported by the cripple wall," he said, "just timber sitting on a concrete foundation wall, literally stabilized only by the weight of the load. . . . It makes you understand more clearly what's involved."

Compared with the cost of rebuilding a house that's jumped off its foundation, Given's $2,500 retrofitting job seems quite a bargain. After seeing the devastation of the recent quake, Given said, "The lesson here is that $2,500 is nothing."

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