about earthquake retrofit
Retrofit is a process in which a house is reinforced so that it will be more resistant to earthquakes. In the Seattle area, houses built before 1980 usually don't meet current safety codes, and are at risk of sustaining serious damage during an earthquake. In areas outside of Seattle, houses built before 1985 are likely to be at risk. At-risk houses have not been adequately bolted to their foundations, and may also have weak understructures that are incapable of withstanding the shear (side-to-side) forces of an earthquake.Buildings that aren't sufficiently enforced may be jolted from their foundations and even collapse in a serious earthquake, often causing irreparable damage. Nothing can completely eliminate earthquake-related damage, but retrofit significantly reduces extent of damage by strengthening a house's understructure and ensuring that it is securely anchored to its foundation. A typical retrofit will include the following measures, as outlined by Seattle's Project Impact:
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Home Bolt Down Steel bolts or special foundation plates are fastened to the house's sill plate (the plate that connects the concrete foundation to the pony wall) to anchor it to the foundation. Floor and Understructure Connection Steel framing clips are attached to the pony wall along the sill plate to bolt the two together. Increasing Shear Strength Sheets of half-inch plywood are nailed along the pony wall to increase its shear (horizontal) strength. Blocking Joists (the floor's supportive framing) are connected with plywood, if not already braced with a rim joist, so that they can be bolted to the pony wall (if the house has one) or directly to the sill plate. |
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Retrofit stabilizes the house by connecting and reinforcing its understructure, so that the house will be as secure as possible during an earthquake. At least one of these four basic measures is employed in any given retrofit, depending how secure or insecure the house already is. Usually all four are necessary. Every house is its own case, though, and many have special requirements. Even if you plan to do the retrofit yourself (see the related link), it's a good investment to have a professional inspect your home.
Contact A-FFIX LLC to schedule a free home inspection.
E-mail us, or call (206) 284-6226 (toll free from anywhere in the US 866-284-6226).
why should I retrofit?
If your house was built before 1980 and you live in an area as prone to earthquakes as Puget Sound, retrofit is an important part of ensuring the well-being of your home and family. Here are some reasons to go ahead and have your house retrofit:|
Retrofit brings a home up to current safety codes and significantly reduces
the damage it will sustain during an earthquake. Houses that are not secured properly may collapse or shake off of their foundations in a major earthquake, rendering them both unlivable and unsafe in the aftermath of a disaster. If a house is severely damaged, a family may be prevented from entering it even to claim possessions. 95% of houses that have been shaken from their foundations during an earthquake have to be demolished. Potential damages to a house not up to code in an earthquake are many times as expensive as the cost of retrofit. Loans for home retrofit are relatively easy to get and are often offered at a reduced interest rate. (See our financing link.) Earthquake insurance is not adequate protection against a severe quake. Insurance does nothing to keep you safe during the earthquake itself and may not provide for interim housing while your home is being repaired after the quake. Deductables for earthquake insurance policies can be as much as 10% of the house's value--$30,000 for a $300,000 home. A homeowner whose house has been wrecked by an earthquake must continue to make mortgage payments whether the home is habitable or not. Accomodations for people who have lost their homes in an area severely impacted by an earthquake are usually limited to schools, community centers, churches and tents. Of the 300,000 people displaced in Turkey by the massive August 1999 quake, more than 30,000 were still living in tents after a year. The devastating 1999 earthquake in Turkey was so devastating because most houses had not been brought up to the national safety standard. The houses that were up to code sustained only minor damage. No one should risk losing their house and home to an earthquake. |
 A house that has been jolted from its foundation  A house damaged in a quake  Collapsed apartment in 1999 Marmara, Turkey earthquake (photo Michel Bruneau, MCEER)  Another building destroyed in Turkey quake (photo Michel Bruneau, MCEER) |
Contact A-FFIX LLC to schedule a free home inspection.
E-mail us, or call (206) 284-6226 (toll free from anywhere in the US 866-284-6226).
how does A-FFIX handle earthquake retrofit?
A-FFIX LLC begins every earthquake retrofit with a home inspection and a detailed analysis. The home inspection is a standard service that we offer for free, in which we do a basic evaluation of the risks in your home and offer a ballpark estimate of the expense of the retrofit. The detailed analysis is an in-depth survey of the house's structure and will produce a specific calculation of expenses. We charge a flat sum for this service because the process is time-consuming, but we will deduct this amount from the total cost of the retrofit if you choose to use our services.Inspection
During the inspection, we:
Visually inspect the house's exterior to determine its roof type and build.
