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Earthquake Seismic Retrofits – Anchors & Shear Walls

EARTHQUAKE … disaster that provides little to NO warning !

To ensure you are prepared, older homes can undergo relatively inexpensive, critically important earthquake seismic safety retrofit improvements.

The two critical components are :

1. Anchor bolts – secure structure to foundation
2. Cripple wall shearing – imagine standing dominoes falling over

The first condition doesn’t keep the house from jumping off the foundation (it’s too heavy for that), but it does keep the house from SLIPPING sideways off the foundation.

Anchor bolts are installed through the mudsill (bottom piece of wall framing) securing the wood structure to the foundation, and the anchor bolts are installed into holes that penetrate vertically into the concrete foundation stem wall (called wedge anchors, a common trade name for these retrofit anchors is “red head”).

A washer is also installed, to keep the nut from stripping off the bolt during a seismic event.

 

anchor bolt

The second condition is what affects most people, their house doesn’t slide off the foundation, but cripple walls and/or non-sheared tall walls fail … just like a bunch of dominoes standing up on end, when one falls and hits the other, they ALL fall, and a similar thing happens to houses during earthquakes, the wall start shaking back & forth side to side, and sometimes they are displaced far enough that instead of coming back to center, they just keep going and the whole wall laterally falls to the ground.

 

PREVENTION … PROTECTION … PRESERVATION !!!

 

You need to fix this stuff before an earthquake …

“I was gonna do that tomorrow” …
“Shoot, i meant to do that …”
“How do i fix it now?” …

All reflect the fact the straw that broke the camel’s back has already been placed … catastrophic repairs are WAY more expensive & severe than preventative repairs, so just do it now !

How ???

HERE … this is THE plan, the one i use as an engineer & general contractor when performing these exact retrofit repairs for clients, the plan is available online and the work is not “that hard”, but it is very dirty and does require skills and special tools (like a right angle impact drill that drills and jackhammers at 90 degrees to create the holes in your foundation stem wall).

Seismic Retrofit Plan A

… and remember, many newer homes ARE properly anchored, but they are NOT properly cripple wall sheared, the most common place they are not up until the 1980’s is the tall walls to both sides of framed opening for a 2-car garage door (the front wall of the garage is prone to rocking side to side and potentially falling, bringing down with it everything that is on top of it … usually kid’s bedrooms).

The state of California currently has in place a program that provides up to $3,000 in grant money directly to home owners in high risk zip codes. To see if you qualify, you can visit their website, or the FEMA website that the program is administered under :

http://resilience.abag.ca.gov/residents/

https://www.earthquakebracebolt.com

It IS going to happen, that is not the relevant, what is is whether you are prepared when a earthquake does hit
#BePrepared

If you have any questions please feel free to leave a comment, glad to help, jeff

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