How Much Does It Cost to Retrofit a Home for Earthquake Protection?
If your home is located in an area known to be hit by earthquakes, you may want to consider having it seismically retrofitted to help protect it from serious damage in the event of an earthquake. Homes that were built prior to the 1970s were not constructed with the right type of technology or techniques to help protect them from earthquakes, and even some newer homes may have been built without the latest in protection techniques. This means that older homes should undergo retrofitting to brace and strengthen them to withstand an earthquake.
Earthquake retrofitting a house costs, on average, $3,000 to $7,000 with the average homeowner spending around $5,000 on retrofitting a standard 1,500 sq.ft. two-story home with cripple walls 1.
Earthquake Retrofitting
| Earthwuake retrofitting costs | |
|---|---|
| National average cost | $5,000 |
| Average range | $3,000-$7,000 |
| Minimum cost | $1,500 |
| Maximum cost | $10,000 |
In this guide
Cost Factors of Earthquake Retrofitting
Engineer Consultation
Retrofit Strategies
Retrofitting Techniques and Main Steps
Homes Without Cripple Walls
Soft Story Situations
Retrofitting Based on the Foundation
Labor Costs of Earthquake Retrofitting
Earthquake Retrofitting Materials
Enhancement and Improvement Costs
Additional Considerations
FAQ
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Earthquake Retrofitting Cost by Project Range
Why Is Earthquake Retrofitting So Important?
Even if your home has gone through an earthquake in the past with minimal damage, there is no way to predict exactly when and where the next earthquake will strike, or how much damage it could do. Older homes that have not been adequately bolted to their foundations could sustain hundreds of thousands of dollars worth of damage in the event of a major earthquake. This is because the home may actually separate from its foundation during seismic activity.
Most home interiors and upper portions actually come through earthquakes alright, with only superficial damage that can be easily repaired. But homes that are not secured to their foundations can have major structural issues following an earthquake, making them unsafe to enter or continue living in until they have been repaired.
By retrofitting your home, you are minimizing the damage that could occur with the next earthquake, ensuring that your home and family stay better protected, and minimizing recovery costs.
Cost Factors of Earthquake Retrofitting
There are a lot of factors that go into determining the cost of your retrofit. The age of your home is the first–the older the home, the more work that will need to be done to strengthen it. Your location will also play a role–homes located in areas on or near cliffs or water may require additional support. If your home has been hit in the past or if the area in question has been impacted by heavy earthquakes before, this can also play a role in determining your cost, as your home may need more work. Larger homes will also typically cost more to retrofit than smaller homes, as there is simply more work to be done.
Finally, the type of construction your home has may play a role. Homes with a cripple wall 1 will cost more to retrofit than homes without one.
Engineer Consultation
To determine the exact extent of the work that needs to be done, most companies will start the process with an engineer consultation. They’ll take a look at your home, where it’s located, what type of foundation and structure it has, and make a determination for the best way to proceed. Foundation bolting 2 is common, but it’s only one step for many homes, and an engineer can help determine what the best path will be.
Many companies will provide this service for a fee that will be recouped if you proceed with the work. For example, you may pay $500 for this initial service, but the final cost of the project will be $500 less, absorbing the fee.
Retrofit Strategies
Most retrofitting strategies are applied on a case-by-case basis, taking into consideration the type of structure and its current condition. Generally, there are several techniques that are done to retrofit a structure, but an apartment building will be tackled differently than a single-story home, while two-story structures may require a different strategy, depending on how they were each constructed.
For this reason, you may find that when you call about foundation bolting 2, you may be offered a different strategy. A few examples of this may include adding hold downs to shear walls to resist overturning if the home is top-heavy, and reinforcing a foundation with additional concrete prior to bolting.
Each home will have its own strategy mapped out, which is why it’s important to have an engineer work with the contractor at the start of the project.
Retrofitting Techniques and Main Steps
Keeping in mind that each structure is different, most homes will have a few different techniques done to help secure the home to the foundation.
There are some basic steps that most homes will need to have done. Keep in mind that some structures may benefit from more or fewer steps than this.
Foundation Bolting
This is the bare minimum piece of earthquake retrofitting: anchoring your home directly onto the foundation. This is what helps keep your home from sliding off the foundation and being damaged during an earthquake. This is sometimes known as anchor bolting and literally means that large bolts are sunk through the base of your home and into the foundation.
Anchoring to Mudsill
The cripple wall 1 of your home’s crawl space is anchored onto the mudsill 3 of your foundation. This is part of the foundation bolting 2 process, as the cripple wall 1 and mudsill 3 can both slide right off the foundation, so the mudsill 3, cripple wall 1, and the foundation all need to be bolted together for the best stability.
