2007 February, Updated 2011 June 13
We live very close to the Hayward Fault so my first order of business after moving in was to install shear walls to ensure that the house doesn't fall off of the foundation during an earthquake. We moved in on Sunday, January 28th and the shear walls were done by the following Sunday, February 4th. I finished in time to see the last half of the Super Bowl.
This photo shows how not to brace your cripple walls. The metal strap will be useless during an earthquake.
Proper shear walls consist of 1/2" structural 1 grade plywood nailed approximately every 4 to 6 inches with 10 d nails. Each side of the house has about 16 total feet of shear wall. The section in the photo above is 4 feet wide.
And the shear walls are not complete unless the mudsill is bolted to the foundation. These are 1/2" diameter x 6 inch long galvanized bolts by Simpson. Drilling the holes for these bolts is no fun at all.
Updated 13 June 2011: After seeing the incredible amount of bolting and shear walls that went into the addition, I decided my shear wall work was a bit subpar, so I added more shear wall panels, more sill anchors, and also put in several Simpson UFP (universal foundation plate) where lack of headroom previously prevented me from putting in sill anchors. If you look close, you can see that I had to chip away the concrete to be able to screw the UFPs to the sills.