Is Your Home Protected From Earthquake Disaster? A Homeowner’s Guide to Earthquake Retrofit

7/18/2019 Is Your Home Protected From Earthquake Disaster? A Homeowners Guide to Earthquake Retrofit

1/48

Is Your Home Protected

From Earthquake Disaster?A Homeowners Guide to Earthquake Retrofit


2/48

A Homeowners Guide to Earthquake Retrofit

Prepared by the Institute for Business & Home Safety. The Institute for Business & Home Safety (IBHS) is

an initiative of the insurance industry to reduce deaths, injuries, property damage, economic losses and human

suffering caused by natural disasters. IBHS is a nonprofit research and communications organization com-

mitted to institutionalizing natural disaster protection as a public value.

acknowledgments

The staff of the Institute for Business & Home Safety (IBHS) wishes to acknowledge the valuable input of all

those involved in preparing this brochure. In particular, we extend our thanks to:

The IBHS Earthquake Peril Committee Members

The IBHS Public Relations Committee Members

The IBHS Retrofit Committee Members

The National Geophysical Data Center (NGDC)

Earthquake Engineering Research Center, University of California, Berkeley (EERC, UCB)

Earthquake Engineering Research Institute (EERI)

cover photo credits

EERI Northridge Earthquake Reconnaissance Team, J. Hall, CIT; F. Desler, APA; Godden Collection,

EERC, UCB; and USGS, D. Perkins

architectural illustrations

W. Spaulding, AIA

disclaimer

The suggestions and recommendations you will read in this guide are based on professional judgment, expe-

rience and research. The authors, contributors and publisher disclaim all warranties and guarantees with

respect to the information in the document and assume no liability or responsibility with respect to the infor-

mation.

(c) 2001 Institute for Business & Home Safety

All rights reserved.

ISBN 1-885312-22-9


3/48

table of contents

introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

earthquakes and your home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Earthquakes: What, When, Where and Why . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Measuring an Earthquakes Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

What You Feel and Why You Feel It . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

What Your Home Experiences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

What You Can Do . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

nonstructural retrofits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Bookcases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Cabinets and Drawers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Picture Frames and Bulletin Boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Ceiling Lights, Suspended Ceilings and Hanging Fixtures . . . . . . . . . . . . . . . . . .13

Windows and Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Large Appliances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Water Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

structural retrofits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Foundation Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Slab-on-Grade Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Crawl Space and Basement Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Post-and-pier Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Floor Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Wall Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Wood-Framed Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Unreinforced Masonry Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Unreinforced Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Garages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Room Additions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

home improvement project list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

before,during and after:be completely prepared . . . . . . . . . . . . . . . . . . . . . . 35

references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

additional sources of information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

table of contents


4/48

A Homeowners Guide to Earthquake Retrofit

Top: Earthquake dam-

age in Kobe, J apan.

Right: San Francisco

Marina fire caused by

broken gas lines.

Background: Shored

building in the Marina

District, San Francisco.

USGS, D. Perkins

F. Desler, APA

EERI, J. Egan


5/48

arthquakes occur suddenly with

little or no warning, during any

season and at any time of day.

Although the West Coast generally has

the greatest earthquake activity, the po-

tential for earthquakes exists in almost

every corner of the United States.

More than 3,360 Americans have died

during earthquakes in the last century,

and homes in all 50 states have suf-

fered damage in the last 250 years.1

So, what can you do to protect your-

self, your home and its contents from

earthquakes? This brochure will help

you by providing information about:

the relationship between your home

and an earthquake;

key areas of your home that are

especially susceptible to damage;

ways you can reduce damage to

your home and belongings; and,

what you can do to protect yourself

and your family.

The information and suggestions pre-

sented in this brochure range from

simple weekend tasks that requirebasic carpentry skills to involved pro-

jects that may require professional

assistance. Before starting on any

activity, make sure you are comfort-

able with the required skill level. If

you are uncertain, contact a profes-

sional engineer, architect or building

contractor.

1introduction

introduction

E

J. Preli

Damage inSan Franciscos

Marina District.

1Based on U.S. Geological Survey numbers.


6/48

Earthquakes: What,When, Where and Why

Did you know that the groundbeneath you is constantly moving? TheEarths surface is broken into many dif-ferentplates, which float on top of theEarths quasi-liquid mantle. Typically,

one plate interacts with another byeither colliding with it, sliding past itor pushing itself underneath it. Theseareas along which plates interact areknown as geologicalfaults.

As plates move over time, the edge ofone plate often catches itself on anoth-er, forcing that portion of the fault toremain motionless while stress builds.

Eventually, the fault reaches a breakingpoint and slips suddenly, sometimes byyards or sometimes only by inches.This sudden vertical or lateral (side-ways) movement releases seismicwaves, which we feel as an earthquake.The point where the fault first slips islocated deep within the earth and is

called the hypocenter. Directly abovethat, on the earths surface, is the epi-center. Figure 1 highlights the key ele-ments of an earthquake.

In the United States, the most activefaults are along the West Coastthemost famous being the San AndreasFault system that runs through thestate of California. This fault system

A Homeowners Guide to Earthquake Retrofit2

earthquakes and

your home

Top: The San

Andreas Fault in

the Carrizo Plain

area, Calif.

Bottom: The fault

scarp of the

Landers earth-

quake, Calif.

Plate

Fault-line

Epicenter

Hypocenter

Plate

Fault-plane

Figure 1: Key Elements of an Earthquake

NOAA/NGDC

NOAA/NGDC


7/48

separates the North American Plate fromthe Pacific Plate. Despite the large numberof earthquakes associated with this andother plate boundaries, earthquakes are notrestricted to just the plate edges. Approx-imately five percent of earthquakes occurwithin the central part of a plate. Theseearthquakes are known as intraplate earth-quakes, and have occurred in recent historyin Charleston, South Carolina, and theMississippi Valley near New Madrid,Missouri.

Remember, even if you dont live in one of

these areas, you are still at risk. The mapspresented in Figure 2 show where earth-quakes have been recorded in the past hun-dred years. As you can see, no place is trulysafe from earthquakes.

3earthquakes and your home

Number of Events: >14,000Data provided by the National Geophysical Data Center

Number of Events: 1,507Data providedby the National Geophysical Data Center

Number of Events: 7,667Data providedby the National Geophysical Data Center

Figure 2: Alaskan, Hawaiianand Mainland Earthquakes


8/48

Measuring anEarthquakes Size

Seismologists estimate the size, or magni-tude, of an earthquake in several differentways. The Richterscale measures the sizeof the earthquakes waves (amplitude);whereas, the moment magnitude scaleestimates the total energy released duringthe slip of a fault. Because the momentmagnitude scale is more objective thanthe Richter scale, it is now more com-monly used. Figure 3 shows differentlevels of earthquakes and their corre-sponding moment magnitudes (Mw).

What You Feeland Why You Feel It

The amount of movement you experi-ence during an earthquake doesntdepend just upon its magnitude. Whereyoure located in relation to the earth-quakes epicenter also has an effect. Thefarther away you are, the less shaking youfeel, since the seismic waves lose energyas they travel through the earth. Imaginea drop of water hitting the surface of apond. As the circular waves travel awayfrom the impact, they lose energy andreduce in size and frequency. In time,they disappear altogether.

Also, the kind of soil underneath andaround you plays a large role in howmuch of the earthquake you experience.Unlike water, soil is not uniform through-


Short History of U.S.Earthquakes:(Moment Magnitude ScaleMW)

1755 Cape Anne, MA ~6.0 Mw

1812 New Madrid, MO ~7.8 Mw1886 Charleston, SC ~7.0 Mw1906 San Francisco, CA ~7.7 Mw1944 Massena, NY ~5.5 Mw1964 Alaska 9.2 Mw1989 Loma Prieta, CA 7.0 Mw1994 Northridge, CA 6.7 Mw

Fissure in

Santa CruzMountains, Calif.

