Seismic upgrades are also known as retrofitting a structure to prevent displacement as a result of an earthquake. The need for a seismic upgrade is defined in the California Building Code (CBC) as an existing building needing to conform to the seismic requirements of a newly built structure. Some of these requirements are identified by the changing use of an existing structure, increasing the occupancy, or storing combustible materials at the property. The CBC believes these types of changes intensify the use of the property, thus making it necessary to make seismic upgrades to the structure. The article will go over the benefits of making seismic upgrades to an existing structure.
The Benefits of Retrofitting
A few decades ago, the building codes in California did not have any set regulations on homes that would resist shaking or displacement associated with an earthquake. Many of the homes that were constructed during that time needed to be retrofitted to safeguard against these natural disasters. Some single-family residences were built before 1980 when building codes lacked seismic-related requirements, so they will definitely need some upgrades to withstand the seismic forces. As per a study done by a group of scientists in 2014, there is a major chance of a 6.7 magnitude earthquake in California. The predictive models used to make this determination can help people understand why they need to do seismic retrofitting.
Earthquake retrofitting decreases the risk of a home suffering irreversible damage in case of a seismic event. This work is considered a cheap solution to seismic improvements. Some of the seismic retrofitting projects can include bolting the foundation of the structure. This task costs a few thousand dollars, and it can be completed in a week. A homeowner can save hundreds of thousands of dollars by preventing major damage to the home.
Completing seismic retrofitting will increase a homeowner’s sense of safety. This ultimately reduces the chance of bodily harm for anyone in the home during a seismic event and decreases the chances of death. Additionally, retrofitting protects the property and belongings inside of the house.
Seismic retrofitting is a financial investment in the property. Losing a home due to a natural disaster can be devastating. By investing in the seismic retrofit, a homeowner is providing extra insurance and protection to their property. It is significantly less costly to retrofit a home than to repair a home that has been damaged by an earthquake.
Ultimately, retrofitting the home will ensure the home’s occupants have a place to live if a seismic event were to occur. Not being sure of where you can live after such a life-changing event can cause immense stress. By being proactive and retrofitting the home, you’re protecting your property and avoiding being left without a home if something were to happen.
Seismic Retrofit Design
Retrofitting a home is to make sure the foundation is not displaced when shaking due to an earthquake that takes place underneath the ground. Reinforcing the structure this way will reduce the risk of damage and allow the home’s inhabitants to shelter-in-place. Here is a list of some seismic upgrades that can be done:
- Brace existing cripple walls at the home’s foundation. Cripple walls are short walls that are situated at the foundation of a home, and they are used to support the floor and exterior walls. If these walls become damaged, they can cause these supports to be displaced, bringing the whole house down, so bracing these walls strengthens the structure by increasing the stability of the cripple walls. Also, the area known as the crawl space underneath the structure can be reinforced to resist earthquakes, much like the cripple wall bracing.
- Foundation bolting is just that – bolting the home to the foundation. This practice ensures the structure of the home does not become displaced from the foundation during a seismic event. Holes will be drilled through a sill plate into the foundation, and then anchor bolts will be installed into those holes. In order for this to be effective, the bolts must be properly installed through the plates.
- If the home has a brick chimney, there are some tactics that can be used to reinforce or strap down the chimney. Keep in mind the bricks of the chimney can fall through the flue system and become a deadly projectile during a seismic event.
- To secure the chimney, a layer of plywood on the roof can be added around the chimney.
- The upper part of the chimney can be replaced with metal to eliminate twisting during an earthquake.
- A diagonal steel brace can be added to the chimney.
- Lastly, if the chimney is not functional, adding a steel tube filled with concrete can help in reinforcing it.
- Reinforce exterior walls made of masonry. New anchorage and ties across the roof can secure the masonry. Additionally, the connections between the roof and the floor joists can be reinforced.
- Homes with living space over the garage are vulnerable to earthquake shaking. These walls can be reinforced. The garage door opening can also be retrofitted by adding plywood sheathing or steel panels to each side of the garage door.
- Homes in certain locations, such as hillsides or on posts or piers, can be more susceptible to land sliding or pier displacement during an earthquake. These homes need to have bracings to support the posts or columns.
- Installation of an emergency gas shut-off device will protect the home’s inhabitants in case of an earthquake. The local gas company should help with determining the necessity for an emergency turn-off.
How Much Does a Seismic Retrofit Cost?
Retrofitting a home can cost up to $7,000 depending on the size of the home, retrofitting technique, location of the home, etc. Homes located on hillsides, homes with basements, or living areas above the garage will be more costly to retrofit. If bolting is the only requirement for retrofitting a home, then it can cost as little as $3,000. The cost will ultimately need to come from a contractor after reviewing the engineer’s recommendations on the retrofitting project.
Hiring Professionals to do Seismic Upgrades
A civil engineer and structural engineer will be needed to make the recommendations on the seismic upgrade. Once the design is complete, a contractor will be needed to complete the project. Seismic retrofitting is common in California due to the increased risk of earthquakes, so the local building department will have some suggestions on how to get started.
Design Everest is a one-stop-shop firm located in California with expertise in seismic upgrade projects. Contact us to get a free quote and consultation today.
