Revised 3/6/2016
Jointly Produced by:
SEAU/USSC
Structural Engineers Association
of Utah & The Utah Seismic
Safety Commission
EXECUTIVE SUMMARY
To be provided by Barry Welliver
WHITE PAPER 06-2008
Revised 3/6/2016
TABLE OF CONTENTS
1. Introduction
2. Today’s Situation
2.1 Earthquake risk
2.2 Quantity and type of URM buildings
2.3 Performance of URM buildings in earthquakes
2.4 Output from earthquake loss model (HAZUS)
3. How Did We Get Here?
4. Available Options
4.1 Code mandated upgrades
4.2 Voluntary upgrades
4.3 Incremental rehabilitation
5. Benefits
5.1 Reduction of earthquake induced losses
5.2 More rapid recovery from seismic event
5.3 Increased value
5.4 Decreased insurance rates
5.5 Historic preservation
6. Potential Costs
6.1 Primary costs
6.2 Additional costs
7. Recommendations
7.1 Mandatory or directed programs
7.2 Financial incentives
7.3 Considerations for historic buildings
Revised 3/6/2016
1. Introduction
To be provided by Barry Welliver
Revised 3/6/2016
2. Today’s Situation
2.1 Earthquake Risk
Utah is considered to be in a high seismic area and likely to experience a large earthquake.
Since 1850, at least 27 independent earthquakes of magnitude 5.0 and larger have occurred in
the Utah region. Seismologists predict that the Wasatch fault has the potential of creating an
earthquake measuring over 7.0 on the Richter Scale.
Earthquakes are caused when stress within the Earth builds up, causing an area of rock to
“snap” along a fault. This breaking causes a release of energy which is measured by how much
ground shaking occurs. The Richter Scale measures the intensity of this “shaking” by using a
seismograph. The seismograph measures the height of the waves produced by the earthquake.
It is an absolute scale; wherever an earthquake is recorded, it will measure the same on the
Richter scale. Each 1-unit increase in the Richter Scale corresponds to a 32-fold increase in
energy release and a 10-fold increase in ground shaking. Table 1 illustrates the energy created
from different magnitude earthquakes measured using the Richter Scale.
Magnitude
-1.5
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
Table 1. Richter Scale vs. Earthquake Energy
TNT for Seismic Energy Equivalence
Energy Yield
6 ounces
Breaking a rock on a lab table
30 lbs
A two-ton truck traveling 75 mph
1 ton
A large quarry or mine blast
29 tons
Smallest earthquake commonly felt
1,000 tons
A small nuclear weapon
32,000 tons
1 million tons
32 million tons
1989 Loma Prieta Earthquake (7.1)
1 billion tons
1906 San Francisco Earthquake (8.3)
32 billion tons
Largest Recorded Earthquake (9.5)
The magnitude scale compares amplitudes of waves on a seismogram, not the STRENGTH
(energy) of the quakes. So, a magnitude 7.0 is 100 times bigger than a 5.0 quake as measured
on seismograms, but the 7.0 quake is about 1,020 times STRONGER than the 5.0! Since it is
really the energy or strength that knocks down buildings, this is really the more important
comparison. This means that it would take about 1,020 quakes of magnitude 5.0 to equal the
energy released by one magnitude 7.0 event.
This explains why big quakes are so much more devastating than small ones. The amplitude
("size") differences are big enough, but the energy ("strength") differences are huge. The
amplitude numbers are neater and a little easier to explain, which is why those are used more
often in publications. But it's the energy that does the damage.
Many have asked how much damage would be caused by a large earthquake on the Wasatch
Front? If the earthquake were to occur on a central part of the Wasatch fault, Utah should
expect damage to buildings to exceed $24 billion in Davis, Salt Lake, Utah and Weber counties.
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This may only represent 20% of the total economic loss. Unreinforced masonry buildings (for
example, brick homes built before 1974) are particularly vulnerable to ground shaking and are
expected to account for 75% of the building losses. Surface faulting and ground failures due to
shaking during a large earthquake will cause major disruption of lifelines (utilities, water, sewer),
transportation systems (highways, bridges, airports, railways), and communication systems.
2.2 Quantity and Type of URM Buildings
Unreinforced masonry buildings (URMs) are defined as those buildings consisting of clay or
concrete bricks or other masonry units with little or no steel reinforcing. The reason URM
buildings are so vulnerable to earthquake damage is the brittle nature of the brick and mortar.
