Seismic foundation retrofitting focuses on correcting specific structural weaknesses that leave many older homes vulnerable during earthquake activity. In the Pacific Northwest, we often see the same problem areas repeated across decades of construction. Our work is designed to address those weak points directly using proven methods and engineered solutions.
Unbolted Foundations
One of the most common issues we encounter is a home that is not properly anchored to its foundation. Many older structures were built before anchor bolt requirements became standard. Without proper anchoring, the house can slide off the foundation when strong ground movement occurs. As part of our seismic foundation retrofitting process, we install approved anchor bolts that secure the structure to the concrete foundation, helping the home move as a single unit instead of separating during a seismic event.
Cripple Wall Instability
Cripple walls are the short stud walls between the foundation and the first floor framing. When these walls lack proper sheathing or bracing, they can collapse under lateral movement. This collapse often leads to major structural damage, even if the rest of the home remains intact. We reinforce cripple walls with structural-grade plywood and fastening patterns designed to increase stiffness and load transfer, significantly improving overall stability.
Sill Plate Connections
The sill plate sits directly on top of the foundation and serves as a critical connection point between the foundation and framing. In many older homes, this connection is weak or incomplete. During seismic foundation retrofitting, we reinforce sill plates with modern connectors and fasteners that improve the load path from the framing down into the foundation. This step helps reduce shifting and uplift during ground motion.
Inadequate Bracing
Some homes rely on outdated bracing methods that do not meet current performance standards. Inadequate bracing can allow excessive movement that stresses framing, finishes, and utility connections. Our team evaluates existing bracing and installs engineered solutions that better distribute seismic forces throughout the structure. These upgrades are tailored to the layout and age of each home.
Professional Assessment And Execution
Every property presents a different set of conditions. We begin each project with a detailed evaluation to identify the specific weak points that need attention. From there, we design a retrofit plan that meets current guidelines and fits the structure as it exists today.
If you are considering seismic foundation retrofitting for your property, call Evergreen Seismic at (206) 984-2580 to discuss it in Burien.