If your house was built before 1986, it 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.

Determine if Your Home Is at Risk

In 1986, Oregon adopted a statewide building code for 1- and 2- 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 laid directly on a foundation. It provides a connection and resting point for the floor joists and the 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 materials covering the wall studs. 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.
• 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. You will need to submit hardware detail sheets for both the parallel connections and the perpendicular connections.
• A rim joist is the wood around the outside of a wood frame to which the ends of floor joists are attached

No Cripple Wall: Reinforce the Sill Plate/Mudsill

Current building code requires the sill plate to be connected 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 help you, 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 sheathed with plywood and are only covered with stucco or wood siding, they need to be covered with plywood or oriented strand board (OSB) sheathing. In a finished basement or crawl space, you probably have a drywall covering your cripple wall on the inside. It is generally easier and less expensive in these cases to add sheathing to 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, you need 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 protects you by providing the following:

• The city provides details to be used in the retrofit based on the type of the foundation of the house.
• A building inspection to check the retrofit work. This helps the homeowner make sure the job is done correctly.
• The homeowner will also have a record in the city database that the work was permitted and inspected.

Step 1: Complete an Application

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

• Use the project description “Seismic upgrade to existing single family dwelling.”
• For Type of work, mark the “Alteration” option.
• For the valuation of the work, list the value of all equipment, materials, labor, overhead, and profit for the work. For homeowners doing their own work this will be typically be 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, figure out the number of hardware pieces you need and the spacing between them. You need to add reinforcing connections every 6 feet.
• Mark the location of beam and post connections.
• Mark the drawing with the location of the reinforcements using the number on the hardware detail sheet in the lower right corner. For example, if you are using a UFR connection:
  • You would write “3” every 6 feet on the walls where the floor joists are parallel to the wall.
  • You would 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, 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

You can request a pre-construction inspection to verify that the plans your home and supplies match the plans you submitted with your permit application.

Be sure that required inspections are completed before any work you do is covered. Inspections are required for the following:

• Foundation bolts/anchor plate installation
• Installation of blocking
• Sheathing installation on cripple wall
• Final inspection

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.

Free viewers are required for some of the attached documents.
They can be downloaded by clicking on the icons below.

Acrobat Reader Windows Media Player Word Viewer Excel Viewer PowerPoint Viewer