Is Your Home Protected From Earthquake Disaster?

Roof Systems
For your home to adequately resist the force of an earthquake, your roof structure must function like the top of a box, keeping the walls tied together and preventing your home from coming apart at the seams. The typical roof system includes a roof covering, roof sheathing and supporting roof frame. Start by inspecting your roof covering - it should be in good condition with no evidence of excessive wear and tear. Nonstructural lightweight coverings, such as wood or asphalt shingles, usually behave well during an earthquake. Tile and slate coverings, which are heavy, tend to tax your entire earthquake-resisting system and are also susceptible to sliding or falling off the roof during an earthquake. Next, consider what lies under the roof covering - the roof sheathing. Both plywood and OSB roof sheathing give strength to the roof regardless of the roof style. Roofs fully sheathed with structural grade plywood or OSB tend to provide the greatest stability to the overall structure. Board sheathing is not as earthquake resistant as plywood and OSB sheathing, but may be adequate in smaller homes. Consult a professional engineer for more specific information. Also, keep in mind that large dormers, skylight openings and any other features that interrupt the sheathing can weaken your roof structure.

Remember: sheathing can only do so much. You must also consider the roof system’s framing - the trusses or rafters that support the roof covering and sheathing. Similar to floor systems, roof-framing systems can rotate or fall over when your home starts to move in an earthquake. To prevent this, blocking can be placed between the rafters or trusses where they rest on the wall. Be sure to nail the blocking to the roof sheathing in order to transfer the lateral loads into the wall. Metal strap connectors or properly placed toe-nailing ensure that the blocking is adequately connected to the wall and rafters. You may not be able to thoroughly examine your roofing system due to limited access. The best time for a complete inspection is just before you re-roof your home. If you have any concerns about your roof ’s covering, sheathing, openings or framing members, talk to a professional engineer or qualified roofing contractor.

Unreinforced Chimneys
Unless specifically designed and reinforced for lateral forces, brick or stone chimneys often come apart or topple during an earthquake, causing serious damage and injury. Usually, only the top portion of the chimney breaks apart during an earthquake; however, in some cases the entire chimney peels away from the side of the home. Check the top of your chimney to be sure it is free of severe cracks (anything wider than the edge of a dime). Take a close look at the mortar between the bricks. It should not scrape away easily with a metal tool. Even if your chimney is in good condition, it may still be at risk, especially if it is tall and slender. Some chimneys have metal straps that hold them to the side of the home. Carefully inspect these fastenings. They should be in good condition with no evidence of poor workmanship or rust. If you are uncertain about what you see, consult with a professional engineer. The engineer may recommend adding a brace between the top portion of the chimney and the roof. You may also need to use metal straps at several points to anchor the chimney to the home.

Room Additions
If you’ve put on an addition or made other modifications in the past, you may have unknowingly weakened your home’s earthquake resistance. Sometimes, homes that were originally very simple and structurally sound undergo changes that make them bigger or fancier, but also more prone to earthquake damage. If you are planning to make major changes to the structure of your house, orif you suspect existing features lack good engineering details, consult a professional engineer.

Garages are particularly vulnerable to earthquake damage. The situation becomes especially serious if the garage has a portion of the home over it. The large garage door opening removes almost an entire side of the box configuration and requires the remaining narrow walls on either side to support the roof and extra rooms. If these walls are not designed carefully to handle the situation, the entire structure may collapse when an earthquake strikes. Strengthening the narrow garage walls generally requires engineering details, such as specially detailed plywood panels, steel bracing or a steel frame. A professional engineer can help you decide what will work best for your home.

Home improvement project list
This list of home improvements divides the different retrofits into cost categories. The categories reflect the cost of each individual item. The cost will be slightly higher if you hire someone to complete the work. You or your contractor can tackle these projects one at a time, but remember, the more you do the stronger your home becomes.

Category $ (<$300) Fasten bookcases and cabinets to nearby walls; Install latches on cabinet doors and drawers; Secure electronic equipment, artwork and other breakable items to the tops of bookcases and cabinets; Anchor large appliances to nearby walls; Secure pictures and bulletin boards to walls; Attach safety cables to light fixtures, suspended ceilings and other hanging items; Apply safety film to windows and doors; Secure water heater to nearby wall.

Category $$ ($300-$1000) Reinforce cripple wall; Strengthen narrow walls on either side of garage opening; Anchor unreinforced chimneys.

Category $$$ (>$1000) Add anchor bolts or steel plates to foundation; Secure post-and-pier foundation; Modify floor system; Strengthen wood-framed walls; Reinforce masonry walls; Retrofit roof system; Evaluate unique room additions. You will give yourself and your family a better chance of escaping harm during an earthquake by taking as many of the precautions outlined in this brochure as possible. But, these steps are only the beginning. To protect yourself as completely as possible, here are some added suggestions:

Before, During and After: Be Completely Prepared
Before an earthquake strikes: Teach everyone to "duck" or drop to the floor, take "cover" under a desk or table and "hold" on to it when an earthquake strikes. Remember the phrase: "Duck, Cover and Hold." Learn first aid and CPR. Put together an emergency kit that includes at least a three-day supply of drinking water and food that needs no refrigeration and, generally, no cooking; emergency cooking equipment, if required; a portable NOAA weather radio; first aid supplies and medications; basic tools, such as a wrench, a flashlight and gloves; portable lanterns and batteries; credit cards and cash; and important documents, including insurance policies. Know where your gas, electric and water main shut-off controls are and how to turn them off if there is a leak or electrical short. Make sure all adult and teenage members of your family know how to shut off each utility. Become familiar with your community’s disaster preparedness plans and create a family plan. Know where the closest police, fire and emergency medical facilities are located. Plan an escape route from your home and neighborhood and designate an emergency meeting place for the family to reunite. Establish a contact point to communicate with concerned relatives. Periodically review your homeowner’s insurance policy with your insurance agent or company to make sure that, if you are the victim of a disaster, you have enough coverage to rebuild your home and life. The typical homeowner’s insurance policy does not include earthquake coverage. If you are in an earthquake-prone area, you should consider purchasing earthquake insurance.

During an Earthquake: If you are indoors, "duck, cover and hold" until the shaking stops. Do not try and run out of a building - you may be hit by falling debris. If you are outdoors, move quickly and safely into the open, away from electrical lines, trees and buildings, and wait for the shaking to stop. If you are driving, carefully and slowly bring your vehicle to a stop at the side of the road away from traffic. Make sure that you do not stop on or under bridges. Do not stop under power lines or near roadway signs that might fall. Once the shaking has stopped, you can continue driving. Watch carefully for possible damage to the roadway.

After an Earthquake Strikes: Check for hazards, such as gas or water leaks and electrical shorts. Turn off damaged utilities. Have the fire department or gas and electric companies turn the utilities back on when the area is secured. Check for injuries and administer first aid as needed. Check your food and water supplies. Do not eat anything from open containers near shattered glass. Listen to and follow the advice and recommendations of local aid organizations, including the emergency management office, the fire department and the utility companies. Keep roads and phone lines clear for emergency use. Be prepared for aftershocks.

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