for Old Foundations
In the aftermath of California’s recent Loma Prieta
and Northridge earthquakes, there is a heightened awareness of
the need to strengthen existing wood-framed residences.
Insurance companies are enforcing stricter guidelines to
qualify for earthquake insurance, as well as requiring seismic
retrofits before issuing renewal policies. Many cities and
counties in California have also adopted new ordinances in
their building codes to address seismic safety.
After the 1989 Loma Prieta quake, the average cost to repair
houses that buckled off their foundations was $25,000 to
$35,000. Many homes were so badly damaged that they were
written off completely and had to be demolished. By contrast,
the average cost to provide sill bolts and cripple wall bracing
to an undamaged house ranges from $1,500 to $2,500. The
cost-effectiveness of correcting these deficiencies is