Figure 3: Moment Magnitude Scale

U.S.GeologicalSurvey,C.Stover

Turnagain Heights

Landslide;

Anchorage, Alaska.NOAA/NGDC


9/48

out. The soil type can have a dramatic effect onthe way seismic waves travel through the earth.

For instance softer, less compact soil can actual-ly increase the forces. More stable soils, such asbedrock or compacted fill, dissipate an earth-quakes energy more quickly.

Three major factors an earthquakes magni-tude, your proximity to the epicenter and thecondition of the soil around you determinethe amount of shaking you feel. The ModifiedMercalli Intensity scale measures this intensityby evaluating the earthquakes effect on youand your home.

What Your Home Experiences

Imagine that a strong earthquake strikes whereyou live. Loose items fall and break. Cabinetsand bookcases tip over, blocking exits. Dust bil-lows everywhere. Gas and water lines break,and phone and electrical service are interruptedfor days. Your home may collapse, slide off itsfoundation or simply come apart at the seams.

Figure 4 illustrates how your home reacts in anearthquake. Because it is not able to move in syncwith the surrounding ground, your home and itscontents can experience substantial damage.

5earthquakes and your home

Building collapse in Marina

District, San Francisco, Calif.

Home at Rest;

Ground at Rest

LeftwardMovement

Begins

RightwardMovement

Begins

Ground Comesto Rest

Groundat Rest;Home

Continuesto MoveDue toInertia

Figure 4: Your Home in an Earthquake

EERI,J.Egan

A sand boil near El Centro, Calif.

provides evidence of an earthquake.

USGS.Reagor


10/48

What You Can Do

You can protect your home by modifying it,

or retrofitting it, in two different ways:

Nonstructural retrofits protect your homescontents against damage with little cost andeffort. Examples of retrofits include: securing water heaters, large appliances,

bookcases, pictures and bulletin boards; latching cabinet doors; and using safety film on windows.

To complete these improvements simplyfollow the instructions in this brochure. Inmost cases, you wont need a building per-mit. Its a good idea, however, to contactyour local building department to makesure.

Structural retrofits strengthen your homesstructure or skeleton so it can better with-stand the force of an earthquake. Yourhomes structure is made up of many differ-ent parts, or components, which must worktogether in order to resist an earthquake.

Modifications to your homes structure tend

to be quite involved and generally requirethe expertise of a registered design profes-sional (engineer, architect or building con-tractor) and your local building depart-ments approval. Use this brochure to iden-tify potential problem areas in your ownhome. If you have any questions or con-cerns about what you see, contact a profes-sional engineer or architect.


Top: Structure shifted

on its foundation in

Watsonville, Calif.

Bottom: Nonstruc-

tural kitchen damage,

Northridge, Calif.

USGS,C.Stover

NOAA/NGDC


11/48

7nonstructural retrofits

nonstructural retrofits

n this section, you will learn inex-pensive and easy ways to protectyourself against some of the damage

earthquakes can cause inside yourhome. Start by looking for objects thatcould fall and break during an earth-quake. Consider items such as waterheaters, bookcases and light fixtures,as well as items that are difficult toreplace because they have monetary or

sentimental value. As you conductyour inspection, think about ways inwhich you can protect them fromdamage. If you have any questionsabout the changes you should make,contact a professional engineer, archi-tect or contractor.

Bookcases

Its true that bookcases are great forstoring books, toys and supplies. Theycan, however, shake and tip over in anearthquake, causing considerable dam-age or injury. For this reason, makesure all bookcases are securely fastenedto nearby walls.

One way to do this is to attacheither L-brackets or Z-brackets to the

bookcase and the wall after pre-

drilling holes in each. Be sure to use a

bracket that can accommodate the fas-

teners you are using. See Figure 5 on

page 8 for details.

Fallen bookcases

at the Lawrence

Livermore Lab,Livermore, Calif.

I

USGS


12/48


Bolt back to back through framewith #8 (or larger) machine screws,oversized washers and nuts. Nomore than 12 apart.

Metal, plastic, orwood ledge barriersprevent objectsfrom falling

Screw throughback into wall.Use washers.

Exterior Bracket

InteriorBracket

Attach object withmuseum gel, or largepatches of hook &loop material (suchas Velcro).

General Notes:

Bracket to Bookcase (Interior or Exterior)#8 (or larger) wood screws; or#8 (or larger) machine screws with washers and nuts

Bracket to Wall (Interior or Exterior)Wood-stud wall: 3 long, #8 (or larger) wood screwsMasonry wall: 3 long, #8 (or larger) screws with

plastic anchors, or 3/16 diameter(or larger) masonry screws

Interior L-Bracket

Wood Screw Drywall

BookcaseWood Stud

Wood Screw orMachine Screw

Exterior L-Bracket

Wood ScrewDrywall

BookcaseWood Stud

Wood Screw orMachine Screw

Figure 5: Securing Bookcases

Exterior Z-Bracket

Drywall

Bookcase

Wood Stud

Wood ScrewWood Screw orMachine Screw


13/48


Attaching the bracket

to the bookcase:

For wood bookcases, attach thebracket with #8 (or larger) wood

screws. The screw should be long

enough to secure the bracket to the

shelf without punching through and

creating a sharp edge.

For plastic and metal bookcases, use

#8 (or larger) machine screws with

washers and nuts to ensure that the

bracket will stay in place. The screw

should be long enough to accommo-

date the bracket, shelf, washer and nut.

Attaching the bracket to the walls:

For wood stud walls, use 3-inch long

#8 (or larger) wood screws to attach

each bracket to the wall. Place screws

in the wood studs to assure that they

are properly supported. Use a stud

locator to find the best places.

For stone or masonry walls, place

plastic anchors in the holes before

you screw in 3-inch long #8 (orlarger) screws or consider using

3/16-inch diameter (or larger)

masonry screws.

For a bookcase with a solid back,

you can pass screws directly through the

back into the wall. Use washers to

spread contact over a larger area between

the screw and the bookcases back. If you

are working with a wood stud wall, use

a stud locator to find the best locationsfor the 3-inch long #8 (or larger) wood

screws. For a stone or masonry wall, use

plastic anchors with the #8 (or larger)

screws or use 3/16-inch diameter (or

larger) masonry screws.

You can prevent items on shelves

from falling by installing ledge barriers

made from strips of wood, metal or plas-tic. Cut them to fit the shelf and attach

them with glue or mechanical fasteners.

You can finish the barriers to match the

shelves. See Figure 5 for details.

Place heavy items on lower shelves.

You can stabilize bookcases that are

not against walls by attaching them

back-to-back with #8 (or larger)

machine screws, oversize washers and

nuts. See Figure 5.

Affix large, heavy items, such as

plants and aquariums, and other break-

ables directly to the shelf to keep them

from falling. You can apply hook and

loop material (such as Velcro) or

museum gel (or museum wax) to secure

these items. For added protection, use

metal, plastic or wood ledge barriers. See

Figure 5 for details.

Necessary Tools andMaterials

L- or Z-brackets Fasteners Plastic anchors for masonry walls Variable speed drill and bits Screwdriver Stud locator

Wood, plastic or metal strips Paint or wood finish Hook and loop material (Velcro) or

museum gel/wax


14/48


Figure 6: Cabinets and Drawers

Provide self-locking doorlatches or mechanical

cabinet catches.

