TORNADO SHELTERS

Tornado Storm Shelter Inside Tornado Storm Shelter
Underground shelter built after the Udall tornado of 1955
External look at Tornado Storm Shelter
This photo shows today's model of the 1955 style shelter. 
These are also buried once they are installed and are just
like the 1955 models

Taking Shelter From the Storm:         COURTESY OF NASA *

Large Photo of Above Ground Storm ShelterEvery year, tornadoes, hurricanes, and other extreme windstorms injure and kill people, and damage millions of dollars worth of property in the United States. Even so, more and more people build houses in tornado- and hurricane-prone areas each year, possibly putting themselves into the path of such storms. Having a shelter, or a safe room, built into your house can help you protect yourself and your family from injury or death caused by the dangerous forces of extreme winds. It can also relieve some of the anxiety created by the threat of an oncoming tornado or hurricane. Should you consider building a shelter in your house to protect yourself and your family during a tornado or hurricane? The answer depends on your answers to many questions, including:

• Do you live in a high-risk area?

• How quickly can you reach safe shelter during extreme winds?

• What level of safety do you want to provide?

• What is the cost of a shelter?

This booklet will help you answer these and other questions so you can decide how best to protect yourself and your family. It includes the results of research that has been underway for more than 20 years, by Texas Tech University’s Wind Engineering Research Center (WERC) and other wind engineering research facilities, on the effects of extreme winds on buildings. This booklet also provides shelter designs that will show you and your builder/contractor how to construct a shelter underneath a new house, in the basement of a new house, or in an interior room of a new house, or how to modify an existing house to add a shelter in one of these areas. These shelters are designed to protect you and your family from the high winds expected during tornadoes and hurricanes and from flying debris, such as wood studs, that tornadoes and hurricanes usually create.

The National Association of Home Builders (NAHB) Research Center has evaluated these designs for construction methods, materials, and costs. Engineers at Texas Tech University have confirmed the design requirements for the expected forces from wind pressure and the impact of typical flying debris. The shelters are designed with life safety as the primary consideration.

Section I: Understanding the Hazards
Almost every state in the United States has been affected by extreme windstorms such as tornadoes and hurricanes. Virtually every state has been affected by a "considerable" tornado (see the terms in Table

I.1). All Atlantic and Gulf of Mexico coastal areas in the United States – including coastal areas of Puerto Rico and the U.S. Virgin Islands – and coastal areas of Hawaii have been affected by hurricanes. Even in states not normally considered to be susceptible to extreme windstorms there are areas that experience dangerous high winds. These areas are typically near mountain ranges, and include the Pacific Northwest coast.

What Is a Tornado?

Tornadoes are categorized by the Fujita scale (see Fujita). They typically occur in the spring and summer months, but can occur at any time in any part of the country. Tornadoes are sometimes spawned by hurricanes.

Not all parts of each state are at equal risk from tornadoes. For example, while Texas has the highest number of recorded tornadoes, the state’s least tornado-prone area—along the Gulf Coast—has been hit by fewer tornadoes than northeastern Arkansas. Comparing the numbers of tornadoes recorded in different areas within a state can give you a better understanding of the potential tornado activity in those areas. Figure I.1 shows the numbers of tornadoes recorded per 1,000 square miles in the United States and its possessions and territories.

What Is a Hurricane?

In the United States, 158 hurricanes were recorded to have made landfall between 1900 and1996. Hurricanes have made landfall in Florida more than in any other state. The second most hurricane-affected state is Texas, but every state on the Gulf Coast and bordering the Atlantic Ocean, as well as U.S. island possessions and territories, are susceptible to damage caused by hurricanes. In recent years, the U.S. territories of American Samoa and Guam have been seriously affected by numerous tropical cyclones.

Do You Need a Shelter?

On the basis of 40 years of tornado history and more than 100 years of hurricane history, the United States has been divided into four zones that geographically reflect the number and strength of extreme windstorms. Figure I.2 shows these four zones. Zone IV has experienced the most and the strongest tornado activity. Zone III has experienced significant tornado activity and includes coastal areas that are susceptible to hurricanes. To learn more about the wind history for the area where you live, check with your local building official, meteorologist, emergency management official, or television weather reporter. Your house is probably built in accordance with local building codes that consider the effects of minimum, "code-approved" design winds in your area. Building codes require that buildings be able to withstand a " design" wind event. A tornado or extreme hurricane can cause winds much greater than those on which local code requirements are based. Having a house built to "code" does not mean that your house can withstand wind from any event, no matter how extreme. The shelter designs in this booklet provide a place to seek safe shelter during these extreme wind events. The worksheet on pages 7 and 8 will help you determine your level of risk from these extreme events and will assist you in your consideration of a shelter. If you decide that you need a shelter, Section II will help you and your builder/contractor plan your shelter.

Taking Shelter from the Storm: Table of Contents

Introduction ..............................................................................................iii

Section I: Understanding the Hazards

What Is a Tornado? ............................................................................ 1

Table I.1: Typical tornado damage................................................. 2

Figure I.1: The number of tornadoes recorded per

1,000 square miles ....................................................................... 3

What Is a Hurricane?.......................................................................... 4

Table I.2: Typical hurricane damage............................................... 4

Do You Need a Shelter? ..................................................................... 5

Figure I.2: Wind zones in the United States ................................... 6

Homeowner’s Worksheet .................................................................. 7

Emergency Planning and Emergency Supply Kit............................. 9

Section II: Planning Your Shelter

Building Damage...............................................................................11

Figure II.1: Effect of extreme winds on building roof

and walls ...................................................................................... 11

Basis of Shelter Design ................................................................... 12

Shelter Size .......................................................................................14

New vs. Existing Houses ................................................................. 14

Foundation Types ............................................................................ 14

Figure II.2: Cross-section: typical basement

foundation, with shelter................................................................ 15

Figure II.3: Cross-section: typical slab-on-grade

foundation, with shelter................................................................ 17

Building a Safe Room Inside Your House

i TAKING SHELTER FROM THE STORM: BUILDING A SAFE ROOM INSIDE YOUR HOUSE

TABLE OF CONTENTS

Figure II.4: Cross-section: typical crawlspace

foundation, with shelter................................................................ 18

Shelter Location ................................................................................20

Figure II.5: Floor plan 1: basement ...............................................21

Figure II.6: Floor plan 2: house on slab-on-grade

or crawlspace foundation............................................................. 22

Figure II.7: Floor plan 3: house on slab-on-grade

foundation ................................................................................... 23

Table II.1: Appropriate types of shelters for

new houses .................................................................................24

Table II.2: Appropriate types of shelters for

existing houses ........................................................................... 24

Construction Materials .................................................................... 25

Shelter Cost.......................................................................................25

Table II.3: Average cost for an 8-foot by 8-foot

shelter in a new house ................................................................ 26

Section III: Building Your Shelter ........................................................ 27

How To Use the Drawings................................................................ 28

* Document from Federal Emergency Management Agency  Mitigation Directorate  500 C Street, SW. • Washington, DC 20472  www.fema.gov
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