Under cyclic loads the mortar may crumble and lose strength allowing the brick to separate and
fall. In cases where these bricks are the only support for roof and floor framing, catastrophic
collapse becomes more likely.
The early Utah pioneers used unreinforced brick extensively in high rise buildings, schools,
business offices, residences, etc. It is estimated that over 185,000 URM buildings are located
within Davis, Weber, Salt Lake, and Utah Counties. These types of buildings are prevalent in
nearly every rural town throughout the State of Utah. In many communities most of their
business district consists of URM buildings. A loss of these buildings could be economically
disastrous for a small community.
Families living in URM homes also face many dangers. The beauty and historic value of old
residences draw many home owners to these types of buildings, yet there is a sleeping monster
living within the walls of the home. This monster (URM bearing walls) will be awakened in an
earthquake.
2.3 Performance of URM Buildings in Earthquakes
Since the first settlers arrived in the Great Salt Lake Valley there have been approximately 27
earthquakes in Utah measuring over 5.0 on the Richter scale. The largest measured earthquake
was a 6.6 which occurred in 1934 near Kosmo, Utah. The following history provides a brief
description of how these earthquakes affected Utah’s communities and their infrastructure.
Ogden
Three distinct shocks rocked the Ogden area on July 18, 1894 with the largest measuring
5.0. Walls cracked and dishes were shaken from tables. Many people were frightened
during the violent motion.
The area around Ogden was strongly shaken on May 13, 1914 measuring 5.5. Windows
were broken and chimneys thrown down in Ogden; near panic was reported at Central
Junior High School. Dishes rattled and furniture moved at Farmington.
Santaquin
A 5.0 earthquake occurred on August 1, 1900, near Santaquin. An adobe house was split
in two and people were thrown from their beds. A chimney was damaged, dishes were
broken, and some plaster fell at Goshen. There were additional reports that the deep
shafts of a mine were shifted so that the cage could not be operated.
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Richfield
On November 13, 1901, a strong earthquake measuring 6.5 caused extensive damage
from Parowan to Richfield. Brick buildings and many chimneys were damaged; some
rockslides were reported near Beaver. Earth cracks with the ejection of water and sand
were reported; in addition, some creeks increased their flow.
After several weeks of preliminary tremors, two strong earthquakes about 12 hours apart
shook Elsinore, Monroe, and Richfield on September 29, 1921. The first shock, at 7:12
a.m., measured 6.0 and lasted 7 to 10 seconds. It threw down scores of chimneys, tore
plaster from ceilings, and fractured walls at Elsinore. In addition, gables of houses were
thrown out and the foundation of a new school sank one foot, leaving gaps between the
walls and the roof. Total damage was estimated at $100,000. A number of brick and
stone buildings were rendered uninhabitable by the 8:32 a.m. earthquake. The Monroe
City Hall, built of rock, was severely damaged. Large rock falls were caused on both sides
of the Sevier Valley.
St. George
Considerable damage resulted at Pine Valley, St. George, and Santa Clara from an 6.0
earthquake on November 17, 1902. Chimneys were destroyed at Pine Valley and Santa
Clara; additional damage occurred at Pinto and Toquerville.
Tremonton
A series of 30 to 60 earthquakes were reported in the vicinity of Garland and Tremonton
between October and December 1909. Some of the shocks were strong enough to throw
down chimneys.
Salt Lake City
A May 22, 1910, a 5.5 earthquake damaged many chimneys at Salt Lake City and several
old buildings. Two aftershocks of less intensity were felt.
Kosmo
On March 12, 1934, at 8:06 a.m., an earthquake occurred near Kosmo, on the north shore
of Great Salt Lake. This tremor, which measured magnitude 6.6, could have caused great
damage in a densely populated area. Because of the sparse settlement in the region there
was very little damage - mostly demolished chimneys and cracked walls in poorly
constructed buildings. Two deaths, however, were attributed to the shock. Considerable
faulting occurred in the epicentral region. Precise leveling revealed that areas sank to
depths up to 390 millimeters. The onset of the shock was abrupt. There were no
foreshocks, but aftershocks continued for 2 days; only one, at 11:20 a.m. on the same day,
was outstanding (magnitude 6.0). There was moderate damage over a broad area,
including Salt Lake City, where plaster fell. All chimneys fell in Kosmo and Monument;
fissures, holes, cracks, and springs appeared in connection with a belt of fractures at least
8 kilometers long.
