Cabin Earthquake Retrofit

Our current cabin was built in 1955.  Rather than a crawl space made up of block walls (as was the case for our former cabin built in 1963), ours is made up of cripple walls.  These are walls built with vertical 2×4 studs between the floor joists and the foundation.  Although they are adequate for supporting the house under normal circumstances, they are a weak link when dealing with the side to side loads of an earthquake, as described on this webpage.

I knew that no amount of do-it-yourself retrofitting would guarantee the cabin surviving a major earthquake.  For one thing, I’m going to lose the chimney for sure in a big quake – the only way to avoid that would be to tear it down and rebuild it.  But I figured that reinforcing the cripple walls would give the best “bang for the buck” by shoring up the weakest link, which could make a difference in saving the cabin from a smaller quake.  There’s a couple of online do-it-yourself guides from the City of Oakland and the City of Los Angeles, and even a standard plan.  So I finally made it to the big box store and got some plywood and rented a nail gun and compressor to do the job.  Photos are below.

Portion of unreinforced cripple wall:

Cripple walls reinforced with plywood (with screened vents):

More cripple walls reinforced with plywood:

Closeup of framing anchor to secure the house to the newly strengthened cripple walls:

Same framing anchor, further away (good thing I have an air compressor and a palm nailer to fit in the tight space to nail the anchors in!):