Seismic Retrofitting Guide for Homeowners

Why some homes need earthquake retrofitting

Seattle lies in a seismically active region, and many homes, especially those built before 1980, were not constructed using modern seismic standards. A voluntary seismic retrofit strengthens a home’s structure to better withstand earthquake forces, primarily by anchoring the house to its foundation and by bracing the cripple walls (the short walls between the foundation and the first floor).

Choosing the right seismic retrofit plan

Homeowners can choose between two seismic retrofit approaches

1. Prescriptive Plan Set: If the home is located in the City of Seattle, Seattle’s Department of Construction and Inspections (SDCI) offers a standardized plan set that simplifies the process. The Washington Association of Building Officials (WABO) also offers a standardized plan set that can be used for other jurisdictions in Washington. This option is ideal for typical wood-framed homes and does not require hiring an engineer. 
2. Engineered Retrofit: For homes that don’t meet the criteria of the prescriptive plan, a licensed structural engineer must design a custom retrofit. This is often the case for homes with complex layouts or unique foundation types.

How to get a home earthquake retrofit permit

To begin, homeowners must apply for a Earthquake Retrofit Permit through their local jurisdiction. The steps include:

1. Research: Determine if your home qualifies for the prescriptive plan or needs an engineered design. The standardized plan sets by SDCI and WABO have checklists to determine if your home qualifies for the prescriptive plans. 
2. Prepare Plans: Use a prescriptive plan set or hire an engineer to create custom drawings.
3. Submit Application: Submit plans and permit application online or in person to your local jurisdiction.
4. Permit Review: SDCI typically reviews prescriptive plan applications within two weeks. If the home is outside the City of Seattle, check with your local jurisdiction about permit turnaround times. Both the prescriptive plan sets and engineered designs qualify for a “subject-to-field-inspection” permit, which can expedite approval. 

Hiring a seismic retrofit contractor

While homeowners can perform the work themselves, most hire a licensed contractor. WABO offers training and maintains a list of contractors familiar with seismic retrofitting. It’s important to verify credentials, experience, and references before hiring.

What to expect during seismic retrofit construction

Once the permit is issued, the retrofit work can be completed. The retrofit typically involves installing anchor bolts or retrofit plates to connect the wood-framed walls to the foundation walls (see photo below) and adding plywood to the cripple walls in the crawl space or basement (see photo below).

During construction, inspections by the jurisdiction’s inspector are required at key stages, such as after installing anchor bolts or retrofit plates and before covering up any retrofitted walls. After completion, a final inspection by the city inspector ensures the work meets code requirements.

Costs and incentives for seismic retrofit

Costs vary depending on the home’s size and complexity, but typical retrofits range from $7,000 to $12,000. Using the prescriptive plan set can reduce the permit review time and permit fees. Some insurance companies offer discounts for retrofitted homes.

Invest in safety, with a seismic retrofit

A voluntary seismic retrofit in the Seattle area is a smart investment in your home’s safety and resilience. By following the prescriptive plan sets by either SDCI or WABO, or by hiring a licensed engineer to prepare drawings, homeowners can efficiently strengthen their homes against earthquakes and potentially reduce future repair costs and risks.