Earthquakes will happen again. The effects need not be disastrous. Most of the damage to wood-frame houses in recent earthquakes could have been prevented.
If you have earthquake damage, NOW is the time to strengthen your home correctly. If your home escaped damage, NOW is the time to evaluate your home and install strengthening measures, before you forget and before the next earthquake.
You can make these changes yourself at relatively low cost if you have basic carpentry skills. Otherwise, contact a licensed professional about making the necessary changes to you home or office. Contact your local building department to modify details to fit local building codes.
WOOD FRAME Bolting the wood frame to the concrete foundation can significantly reduce earthquake damage. Every 3 to 4 feet along the foundation, drill a hole using a right angle drill with a 1/2-inch bit, blow the concrete powder out of the hole with a small piece of flexible tubing, and hammer in an extension bolt, 1/2-inch in diameter and about 7 1/2 inches in length. Tighten the nut on the extension bolt. Photo by Lori Dengler.
How do you locate professionals to advise you on the resistance of your building to earthquake shaking? Who should perform the needed construction?
Civil and structural engineers and architects are trained to provide such information about structures. Geologists, foundation engineers, and geotechnical engineers are trained and licensed to evaluate soil conditions and recommend appropriate action. A contractor has to implement the detailed plans and specifications prepared by an architect or engineer.
A good place to start is to call a professional organization and ask about the types of work that might be required; how to select an engineer, geologist, or architect; and a list of members in your area.
Contact several firms or individuals to determine whether they do the types of work you need. Make sure the firm has the necessary licenses and has experience in strengthening structures to resist earthquake shaking. Check to see how satisfied other clients were.
Recognize that the quality of the advice given and the work performed, as well as the price you pay, may depend on the care you take in making your selection.
Become informed. Even if you do not understand the technical details, ask enough questions to understand the concepts and relative importance of the issues involved. You have a right to understand what needs to be done and why.
State and federal agencies do not inspect individual buildings. Your local building department may be willing to inspect your building, but they are not authorized to recommend actions to be taken.
Reinforcing the cripple walls between the foundation and the first floor of a wood-frame house can significantly reduce earthquake damage. This Ferndale home in 1992 would not have been so severely damages had the cripple walls been reinforced. Photo by Kevin Bayless.
You can receive a free copy of A Guide to Strengthening and Repairing Your Home Before the Next Earthquake by contacting the Governors Office of Emergency Services
Post and Pier perimeter bracing. Photo courtesy of California Office of Emergency Services.
A pier and post or post and beam foundation consists of wood posts which support the entire structure and are, in turn, supported on isolated concrete footings. Many homes in rural North Coast areas use this foundation system. This type of foundation is particularly vulnerable to the strong side-to-side shaking from earthquakes because it does not have a substantial bracing system.
There is no question that the best foundation system for any structure is a continuous perimeter foundation. The perimeter foundation keeps the structure from moving laterally, preventing posts from tilting. For many North Coast residents, the cost of installing such a foundation is prohibitive. However, it is possible to significantly strengthen your pier and post foundation at relatively low-cost.
A bracing system should provide a minimum resistance to lateral forces for your home. The bracing should be installed around the perimeter of the structure and, at a minimum, every second line of interior posts, in each direction. Care should be taken in laying out the spaces to be braced such that braces from two directions do not meet at the same post. This type of strengthening should be considered adequate for short term stabilization until you are able to install a permanent, contiguous, poured-in-place foundation system. This bracing system can also be used for porches and other exterior features.
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