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Retrofit Overview

Retrofit is the process of bolting together and strengthening a building's understructure so that it is betetr able to resist earthquakes. Recently constructed houses, if built according to code, have the structural strength they need to withstand the side-to-side (shear) force of an earthquake. But homes built before 1980 (in the Seattle area) or 1985 (in the wider Puget Sound region) lack many of the basic components of structural strength that are needed to stay strong during an earthquake:

• A sill plate that's bolted or attached with plates to the foundation
• Pony walls that are reinforced with shear paneling
• First-floor floorboards (joists) that have been braced and connected to the rest of the understructure

In 1965, the state of Washington reformed Uniform Building Codes to require that new structures be bolted to their foundations. Past earthquakes have shown time and again that houses that aren't bolted to their foundations are vulnerable to dramatic structural damage-- jolting completely off their foundations. This kind of structural damage can't be repaired, meaning that houses that have been disconnected from their foundations have to be demolished.

In 1975, the building code in Washington state was reformed again to require pony walls (the walls that connect a house's foundation to its first floor) to be strengthened with shear paneling-- plywood flats that are attached to the wall with a special nailing pattern. Without strong pony walls, a house can cave in on itself as walls give under a quake's shear (side-to-side) pressure. In the years following 1975, building codes have become even more stringent.

Houses that were built before the building codes were enforced (about five years after the code was revised in Seattle and ten years after in other parts of the state) are likely to be missing these important elements of structural strength.

Your house could also be at risk if:

• Unpermitted work (often remodeling) has been done to it-- this work has not been approved by inspectors and often doesn't meet building codes
• Parts of the understructure have deteroriated due to leaking pipes, exposure to the elements, or insect infestations
• Structural elements in your home have been built to meet current building codes, but the rest of the building doesn't meet code. This can actually put your home at greater risk, because greater strength in just one section of the home will decrease your house's structural "give" (its ability to accomodate seismic motion) without increasing its overall strength

Retrofit is the process of adding these elements of structural strength to houses to give them the best chance of surviving an earthquake. If your house is at risk, consider scheduling a free home inspection to have an experienced professional assess the risks in your home.

House Understructure 101

Foundation

The foundation of a building is its basic source of support. Most foundations are flats of concrete with raised perimeters that support the building.

Many older houses have nonstandard foundation types. Cinder block foundations are made of hollow cinderblocks that have been cemented together using mortar. Pier-and-post or car-decking foundations are made of connected wooden posts that have been embedded in a concrete pier. Some foundations are flats of brick. These foundation types have less shear strength (resistance to side-to-side motion) than standard concrete foundations do, and will need specialized structural improvements to be retrofit.

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. In homes that have been built up to code, the sill plate will be bolted to the foundation.

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 flooring and the rest of the house. Single-floor homes and homes without a basement don't have pony walls- the sill plate connects directly to the floor framing.

Crawlspace

A crawlspace is the narrow area between the foundation and the flooring in a house that doesn't have a basement.

Floor Framing (Joists)

The floor framing is a series of wooden joists, or boards, that range in size from 2"x6" to 2"x12" and run parallel beneath the floor, providing it with support. In most homes, joists are connected on either end by a perpindicular board (the rim joist or rim board) that increases the strength of the network of joists.

Elements of Retrofit

Bolting the Foundation

Steel bolts or special foundation plates are used to connect the sill plate to the foundation. Bolts are used to make this connection if the house has a pony wall (a basement wall between the foundation and the first floor). Foundation plates are used if the home has a full-height foundation or a crawlspace and the first floor of the home must be connected directly to the foudnation.

If the foundation is cracked, cracks are filled in with epoxy to restore the foundation's structural strength.

If the house has an unconventional foundation, special measures have to be taken to secure it, since these types of foundations have less shear strength and interact with the understructure of the home differently than concrete foundations do. For post-and-pier or car-decking foundations, each post is connected with metal plates to its concrete base (the pier) and the beam it supports. The parallel beams that the posts support are braced with a long perpindicular piece of lumber similar to a rim board.

Brick foundations, which are used in some turn-of-the-century homes, are especially difficult to retrofit because of their structural instability- the mortar between the bricks can crumble under strong seismic pressure, causing the foundation to crumble. During retrofit, brick foundations are encased in concrete, giving them the structural strength of a concrete foundation.

Connecting the Floor and the Understructure

Framing clips are used to connect the pony wall (or, if the home doesn't have one, the sill plate) to the floor framing.

Increasing Shear Strength

Sheets of half-inch plywood are nailed along the pony wall with a special nailing pattern to increase shear (horizontal) strength. If the pony wall is higher than 48", anchors are also installed along the bottom edges of the wall to provide further reinforcement.

Blocking

If the joists haven't already been braced with a rim joist (a long piece of lumber backing the parallel joists), one is added so that the floor framing can be bolted to the pony wall, if the house has one, or to the sill plate.

Why Should I Have My House 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 be shaken off of their foundations during a major earthquake, making them inaccessible and uninhabitable in the aftermath of a disaster. If a house is severely damaged, a family may be prohibited 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 more expensive than the cost of retrofit.

Loans for home retrofit are relatively easy to get and are often offered at a reduced interest rate.

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.

How Does A-FFIX Handle 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 allow us to calculate expenses more exactly. We charge a flat sum for a detailed analysis because the process is time-consuming, but we will deduct this fee 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.

Earthquake Retrofit Links

Home Retrofit & Free Retrofit Classes— Information from the City of Seattle about home retrofit and about free retrofit classes for homeowners, which are offered by the City every month.

Hiring Contractors for Home Retrofit —The City of Seattle's tips for hiring contractors.

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.

• retrofit
• securing possessions
• windowfilm
• preparation
• gas shut-off
• about A-FFIX
• links
• home