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Cache Valley
Damages estimated at $1 million resulted from an August 30, 1962, shock in the East
Valley fault zone. The magnitude 5.7 earthquake caused significant damage at Franklin,
Lewiston, Logan, Preston, and Richmond. Cache County was designated a disaster region
by the Small Business Administration. The greatest damage occurred at Richmond where
at least nine houses were declared unsafe for occupancy, one church was damaged
beyond repair, numerous houses lost walls, and 75 percent of the older brick chimneys
fell. At Logan, principal building damage was cracked and twisted walls. Brick and timber
fell through a church roof. At Lewiston, one brick wall fell and many chimneys were
damaged. A sugar refinery near Lewiston sustained major damage when large pieces of
cement coping fell, penetrating lower-level roofs. Four schools in Cache County were
seriously damaged.
Marysvale
On October 4, 1967, a magnitude 5.2 earthquake caused damage in the Marysvale area.
Ceilings and walls cracked in numerous houses in Marysvale (VII). About 1 mile north of
Marysvale, well water was badly muddied for 24 hours. At Koosharem, chimneys and
plaster cracked. Chimneys were partially knocked down at Joseph.
Abridged from Earthquake Information Bulletin, Volume 9, Number 4, July - August 1977, by
Carl A. von Hake.
The following is a list of significant earthquakes which occurred in regions where a significant
number of URM buildings exited at the time of the earthquake. These quakes portray how
devastating a large earthquake can be in a well-populated region.
Peru
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An 8.0-magnitude earthquake struck on the evening of August 15, 2007 at 6:41, just off
the coast of Peru. The province of Ica was the most damaged, but even in Lima, 150km
(95 miles) from the epicenter, people stood trembling on the streets as buildings around
them shook. Severe aftershocks continued into Thursday morning, the strongest of which
measures 6.3. Pisco's mayor says 200 people are buried in the rubble of a church which
collapsed during mass. In Chincha, about 200 people wait outside a badly damaged
hospital, fearing it might collapse. Juan Mendoza, mayor of Pisco, told a radio station that
"the dead are scattered by the dozens on the streets". He estimated that 70% of his
coastal city was in ruins. "We don't have lights, water, or communications. Most houses
have fallen, churches, stores, hotels, everything is destroyed," he said.
(BBC news report)
San Francisco, CA
The California earthquake of April 18, 1906 ranks as one of the most significant
earthquakes of all time. Today, its importance comes more from the wealth of scientific
knowledge derived from it than from its sheer size. Measuring 7.9 on the Richter Scale,
this earthquake devastated the Bay area. Buildings crumbled, fires were ignited, and lives
were lost.
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Turkey
The most powerful earthquake to hit Turkey left at least 1,000 people dead. The 1999
earthquake measuring 6.7 on the Richter scale struck the industrialized town of Izmit in
western Turkey at just after 3:00 am on Tuesday local time. Many residents of the heavily
populated town were asleep in bed and had no chance of escape. Few of Izmit's buildings
were built to withstand earthquakes and whole districts collapsed. Buildings were also
destroyed in Turkey's largest city, Istanbul, about 50 miles (80 km) north west of Izmit.
2.4 Output from Earthquake Loss Model (HAZUS)
In 2004, the Utah Geological Survey released a special study, ”Earthquake-Hazards Scenario for
a M7 Earthquake on the Salt Lake City Segment of the Wasatch Fault Zone, Utah”. The purpose
of the report is to discuss and map geologic hazards that may result from this scenario
earthquake. The geologic hazard maps coupled with data on the built environment will provide
a basis for a better understanding of estimated losses.
The geologic maps developed for this scenario include, peak horizontal acceleration (ground
shaking), liquefaction (lateral spreading and settlement), landslide (wet and dry conditions),
tectonic-subsidence hazard.
Based on the 2000 census, 1.7 million people, or over 70% of the state population, would be
affected from this Salt Lake City Segment earthquake. This area includes nine counties as well
as the cities of Ogden and Provo. The disruption of basic services, the damage to the built
environment, and the number of casualties, can be quantified by using a loss-estimation model,
HAZUS. HAZUS stands for Hazards US and is a software product created and developed by the
Federal Emergency Management Agency, FEMA. HAZUS can generate estimates of losses due to
geologic effects as well as losses by building types. It can provide emergency planners, county
emergency managers, first responders, and state and local government officials with the
number of fire starts, amount of debris generated, number of shelters that will be needed, cost
to repair or replacement of damage buildings, and damage to infrastructure and critical
facilities.
Based on county assessor data, there are over 185,000 URMs in the nine county scenario region.