Cripple Wall Bracing
The cripple wall 1 itself needs to be reinforced and braced, usually with plywood 4. On its own, most older cripple walls 1 can not handle the movement that occurs during an earthquake, and that may lead 5 to collapse or to the home falling from the foundation. By bracing the cripple walls 1, it minimizes movement and ensures that the home is more secure.
Cripple Wall Anchoring to the Floor
It isn’t enough to bolt the cripple wall 1 to the foundation; it also needs to be bolted to the floor above. This is done through shear bolting, but may also involve creating a frame on the interior of the cripple wall 1, and bolting this to both the wall and to the floor above.
Shear Wall Reinforcing
Sometimes in top-heavy structures, such as an apartment above a garage, the shear walls themselves need extra reinforcement. This can be done on both the vertical and horizontal surfaces of the upper story, usually using steel grates, but can sometimes be done with additional stud reinforcement on the interior of the walls.
Cost
Keep in mind that there can be a range of costs for each of these steps, that not every step is always required, and that your project may have higher or lower costs for each one depending on multiple factors.
In the following table, you will find the average cost for each technique used on a 1,500 sq.ft. two-story home:
| Retrofit technique | Cost |
|---|---|
| Anchoring to mudsill 3 | $500 - $1,500 |
| Cripple wall 1 bracing | $500 - $1,500 |
| Cripple wall 1 bolting | $500 - $2,000 |
| Foundation bolting 2 | $1,000 - $3,000 |
| Shear wall reinforcement | $2,000 - $5,000 |
Homes Without Cripple Walls
Some homes do not have cripple walls 1, which can mean a lower cost for the overall project, as bracing and bolting of this section are not needed. However, the joists of the home will still need to be bolted to the mudsill 3 and to the foundation to help prevent the home from sliding off. This includes the floor joists, rim joists, and end joists. All of them need to be bolted to the mudsill 3 and foundation in order to secure the home. This is because homes without a cripple wall 1 are at more risk for damage than those that have them.
Soft Story Situations
Apartment buildings and multi-family homes have additional considerations in earthquake retrofitting. In this case, a “soft-story building” is considered any building tall enough that it would sway during an earthquake, causing cracks and weakening the walls and foundation.
In this situation, steel beams are usually used to reinforce the structure and prevent any swaying from occurring. The same foundation bolting 2 should occur, but inner reinforcement of the walls is also necessary to prevent structural damage.
Retrofitting Based on the Foundation
The foundation that your home is built on will play a role in retrofitting as well. Brick foundations cannot be reinforced and bolted the same way that a concrete foundation can. Complicating matters, some concrete foundations, too, are too old or too thin to bolt in their current condition. In this case, a hole is generally dug and additional concrete added to help strengthen the foundation before the bolting can occur.
| Foundation type | Recommended technique | Cost |
|---|---|---|
| Slab on grade 6 | Install anchor bolts to sill 3 plates | $500 - $1,500 |
| Brick | Test mortar 7 for strength Bolt bricks into sill 3 plate Add bracing to the interior of the brick wall | $2,000 - $7,000 |
| Footing 8 and stem wall | Bolt the stem wall to the foundation using foundation plates Add foundation anchors Brace the cripple walls 1 Anchor cripple walls 1 to the foundation with bolts Bolt house to cripple walls 1 and stem walls | $3,000 - $7,000 |
| Basement | Anchor home to the mudsill 3 Brace cripple walls 1 Bolt mudsill 3 to cripple walls 1 Attach cripple walls 1 to the foundation using foundation plates | $3,000 - $7,000 |
| Permanent wood | Install anchor bolts to sill 3 plates Reinforce walls with plywood 4 and bracing Install bolts through studs to wood foundation Pour concrete slab 9 and anchor to wood walls | $5,000 - $9,000 |
| Thin/old concrete | Excavate to sides of foundation and fill with new concrete Brace cripple walls 1 as needed Bolt foundation to sills 3 with foundation plates Bolt stem walls to the mudsill 3 | $5,000 - $9,000 |
Labor Costs of Earthquake Retrofitting
In most cases, professionals charge by the service being performed, rather than by the hour. This is because there can be a wide range of time required for a retrofit, depending on what’s found when the walls are opened. It’s not uncommon for a retrofit to take between a few days and a few weeks for the average home. From this end, it is not uncommon for the labor to cost up to 70% of the total for the project for major retrofits, especially those on a hillside, which can cost up to $10,000. For most homeowners, you can expect that out of the $5,000 total, you are paying at least $3,000 in labor, if not more.
