Home Retrofit

A home that has been retrofitted is able to resist much greater earthquake forces and has a lower risk of being damaged. During an earthquake, the strength of a home is put to the test. Ground forces try to tear the home apart and in many cases, cause severe damage. If you live in an area prone to earthquakes, it’s important that the structural frame of your home is strong enough to absorb an earthquake’s energy . Fortunately, advances in structural engineering, lessons learned from past earthquakes and research performed by the scientific community have paved the way for the development of new construction techniques that better equip homes to withstand an earthquake. Local and regional building codes now require all new homes to meet these higher construction and safety standards. Since many existing homes were constructed prior to the development of these newer code requirements, a retrofit may be necessary to increase structural safety. A retrofit adds bracing and reinforcement to strengthen the critical connections within a home.

A home that has been retrofitted is able to resist much greater earthquake forces and has a lower risk of being damaged. Upgrading a home to the latest building code standards, however, is not always practical for most older homes. This type of upgrade would require the homeowner to hire a licensed structural engineer and a specialty contractor to perform a detailed structural evaluation. This evaluation would include the removal of many finish materials, such as sheetrock, stucco, siding, etc., to examine the construction of the home. Fortunately, there are less intrusive ways to retrofit older homes and improve their structural safety and performance during an earthquake.

FREE Home Retrofitting inspection: 818.612.1000

Do I Need to Retrofit My Home?

There are certain types of homes that are more likely to need a retrofit than others. A quick analysis of your home can help determine if your home fits that criteria.

1. Am I living in an area prone to earthquakes?
There are geographic areas that are considered high seismic regions. These seismic areas are based on the likelihood of an earthquake occurring and its severity. The easiest way to find out if you are living in a high seismic area is to call your local building department and ask if you are in Seismic Zone 3 or 4 (for California residents) or Seismic Design Category D, E or F. These designations are assigned to regions with high seismic potential.

2. Was my home built within the last 20 years?
As a general rule of thumb, homes built within the last 20 years were designed to conform to stricter building codes and will be better equipped to resist the force of an earthquake. Homes built prior to that timeframe are typically more vulnerable to earthquake damage.

3. Is my home built on a raised foundation?
If your house is not built directly on a concrete slab, chances are it’s built on a raised foundation. This means the home
was built on a system of posts, beams and “cripple walls” (cripple walls are short wood-framed walls running underneath
and around the perimeter of the house). These homes typically have crawl spaces underneath them. They are susceptible to damage because the supporting structure under the house may not have been built to resist seismic forces and thus is considered a weak area. Past earthquakes have shown these areas are highly suceptible to structural failures.

4. Is my home built on a hillside?
Homes built on a hillside typically have raised foundations and crawl spaces as those described above and can experience similar failures. However, these failures tend to be more severe because the posts and cripple walls supporting the home are built at different heights due to the uneven terrain.

5. Is there living space above my garage?
Garages are vulnerable areas in a house due to the large garage door opening. Because of this large opening, the narrow
walls on either side of the garage door must be designed to resist earthquake forces. This is extremely important if there is a living space above the garage because these rooms add weight that the garage must support. Current building codes require that these narrow walls be specially designed to resist earthquake forces. Older homes, however, typically did not address this issue and are more vulnerable to damage during an earthquake as shown in the illustration. If you live in an older home with a living space above the garage or on a hillside, you’ll need to consult with a licensed structural engineer for design solutions.

FREE Home Retrofitting inspection: 818.612.1000

I Know I Need to Retrofit My Home, How Do I Get Started?

Now that you have identified the areas of your home that may need reinforcing, this next section addresses how you can do the work yourself. Before you begin your retrofit project, you’ll need to determine whether or not your home has cripple walls. Cripple walls are the short wood-framed walls running underneath and around the perimeter of your house. These walls are constructed on top of the foundation and are generally 12 to 30 inches high, but can be as high as 12 feet when located on a hillside.

Start by answering the following questions:
• Does your house have a cripple wall between the foundation and floor framing?
• If your house has a cripple wall, how tall is it?
• If your house has a cripple wall, is the mudsill wider than the studs?

Based on your answers, you can then follow one of the retrofit scenarios listed below: