Earthquake retrofit begins in crawl space

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Last week, a reader asked our opinion about insulating his crawl space and doing a little earthquake retrofitting under his home. We recommended that he install batt insulation between the floor joists, retrofit the cripple walls with plywood sheathing to make a shear wall, and put down a plastic vapor barrier over the dirt in the crawlspace. Last week's column addressed insulating the floor. Today's column sets out the reasons to reinforce the cripple walls and the method for doing so. We've mentioned that we experienced the Loma Prieta earthquake in 1989. Fortunately, our Alameda, Calif., homes suffered no damage. We'd just put a new foundation under Bill's house, and Kevin's "Old Vic" came equipped with a concrete foundation. But Loma Prieta made its impression and convinced Kevin that shear panels under his house were the way to go. Cripple walls are short wood-framed walls extending from the mudsill resting on the top of the perimeter-raised concrete founda...