HAZUS suggests that nearly half of these structures will be substantially damaged in the scenario
earthquake. Building-related losses exceed $42.6 billion which includes structural and
nonstructural damage. Losses for URMs will constitute roughly one-third of the building-related
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losses. HAZUS estimates that daytime Level 3 and Level 4 casualties from URMs could reach
8800. A Level 3 casualty is a life-threatening injury and a Level 4 casualty is a fatality.
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3. How Did We Get Here?
As discussed in earlier sections of this paper, Utah has a relatively large inventory of URM
buildings as compared to other states with similar or greater risk of a catastrophic seismic event.
The use of masonry in construction in Utah has varied significantly from the early 1850’s when
the early settlers began to build permanent structures to the present. All masonry construction
prior to the adoption and implementation of the 1973 UBC in Utah with its new requirements
for seismic resistance would be considered to be URM, unless documented otherwise.
There are a number of reasons why there is such a large inventory of URM buildings in Utah.
The early settlers came from New England and northern Europe. Their building traditions,
knowledge and expertise were based on masonry construction. The Wasatch Front, where the
majority of the early concentrated construction occurred, was characterized by scarce lumber
resources, plentiful clay, plentiful stone, and adequate limestone to create mortar. In addition,
the early settlers that were building permanent structures had immigrated and concentrated in
this area due to their religious faith for the most part. The religious leaders emphasized that the
settlers must build permanent structures out of high quality materials to last into the future.
Early on, the religious leaders also emphasized the need for the new communities to be
independent and self-sufficient, minimizing the amount of imported construction materials.
Constructing with locally produced brick addressed both of those concerns.
These early construction techniques and materials set the standard which continued for the
construction of the preponderance of the existing URM inventory built from 1890’s to 1930’s. In
the early 1900’s the brick fabrication became more consolidated with a few major fabricators,
but they still used the local clays and masonry was still a viable construction material. After
World War II, there was a change in the fabrication equipment and processes, which required a
higher quality clay than was locally available. Fabricators began to import clay from other
states. This change made the cost of the finished product increase. As costs of brick went up,
construction techniques changed. The use of masonry began to be limited to veneer vs. solid
wall. In the 70’s and 80’s, vinyl and aluminum siding became the more economical choice and
even less masonry was used in construction.
While these URM structures were constructed before there was a knowledge of the earthquake
risk in our state, the buildings were built to last having already had an 80- to over 100-year life
span. If these buildings were to be seismically retrofitted and have normal maintenance
performed, they would be expected to last another 100 years or more. For many decades, older
homes and businesses were demolished and rebuilt utilizing the new construction codes. Even
though the new construction is designed to meet the current seismic requirements, the new
construction techniques and materials do not have the expected life span of the existing
buildings in many cases. However, the demand for preserving safe and well maintained existing
buildings is anticipated to increase. The decision to demolish in the past was typically driven by
economic concerns. Now other considerations like reducing waste, construction/demolition
related environmental issues, protecting scarce resources, and minimizing the energy put into
fabricating new building material are included in the decision making process.
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4. Available Options
4.1 Code Mandated Upgrades
The State of Utah currently adopts the 2006 International Building Code (IBC) and 2006
International Residential Code (IRC) for the design of buildings. These codes mandate that an
existing building undergoing a significant addition, alteration or repair meet the seismic
requirements for a new structure1 (IBC 3403 & IRC R102.7.1). A “significant” alteration or
addition would be one that causes any of the existing structural elements to be decreased in
capacity by 5-10% or more or that increase the force to any structural element by 5-10% or
more.
As an example, let’s consider the small URM residence shown in Figure 1. The home owner
wishes to add a small addition onto the back of the house to enlarge the kitchen area and add a
covered porch. To open up the kitchen area a good portion of the back wall will be removed.
Because more than 5% of the back wall is removed, the IBC mandates that a seismic analysis of
the entire residence be performed, not just for the addition.
Figure 1. Addition to URM Residence
The State of Utah also requires existing buildings which undergo a “change of use” to meet the
seismic requirements for a new building when the occupant load is increased by 100% or more3
(Section 3406.4 of the Utah Amended Code). An example of this would be when an existing onestory office building (1-occupant per 100ft2) is converted to retail (1-occupant per 30ft2).
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Starting January 1, 2007, the State of Utah began allowing jurisdictions to adopt the 2006
International Existing Building Code (IEBC). The IEBC provides the designer with several options
for analyzing existing buildings. While the IEBC provides the designer with flexibility, it also
provides a benefit to the building owner by sometimes only requiring existing buildings to be
checked for 75% of the seismic forces required for new buildings2 (IEBC 807.5.2 and 506.1.1.3).
