How much does it cost to retrofit a home for earthquake protection?
Earthquakes can be debilitating disasters and quickly wreak havoc on all kinds of structures. Retrofitting a home for earthquake protection reinforces the home’s structure and makes it more difficult to remove the home from its foundation in an earthquake. Homes that are in higher risk areas for earthquakes according to the U.S. Department of the Interior, U.S. Geological Survey Hazard map (see image) have a greater need for being retrofitted. On average, the cost to retrofit a 1,500 square foot home is $4000-$7000.
The total cost of an earthquake project is largely dependent on the home’s current structural quality and efficiency and location. There are many things that can be done to strengthen and retrofit a house, including the following. Talk to your contractor to find the biggest needs for your home and area.
The most common retrofitting procedure improves a home’s bond with the foundation by adding a piece of wood (called the sill 2 or mudsill 2) to the top of the foundation and reinforcing it with bolts. Bolts that have weakened over time or withstood an earthquake may need to be tightened or replaced after 5-8 years. Expansion bolts are less expensive but more powerful and work well with homes with strong concrete foundations, typically newer houses. Epoxy-set bolts 3 work better with older homes, but they are more expensive. On average, the process costs $2000-$4000.
The cripple wall 4 is the short frame that runs from a home’s foundation to the bottom of the main floor. When an earthquake occurs, the most common damage is from the cripple wall 4 collapsing, which can drop the main floor. Bracing the cripple wall 4 typically includes reinforcing it with plywood 5 in the opposite direction of the original wall, which protects against side-to-side earthquake movement. The process typically costs $1000-$2000.
Also known as floor framing, this process adds a grid underneath ground-level flooring to add additional support. With strengthened side joists and support throughout, the floor is less likely to collapse or move side to side in an earthquake. The average cost is $1000-$2000.
Enhancement and improvement costs
- Because retrofitting a home can be an invasive and messy process, it can be a good time to update wiring, plumbing, or HVAC systems.
- Adding a seismic inspection to see what other areas of the home require retrofitting can add $200-$400 to the total cost.
Additional considerations and costs
- In some cases, especially older homes or homes that have been remodeled, a consultation with an engineer is recommended. This can also be a good process for homes in unique locations, such as on hillsides or stilts, large homes, or homes with existing issues. On average, an engineer consultation will add another $150-$300 to your costs.
- Because retrofitting a home can substantially change the home’s structure, permits are required in most areas. Check with your contractor for local codes and regulations.
- Many insurance companies offer a lower rate on earthquake coverage once a home is retrofitted. In many areas, including parts of California, it can save 5% off standard earthquake coverage rates.
- Homes built before 1980 had different foundation regulations, often without quality bolting techniques. These unbolted foundations typically lead 6 to water leaking in between the mudsill 2 and the foundation, rusting the bolts and making them less effective. If this is the case in your home, your foundation bolting 1 process will be more extensive because the current foundation is nearly unconnected to the home, which can raise the price by up to 30%.
- Retrofitting a brick foundation isn’t recommended by most professionals because of the unsteady nature of bricks during an earthquake. If you have a brick foundation, you’ll likely need to replace it with a concrete version before earthquake modifications can be made. This typically costs $5-$8 per square foot.
Remodeling Terms Cheat Sheet
Definitions in laymen's terms, cost considerations, pictures and things you need to know.
See full cheat sheet.
1 Foundation bolting
: Strengthening a home's attachment to its foundation by adding a piece of wood called the sill, and reinforcing it with bolts
: (Also known as Mudsill) The lowest horizontal support of a building, typically made of wood, placed on the foundation, on the ground, or below ground level to protect the building slab and secure framing
3 Epoxy-set bolts
: A bolt set in concrete, brick or masonry, that is anchored into its hole using an epoxy adhesive to secure it
4 Cripple wall
: Short walls, less than a full story in height, that run between the foundation and the first floor, creating a crawl space. These must be properly braced to enable them to withstand an earthquake
: An engineered construction material manufactured from thin slices of wood glued together in alternating grain patterns for strength
: A naturally occurring heavy metal that is highly toxic to humans, and has been used in paint, gasoline, piping, and other applications
Cost to retrofit a home for earthquake protection varies greatly by region (and even by zipcode). To get free estimates from local contractors, please indicate yours.