If your house was built before 1986, it might not meet modern building standards and may be more vulnerable to earthquake damage. You can strengthen your home by making sure the wood portion of the house is connected to the concrete foundation with anchor bolts as required by current state building codes. These connections help move the forces generated from an earthquake through the house walls to the foundation, making your home more stable.

Determine if Your Home Is at Risk

In 1986, Oregon adopted a statewide building code for single-family and two-family homes. This code required the wood structure of the house be attached to the foundation using ½" diameter bolts every 6 feet. If your house was built in 1986 or later, you should already have these bolts. If your house was built before 1986, you should consider a seismic upgrade to protect your house and your family's safety.

Decide if You Can Do the Work Yourself

You can apply for the permit and strengthen your foundation yourself if you can answer “Yes” to the following questions:

• Are your house walls made of wood (wood-frame construction)
• Does your house have a concrete foundation around the entire house (continuous perimeter concrete foundation)?
• Is your house 2 stories or less?
• If you have brick or stone on the outside walls, is it less than 4 feet in height?

If you answered “No” to any of the questions above and your house was built before 1986, you will need to contact an engineer to assess how to strengthen your house.

View the upgrade notes and coding requirements document for more detailed information.

Assess What Work You Need to Do

You will need to get under your house in the crawl space or the basement to get information about how the house is connected to the foundation. You can purchase the supplies online or at any home improvement store.

Understand the Terms

The following words are important to understanding how a house is built:

• A sill plate/mudsill is the horizontal part of a frame wall that sits directly on the foundation. It connections the foundation to the floor joists and the vertical studs or the cripple walls.
• Cripple walls are short, wood-framed walls between the sill plate and the floor of your home. They are used to raise the house above ground, usually to provide access to utility lines.
• Sheathing is a layer of wood or other material covering the wall studs. It strengthens the walls and helps them resist movement. Stucco and wood siding are common sheathing materials for cripple walls, but not strong enough to withstand earthquake forces. Cripple walls need to be sheathed by plywood or oriented strand board (OSB) sheathing to provide adequate earthquake resistance.
• A joist is a strong, heavy board that supports a floor or ceiling. The floor joists will run parallel to some of the outside walls and perpendicular to other outside walls. When upgrading your home, you will need to submit hardware detail sheets for both the parallel connections and the perpendicular connections.
• A rim joist is the wooden board that forms the out edge of the wood frame. It connects to the ends of floor joists and helps tie the structure together.

No Cripple Wall: Reinforce the Sill Plate/Mudsill

Current building code requires the sill plate to be attached to the concrete foundation using ½" diameter bolts every 6 feet. You can reduce your home's risk of earthquake damage by making sure your sill plate has these bolts. When you apply for your building permit, you need to identify the connection method you plan to use. To make this process easier, we have created the documents you need to include in your permit application for several of the available connection options:

Table 1: Anchor connection options

Cripple Wall: Reinforce Cripple Walls

If your house has cripple walls, the floor system is resting on the cripple walls rather than resting directly on the sill plate. Current building code requires the rim joist to be attached to the top of the cripple walls with metal anchors. Code also requires the bottom of the cripple walls to be connected to the foundation by metal anchors.

If your cripple walls are not reinforced with plywood or oriented strand board (OSB) sheathing and are only covered with stucco or wood siding, they need to be covered with plywood or oriented strand board (OSB) sheathing to strengthen the walls and help protect your home from structural damage. In a finished basement or crawl space, you probably have a drywall covering your cripple wall on the inside. In these cases, it is generally easier and less expensive to install sheathing on the exterior side of the wall.

If you have cripple walls, we have created the documents you need to include in your permit application. Choose the details below based on whether your sheathing will be on the outside or inside of the cripple walls.

Reinforce the Beam to Post Connections

If you have posts supporting the floors, it is important to reinforce the connections between the floor beams and the posts as shown in Detail 13.

Apply for a Building Permit

A permit is required to perform a seismic upgrade. The building permit ensures the work meets safety standards and protects you by providing the following:

• The city provides details to be used in the retrofit based on the foundation type of the house.
• A building inspection to confirm the retrofit work is done correctly.
• A record in the city database showing the work was permitted and inspected.

Step 1: Complete an Application

Fill out a residential building permit application with the following information:

• Project description: “Seismic upgrade to existing single family dwelling.”
• Type of work: Mark the “Alteration” option.
• Valuation of the work: List the cost of all equipment, materials, labor, overhead, and profit for the work. For homeowners doing their own work, list the cost of the materials.

Step 2: Prepare Your Drawings and Supporting Documents

• Print the hardware detail sheets for the sill reinforcement and the cripple wall reinforcement.
• Draw an outline of the outside walls of the house, including all the dimensions. (foundation outline sheet)
• Based on the dimensions, calculate the number of hardware pieces you need and the spacing between them. Reinforcements should be installed every 6 feet.
• Mark the location of beam and post connections.
• Mark the reinforcement locations on the drawing using the hardware detail sheet numbers in the lower right corner. For example, if you are using a UFR connection:
  • Write “3” every 6 feet on the walls where the floor joists are parallel to the wall.
  • Write “4” every 6 feet on the walls where the floor joists are perpendicular to the wall.

Step 3: Submit the Application and Drawings to the City

Submit the application, foundation outline sketch and downloaded hardware detail pages to the Permit Application Center along with the permit fee.

If your permit materials are in order, the permit will be issued immediately, and you can begin the work.

Step 4: Complete the Work and Have It Inspected 

Pre-Construction Inspection: You can request a pre-construction inspection to verify that materials match the plans you submitted with your permit application.

Required Inspections: Schedule inspections at the following stages before covering any work: 

• Foundation bolts/anchor plates installation
• Installation of blocking
• Installation of sheathing on cripple walls
• Final inspection after all work is completed

Additional Information

• Questions to ask a contractor - The Oregon Construction Contractors Board guide to selecting a contractor for seismic retrofitting.
• Step-by-step guide - Simpson Strong-Tie's Retrofit Guide to help you reinforce the frame of your house.

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