Install self-locking or mechanical drawerclosures (baby-proof latches, drawer lock,

or other speciality latches).

Top connections tie units together for amore stable configuration. Use steelstraps with #8 (or larger) machine

screws with nuts and washers.

Brackets for fastening units to:Wood Stud Walls:

Use #8 (or larger) woodscrews with 3 min.embedment in studs.

Masonry Walls:Use 3 long #8 (or larger)screws with plastic anchorsor 3/16 diameter (or larger)masonry screws.

Cabinets:Use#8 (or larger) machinescrews with nuts andwashers.

Cabinets and Drawers

Like bookcases, cabinets can tip over and

their doors can open, spilling their con-tents. Furthermore, the drawers, whichsometimes have sharp edges, can slide outand hurt you, or your family.

To secure them, do the following:

Attach cabinets to the wall and floors

using L-brackets or Z-brackets. Again,

be sure to use brackets that can accom-

modate the diameter of the fasteners.

You should follow the specific direc-

tions given in Figure 6 and in theBookcases section for securing the

bracket to the wall and cabinet.

Interior damage to kitchen, Coalinga

J unior High School, Coalinga, Calif.

EERICoalingaEarthquakeRecon

naissance

Team,S.R

ihal,Cal.Poly.


15/48


Secure itemswith L-Brackets

(see Figure 5 forattachment

details).

Useadhesivebackedlatches.

Attach hookand loopmaterial(such as

Velcro)between

object andtable surface.

Figure 7: Secure Heavy Objects

Necessary Toolsand Materials

L- or Z-brackets Fasteners Door or drawer latches Plastic anchors for masonry walls Variable speed drill and bits Screwdriver Stud locator

You can fasten several units togeth-

er to form a wider footprint using

#8 (or larger) machine screws.

Attach simple mechanical or self-

locking latches to cabinet drawers so

they cannot slide open.

Install mechanical or self-locking

latches to prevent your cabinet doors

from swinging open and spilling their

contents. Your local hardware store has

a large variety of latches, many of

which are small, unobtrusive and easy

to operate. See Figure 6 for details.

Most of us place heavy objects such

as televisions, computers and stereos

on top of cabinets, bookcases and

tables. You should fasten these items

down so they will not slide off during

an earthquake. Several methods of

attachment are shown in Figure 7.


16/48


Picture Framesand Bulletin Boards

The photographs, bulletin boards and art-work you display in your home add to itscharacter. But these items can easily fall dur-ing an earthquake if you do not fasten themproperly to a wall in the following way:

Use closed screw-eyes, instead of tradi-

tional picture hangers, for securing picture

frames, bulletin boards and mirrors.

Depending on the weight of the object

and the screw-eyes maximum weight

limit, screw one or more closed screw

eyes into wall studs. Use a stud finder to

figure out where to put them.

Attach picture wire to one side of the

frame. Thread the wire through the

closed screw-eye, fastening it securely to

the other side of the frame. See Figure 8.

If you use an open screw-eye instead of a

closed screw-eye, be sure to close it with

pliers once you have hung the picture.

Always mount heavy or sharp wall hang-

ings away from areas where they could fall on

children.Necessary Toolsand Materials

Stud locator Screwdriver Variable speed drill and bits Screw-eyes Heavy picture wire Pliers

Damage to framed pictures,

Northridge, Calif.

Drywall

Wire

Wood Stud

ClosedScrew-Eye

Picture

Figure 8: Secure Picture Frame to Wall

J.Preli


17/48


Ceiling Lights,Suspended Ceilings

and Hanging FixturesIf they arent well attached and supported,ceiling lights, suspended ceilings and hang-ing fixtures, such as chandeliers and ceilingfans, can fall in an earthquake and serious-ly injure those below. Here are some waysto protect yourself:

Secure ceiling lights to supports using

safety cables.

Use a chain strap or a minimum 14-

gauge wire to attach the light fixture to

a nearby ceiling support. Locate the

support visually or use a stud locator.

Be sure to leave the safety cables slack;

they should not support the weight of

the lights under normal circumstances.

See Figure 9 for details.

If your ceiling light has a cover, keep it

from falling during an earthquake by

fastening it to the fixture itself or to the

homes permanent structure.

Pay special attention to your homes

fluorescent lights. Installing plastic

sleeves over the fluorescent light tubes

will keep the glass from scattering if

they break. As an alternative, consider

using Teflon fluorescent lights, which

are shatter-resistant.

Use safety cables every few feet to

attach suspended or false ceilings to the

structure of your home.

Use chain straps, plumbers strapping

(metal strapping with holes) or heavy

wire (minimum 14-gauge) to secure sus-

pended or false ceilings. See Figure 9.

Use screws, bolts or other appropriate

fasteners to attach the safety cables to

both the suspended ceiling and the per-

manent structure.

You can prevent the ceiling panels from

flying upward by installing adjustable

compression struts. Contact your sus-

pended ceiling manufacturer for

details. See Figure 9.

Top: Failure of pendant light fix-tures in the Dawson Elementary

School library, Coalinga, Calif.

Bottom: Damage to suspended

ceiling and recessed ceiling lights,

Philippines.

EERICoalingaEarthquakeReconnaissance

Team

S.R

ihal,Cal.Poly.

EERI,S.Swan,E

QEInter.


18/48


Make sure chandeliers, ceiling fans, other

suspended fixtures and hanging plants are

safely secured to the permanent structure.

Connect all suspended items to strong

supports with safety cables capable of

supporting each items entire weight.

Each cable should remain slack and

not support the items weight under

normal circumstances.

Keep in mind that hanging items tend

to sway easily. Make sure these objects

will not collide with anything if they

swing in an earthquake.


Safety cables, chain straps,heavy wire or plumbers strapping

Fasteners Adjustable compression struts Screwdriver

Variable speed drill and bits Stud locator Plastic sleeves for fluorescent lights Light covers

Figure 9: Secure Lights and Suspended Ceilings

Use chain straps or 14-gauge wireat each corner or at least at

diagionally opposite corners.

Adjustable compression strutsprevent upward movement.

Safety cables arevery important.

General Notes For exposed fluorescent light bulbs use

protective sleeves. Secure light covers in place. To secure a wire or chain, use a

minimum of 3 tight turns in 1-1/2 at each end.


19/48


Windows and Doors

Your homes windows and glass doors mayseem harmless enough. But in an earth-quake, glass can break explosively, serious-ly injuring anyone nearby. One way to pro-tect yourself and your family from brokenglass is to apply safety film to windows andglass doors:

Use a protective film (minimum thick-

ness of 4 mils) on all types of glass, includ-

ing tempered glass and annealed glass. You

can buy it in rolls at your local hardware

and home improvment stores, or contactthe International Window Film Associ-

ation for the nearest distributor. Be sure to

install the film according to the manufac-

turers instructions.

As an alternative, consider professional

installation.

Large Appliances

An earthquake can cause refrigerators,washing machines and other large appli-ances to slide or fall over. Heavy objects onwheels may roll if brakes or stops are notprovided and locked. To secure these items:

Anchor large appliances to walls using

safety cables or straps. The restraint should

be located in the mid- to upper-portion of

the appliance. Use the following method:

Choose a screw-eye that is sized appro-

priately for the appliance. For example,

use a 3/8-inch diameter screw-eye (orlarger) for a refrigerator.

For wood stud walls, use a stud locator

to find the best wall location to install

the screw-eye. For stone or masonry

walls, place plastic anchors in the pre-

drilled holes before you install the

screw-eye.

Connect coated wire cable to the

screw-eye at one end and to a snap-

hook fastener at the other end.

Attach the cable to the appliance with

the snap-hook fastener.

