An Unsecured Home During An Earthquake
An earthquake moves the foundation under a home from side to side, laterally. If your house is not secured, it can slide off.
The most basic and well known part of the retrofitting process involves bolting or attaching the sill plate. The sill is the piece of lumber that bears directly on the concrete.
This can be performed with a side plate attachment if there are clearance issues or by direct bolting.
Sill Attachment with direct bolting
After the sill is properly attached, we need to move up the home, and connect the wood framing, floor joists, or cripple walls to the sill. If there is no cripple wall, we use a shear transfer tie or framing angle to connect directly to the floor framing.
sill Attachment with shear transfer tie
If your home has short walls between the floor framing and sill, you have a cripple wall. These are a weak point in the framing and need to be addressed with reinforcement. Shear grade plywood — there is such a thing, and you can’t get it at Home Depot — is attached to the cripple walls with specific nails at a specific pattern. This reinforces the wall, and allows the wall to transfer lateral loads down to the sill.
reinforce Cripple Wall
Mobile Home Seismic Bracing
Secure Seismic provides and installs mobile home reinforcement products from Central Piers. Central Piers’ Seismic Piers are a purpose built and designed product for providing lateral foundational capacity for modular homes. These piers, when installed, keep your mobile home from sliding away. They are reasonably priced and quick to install. A typical installation on a double wide unit can be completed in one day. They are engineered and approved in most jurisdictions, and work to keep your home in place while in some cases qualifying you for insurance.
Mobile Home Seismic Attachment
Mobile Home Seismic Attachment
Natural Gas Shutoff Valves
We install automatic gas shutoff valves from Little Firefighter. These products are required by law in parts of California. One of the first things experts say to do in an earthquake is shutoff the gas. Fires are a huge cause of destruction and damage after an earthquake. In the event of an earthquake, the last thing you are going to be thinking about is heading outside to your gas meter and shutting if off, and that’s assuming you are home when the earthquake happens. The shutoff valves we install are automatic and all but immune to nuisance trips. They have been around for decades, and have been built to be bulletproof and reliable.
Multi Unit Gas Valve with Rack
Non-Structural Furniture and Appliance Attachments
In the event of an earthquake, you are instructed to stay inside your home…except for the aforementioned instruction to shut your gas off, which you won’t need to do if you have an automatic shutoff installed. You are supposed to stay in your home and get under a heavy piece of furniture to provide cover from falling objects. If your older home is properly attached to its foundation, or if your home is newer and properly built to current codes, you still need to think about restraining heavy objects around the house, like the hot water heater, TVs, large appliances, and kitchen cupboards. Secure Seismic can assess your home and install all of attachment hardware required.
Hot Water Heater Attachment
A few specific things can complicate your home attachment. These conditions add risk to your existing home and complication to your potential retrofit. Be especially cautious when having your home evaluated and choosing an engineer or contractor if these conditions exist in your home, this stuff can be tricky.
Soft story conditions exist when the roofline of your home extends over the main foundation or when the main foundation is broken with a large opening like a garage. Totally fixable…but not simple. The lateral loads must be taken back to the foundation, overturn and uplift along the foundation wall needs to be assessed, and the opening needs to be spanned with a brace.
Brick, block, or unreinforced masonry (URM) foundations are tricky as well. There are no set recipes for dealing with these conditions. Hollow cinder block can be filled with concrete or grout, and then treated like a normal concrete foundation. Brick can be demoed and replaced with concrete, but it can also be augmented with an adjacent foundation designed to support lateral loads as a more cost effective fix. Same warnings as above: make sure whomever you hire knows what they are doing. These foundations will not perform well in an earthquake without being addressed.
Existing CMU (Concrete Masonry Unit) Stem Wall
Existing CMU Stem Wall