Despite living along a major fault line, the state of Oregon didn’t have a seismic building code until the 1990s — meaning most of the homes there wouldn’t be prepared for a substantial earthquake if one occurred.
Ask This Old House host Kevin O’Connor traveled to Portland, Oregon to help one resident retrofit her home to protect it from earthquake damage.
How to Retrofit a House for an Earthquake
- The work involved with a seismic retrofit often requires a consultation with an engineer, and any work involving gas must be done by a licensed professional. Consulting with a person who is licensed to do seismic retrofits can help identify key areas to work with in order to minimize damage.
- The house can be secured to the foundation by securing metal L brackets into the rim joist and the sill plate at locations determined by the engineer with a palm nailer and 10-penny nails.
- To connect the sill plate to the foundation, drill screw anchors into the anchor plates and the foundation, and wood screws through the anchor plates to the sill plate. Predrill the sill plate to prevent it from splitting.
- To prevent gas from leaking into the house during an earthquake, an automatic gas shutoff valve can be installed by a licensed gas fitter.
- Shut off the gas to the meter.
- Disconnect the gas pipes starting from the meter until you reach a level gas pipe.
- Thread the gas shutoff valve into the pipes using pipe dope and nipples.
- Reconnect the remaining gas pipes to the meter and turn the gas back on. Check for any leaks in the new gas work.
- Secure any valuables and knickknacks to the wall, shelves, and floor using museum putty and zip ties.
- Secure the water heater to the surrounding walls using straps.
While the specialty hardware that was used to secure the house to the foundation can be found at most home centers, determining the proper location for that hardware may require a consultation with an engineer.
The seismic gas shutoff valve installed was a Northridge Valve, which is manufactured by Seismic Safety Products. Gas work is extremely dangerous and should always be left to licensed professionals.
The museum putty used to secure valuables to the shelves is manufactured by QuakeHOLD.
Expert assistance with this project was provided by NW Seismic and Christopher Higgins.