Replace rigid water or gas connec-

tions on large appliances with flexible

connectors.

Check to see if your local building

codes allow you to use flexible connec-

tors and whether a professional must

install them.

Always lock the rollers of any large

appliances or pieces of furniture.


Coated wire cable or otherstrapping system

Screwdriver

Variable speed drill and bits Stud locator Screw-eyes Hook fasteners Flexible connectors Plastic anchors

USGS,M.

Hopper

Damaged building, Coalinga, Calif.


20/48


Water heater burned in residential

fire caused by a gas leak.

Figure 10: Retrofitted Water Heater

Heavy-duty shelving bracketlocated within the top 1/3 of thewater heater.

Heavy-duty shelving bracket locatedwithin the lower 1/3 of the water

heater. It must be a minimum of 4above controls.

Existing WallsExisting Water Heater

2x4 WoodBlocking

Water HeaterControl

3/4 Plumbersstrapping snug

around water heater

B

enRotholtz

Note: See general notes on page 17for additional information

Water Heaters

Water heaters can move or tip over in anearthquake and the broken water pipe canflood your home, destroying ceilings,floors, walls, furniture, artwork and familyphotos. If your heater runs on flammablegas and the gas line breaks, the situationbecomes far more serious.

In many areas of the country where earth-quakes are common, local building codesmay require that water heaters be laterallybraced or strapped to resist seismic forces.Most hardware stores sell retrofit kits for dif-

ferent-sized water heaters. In addition, sever-al generic restraint systems are available.Before you decide on a retrofit method,check with your local building depart-ment and make sure that it is approvedfor use in your area or goes beyond whatis required by your local building code.


21/48


Secure water heaters (up to 50 gallons)

to stud walls using the simple, generic

method detailed in Figures 10 through 12.

You can anchor the water heater usingitems that are readily available from the

local hardware store.

To begin: fasten two 2 x 4 wood block-

ing strips to the nearby wall - one at a

height within the upper one-third

(1/3) of the water heater and the other

within the lower one-third (1/3) of the

water heater. The lower 2 x 4 should be

at least four (4) inches above the water

heater control. If you are working with

a wood or metal stud wall, attach the

blocking directly to the studs. Use a

stud locator to find the studs.

ExistingWaterHeater

Extend blocking at least two (2) studsbeyond bracket attachment.

Existing Wall

Attach blocking towall, see GeneralNotes below.

2 x 4 Wood Blocking(two (2) places)

Use one (1) heavy-dutyshelving bracket in four(4) places.

Attach bracket to blockingwith two (2) #16 (or min.1/4) by 1-1/2 lag screws.

Attach bracket to plumbers strapping with aminumum 1/4 x 3/4 hex bolt. Use awasher under the nut. Keep 1 between endof bracket and center of bolt.

Attach bent ends of strapping with a minu-mum 1/4 x 1 hex bolt. Use washersunder head and nut. Keep 1 between end ofstrapping and center of bolt.

Use minumum 3/4 plumbersstrapping. Wrap around waterheater and provide snug fit.

General Notes:Blocking Attachment to Wall

1) Wood Stud Wall: Use two (2) #16 (or

minimum 1/4) x 3-1/2 lag screws withhex head and washer under head of screw.

2) Concrete or Masonry Wall: Use 3/8masonry anchors with 1-5/8 embedmentinto existing wall at 12-16 on center.

3) Steel Stud Wall: Use two (2) #10-16 self-

drilling sheet metal screws with hex head andwasher under head of screw.

4) Wood and Steel Stud Walls: Center screws onstuds.

Figure 11: Straight Wall Configuration

M ethod recommended by NIST. See NIST Report GCR 97-732 reference pg. 37. refers to the connections diameter.


22/48


2 x 4 Wood Blockingfour (4) places

Figure 12: Corner Wall Configuration


2 x 4s Stud locator Screwdriver Hammer drill & bits

(stone & masonry walls)

Variable speed drill & bits(wood & metal stud walls) Various fasteners Heavy-duty shelving brackets Plumbers strapping Flexible connector

Fasten heavy-duty shelving brackets to the

wood blocking. These brackets should fit

snugly against the water heater.

Wrap plumbers strapping (metal strap-

ping with holes) around the heater and

secure it to the brackets.

Remember: Use flexible, not rigid, water

and gas connectors and check with local build-

ing code officials to see if you must hire a

licensed plumber to modify the connections.

Make certain all adult and teenage family

members know where to locate the gas shut-

off valve and how to operate it.

Extend blocking atleast two (2) studsbeyond bracketattachment.

Existing Wall

Attach blocking towall, see GeneralNotes, below.

Use one (1)heavy-duty shelv-ing bracket in

four (4) places.

Attach bracketto blocking withtwo (2) #16 (ormin. 1/4) by1-1/2 lagscrews.

Attach bracket to plumbersstrapping with a minumum

1/4 x 3/4 hex bolt. Usea washer under the nut.Keep 1 between end ofbracket and center of bolt.

Attach bent ends of strapping with aminumum 1/4 x 1 hex bolt. Usewashers under head and nut. Keep 1between end of strapping and center

of bolt.

Use minumum 3/4 plumbersstrapping. Wrap around waterheater and provide snug fit.

General Notes:Blocking Attachment to Wall

1) Wood Stud Wall: Use two #16 (or minimum 1/4) x 3-1/2 lag screwswith hex head and washer under head of screw.

2) Concrete or Masonry Wall: Use 3/8 masonry anchors with 1-5/8embedment into existing wall at 12-16 on center.

3) Steel Stud Wall: Use two (2) #10-16 self-drilling sheet metal screwswith hex head and washer under head of screw.

4) Wood and Steel Stud Walls: Center screws on studs.

Method recommended by NIST. See NIST Report GCR 97-732 reference pg. 37. refers to the connections diameter.


23/48

19structural retrofits

structural retrofits

hen an earthquake strikes,your homes structure is putto the test. The skeleton

must absorb the earthquakes energy andprovide a stable path to transfer the forcesback into the ground. For this to happen,your homes structure must be tied togeth-er; that is, your homes roof should betightly attached to the walls, and yourwalls should be fastened to each other,braced and anchored to a strong founda-tion. Figure 13 on page 20 shows howthe components of a home can be securedto each other, so that they function as asingle unit during an earthquake.

Keep in mind that the purpose of thissection is to help you identify keyareas of your homes structure that are

susceptible to earthquake damage. Ifyou are uncertain about what you see,or if you decide to have work done,enlist the help of a professional archi-tect, engineer, building contractor oryour local building department.

Remember that an ideal time to inspectand retrofit your homes structure is whenyou are making a significant change to

your home such as adding on a room orremodeling. In either case, it is importantthat your work conforms to local buildingcode requirements. Although the existingportion of your home may not need to beupgraded to current code requirements,now may be a good time to do so. Contactyour local building code official to findout what is required for your project.

W

J.Preli

Cripple wall

foundation failure,Northridge, Calif.


24/48


Roof Rafters/Trusses

Figure 13: Typical Wood Frame House

Roof Covering

Blocking Framing Anchor

Top Plates

Floor J oists

Floor Sheathing

Wall Studs

Top Plates

Floor Sheathing

Floor J oists

Top Plates

Mud Sill (Sill Plate)

Cripple Wall Stud

Anchor Bolt

Foundation Wall

Foundation ReinforcementBrick Ledge

Weep Holes

Foundation Footing

Metal Ties

Brick Veneer

Floor Ties

Lap Siding

Structural-GradePlywood or OSBSheathing

Roof Sheathing

Sill Plate

Band J oist

Band J oist


25/48

Foundation Systems

Earthquakes can create ground motion in

any direction. During a quake, yourhomes foundation moves with the earth,but the rest of your home reacts more slow-ly due to its inertia. See Figure 4 on page5. This creates a tremendous amount ofstress on the connections between thefoundation and the remaining structure. Ifthese connections are not strong enough,your home may slide or fall off its founda-tion. In fact, this is one of the most com-mon and costly types of structural damage.Depending upon the foundation, however,this may be relatively easy to fix.

