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Retrofit Your Home with a Firm Foundation
by George Hower, Staff Writer
Published on April 29, 1995
People who live on the East Coast probably would no more want to experience California's earthquakes as Californians would want to experience their hurricanes.
General contractor Howard Cook has
seen what hurricanes can do (``It looks like a World War I battlefield -- everything is leveled''), has experienced earthquakes, and says flatly, ``I would much rather go through an earthquake.''
Cook owns QuakeProof, a Santa Rosa company that reinforces structures to help make them earthquake resistant. Before coming to Santa Rosa, he was hired by the Federal Emergency Management Agency (FEMA)
to inspect earthquake-damaged dwellings in Santa Cruz after the 1989 Loma Prieta earthquake, and again in 1992 when a large quake rocked Ferndale. With that experience behind him, he says ``When I drive around Sonoma County,
especially in the older neighborhoods, I can look at a house and from the outside tell if it is going to fall.'' While he can't tell from lookingwhether a home has, or hasn't, been reinforced, he's making an educated
assumption, based on his belief that less than 1 percent of older homes have been reinforced.
Cook's secret: He looks for older homes with cripple walls.
``The way you can tell if your house has a cripple wall is
if you have to walk up a number of steps to get into your door,'' Cook says. ``Unreinforced cripple walls collapse and the house falls down. Houses without foundation bolts simply slide off their foundation. Rectifying these
weaknesses is cheap and a little protection goes a long way.''
Cook says if you do the work yourself you can usually do it for under $500 in materials. Even $75 in plywood nailed to the corners of the cripple wall makes a tremendous difference, and securing your
house to the foundation is the best insurance you can buy, he says.
That's what Santa Rosa residents Chet and Jo Ihinger, who live on a tree-lined section of Slater Street, did. The 2-1/2-story house they bought in 1974
had slid off its foundation on Oct. 1, 1969 when Santa Rosa experienced three earthquakes. (The first, at 9:56 p.m. measured 5.6 on the Richter Scale. It was followed by a 3.5 at 10:14 p.m. and a 5.7 at 11:19 p.m.) So they had
the 1905 Victorian bolted to its foundation to help prevent history from repeating itself when the next big one strikes. And it will, Cook believes.
``People have to realize how dangerous the (earthquake likelihood) is
here in Sonoma County,'' Cook says. ``The Rodgers Creek fault runs through Sonoma County and right through the city of Santa Rosa.''
Some people, including Cook, feel the Rodgers Creek fault is one of California's most
dangerous. United States Geologic Service seismologist Bill Ellsworth says it's dangerous because it runs through an urban area -- Santa Rosa. ``The worst place to be is right on top, like Kobe, Japan, or Northridge.''
``We are actually having earthquakes all the time in Sonoma County,'' Cook says, ``but they are usually 3-pointers on the Richter Scale.'' Some people feel a 3-pointer, some don't.
The Richter Scale measures the total energy generated by an earthquake, Ellsworth says. If you go from 6 to 8 on the scale, the energy released is 1,000 times stronger, Ellsworth says.
The trouble in Santa
Rosa, Cook says, is the geology. Many neighborhoods are on unconsolidated soil, soil that is loose and not compact. Ellsworth says this softer, unconsolidated soil tends to magnify power unharnessed by an earthquake. Another
problem in Sonoma County: liquefaction. This occurs when you have what Ellsworth calls a waterfilled layer of sand. When an earthquake hits, this kind of terrain really jiggles. You're better off if your house is on bed rock,
Cook says.
Cook says a tremendous amount of energy is building up in the Rodgers Creek Fault. ``Fortunately, the fault is not long enough to produce an earthquake bigger than a 7.5,'' he says. ``Unfortunately, an
earthquake that size can cause general devastation.''
The Ihingers had the cripple walls reinforced with plywood bracing, which should prevent it from collapsing on its own foundation. Shear walls, also made from
plywood, were added to the pier and post foundations. (Pier and post foundations are no longer a legal foundation in California, Cook says.)
They also had cabinets, bookcases, a grandfather clock made 105 years ago and
other Victorianera furnishings securely fastened to 2-by-4 framing behind the lathe and plaster walls to reduce the chance they could fall on anyone in the house and to reduce damage.
``I feel a lot more secure than I did before,'' says Chet Ihinger, a retired teacher and retired courier for Sonoma Title. ``I think this house will stand up pretty well.''
The Ihingers also stocked up on
food, water and other emergency items they would need if their home is damaged and they have to move out. They keep these emergency items in a camper shell stored in an unattached garage.
The Ihingers reinforced their
house last year pretty much along the standard lines that California's Office of Emergency Services recommend.
The work also follows what Cook says is now the conventional wisdom in earthquake reinforcement for homes.
While Cook did not do the original reinforcing on the Ihinger home, at their request he recently did a few things to finish the job.
``A lot of older houses were built without foundation bolts or were built using
unreinforced cripple walls,'' Cook says. ``Cripple walls are short walls built below and supporting the floor of a house. (Foundations and cripple walls) are the two most common and most serious structural weaknesses you will
find in older homes.''
``Earthquakes subject these walls to severe lateral movement pressure, and they often collapse if not properly reinforced. Reinforcing them is a simple procedure consisting of nailing plywood all
around the inside of the wall under the house.''
Plywood is very rigid, Cook says, and when you put plywood on cripple walls or post and pier foundations you are basically creating a brace between corners diagonally opposite each other, helping reduce the
lateral movement.
When Cook is called to inspect a house, he first looks for safety hazards. Next he instructs people in proper safety procedures to be followed when the shaking starts and after it stops. Next, he
identifies structural weaknesses and shows how to correct them. And then he tells them what to do to protect personal property.
If people do not want to do the work themselves, he will give a written estimate of what it
would cost for him to do it.
There is no charge for any of this, he says.
If you invest a couple thousand dollars in reinforcements, Cook says, you could have a home still standing after an earthquake. If you have
earthquake insurance, you may find you will pay more for the deductible on the insurance than you would to reinforce the residence. ``For about $600 I can go in and shear the cripplewalls,'' Cook says. ``You don't have to do
the whole thing but you should get foundation bolts in.''
Cook was living in Ferndale at the time of the 7.2 earthquake. ``It is a terrifying experience. It feels like King Kong has your house in both hands and is
shaking it as hard as he can. Everything goes flying, furniture topples over, it feels like the end of the world has come and you want to run out of the house but can't, because every time you try to stand up you get knocked
down.
``When it is over the house looks like it had been put in a giant paint can shaker. Everything is tipped over and strewn on the floor.''
If you are in a house when an earthquake strikes, he says, try to get to an inside wall or inside corner. The old advice to get in a doorway is now bad advice, he says, because the swinging door will
batter you.
``Don't try to get outside unless you see fire or a gas explosion. I documented injuries for FEMA and 99 percent were from people getting slammed against a wall or appliance when trying to run outside.''
There will be another earthquake, he says. ``We just don't know when.''
Cook and other earthquake service people are listed under Earthquake Products and Services in the Yellow Pages of the telephone book. Cook says
he will send you free literature if you send a stamped, self-addressed envelope to him at 331 Benton St., Santa Rosa 95401.
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