Although the buildings may be designed to this lower force level, the minimum code IBC code
requirements for safeguarding the public are still met. The IEBC provides a win-win approach for
the designer, building owner, and local building department.
The State of Utah currently mandates that all buildings constructed prior to 1975 be evaluated
by a licensed engineer when undergoing reroofing or alteration of a roof appendage. This
evaluation requires that applicable parapets and other roof appendages be seismically braced. It
also requires that wall anchors be installed to tie the roof deck to the walls if necessary.
In summary, existing buildings which undergo significant additions, alterations, repairs or a
change of use may be required to provide a seismic analysis showing that they comply with the
seismic requirements for a new building. Unfortunately, due to the brittle nature of URM
construction, and the weight of these buildings, it is virtually impossible for a URM building to
meet the seismic requirements of either the IBC or the IEBC without significant improvements.
4.2 Voluntary Upgrades
In 1996, the Earthquake Preparedness Information Center (EPICENTER) hired a local engineering
firm to develop “The Utah Guide for the Seismic Improvement of Unreinforced Masonry
Dwellings”. This guide was intended to describe to home owners and contractors alike the
potential dangers of URM residences and to help them understand how they can improve their
seismic performance. The guide discusses typical features of URM construction and portrays
typical deficiencies of several “model” home types. Several figures are provided to show home
owners what improvements can be made to the existing structural elements to improve the
buildings overall seismic performance. This guide is available online at www.seau.org.
4.3 Incremental Rehabilitation
Seismic rehabilitation of existing buildings can be expensive and disruptive. These two factors
are frequently cited when building owners are faced with decisions about how to improve the
seismic safety of their structures. Often the process is conceived as an effort of overwhelming
proportions and the decision to forego improvements seems to be the only choice available.
There is an alternative however which has been promoted by the Federal Emergency
Management Agency (FEMA) termed Incremental Seismic Rehabilitation (ISR). This new concept
is based on the hypothesis that seismic improvements of existing buildings would be more
readily initiated if there were a way to reduce the initial costs and the disturbance to a building’s
occupants during the process.
Incremental seismic rehabilitation is a technique which seismically strengthens a building
through a series of stages that are coordinated with regular building maintenance and capital
improvement projects. This approach helps reduce both the costs and disruption to building
operations by tackling the improvements over an extended timeframe. Through careful
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planning, engineering and commitment to full implementation ISR will ultimately attain the full
damage reduction benefits of the more disruptive single-stage rehabilitation.
URM buildings are excellent candidates for the ISR approach since there are significant benefits
to be achieved by making improvements during re-roofing and remodeling a structure. Some of
the most significant upgrades to the seismic deficiencies of URMs include making attachments
of the heavy walls to the roof and floor(s) and bracing brick chimneys. When initiated during
normal maintenance or planned improvements, these projects are very cost effective.
The philosophy of ISR is that beginning down the road toward seismic safety is worthwhile. The
“do all or do nothing” approach extends the period of seismic vulnerability and continues the
gamble that an earthquake will not occur anytime soon. Incrementally improving a building can
be a difference maker when evaluating risk and should be considered a viable alternative.
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5. Benefits
5.1 Reduction in Earthquake Induced Losses
What benefits could be gained by retrofitting URMs? Building-related losses from the M7 Salt
Lake City Segment scenario earthquake are over $42.6 billion. Roughly a third of the losses,
$14.2 billion, are attributed to URMs. Retrofitting these structures may save them from
demolition, however retrofitting URMs has been shown to be effective in improving the lifesafety potential of these structures. The 1994 M6.7 Northridge (California) and the 2001 M6.8
Nisqually (Seattle) earthquakes illustrated that retrofitted URMs performed better than nonretrofitted URMs. The picture below shows some of the damage that occurred to URMs from
the Nisqually earthquake. Next to the damaged URM is a retrofitted one that shows little
damage resulting from this quake.
A substantial number of small businesses are located in URM structures. One reason small
businesses are located in these structures is because of lower costs to rent or own. HAZUS
results suggest that the more significant issue with URM buildings is not regards to their failure
but with the non-structural components, contents, and inventory located inside these
structures. The scenario earthquake analysis from HAZUS shows that for every dollar lost to
structural damage there are 5 dollars lost to non-structural and content damage and inventory
losses. Couple these non-structural losses with structural losses from URMs and a picture is
painted of businesses unable to recover after the earthquake.
