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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:
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.
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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)
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More than
250,000 homes in King County do not meet current earthquake safety codes.
In an area that is at a high risk for earthquakes, retrofit will protect a house from the
most serious potential damage, and is an investment that will pay
for itself many times over. If you are a long-term resident in this region,
retrofit is vital to keeping you, your family, and
your house safe in the years to come.
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
Retrofit stabilizes a building by reinforcing and bolting together its understructure.
A house's understructure is composed of four main parts: the foundation, the sill plate, the
pony wall, and the floor framing. Each of these components could endanger the rest of the house
if not properly secured.
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.
/back to retrofit
Floor Framing
Floors are supported by a parallel series
of wooden joists that range in size from 2x6 to 2x12.
In most homes, these joists are connected at the ends by a perpindicular board (called
the rim joist), which strengthens the network of boards. Older homes sometimes
lack this
beam, and plywood must be placed between the joists to increase their
strength and allow for bolting to the pony-wall or sill-plate. Floors that do
have a rim joist may still be in danger of being jolted from their understructure, since often the rim joist
is inadequately secured to the wall (or sill plate) beneath.
/back to retrofit
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—
A resource put together by
Seattle's Project Impact for anyone interested in having their 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.
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