The cripple walls are the section of your house that rest right above the Mudsill. They support the weight of the house and create a crawl space. If the cripple wall is covered on the exterior with only stucco or wood siding, it is not strong enough to resist earthquakes. You will need to strengthen your cripple wall to prevent serious damage to your home by bracing the cripple walls with plywood. Cripple walls that are not braced may collapse with the side-to-side swaying of the house during an earthquake, causing the house to fall.
To secure the home, new lumber would be added as backing to create solid edges for the shear wall nailing. Expansion bolts would be placed, and the framing anchors would connect the rim joist to the top of the cripple wall. The cripple walls are now braced. Bracing the cripple walls by using structural-grade plywood is simple and provides greater resistance to earthquakes. Bolting your Mudsill to the foundation and adding plywood to the cripple walls are the two most cost-effective steps you can take to earthquake-safe your home in Los Angeles County.
On many homes, it is not possible to install foundation bolts because there is too little room between the top of the Mudsill and the floor of the house. This is because either there is no cripple wall or the cripple wall is extremely short. In these cases, special hardware known as “foundation anchor plates” is used to secure the house to the foundation.