There are also a significant number of two, three, and four story apartments in the downtown
area of Salt Lake City and most of the larger communities along the Wasatch Front. An analysis
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of HAZUS reveals that the number of casualties can be significantly reduced by retrofitting or
eliminating URMs. HAZUS estimates that daytime Level 3 and Level 4 casualties from URMs
could reach 8,800. With the retrofitting or elimination of URMs, this number is reduced to
2,500. A Level 3 casualty is a life-threatening injury and a Level 4 casualty is a fatality.
The map below shows the number of buildings that will need to be inspected after the scenario
earthquake. Over 76,000 of the red-tagged structures and more than half of the yellow-tagged
structures will be URMs. These numbers represent about one-third of the structures needing
post-earthquake inspections. URMs are also a major contributor to the debris that is left in the
aftermath of the earthquake. Brick/Wood debris makeup 46% of the 35 million tons of debris
generated from the earthquake. Programs that create incentives to retrofit these structure will
help reduces these post-earthquake recovery
issues.
5.2 More Rapid Recovery from Seismic Event
Is this in Bob Carey’s write-up?
5.3 Increased Value
One of the benefits of seismically retrofitting URM buildings is the potential to increase the
value of the property. From a buyer’s standpoint, there would be increased confidence on the
purchase of a structural building which has been seismically upgraded, knowing that in case of a
seismic event, the property would much safer for those who are inside, and experience less
catastrophic damage.
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5.4 Decreased Insurance Rates
The potential cost of repairing damage from earthquakes has been growing because of the
increased development in the seismically active areas in the state of Utah, as well as the
vulnerability of the older buildings in these areas which have not yet been seismically upgraded
to the current building standards. Insurance companies who provide earthquake insurance
realize this, and may increase the premiums in these areas of greater seismic risk.
In an article from the Insurance Information Institiute titles “Earthquakes: Risk and Insurance
Issues”, it states: “Premiums also differ widely by location, insurer and the type of structure
that is covered. Generally, older buildings cost more to insure than new ones. Wood frame
structures generally benefit from lower rates than brick buildings because they tend to
withstand quake stresses better. Regions are graded on a scale of 1 to 5 for likelihood of quakes,
and this may be reflected in insurance rates offered in those areas. The cost of earthquake
insurance is calculated on “per $1,000 basis.” For instance, a frame house in the Pacific
Northwest might cost between one to three dollars per $1,000 worth of coverage, while it may
cost less than fifty cents per $1,000 on the East coast.
A brick home would cost approximately $3 to $15 dollars per $1,000 in the Pacific Northwest,
while it would cost between 60 to 90 cents in New York. Earthquake insurance is available from
most insurance companies in most states.”
With that said, another potential benefit of seismically retrofitting URM buildings is the
potential to decrease the premium to be paid for earthquake insurance. The California
insurance code states that the CEA policyholders who have retrofitted their homes to withstand
earthquake shake damage according to standards and to the extents set by the CEA governing
board receive a 5% premium discount.
5.5 Historic Preservation
The majority of buildings on the National Register of Historic Places in Utah are URM buildings.
There are some great benefits to be gained by the State of Utah aggressively encouraging
seismic rehabilitation of these buildings.
First, historic buildings in general are a cultural asset that must be preserved. Their preservation
can be considered a window into our society’s past from which we gain a sense of identity that
in turn gives definition to where we are going as a society. Seismic rehabilitation helps ensure
that these buildings will survive a catastrophic event.
Second, when the majority of the historical URMs were constructed, 1890’s – 1930’s, they were
built of high quality and durable materials. The buildings that exist that have had normal
maintenance throughout the years are now 70- to over 100-years old. With seismic
rehabilitation to protect against a catastrophic event and continued maintenance, these
buildings can be expected to last for and additional 100 years or more. This expected lifespan is
likely longer than a new building constructed with current materials and techniques. Historic
preservation reverses the decline of a community due to the deterioration of buildings and
significantly increases property values. This phenomenon can be seen in the “Avenues”
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community in Salt Lake City where rehabilitation of homes has occurred since the late 1970’s to
the present.
Third, historic preservation is innately “green”. The demand for environmentally responsible
construction methods is expected to increase. An existing historic building represents a
significant amount of natural resources already invested and is one of the best ways of meeting
material reduction, reuse and recycling goals. The decision to go “green” and purchase a
historic building as a home or business, should consider the life expectancy and life safety issues
of the building as opposed to the alternative of constructing new. The fact that a building has
been seismically rehabilitated would be a strong consideration in favor of going “green.”