Work through the standard home retrofit checklist, checking the structural security of the house's interior, crawlspaces, basement and unfinished areas.
Assess any potential earthquake hazards within the house, such as bookshelves and large appliances, and suggest straps or mats to make them more earthquake-safe.
Interview the house's owner(s). We discuss the building, its date of construction and anything that may be unusual about it. Your house may not need retrofit if it is already structurally sound.
If, after the inspection, you feel ready to proceed with a retrofit —or would like more information about a potential retrofit— we will make a more detailed analysis of your house.
Analysis
During the analysis, we:
Take precise measurements of the basement floor plan and/or crawl spaces, which we will diagram and use to calculate the method and cost of retrofitting the house.
Draw up and present a formal estimate to the house's owner(s) within one week of the assessment, if the house fits within the Standard Earthquake Plan of the City of Seattle (i.e., it has a typical structure and can be retrofit normally). If the building is unusual and will require an atypical retrofit (for example, if parts of the foundation need to be replaced), our structural engineer will analyze the building and create a plan for retrofit with the homeowner's approval. The estimate will be presented once the engineer's plan is complete, usually within two weeks.
Once the formal estimate has been presented, it's up to you to decide whether you would like to employ us for your home retrofit. A retrofit can take anywhere from several days to several weeks to complete, depending on the house. A-FFIX LLC has retrofit a wide variety structurally challenging houses, and will always go the extra mile to ensure the safety of your home and family.
Contact A-FFIX LLC to schedule a free home inspection.
E-mail us, or call (206) 284-6226 (toll free from anywhere in the US 866-284-6226).
the understructure of a house
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Foundation
The foundation is a building's basic support. Most foundations are solid flats of concrete. A building will not be structurally secure in a serious earthquake unless the components of its understructure (the sill plate and/or pony wall) have been properly bolted to this concrete foundation. In the worst case scenario, an improperly secured house will be jarred off of its foundation in a severe earthquake. This damage is almost always irreparable. Some foundations are made of cinder blocks, hollow concrete blocks that generally haven't been reinforced to withstand the side-to-side (shear) motion of an earthquake. Cinder blocks can shift or collapse under shear stress, sending a house toppling. Some older homes may have brick foundations, which are particularly vulnerable because of mortar's instability. It is less expensive to have a foundation retrofit than to have it replaced— call us to learn more. Sill Plate The sill plate is the 2x4 or 2x6 wood flat that covers the concrete foundation and connects it to the pony wall (or, if the house doesn't have a pony wall, to the floor framing). If the sill plate hasn't been anchored to the foundation, it can become the weak point where a house can be jolted from its understructure and severely damaged. /back to retrofit |
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Pony Wall
A pony wall, also called a cripple wall, is a plywood-enforced wall that rests on top of the sill plate, supporting the floor framing and the rest of the house. The walls of a house's bottom floor (generally the basement) are usually pony walls. Many single-floor houses have no pony wall, and the sill plate connects directly to the floor framing instead.
The main weakness in a pony wall is a lack of shear (horizontal) support—it doesn't have enough plywood bracing to stabilize it against an eathquake's horizontal rocking. Even houses with some shear support may not have enough to be safe.
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Floor Framing
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Your house may have an unconventional understructure that doesn't match these descriptions. If so, it can still be retrofit, but the retrofit will require special engineering to ensure that the structure is reinforced correctly. A-FFIX has extensive experience working with unconventional homes, including houses with cracked or insubstantial foundations and deteriorated joist and beam structures. We are happy to share our expertise.
Contact A-FFIX LLC to schedule a free home inspection.
E-mail us, or call (206) 284-6226 (toll free from anywhere in the US 866-284-6226).
earthquake retrofit links
Some informative links related to retrofit.
Home Retrofit—
Retrofit Classes — Information on Project Impact's classes in retrofit for Northwest homeowners.
Retrofit Financing — Some information on financial resources for homeowners considering retrofit. Look under "Home Retrofit Accomplishments."
Tips for Hiring a Contractor — The Department of Labor and Industries's pointers for making your experience with a contractor as pleasant as possible.
Retrofit Training Materials — Training materials for contractors and inspectors; excellent information about house understructures and the retrofit process.
Project Impact's Retrofit Resources - More how-to information for home retrofit.