Earthquake Safety Retrofit for Homes
Earthquake retrofitting is the process of reinforcing homes to make them more resistant to earthquake damage. According to Earthquake Prepared, most structural damage comes from the shearing force, or side-to-side shaking, of an earthquake. This shearing force can shake buildings off their foundations and cause collapse of the understructure that holds up the building, rendering the building uninhabitable. Earthquake retrofitting involves strengthening the understructure and securing heavy appliances, such as the water heater. Does this Spark an idea?
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Foundation Anchors
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Most houses in earthquake-prone West Coast cities are built on concrete foundations. Making a house earthquake-resistant involves bolting the sill plate securely to the concrete foundation. The sill plate is the piece of lumber that rests on the foundation and supports the whole house. There should be a half-inch bolt anchored into the foundation at least once every 2 to 4 feet that goes up through the sill plate, said EarthquakePrepared.com. A large square washer is held to the sill plate by a nut. The bolts will help keep the house from sliding off its foundation.
Pony Walls
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Much of West Coast home construction employs wood-framed pony walls. These are the basement walls between the foundation sill plate and the top plate on which the floor joists rest. These walls need to be reinforced with sheets of half-inch plywood nailed solidly to the foundation sill plate, top plate and each stud, said EarthquakePrepared.com. Homes with basement walls made of cinder block, brick or stone need to be evaluated by a seismic structural engineer or contractor, said EarthquakePrepared, because these materials are relatively weak against earthquake forces and there's no simple fix.
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Joists
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The joists that support the floor typically are nailed to the understructure's top plate and to either a solid rim joist or to pieces of blocking at the rim that hold the joists apart. In either case, earthquake reinforcement requires that the joists and rim be secured to each other and to the top plate with steel framing clips that are nailed into the structural members.
Securing Water Heater
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Home water heaters are inherently top-heavy and probably will tip over in an earthquake, reports the California Office of Emergency Services website. This is likely to rupture the gas line feeding the water heater, posing a danger of fire. Water heaters should be fastened to wall studs with 24 ga. steel straps at top and bottom of the heater whose ends are screwed into the wall studs. Water heaters should also have flexible connectors to their gas and water supplies rather than rigid pipes.
Other Steps
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Other steps to prepare a home for an earthquake include securing other major appliances, tall furniture and large mirrors to the home's floors or walls, knowing where the shut-offs are for gas, water and electricity service, moving hazardous household chemicals to secured cabinets or low shelves, and putting together a kit of emergency food and supplies, according to the California Office of Emergency Services.
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References
- Photo Credit ruined house image by Alex White from Fotolia.com
