How Much Does an Earthquake or Seismic Retrofit Cost?

What Is a Seismic Retrofit?

A seismic retrofit helps stop a home from sliding off its foundation during an earthquake. Seismic retrofits also reinforce walls, ceilings, and chimneys to minimize damage.

Most homes in earthquake-prone areas built before 1980 need a seismic retrofit, but even homeowners for newer houses should consider the cost for a home inspection. Earthquake retrofits are especially important for homeowners in western states like California, Oregon, and Washington—and may reduce your annual homeowners insurance costs.

To complete your home’s earthquake retrofit, you can use the following methods independently or together, depending on your home’s condition and architecture:

• Bolting foundations

• Bracing foundations with a cripple wall, then bolting

• Reinforcing shear walls

• Reinforcing or redoing brick chimneys

• Adding an automatic seismic gas shutoff valve

Seismic Retrofit Cost per Square Foot

On average, you’ll spend between $3 and $7 per square foot for a seismic retrofit. On the lower end, you can expect a simple universal foundation plate installation. On the higher end of the earthquake retrofit cost spectrum, you can expect more complicated work like building a cripple wall or installing plywood or shear walls.

Seismic Retrofit Costs by Task

Bracing and bolting walls costs anywhere from $550 to $7,000 or more, depending on how it’s done. The methods vary depending on the architecture of your home. Let’s explore four common retrofit methods, as well as a fifth task that’s important for any seismic retrofit:

Anchoring a Mudsill

Anchoring a mudsill costs between $1,000 and $3,000. This process places anchor bolts through the mudsill—also called a sill plate—and into the stem or cripple wall. This technique is common in homes with brick foundations or crawl spaces and is meant to prevent the wall and mudsill from slipping off the foundation.

Cripple Shear Wall Bracing

Bracing cripple shear walls costs between $1,000 and $2,500. This process uses plywood sheathing and 2-by-4 blocking to reinforce the cripple wall. Cripple walls are short walls that close off the crawl space in your home. Older homes are prone to collapsing during earthquakes when they aren’t braced.

Cripple Wall Bolting

Bolting cripple walls costs between $1,000 and $3,000. Instead of anchoring to a mudsill, the crawl space walls are bolted to the floor above. This process still involves bracing cripple walls.

Universal Foundation Plate

Universal foundation plate (UFP) retrofitting costs between $550 and $1,500. The plates alone go for about $20 each. This is the most basic earthquake retrofit you can do to your home.

Earthquake Valve Installation 

Installing an earthquake gas shutoff valve costs around $250 to $750, with most homeowners paying around $350. The four preceding tasks involve methods of bracing and bolting, but this task is separate and often required for home sales. Some cities even require and charge for inspections.

Earthquake gas shutoff valves themselves run from $100 to $250, or $500 to $1,500 or more for commercial-grade earthquake valves.

Seismic Retrofit Costs by Foundation Type

The foundation type upon which your home sits can affect the overall earthquake retrofit cost. Slab foundations are the most affordable for retrofitting (as low as $550), while brick, post and pier, and wood foundations can all lead to a seismic retrofit cost of $10,000 or more.

Basement Foundation Retrofit Cost

Except for older homes, areas with a lot of seismic activity don’t commonly have basements. Homes built on a basement foundation cost between $3,000 and $5,000 to seismic retrofit. 

Materials for a basement foundation earthquake retrofit include plywood, bolts, and metal wood connectors. The contractor will anchor the house to the basement for optimal earthquake protection.

Brick Foundation Retrofit Cost

The average seismic retrofit cost for a brick foundation starts as low as $2,000 but can easily surpass $10,000 if the bricks and mortar are in poor condition. The brick must be mortared to the mudsill, which then must be anchored to the house. The project will require more labor and materials if the mortar isn't properly connected to the mudsill.

Footing and Stem Wall Foundation Retrofit Cost

Earthquake retrofitting a house with a footing and stem wall foundation costs between $3,000 and $7,000. A house with a footing and stem wall foundation uses a wood-framed base floor filled with concrete. Because a local foundation installation contractor must install foundation plates beneath this concrete floor, it could involve high labor costs.

Post and Pier Foundation Retrofit Cost

An earthquake retrofit for a house on a post and pier foundation costs between $3,000 and $10,000 or more. A post and pier foundation is an older style of construction that uses spaced piers with posts attached to them. Instead of floor joists spanning the foundation (either to the mudsill or a stem or cripple wall), these regularly spaced posts hold up the home. Retrofitting a post and pier foundation requires tying the posts to the piers and then the house with T-straps or another anchoring material.

Slab Foundation Retrofit Cost

The earthquake retrofit cost for a home on a slab foundation can be as low as $550, though your expenses may reach $2,500. Houses built on slabs don’t have crawl spaces or cripple walls, meaning labor is minimal. The house merely needs to be anchored to the slab.

Wood Foundation Retrofit Cost

Retrofitting a house on a wood foundation is expensive, from $5,000 to $10,000 or more. Wood foundations aren’t ideal for seismic activity. If your home sits on a wood foundation in an earthquake-prone area, the contractor may recommend replacing portions or all of the foundation.