SLAB-ON-GRADE FOUNDATIONS

Slab-on-grade foundations are just that:concrete slabs that rest on the ground. Inan earthquake-prone area, a homes wood-frame structure should be connected tothe slab with either anchor boltsor othersteel connectors (including steel plates).Figure 14 on page 22 illustrates bothtypes of connections.

If your home has anchor bolts, it can bedifficult to conduct a thorough inspection,since you must get access to the top of thesill plate. This almost always requires thatyou remove an inside or outside finishedwall, so consider doing this when remodel-ing your house. Your inspection shouldreveal minimum 1/2-inch-diameter anchorbolts with washers and tightened nuts con-necting the sill plate to the foundation.These bolts should be spaced no more than

six feet apart. Make sure that the bolts arein good condition and show no rust andthat the nuts are tight. The concrete sur-rounding the bolt should be strong andfree of any severe cracks (wider than theedge of a dime).


Top: Separation of

porch from rest of

house due to unan-

chored foundation,

Petrolia, Calif.

Bottom: Home has

shifted off its unan-

chored slab-on-grade

foundation, Coalinga,

Calif.

L.Brewer,U

SGS

SteinbruggeCollection

EERC,U

CB


26/48


Figure 14: Concrete Slab-on-Grade Froundation

Concrete Slab-on-Grade Foundation

Sill Plate(Mud Sill)

(1) Mud Sill Anchor

(2) Steel Flat PlateFoundationReinforcement

(3) Anchor Bolt

StudConnectors(Framing

Ties)

Note: Three different methods of hold-down are presentedhere. However, only one system is usually required.

Steel plates connect the homes sill plate tothe foundation. Carefully inspect the platesalong the outside perimeter of the struc-

ture. This may require removing the exteri-or cladding. Both the plates and fastenersshould be in good condition. Keep an eyeout for rust or signs of poor workmanship.The plates should be no more than six feetapart. Next, take a close look at the foun-dation. Are there severe cracks (wider thanthe edge of a dime) in the concrete? Thereshouldnt be.

If the foundation is in poor condition oryou must add additional anchorage, ask a

professional engineer for help.

Cripple wall foundation failure

and utility damage, Northridge,

Calif.

J.Preli


27/48

23

CRAWL SPACE ANDBASEMENTFOUNDATIONS

A foundation with a crawl space or basementtypically has enough room underneath the firstfloor so that you can inspect the foundationand the underside of the floor-framing mem-bers, orjoists, as long as the space is unfinished.The main difference between a crawl space anda full basement is the amount of headroomavailable.

The walls that rise from the foundation foot-ings to the first floor are called foundationwalls. They are typically made with masonryblocks or concrete. In some cases, a short woodstud wall, or cripple wall, is positioned aboveground between the top of the concrete ormasonry foundation wall and the first floor.Cross sections of the three basic types of wallsystems are highlighted in Figure 15.


Figure 15: Three Types of Foundation Walls

ExteriorSheathing

CrippleWall

Top Plates

Wood StudCripple Wall

Anchor Bolt

Sill Plate

FoundationFooting

Reinforcement

Foundation Footing

Sill Plate

SolidConcrete

Wall

Grout Inside Cavity

HorizontalReinforcement

FoundationFooting

Reinforcement

Anchor Bolt

Wood Stud Cripple Wall Reinforced-Concrete Wall Reinforced-ConcreteBlock/Masonry Wall

Cripple wall foundation failure,

Northridge, Calif.

R.Shackelford,R.C

hap

man

Foundation WallReinforcement

Foundation

WallReinforcement

FoundationWall


28/48


Connections

Steel plates or minimum 1/2-inch-diam-eter anchor bolts should connect the wood-

framing sill plate to the concrete or mason-ry wall. These connections should be spacedno more than six feet apart. All componentsshould be undamaged and rust-free. Also,examine the overall condition of the foun-dation wall. Make sure you dont see anysevere cracks (wider than the edge of adime) in the masonry or concrete. If a woodcripple wall is present, it should show noevidence of termites or rot.

If the foundation wall needs repair, or

you need to add additional anchorage,check with a professional engineer for asuitable retrofit method.

Bracing

For cripple walls, exterior lap sidingalone cannot adequately resist the earth-quakes lateral forces. You may need to addinterior bracing, if it is not already there, to

prevent the cripple wall from collapsing inan earthquake:

Nail 3/8-inch minimum structural-

grade plywood or oriented strand board(OSB) sheathing to the inside of thewall. Ideally, the entire wall lengthshould be covered. However, if youhave limited access, place sheathing ineach corner of your home. While thesheathing panels can be oriented in anydirection, take care to ensure that eachedge is supported by a stud or solidblocking.

2

Figure 16 illustrates thismethod. If you have any questions

about bracing weak cripple walls, con-tact a professional engineer.

Adequately reinforced concrete founda-tion walls do not typically require addition-al bracing. Masonry foundation walls, how-ever, may benefit from an upgrade. Becauseof the difficulty in evaluating masonrywalls, consult a professional engineer.

Figure 16: Strenghtening Cripple Walls with Plywood Panels

First Floor

Band J oist

Air Holes

Structural-GradePlywood or OSB

Panels

Bridging

Band J oist

J oist Ties

LapSiding

Top Plates

Wood StudCripple Wall

Blocking(around

anchor boltsor over

plate anchor)

Sill Plate

Anchor BoltFoundation

Wall

Sill PlateAnchor

Floor J oists

2 For design details, see APAs Earthquake Safeguards referenced on pg. 37.


29/48


POST-AND-PIERFOUNDATIONS

A home can also be supported by a post-

and-pier foundation (Figure 17). Largebeamsrun under the homes floorjoistsandare held up by posts. Each post rests on aseparate concrete footing or pier. Somepost-and-pier foundations are hidden fromview by a cripple wall that runs around thehomes outside perimeter. This type offoundation is very susceptible to collapseduring an earthquake. To better resist seis-mic forces, all of the foundations compo-nents, including the beams, posts andpiers, must be securely tied together.

When inspecting the foundation for possi-ble problems, carefully examine the waythe components are anchored together.The connection between the beam and thepost should be strong and without rust, rotor evidence of poor workmanship. Oneway to help your home better withstand an

Figure 17: Post-and-Pier Foundation

J oist Strap

Ground

Reinforced

Connection

Post

Concrete Pier

Anchored Post-Base

Floor J oist

Beam

J oist Hangers

Post-and-pier with cripple wall foundation

failure, Ferndale, Calif.

L.Brewer,U

SGS

B

A

Note: This drawing illustrates two differentways floor joists can frame into a beam.


30/48


earthquake is to have the connection rein-forced with steel plates or with plywood orOSB connectors. Pre-manufactured metalstraps or fixtures are available at most hard-ware stores (A in Figure 17). This rein-

forcement is especially important if thejoint in the beam falls on top of the post.

The other critical joint in this foundationlies between the post and the pier. Examinethis area carefully. The post should besecurely fastened to the pier, and all com-ponents should be well constructed, free ofrust, severe cracks (anything wider than theedge of a dime) and rot. Most new con-struction will have the post attached to theblock with a built-in metal fixture (B in

Figure 17). In older construction, the postmay simply rest on the top of the block.Reinforce the connection by nailing heavy-gauge straps onto at least two sides of thepost and then bolting them into the con-crete block.