Earthquake Retrofitting Materials
The materials used on each job may vary, but generally, you can expect to see the following:
| Material | Typical use | Cost |
|---|---|---|
| Wall bracing | Shear wall reinforcement Cripple wall 1 reinforcement | $2.50-$5.50 / sq.ft. |
| Plywood 4 | Cripple wall 1 reinforcement | $6-$10 / sheet |
| Framing straps and braces | Support for homes without cripple walls 1 Attaching cripple walls 1 to joists | $10-$60 / each |
| Epoxy-set foundation bolts 2 | Attaching cripple walls 1 to foundations Attaching mud 10 slips to cripple walls 1 Attaching cripple walls 1 to joists | $20-$60 / each |
| Foundation plate | Attaching cripple walls 1 to foundations | $40-$70 / each |
| Foundation brackets 11 | Attaching cripple walls 1 to foundations | $50-$75 / each |
Foundation anchors | Attaching cripple walls 1 to foundations | $50-$75 / each |
Enhancement and Improvement Costs
Seismic Review
If you are unsure of the risk to your property, you can opt to have a seismic review done of your area, which can tell you how you may be impacted. Keep in mind that it can be impossible to predict damage. A review can cost between $100 and $500, depending on the level 6 of detail.
Additional Considerations and Costs
- In most cases, earthquake retrofitting is not covered by insurance, but you may qualify for a lower insurance rate once it’s done.
- All professionals who work on earthquake retrofitting your home should be licensed and have a permit for the job. Make sure you follow up to confirm both.
- PACE financing may be available to you to help meet the costs of the retrofit. This is an affordable financing option that is available for upgrades that include energy efficiency and storm protection. This is not a loan, but a property assessment, that allows you to borrow the money based on the property you are updating at a low-interest rate. Speak to your contractor for more information.
- There are some DIY options available for retrofitting, including bracing your cripple walls 1 with plywood 4 and bolting your foundation. Keep in mind, however, that these retrofits may not be enough without an engineer to look over the project first.
- To prepare for an earthquake, make sure you secure heavy objects and appliances with brackets 11 or straps, prepare a survival kit with food and medical supplies, and keep it in a safe location in your home where you can take shelter during an earthquake. This may be in a doorway or a reinforced area of the home.
FAQ
- What does it mean to retrofit a home?
Retrofitting means making modifications to a home after it was built, usually to strengthen the structure or correct an issue that was apparent at the time of construction.
- How much does it cost to retrofit a mobile home?
Mobile homes would require a foundation for earthquake retrofit. If they have a foundation, then they are subject to most of the same costs as other homes, with costs starting at $3,000.
- Does my home need earthquake retrofit?
If your home was built prior to the 1970s, then yes, it most likely requires a retrofit.
- How long does it take to retrofit a house?
It can take anywhere from a few days to a few weeks, depending on the scope and level of work.
- How do you tell if your house is bolted to the foundation?
In many instances, the bolts will be visible, but you can call for an inspection to be sure.
- What magnitude earthquake can a house withstand?
This will depend on many factors, including the size, location, and age of the home, depth and proximity of the epicenter of the earthquake, and whether the house has been reinforced or retrofitted. Many existing homes in the United States can withstand earthquakes to a magnitude of 7.0 without significant damage.
Remodeling Terms Cheat Sheet
Definitions in laymen's terms, cost considerations, pictures and things you need to know.See full cheat sheet.
4 Plywood: An engineered construction material manufactured from thin slices of wood glued together in alternating grain patterns for strength
5 Lead: A naturally occurring heavy metal that is highly toxic to humans, and has been used in paint, gasoline, piping, and other applications
7 Mortar: A mixture of Portland cement or lime or a combination of both, sand, and water used to bind bricks, stones, and concrete masonry units together
8 Footing: A support for the foundation of a house that also helps prevent settling. It is typically made of concrete reinforced with rebar, but can also be made of masonry or brick. It is usually built under a heavier part of the house like a wall or column, to distribute the weight of the house over a larger area.
9 Concrete slab: A flat area of concrete that can be used for a variety of purposes, such as a patio or a driveway
11 Brackets: A support that projects outward from one surface to hold another surface to it, such as attaching a shelf to a wall or piece of furniture. Brackets can also be used to strengthen joins between two materials
How much does it cost to retrofit a home for earthquake protection in my city?
Cost to retrofit a home for earthquake protection varies greatly by region (and even by zip code). To get free estimates from local contractors, please indicate yours.
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