Seismic Retrofit Costs by House Type

In addition to the foundation, the house type can impact your overall earthquake retrofit costs. Below, we'll explore some more unique home types where retrofit costs may not align with the standard house type.

Mobile Home Earthquake Bracing Cost

An earthquake-resistant bracing or engineered tie-down system for a mobile home costs approximately $2,000 to $10,000. The systems use one of three methods:

• Primary support column (PSC) earthquake anchoring costs around $2,800–$9,200.

• An earthquake-resistant bracing system (ERBS) costs around $2,000–$4,000. These use anchors in the ground with tie-down straps.

• Pouring a slab foundation with footings runs around $6,000–$25,000. This isn't a common option but provides excellent protection.

Manufactured Homes Earthquake Retrofit Prices

Depending on the foundation type, manufacturers can use either a mobile home or traditional home strategy. To use home methods for bracing, you'll need a foundation or basement.

• Foundation installation costs around $4,080–$13,430.

• Installing a basement costs around $60,000–$150,000.

Soft Story Retrofit Cost

Retrofitting a soft story costs anywhere from $10,000 to $80,000. For apartment buildings, property owners can expect to pay $80,000 to $350,000 or more.

A soft story is any multistory building with a large opening where a shear wall for structural support would normally go. The most common example for residential homes is a second story over a garage or carport. You’ll need to reinforce the area around the garage doors and often the adjoining walls to carry more weight and make them more rigid.

Hillside House

Retrofitting a house on a hillside for seismic activity can increase the average earthquake retrofit price. Expect to pay anywhere from $7,000 to $20,000. Homes built into a hillside tend to have weaker support structures that can't withstand seismic activity, as well as a house built onto a flat area.

Seismic Retrofitting Costs Near You

You only need to consider a seismic retrofit if you live in an area prone to earthquakes, typically on the West Coast. Costs can vary depending on the city you live in.

Seismic Retrofit Cost Breakdown

We can break down the cost of a seismic retrofit into two main categories: labor and materials. Labor makes up the bulk of the cost, meaning a DIY retrofit could save you significant money. But the work is complex and can be dangerous—and you have to build to code—so it's typically better to hire a foundation professional.

Labor

Labor makes up anywhere from 60% to 90% of the total price of a retrofit. On average, you’ll spend 70% of the total on labor, or $2,330 to $5,330 for the average project.

The actual amount varies based on what your home needs. For example, if you only need bolting without plates or a new cripple wall, most of the price comes from labor. But if you need plates installed, a new knee wall, and sheathing, more money will go into the materials.

Materials 

Materials make up roughly 30%of the total seismic retrofit cost. Common material expenses include:

• Foundation plates: $20–$50 per plate

• Foundation anchors: $50–$100 per anchor

• Foundation brackets: $25–$75 per bracket

• Gas shutoff valve: $100–$250

• Plywood: $5–$10 per sheet

• Wall bracing: $2–$10 per square foot

DIY Retrofitting Costs vs. Hiring a Pro

If you understand the code requirements for a retrofit, a DIY install might save you 70% of the total earthquake retrofit cost. But even if you decide to do this project yourself, it's best to familiarize yourself with the codes and engineering requirements. Find a local structural engineer to inspect your property and recommend reinforcements.

Hire a professional for quick work that meets or exceeds code requirements and gives you peace of mind from earthquake damage. Repairing a home that has slid off its foundation costs tens of thousands of dollars. For a fraction of the price, find a local foundation repair contractor, with typical foundation repair costs running from $2,150 to $7,550.

FAQs

How do I retrofit my house for earthquakes?

To retrofit your house for an earthquake, you or a foundation pro must secure your home's walls to the foundation or the floor. You might also consider reinforcing shear walls and chimneys. Ultimately, the method of retrofitting your house can vary based on your foundation and house type.

Does my home need an earthquake retrofit?

Only a pro can tell you if your home needs a seismic retrofit, but most homes built before 1980 in an earthquake zone tend to need one. If you live in a newer home or don't live in an earthquake zone, you probably don't need a retrofit—but it never hurts to get an inspection. While the cost of a seismic retrofit may seem daunting, remember that the cost to repair a house after earthquake damage is significantly more, sometimes reaching $30,000.

How do you tell if your house is bolted to the foundation?

If you're comfortable looking under your house, you can see the bolts sticking through the sill plate, or you may see universal foundation plates connecting the wood to the foundation. If you can't tell if your house is bolted to the foundation, find a local home inspector to look for you.

How effective are earthquake retrofits?

Properly retrofitted homes are much stronger against earthquakes. A seismic retrofit could keep your family safe in the event of an earthquake and prevent major and costly damage to your home. You may even see your homeowners insurance premium drop when you get an earthquake retrofit because insurance companies know how effective they are.

Does seismic retrofit increase the home value?

A seismic retrofit should add value to your home if you live in an area prone to earthquakes, like California, Oregon, and Washington. If you have recently retrofitted your home for earthquakes, consider hiring a local home appraiser to reassess the value of your home.