Identify your building's potential weaknesses and begin to fix them.
Buildings are designed to withstand the downward pull of gravity, yet earthquakes shake a building in all directions – up and down, but most of all, sideways. There are several common issues that can limit a building's ability to withstand this sideways shaking.
Additional information, including how-to instructions, is available at www.daretoprepare.org.
Common building problems
Most houses are not as safe as they could be. The following presents some common structural problems and how to recognize them. Once you determine if your building has one or more of these problems, prioritize how and when to fix them, and get started.
Larger imageThis cutaway diagram shows how weak cripple walls can be strengthened by properly attached plywood sheets.
Inadequate foundations. Look under your house at your foundation. If the foundation is damaged or built in the “pier and post” style, consult a contractor or engineer about replacing it with a continuous perimeter foundation. Look for bolts in the mudsills. They should be no more than 1.8 meters (6 feet) apart in a single story and 1.2 meters (4 feet) apart in a multistory building. Adding bolts to unsecured houses is one of the most important steps toward earthquake safety. This can be done by a contractor or by someone skilled at home maintenance.
Unbraced cripple walls. Homes with a crawl space should have panels of plywood connecting the studs of the short "cripple" walls (see figure). You or a contractor can strengthen the cripple walls relatively inexpensively.
Soft first stories. Look for larger openings in the lower floor, such as a garage door or a hillside house built on stilts. Consult a professional to determine if your building is adequately braced.
For those who rent
As a renter, you have less control over the structural integrity of your building, but you do control which apartment or house you rent:
- Structures made of unreinforced brick or block walls can collapse and cause great loss of life.
- Apartment buildings with "tuck-under" parking space openings can also collapse.
- Foundation and cripple wall failures can cause expensive damage but less loss of life.
- Objects attached to the sides of buildings, such as staircases, balconies, and decorations, can break off in earthquakes.
Ask the landlord these questions:
- What retrofitting has been done on this building?
- Have the water heaters been strapped to the wall studs?
- Can I secure furniture to the walls?
Unreinforced masonry. All masonry (brick or block walls) should be reinforced. Some communities have a program for retrofitting buildings made of unreinforced masonry. If your house has masonry as a structural element consult a structural engineer to find what can be done. Inadequately braced chimneys are a more common problem. Consult a professional to determine if your chimney is safe.
If you live in a mobile home...
Look under your home. If you only see a metal or wood “skirt” on the outside with concrete blocks or steel tripods or jacks supporting your home, you need to have an “engineered tie-down system” or an “earthquake-resistant bracing system” (ERBS) installed. An ERBS should have a label on the bracing that says, “Complies with the California Administrative Code, Title 25, Chapter 2, Article 7.5.”
The seven steps to earthquake safety
