Download PDF version (296.7k) Log In or Register to view the full article as a PDF document.

Seismic Support 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 indisputable.