Keep in mind that strong connectionsbetween the various components may notbe enough - the earthquakes movement

may still knock the home off its founda-tion. That is why extra connections andlateral bracing may be necessary. If yourhome has an exterior cripple wall, bracingand anchoring it further can provide thenecessary protection. Refer to the previousdiscussion on cripple wall foundations forinspection and retrofit techniques.

If your home does not have an exteriorcripple wall, lateral bracing and strong con-nections between the posts are critical.

Simple toe nailing is not sufficient. Sincethe seismic evaluation of post-and-pierfoundations is complex, you should con-sult a professional engineer.

Failure of wood frame dwelling. A

post-and-pier foundation with a

cripple wall, Kern County, Calif.

SteinbruggeCollection,EERC,U

CB

Post-and-Pier Foundation; undam-

aged (top) and damaged (bot-

tom), Costa Rica.

EERI,S.SwanEQEInter.


31/48

27

Floor Systems

An earthquake exposes the floor to sub-

stantial forces that can distort and damagethe floor system, jeopardizing the strengthof your home. The floor system typicallyconsists of floor joists, floor sheathingandband joists, which are located along thefloors perimeter (Figure 18).

If you have access to the underside of yourfloor, make sure that your floor system istied together and that the sub-floor issecurely connected to the underlyingfloor joists. To reduce the possibility of

rotation in an earthquake, each joistshould be nailed to a band joist. Blocking

or bridging can also be placed between

joists to keep them from falling over. Theforces absorbed by the band joist or block-ing must, in turn, be transferred to thefoundation. Secure this connection byusing metal ties or framing anchors.Finally, make sure you do not find any evi-dence of poor workmanship, rust or rot.

It may be difficult for you to access theseareas. Often, the best time to evaluate yourfloor system is when you are planning toremodel. If your inspection reveals any

problems, consult a professional engineerfor the best way to retrofit your floor system.


Figure 18: The Floor System

Floor Sheathing

BandJ oist

FramingAnchor

Sill Plate

Bridging

J oist Hanger

Foundation Wall

Anchor Bolt


32/48


Wall SystemsDuring an earthquake, the walls in yourhome, especially the exterior walls, play animportant role in preventing your home fromcollapsing. The walls along with the floorsand roof create a box. As the ground shakes,the floors and roof sway back and forth, whilethe walls in between try to stop your homefrom moving too far. To do their job, yourwalls must be strong and securely tied to theroof, floor and foundation.

WOOD-FRAMEDWALLS

Traditionally, the exterior walls of wood-frame houses are supported with wood studsattached to structural-grade plywood, orien-ted strand board (OSB) or diagonal wood

sheathing. To protect the exterior walls fromthe elements, they are covered with lap sid-ing, stucco, stone or brick veneer. In order for

this system to resist damage from earthquakeforces, it must be well designed with theappropriate hardware in place to ensure astrong connection between all of the ele-ments. See Figure 13 on page 20 for details.

Also, consider the number, size and locationof the windows and doors, including garagedoors, in your home. Too many can weakenyour walls and lead to possible collapse in anearthquake. Imagine a closed box with sever-al openings: it will cave in much easier than

one with no openings.Unlike wood siding, brick and stone veneersrequire special attention because of theirweight. During an earthquake, this heavyveneer can fall off, causing injury and signifi-cant damage. It is very important that thesewalls be tiedto the wood-frames behind themwith simple metal ties secured in the mortar.Sound building practices usually provide suffi-cient ties for the first story - even when notdesigned specifically for earthquakes. Special

attention, however, may be required for thesize and spacing of the ties in the upper stories.

Because it is difficult to access these areas,the best time to inspect is while you areremodeling or adding on to your home. Ifyou have any concerns about your homesexterior walls, openings or veneer, contact a

Above: Failure of a wood stud wall

to sill plate connection. Note

anchor bolt and sill plate are still

connected, San Fernando, Calif.

Below, right: Failure of a unrein-

forced brick-veneer wall, San

Fernando, Calif.

Steinbrugg

eCollection,EERC,U

CB

SteinbruggeCollection,

EERC,U

CB


33/48

29

professional engineer. Ask him or her todetermine how well your walls can with-stand an earthquake and to recommend

necessary retrofit measures.

UNREINFORCED MASONRYWALLS

If your homes walls are made entirely ofbrick, stone, clay tile, concrete block oradobe, they could be susceptible to earth-quake damage. In newer masonry homeson the West Coast, these types of walls areoften reinforced with steel bars groutedinside the walls. If the walls are reinforcedand well anchored to the foundations,floors and roofs, they can usually withstand

an earthquake. But masonry that is in poorcondition, unreinforced or not securely tiedto the rest of the structure, has the potentialto collapse. Figure 19 highlights the differ-ences between reinforced and unreinforcedconcrete block masonry walls.

A proper retrofit generally requires anchor-age designed specifically for earthquakes.

Since evaluating structural masonry wallsfor general soundness and specific seismicfeatures is quite complex, it would be bestto consult a professional engineer.


USGS,M.Hopper

Figure 19: Reinforced vs. Unreinforced Masonry Walls

Vertical ReinforcementSecured with Grout

UnreinforcedReinforced

HorizontalReinforcement

ConcreteMasonryBlocks

Second floor wall failure in an

unreinforced masonry home.

Note the apparently undamagedtwo-story wood frame building on

right, Coalinga, Calif.


34/48


35/48

31

Board sheathing is not as earthquakeresistant as plywood and OSB sheathing,but may be adequate in smaller homes.

Consult a professional engineer for morespecific information. Also, keep in mindthat large dormers, skylight openings andany other features that interrupt thesheathing can weaken your roof structure.

Remember: sheathing can only do somuch. You must also consider the roof sys-tems framing - the trusses or rafters thatsupport the roof covering and sheathing.Similar to floor systems, roof-framing sys-tems can rotate or fall over when your

home starts to move in an earthquake. Toprevent this, blocking can be placedbetween the rafters or trusses where theyrest on the wall. See Figure 20. Be sure tonail the blocking to the roof sheathing inorder to transfer the lateral loads into thewall. Metal strap connectors or properlyplaced toe-nailing ensure that the blockingis adequately connected to the wall andrafters.

You may not be able to thoroughly exam-

ine your roofing system due to limitedaccess. The best time for a completeinspection is just before you re-roof yourhome. If you have any concerns about yourroofs covering, sheathing, openings orframing members, talk to a professionalengineer or qualified roofing contractor.

Unreinforced Chimneys

Unless specifically designed and reinforcedfor lateral forces, brick or stone chimneys

often come apart or topple during an earth-quake, causing serious damage and injury.Usually, only the top portion of the chim-ney breaks apart during an earthquake;however, in some cases the entire chimneypeels away from the side of the home.

Check the top of your chimney to be sureit is free of severe cracks (anything widerthan the edge of a dime). Take a close look

at the mortar between the bricks. It shouldnot scrape away easily with a metal tool.Even if your chimney is in good condition,it may still be at risk, especially if it is talland slender. Some chimneys have metalstraps that hold them to the side of thehome. Carefully inspect these fastenings.They should be in good condition with noevidence of poor workmanship or rust.

If you are uncertain about what you see,consult with a professional engineer. The

engineer may recommend adding a bracebetween the top portion of the chimneyand the roof. You may also need to usemetal straps at several points to anchor thechimney to the home (Figure 21).


Chimney damage, San Fernando,

Calif.


