Earthquakes are a fact of life in the Bay Area. The same geologic features that create our dramatic mountains-meet-ocean vistas mean we have to live with a little bit – or sometimes a lot – of shaking.
California’s building codes are continually updated based on emerging research and lessons learned from each quake to make new buildings safer, but new regulations don’t apply to older homes. These structures are especially vulnerable to earthquake damage, but there are things you can do to safeguard your family and your investment.
These are a few of the top hazards for older homes:
Insecure Foundation
When the earth moves, a home’s foundation moves. If the top of the structure doesn’t move with it, the home can be severely damaged.
Older homes may not be properly secured to their foundations. Your licensed architect or engineer can inspect your foundation and suggest retrofitting for these common problems:
Unbolted or Improperly Bolted Foundation
Your home should be bolted to its foundation using large nuts, washers, and anchor bolts or steel plates.
Unreinforced Cripple Walls
If your home has a crawl space, it may also have one or more cripple walls supporting the weight of the home. These need to be properly reinforced to withstand severe shaking.
Post and Pier Foundation
If your home rests on wood posts that sit on top of individual pads (piers), they may need retrofitting to ensure stability during a quake.
Unreinforced Masonry Foundation
Foundations made of brick or stone can weaken over time. Your architect or engineer can help determine if reinforcing the foundation will be adequate, or if you will need to replace your foundation.
Wall Instability
The shaking from an earthquake can make different parts of your home move in different directions. If your home was built before 1975, the anchorages between walls and the roof or floor may be too weak to prevent separation. (If it was built before 1995, when new, stronger regulations came in after the Northridge earthquake, it’s also worthwhile to have the anchorages checked.)
Re-roofing can be a cost-effective time to inspect and, if necessary, replace anchorages that aren’t up to current seismic code and install reinforcement to help your home’s walls withstand the lateral movement of a quake.
Plate Glass
The large glass windows and sliding doors that make mid-century modern homes so appealing can be a serious hazard during an earthquake.
Replacing plate glass is one of the best upgrades you can make to your home, but it can be pricey. If replacing windows is out of your budget, consult a professional architect, engineer or window specialist for other options.
Brick or Unreinforced Masonry Chimneys
Brick and other types of unreinforced masonry can topple during an earthquake. The 1994 Northridge quake demonstrated that simply bracing your chimney to your home is inadequate protection.
Have your chimney inspected by a licensed architect or engineer, who may be able to suggest alternatives that can reduce potential problems.
Over-Garage Rooms
Many people with smaller, older homes add over-garage rooms to increase available living/working space. Because most garages have a large door opening and no interior walls, they are not strong enough to support an upper story in an earthquake, especially when the garage door isn’t in line with the main part of the home (as in most L-shaped homes).
Your architect or engineer can suggest retrofits to make an above-garage room more stable during a quake.
Water Heaters
The violent lateral movement of an earthquake can displace a water heater and create both water and fire hazards. To prevent this, your water heater must be properly braced to a wall.
Your licensed plumber, contractor, architect or engineer can help you retrofit your water heater to make it safer during a quake.
General Earthquake Safety
There are also lots of smaller steps you can take to improve your home’s earthquake safety:
Gas & Water
Everyone teen and older in the family should know where and how to shut off the gas and water to your home. Keep an emergency gas meter shutoff wrench (available at hardware stores or online) attached to your gas meter.
Secure Heavy Furniture and Electronics to Walls
Tall, heavy furniture and large electronics like T.V.s should be secured to a wall to prevent tipping during an earthquake.
Cabinet Latches
Any of a variety of latches designed to keep cabinets securely shut during a quake can keep your dishes safe.
Pictures, Artwork & Mirrors
Anything heavy hanging on your walls should be secured to one or more walls studs using screw hooks or commercial earthquake picture hangers.
Small Breakables
Anything small and breakable you couldn’t stand to can be secured using special putty, wax or gel adhesives.
Consult a Professional
A California-licensed architect or structural engineer knows current seismic codes and can help you inspect your older home for earthquake hazards and recommend ways to remediate them.