J.A.V. CONSTRUCTION.
Juan Adrian Velasco Construction.

THIS IS HOW A CRIPPLE WALL
BRACING JOB IS DONE.

We drill the holes to insert the anchor bolts.                    

Inserting the bolt into the predrilled hole.

Most houses have a short wood-framed wall in the sub-area crawl space. This wall my be anywhere from a few inches to several feet in height, running upward from the top of the concrete foundation to the bottom of the main floor.
This is referred to as a cripple wall. Cripple wall collapse is a main source of earthquake related failure. The collapse of this wall will often result in the main floor dropping to the ground. The house is vaulted off to the side of the foundation as the cripple wall rolls out from under it.

 Bracing of the cripple wall to keep if from collapsing during seismic movement is a very important part of earthquake retrofitting.
The bracing is accomplished by attaching structural grade plywood tightly to the wall framing. In engineering language, this strong or stiffened wall is referred to as a shear wall.

The stiffening effect is accomplished in the lengthwise direction of the plywood, which means that plywood run along the side walls of a house will brace it in the front-to-back direction while plywood run along the front and back walls will brace the house in the side-to-side direction. Accordingly, it is important to brace all sides of a house for the best seismic protection.

It is usually not necessary and may even be undesirable to brace the entire lengths of the cripple walls. Over-bracing means unnecessary work and cost, and many engineers think that it is important to maintain some flexibility in the sub-areas of the house.

It is also important to complete the connection from the foundations, through the walls, and into the overhead floor framing. This will provide for good load transfer. Load transfer is an engineering term which in everyday language means that the effects of the earthquake movements are transferred from one of the buildings components into the next – ground to foundation, foundation to sill, sill to wall, wall to floor. Good detailing of all of these connections is an important part of retrofitting technique.