CB


36/48


Figure 21: How to Reinforce a Chimney

Flue Metal Strap

Metal Straps

House Frame

Chimney

Metal Straps

Note: (1) Wood blocking should be added to joists underneath metal straps.(2) See FEMA-232 for specific details, referenced on pg. 37.

Metal Straps aresecured to underside

of roof joists.

Chimney

Metal Straps aresecured to top of

ceiling joists.

Metal Straps aresecured between

floor sheathing andfloor joists.

Metal Straps aresecured to underside

of floor joists.

Flue

Cross Section


37/48

33

Room Additions

If youve put on an addition or made othermodifications in the past, you may have

unknowingly weakened your homes earth-quake resistance. Sometimes, homes thatwere originally very simple and structural-ly sound undergo changes that make thembigger or fancier, but also more prone toearthquake damage.

If you are planning to make majorchanges to the structure of your house, orif you suspect existing features lack goodengineering details, consult a professionalengineer.


Garages

Garages are particularly vulnerable to

earthquake damage. The situation be-comes especially serious if the garage hasa portion of the home over it. The largegarage door opening removes almost anentire side of the box configuration andrequires the remaining narrow walls oneither side to support the roof and extrarooms. If these walls are not designedcarefully to handle the situation, theentire structure may collapse when anearthquake strikes.

Strengthening the narrow garage wallsgenerally requires engineering details,such as specially detailed plywood panels,steel bracing or a steel frame. A profes-sional engineer can help you decide whatwill work best for your home.

STRUCTURAL CHANGES THATINCREASE THE RISK OFEARTHQUAKE DAMAGE INCLUDE:

replacing large portions of walls

with windows or glass doors;

adding large skylights or

additional stories;

opening large portions ofexisting floors; or

additions that create an L

configuration.

Top: Two stories now crushed to one

story due to weak lower level (note

crushed auto), San Fernando, Calif.

Bottom: Damage due to inadequate

lateral bracing on the ground level,

San Francisco, Calif.


CB

U.S.GeologicalSurvey

(D.Perkins)


38/48


home improvement

project list

his list of home improvementsdivides the different retrofits intocost categories. The categories reflect

the cost of each individual item. The costwill be slightly higher if you hire someone

to complete the work. You or your con-tractor can tackle these projects one at atime, but remember, the more you do thestronger your home becomes.

Category $ ($1000) Add anchor bolts or steel plates to foundation;

Secure post-and-pier foundation;

Modify floor system;

Strengthen wood-framed walls;

Reinforce masonry walls; Retrofit roof system;

Evaluate unique room additions.

T


39/48

35

ou will give yourself and your fami-ly a better chance of escaping harmduring an earthquake by taking as

many of the precautions outlined in thisbrochure as possible. But, these steps areonly the beginning. To protect yourself ascompletely as possible, here are some

added suggestions:

Before anEarthquake Strikes:

Teach everyone to duck or drop to thefloor, take cover under a desk or tableand hold on to it when an earthquakestrikes. Remember the phrase: Duck,Cover and Hold.

Learn first aid and CPR.

Put together an emergency kit thatincludes at least a three-day supply ofdrinking water and food that needs norefrigeration and, generally, no cooking;emergency cooking equipment, ifrequired; a portable NOAA weatherradio; first aid supplies and medications;basic tools, such as a wrench, a flashlightand gloves; portable lanterns and batteries;credit cards and cash; and important doc-uments, including insurance policies.

Know where your gas, electric andwater main shut-off controls are andhow to turn them off if there is a leakor electrical short. Make sure all adultand teenage members of your familyknow how to shut off each utility.

Become familiar with your communitysdisaster preparedness plans and create afamily plan. Know where the closestpolice, fire and emergency medical facili-ties are located.

Plan an escape route from your home

and neighborhood and designate anemergency meeting place for the familyto reunite. Establish a contact point tocommunicate with concerned relatives.

Periodically review your homeownersinsurance policy with your insuranceagent or company to make sure that, ifyou are the victim of a disaster, you haveenough coverage to rebuild your homeand life. The typical homeownersinsurance policy does not include

earthquake coverage. If you are in anearthquake-prone area, you should con-sider purchasing earthquake insurance.

before, during and after: be completely prepared

before, during and after:

be completely prepared

Y

EERI,J.Eagan


40/48


During an Earthquake: If you are indoors, duck, cover and

hold until the shaking stops. Do not tryand run out of a building you may behit by falling debris.

If you are outdoors, move quickly andsafely into the open, away from electri-cal lines, trees and buildings, and waitfor the shaking to stop.

If you are driving, carefully and slowly

bring your vehicle to a stop at the side ofthe road away from traffic. Make surethat you do not stop on or underbridges. Do not stop under power linesor near roadway signs that might fall.Once the shaking has stopped, you cancontinue driving. Watch carefully forpossible damage to the roadway.

After an Earthquake Strikes:

Check for hazards, such as gas or water

leaks and electrical shorts. Turn offdamaged utilities. Have the fire depart-ment or gas and electric companiesturn the utilities back on when the areais secured.

Check for injuries and administer firstaid as needed.

Check your food and water supplies. Donot eat anything from open containersnear shattered glass.

Listen to and follow the advice andrecommendations of local aid organi-zations, including the emergency man-agement office, the fire departmentand the utility companies.

Keep roads and phone lines clear foremergency use.

Be prepared for aftershocks.

D.Perkins,U

SGS

C.Stover,USGS


41/48

37references

references

APA: The Engineered Wood Association. Earthquake Safeguards.

Tacoma, WA: APA, 1997.

Association for Bay Area Governments. Techniques for Mitigating

Earthquake Hazards. 18 March 1999.

California Governors Office of Emergency Services and Federal Emergency Management Agency.

An Ounce of Prevention: Strengthening Your Wood-frame House for Earthquake Safety.

Sacramento, CA: California OES, 1993.

California Governors Office of Emergency Services and Federal Emergency Management Agency.Guide to Strengthening and Repairing Your Home Before the Next Earthquake. Sacramento,

CA: California OES, 1995.

California Seismic Safety Commission. The Homeowners Guide to Earthquake Safety.

Sacramento, CA: California SSC, 1998.

Federal Emergency Management Agency. Reducing the Risks of Nonstructural Earthquake

Damage. FEMA 74. Washington, DC: FEMA, 1994.

Federal Emergency Management Agency. Homebuilders Guide to Seismic Resistant Construction.

FEMA 232. Washington, DC: FEMA, 1998.

Federal Emergency Management Agency. Identification and Reduction of NonstructuralEarthquake Hazards in Schools. FEMA 241. Washington, DC: FEMA, 1993.

Federal Emergency Management Agency. FEMA: Mitigation How To Series.

Gray, Ralph Gareth. Riding Out the Big One. Fine Homebuilding. Two Part Series:

December 1990/January 1991.

Kimball, Virginia. Earthquake Ready: The Complete Preparedness Guide. Malibu, CA:

Roundtable, 1992.

Mroz, M.P., and T.T. Soong. NIST GCR 97-732: Fire Hazards and Mitigation Measures

Associated with Seismic Damage of Water Heaters. Gaithersburg, MD: National Instituteof Standards and Technology, 1997.

Southern California Earthquake Center. Putting Down Roots in Earthquake Country. 1995.

