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Time: 1-2 days
Cost: $2000 and up
Skill Level: Expert – for licensed professionals only
Tools List for Earthquake Protection:
Metal L brackets
10 penny nails
Automatic gas shut off valve
Water heater straps
1. 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.
2. 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.
3. 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.
4. To prevent gas from leaking into the house during an earthquake, an automatic gas shut off valve can be installed by a licensed gas fitter.
5. Shut off the gas to the meter.
6. Disconnect the gas pipes starting from the meter until you reach a level gas pipe.
7. Thread the gas shut off valve into the pipes using pipe dope and nipples.
8. Reconnect the remaining gas pipes to the meter and turn the gas back on. Check for any leaks in the new gas work.
9. Secure any valuables and nick knacks to the wall, shelves, and floor using museum putty and zip ties.
10. 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 (http://www.seismic-safety.com/). 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 (http://www.quakehold.com/emergency-management-emergency-preparedness-index.html).
Expert assistance with this project was provided by NW Seismic (https://www.nwseismic.com/) and Christopher Higgins.
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How to Retrofit a Home for an Earthquake | Ask This Old House