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6. Potential Costs
6.1 Primary Costs
So, what can one expect to pay for the seismic strengthening of an existing building? This
answer must be qualified by first having a clear understanding of how the building was
constructed and consideration for other renovation work that is being done in conjunction with
the seismic retrofit.
For example, the owner of a small single story URM home may wish to seismically retrofit the
home while also performing a significant remodel. One of the main costs for typical seismic
improvements is the removal and replacement of finish materials. If interior lath and plaster is
removed as part of upgrading electrical and plumbing items the wood stud walls can then be
sheathed to act as shearwalls. If re-roofing is to occur, the contractor then has access to tie the
roof system to the existing URM walls. New plywood roof sheathing can also be provided to
provide strength and stiffness to the roof, which provides the added benefit of a new substrate
for the new shingles. If new flooring is to be installed, tying the floor system to the existing
walls could be accomplished with little cost. If no interior demolition is to occur, or the home is
not to be re-roofed in conjunction with the seismic retrofit, the costs for these seismic
improvements could increase significantly.
Depending on the condition and thickness of the URM walls with respect to their height,
additional strengthening of the URM walls themselves may not be necessary in order to
maintain life-safety, not necessarily to eliminate damage to the structure.
Since tall narrow URM chimneys pose a significant hazard during a seismic event, particular
attention should be paid to these areas. It is relatively inexpensive to remove a portion of the
chimney to reduce the height to an acceptable level. Quite often, the mortar in chimneys has
deteriorated to the point that the brick can be removed with only a small hand chisel and
hammer. The top of the chimney can then be re-built, using the original bricks, to match the
original architectural detailing.
6.2 Additional Costs
There are many other areas where efforts can be made to improve the seismic resistance of
URM buildings. After all efforts are expended to accomplish the upgrade items listed previously,
the owner should consider other seismic upgrade alternatives as well.
For example, some building owners may desire to provide additional insulation value for
exterior URM walls. In some cases, it may be possible to utilize new stud walls (which also act as
new insulated walls) on the interior of the URM walls, to attach to and help resist seismic forces
on the URM walls. At the very least, these new stud walls can provide additional protection
against collapse of thin or deteriorating URM walls.
Other effective, but possibly more costly measures for strengthening existing URM walls may
include:
*
Re-pointing of crumbling or deteriorated mortar;
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*
Providing concealed ties between wythes (layers) of brick which otherwise may not be tied
together;
*
Reinforced shot-crete (gun-ite) walls added to either the inside or outside face of the wall,
and tied to the URM wall;
*
Center-coring of walls, which involves drilling vertically down from the top of the wall, and
installing reinforcing and grout to strengthen the existing wall.
Each of these methods can be considered for every URM building. However, even if the budget
does not allow all recommended upgrades to be completed right away, the primary repairs
indicated herein should still be considered and installed, likely at minimal additional cost.
Costs?
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7. Recommendations
7.1 Mandatory or Directed Programs
While it has been known for some time that URMs pose a significant risk during a seismic event,
very few efforts have been made to seismically retrofit the abundance URM buildings in Utah.
Because earthquakes are rare events retrofitting is not typically the highest priority for building
owners with limited funds. Governments convey mixed messages by not requiring seismic
retrofits in some cases, even when mandated by the building codes. It is important that the
State of Utah and local governments realize that they have a stake in the future of these
buildings, in both protecting human life and economic continuity.
It is not necessary to look very far for examples of successful URM programs. States such as
California, Washington, Oregon and Nevada have each had an abundance of URM buildings
located within high seismic regions. Each of these states has developed significant programs,
both locally and statewide, to provide incentives to building owners who perform seismic
upgrades. Retrofitted URMs can be seen throughout downtown Seattle, WA while programs
instituted in Portland, OR have caused the quantity of URMs in the city to be greatly reduced. In
1986 California passed the “URM Law”3(SB 547, Section 8875 of the California Code). This law
required all jurisdictions located within high seismic regions to create an inventory of its URMs
by 1990, adopt a loss reduction program, and then report progress to the state’s Seismic Safety
Commission. In 1990, ten San Francisco Bay Area Counties had a total of 6800 URMs with that
number being reduced to 3000 by 2003.