F.Desler,APA

B

ayAreaRegional

E

arthquake

P

repardnessProject


42/48


APA - The Engineered Wood AssociationP.O. Box 11700Tacoma, WA 98411-0700Tel: 253-565-6600Help Desk: 253-620-7400Fax: 253-565-7265http://www.apawood.org/

American Society of Civil Engineers (ASCE)

1801 Alexander Bell DriveReston, VA 20191-4400Tel: 703-295-6000Fax: 703-295-6222http://www.asce.org

American Red CrossCheck your local phone directory forthe chapter nearest you.http://www.redcross.org

Association of Bay Area Governments (ABAG)P.O. Box 2050Oakland, CA 94604-2050Tel: 510-464-7900Fax: 510-464-7970http://www.abag.ca.gov/

Applied Technology Council (ATC)555 Twin Dolphin Drive, Suite 550Redwood City, CA 94065Tel: 650-595-1542Fax: 650-593-2320http://www.atcouncil.org/index.htm

Building Officials and Code AdministratorsInternational, Inc. (BOCAI)4051 West Flossmoor RoadCountry Club Hills, IL 60478-5795Tel: 708-799-2300Fax: 708-799-4981http://www.bocai.org

California Division Of Mines and Geology801 K Street, MS 14-33Sacramento, CA 95814-3532Tel: 916-445-5716Fax: 916-445-1853http://www.consrv.ca.gov/dmg

California Office of Emergency Services1300 Clay Street, Suite 408

Oakland, CA 94612Tel: 510-286-0895Fax: 510-286-3581http://www.oes.ca.gov/

California Seismic Safety Commission1755 Creekside Oaks Drive, Suite 100Sacramento, CA 95833Tel: 916-263-5506Fax: 916-263-0594http://www.seismic.ca.gov

California Universities for Research

in Earthquake Engineering (CUREe)1301 S. 46th StreetRichmond, CA 94804-4698Tel: 510-231-9557Fax: 510-231-5664http://www.curee.org

Center for Earthquake Researchand Information (CERI)University of MemphisMemphis, TN 38152Tel: 901-678-2007Fax: 901-678-4734http://www.ceri.memphis.edu/

Central U.S. Earthquake Consortium (CUSEC)2630 E. Holmes RoadMemphis, TN 38118Tel: 901-544-3570Fax: 901-544-0544http://www.cusec.org

additional sources

of information


43/48

39additional sources of information

Earthquake Engineering

Research Center (EERC)NISEE/EERC1301 South 46th StreetRichmond, CA 94804-4698Tel: 510-231-9403Fax: 510-231-9461http://nisee.ce.berkeley.edu/

Earthquake EngineeringResearch Institute (EERI)499 14th Street, Suite 320Oakland, CA 94612-1934Tel: 510-451-0905Fax: 510-451-5411http://www.eeri.org/

Federal EmergencyManagement Agency (FEMA)P.O. Box 2012

Jessup, MD 20794-2012Tel: 1-800-480-2520http://www.fema.gov

Institute for Business & Home Safety (IBHS)4775 E. Fowler

Tampa, FL 33617Tel: 1-866-657-4247Fax: 813-286-9960http://www.ibhs.org

International Code Council (ICC)5203 Leesburg PikeFalls Church, VA 22041Tel: 703-931-4533Fax: 703-379-1546http://www.intlcode.org

International Conference

of Building Officials (ICBO)5360 South Workman Mill Road

Whittier, CA 90601-2298Tel: 562-699-0541Fax: 562-692-3853http://www.icbo.org

International Window Film Association

318-A Brown StreetP.O. Box 3871Martinsville, VA 24115-3871Tel: 540-666-4932Fax: 540-666-4933http://www.iwfa.com

Mid-America Earthquake Center1241 Newmark Lab MC-250205 N. MathewsUrbana, IL 61801Tel: 217-244-6302Fax: 217-333-3821http://mae.ce.uiuc.edu

Multidisciplinary Center forEarthquake Engineering Research (MCEER)MCEER/ISState University of New York @ Buffalo304 Capen HallBuffalo, NY 14260-2200Tel: 716-645-3377Fax: 716-645-3379http://mceer.buffalo.edu

National Information Service forEarthquake Engineering/California Institutefor Technology (NISEE/CALTECH)1301 South 46th StreetRichmond, CA 94804-4698Tel: (510) 231-9403Fax: (510) 231-9461http://www.eerc.berkeley.edu

National Institute forUrban Search andRescue (NI/USR)P.O. Box 90909

Santa Barbara, CA93190Tel: 800-767-9983Fax: 805-966-6178http://www.niusr.org/


44/48

National Oceanic and Atmospheric

Administration (NOAA),National Geophysical Data Center (NGDC)325 BroadwayBoulder, CO 80303Tel: 303-497-6826Fax: 303-497-6513http://www.ngdc.noaa.gov/ngdc.html

Nature of the NorthwestInformation Center800 NE Oregon Street, Suite 177Portland, OR 97232Tel: 503-872-2750Fax: 503-731-4066http://naturenw.org

Pacific Earthquake EngineeringResearch Center (PEER)Richmond Field StationUniversity of California, Berkeley1301 S. 46th StreetRichmond, CA 94804-4698Tel: 510-231-9554Fax: 510-231-9471http://peer.berkeley.edu

Simpson Strong Tie4637 Chabot Dr., Suite 200Pleasanton, CA 94588Tel: 925/460-9912Fax: 925/847-0694http://www.strongtie.com/index.htm

Southern Building CodeCongress International, Inc. (SBCCI)900 Montclair RoadBirmingham, AL 35213-1206Tel: 205-591-1853

Fax: 205-591-0775http://www.sbcci.org

Southern California

Earthquake Center (SCEC)University of SouthernCaliforniaLos Angeles, CA 90089Tel: 213-740-5843Fax: 213-740-0011http://www.scec.org/

University of California BerkeleySeismological Laboratory202 McCone HallBerkeley, CA 94720-4760Tel: 510-642-3977Fax: 510-643-5811http://www.seismo.berkeley.edu/seismo/

USGS National Earthquake InformationCenter (NEIC)P.O. Box 25046 , Denver Federal CenterDenver, CO 80225Tel: 303-273-8500http://gldss7.cr.usgs.gov orhttp://wwwneic.cr.usgs.gov/



45/48

41


46/48

checklistHow well will your home resist damageduring a 3.0 earthquake? How aboutone that is a 6.0 or greater? Most homestypically will need some type of rein-forcement to withstand a major earth-quake. Here is a checklist that will helpyou focus on how to strengthen yourhome.

To answer some of these questions youmay need to enter uncomfortable orsmall spaces. You may want to have anexperienced inspector or professionalengineer or architect check your home,instead. Whatever choice you make, takesome time to do this before the nextearthquake strikes.

Observation Recommendation Page

Unsecured bookcases and cabinets Fasten to nearby walls 7

Cabinet doors and drawers that swing open easily Install latches 10

Electronic equipment and artwork that can topple Secure items to bookcases and cabinets 11

Pictures and bulletin boards that can fall Fasten securely to walls 12

Hanging fixtures and suspended ceilings Attach safety cables 13

Large appliances that can tip over Anchor to nearby walls 15

Unprotected windows and doors Apply safety film 15

Water heater that can tip over Secure to nearby wall 16

Home not anchored to foundation Add anchor bolts or steel plates 21

Weak cripple wall Reinforce cripple wall 23

Unsound post-and-pier foundation Secure post-and-pier foundation 25

Weak floor system Modify floor system 27

Inadequate walls Strengthen wood-framed walls 28

Unreinforced masonry Reinforce masonry walls 29

Poor roof support Retrofit roof system 30

Unsecured chimney Anchor unreinforced chimney 31

Room over garage Strengthen the support 33

Unique addition Have engineer evaluate 33



47/48


48/48

Is Your Home Protected From Earthquake Disaster? A Homeowner’s Guide to Earthquake Retrofit

Documents

Transcript of Is Your Home Protected From Earthquake Disaster? A Homeowner’s Guide to Earthquake Retrofit