In order to develop a successful URM program a strategic plan should be developed that:
1. Defines the goals,
2. Identifies appropriate programs,
3. Identifies priorities for those programs, and
4. Defines milestones when goals are accomplished.
Strategic plans can be implemented over a transition period of 1, 2, 5, 10, 20 and 50 years into
the future. No one really knows how much time we have before an earthquake hits some part
of our State. We may have days, a few years, or many years. Using a phased approach will result
in some short-term benefits, while other goals, if implemented over the long term, will yield
tangible benefits that will significantly impact losses. Short-term goals include development of
scenario risk analyses that can be used to educate the public, and increase the effectiveness of
the planned programs; and selection of towns for Pilot Programs. Mid-term and long-term goals
include land-use development programs and development of incentives for retrofitting, and at
the State, local, and individual level. Entire neighborhoods of URM buildings could be
transformed through redevelopment; lifelines relocated; hospitals strengthened.
7.2 Financial Incentives
For any program to be successful, it must get the attention of its audience. In this case, a
successful URM program must address the bottom line of the building owner. Financial
incentives have been the key to successful programs throughout the United States. Below is a
list of some financial incentives that have been instituted by local jurisdictions to pique the
interest of building owners:
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Waiver of permit fees
Permit fee reductions
Local tax breaks
Grants
In addition to the above mentioned local financial incentives, state and federal incentives should
also be considered. As an example, the state may choose to provide a tax rebate to building
owners which have seismically upgraded their buildings similar to rebates given in Utah for
hybrid vehicles or the addition of solar panels to a residence. The federal government currently
provides a 20% tax credit for work certified by the National Park Service on National Register
buildings. Projects selected for FEMA pre-disaster mitigation funds may be funded for up to
75% of the applicable project costs.
Financial incentive may not be the only way to promote a local or statewide URM program.
Many of the successful URM programs mentioned previously also incorporated items such as a
tool lending program, workshops for home owners and contractors, etc. The City of Portland
chose to waive the requirement to meet additional code-prescribed items such as energy when
voluntary seismic upgrade was performed.
7.3 Considerations for Historic Buildings
There are benefits to encouraging seismic rehabilitation of historic buildings as discussed above.
However, unless there is a life safety issue as determined by the building official there is
currently no mandatory rehabilitation requirement. Effective methods to encourage
rehabilitation are through a combination of education and financial incentive. For historical
buildings in Utah, there are several existing financial incentives and financial assistance/loans
available depending on the type of project and building ownership. A full listing of available
financial assistance can be found at the Utah State Historic Preservation Office’s website.
There are two different rehabilitation tax credits already available that could benefit the
majority of private historic building (commercial and residential) owners. However, these tax
credits have not been used very much due to lack of knowledge of their existence on the part of
home and business owners.
One tax credit available is the Federal Rehabilitation Tax Credit. It is interesting to note that
there are two available tax credits available. There is a 20% Federal Investment Tax Credit (ITC)
available for rehabilitating historic buildings (listed on the National Register) used for
commercial or residential rental use and a 10% ITC for renovating non-historic buildings (not
listed on the National Register) being used for commercial (but not residential rental) and
constructed before 1936.
The second tax credit available is the Utah Historic Preservation Tax Credit. A 20 % nonrefundable state income tax credit for the rehabilitation of historic buildings that are used as
owner occupied residences or residential rentals. Twenty percent of all qualified costs may be
deducted from taxes owed on Utah income or corporate franchise tax.
Even for those who were aware of the tax credits for historical buildings, there are some
misconceptions. For example, a home owner may think that their home must be individually
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listed on the National Register with an official marker plaque affixed to the front to qualify for
the Utah Historic Preservation Tax Credit. Utah has many Historic Districts which are listed on
the National Register. The district is an area or neighborhood that has a concentration of
historic buildings (eg., Avenues, Capitol Hill, University, Gilmer Park , Central City, South Temple,
City Creek, Exchange Place, and Warehouse). Any building in that area over 50 years old would
qualify. This greatly increases the number of qualified buildings since within a Historic District
there is just a small percentage that are individually listed on the National Register due to their
specific historic significance.
For both tax credits, there are limits on what kind of rehabilitation work qualifies. However,
seismic rehabilitation work would most likely be considered to be qualifying work in both cases.
The existence of the tax credits is a good start but has not been used to its full advantage yet. It
is recommended that an effort to communicate and educate the community and building
owners as to the financial incentives available at the same time as to the benefits of seismic
rehabilitation. It is also recommended to provide training to building officials and historic
preservation officials in the latest International Existing Building Code. With this training and
the knowledge of what kinds of financial incentive are available, the officials will be better
prepared to work with owners when they are applying for historic building rehabilitation project
approval.