Tornado 

Protection

Selecting Refuge Areas in 

Buildings

FEMA P-431, Second Edition / October 2009

Community 

Affairs

FLORIDA DEPARTMENT OF
About the Cover

The photograph on the cover shows the remains of a central corridor in the Kelly Elementary School, in Moore, Oklahoma. 

This extensive damage was caused by one of the tornadoes that struck Oklahoma and Kansas on May 3, 1999. The corridor 

walls, which consisted of lightweight steel frame members with masonry infill topped by clerestory windows, were unable 

to withstand the extreme loads caused by lateral and uplift wind forces. This type of corridor construction is common and 

creates special challenges for building administrators and design professionals who must identify refuge areas in schools 

and other buildings. 
Contents



Contents

Foreword................................................................................iii

Introduction.............................................................................v

Chapter 1: Tornado Profile......................................................1

Chapter 2: Effects of High Winds............................................7

Wind Effects on Buildings..........................................................................7

Atmospheric Pressure Changes................................................................8

Debris Impact ............................................................................................9

Selecting Refuge Areas...........................................................................10

Chapter 3: Case Studies.......................................................11

Xenia Senior High School .......................................................................13

St. Augustine Elementary School and Gymnasium.................................21

 St. Augustine Elementary School Building ..................................22

 St. Augustine Elementary School Gymnasium ............................25

Kelly Elementary School..........................................................................27
Tornado Protection: Selecting Refuge Areas in Buildings

Contents

ii

Chapter 4: Selection Procedure............................................ 37

Determine the Required Amount of Refuge Area Space ........................ 38

Review Construction Drawings and Inspect the Building ........................ 39

Assess the Site........................................................................................ 42

Example of Refuge Area Selection Process ........................................... 46

General........................................................................................ 46

Required Refuge Area Space...................................................... 46

Architectural and Structural Characteristics................................. 46

Identifying the Best Available Refuge Areas................................ 52

Verifying the Best Available Refuge Areas .................................. 55

Selecting the Best Available Refuge Areas in 

Other Types of Buildings.......................................................................... 55

Mid-Rise and High-Rise Buildings ............................................... 55

Large Stores and Movie Theaters ............................................... 56

Chapter 5: Conclusions.......................................................... 57

Information Sources............................................................... 61
Foreword

iii

Foreword

Tornadoes cause heavy loss of life and property damage throughout much 

of the United States. Most schools and other public buildings include areas 

that offer some protection from this danger, and building administrators 

should know the locations of these areas.

This booklet presents case studies of three schools that were struck 

by tornadoes: Xenia Senior High School in Xenia, Ohio; St. Augustine 

Elementary School in Kalamazoo, Michigan; and Kelly Elementary School 

in Moore, Oklahoma, which were struck on April 3, 1974; May 13, 1980; 

and May 3, 1999, respectively. The resulting damage to these schools was 

examined by teams of structural engineers, building scientists, engineering 

and architectural faculties, building administrators, and representatives of 

the architectural firms that designed the buildings. From these and other 

examinations, guidance has been developed for selecting the safest areas 

in existing buildings – areas that may offer protection if a tornado strikes 

– referred to in this booklet as the best available refuge areas.

The guidance presented in this booklet is intended primarily to help 

building administrators, architects, and engineers select the best available 

refuge areas in existing schools. Building administrators, architects, and 

engineers are encouraged to apply this guidance so that the number of 

injuries and deaths will be minimized if a tornado strikes an occupied 

school.

For the design of safe rooms in schools yet to be constructed, refer to 

FEMA 361, Design and Construction Guidance for Community Safe 

Rooms, Second Edition.

Introduction



Introduction

The likelihood that a tornado will strike a building is a matter of probability. 

Tornado damage to buildings is predictable. Administrators of schools and 

other public buildings should have a risk analysis performed to determine 

the likelihood that a tornado will occur and the potential severity of the 

event. If a building is determined to be at sufficient risk, the safest areas of 

the building – areas that may offer protection if a tornado strikes – should 

be identified. This booklet refers to such areas as the best available refuge areas. In many buildings, the best available refuge areas are large 

enough to accommodate the number of people who normally occupy the 

building. A qualified architect or structural engineer should assess an existing building and identify the best available refuge areas.

This booklet presents information that will aid qualified architects and engineers in the identification of the best available refuge areas in existing 

buildings. Architects and engineers who are designing tornado safe rooms 

within new buildings may also find this booklet useful, but should refer to 

Design and Construction Guidance for Community Safe Rooms, Second 

Edition (FEMA 361) for more detailed information. FEMA 361 includes 

design criteria, information about the performance of specific construction 

materials under wind and debris impact loads, and examples of construction plans and costs.

The Wind Engineering Research Center at Texas Tech University provided 

much of the substance of this booklet. Dr. Kishor Mehta of the Center assisted in the preparation and review of the material. Invaluable assistance 

was provided by the architects and engineers of the buildings presented 

as case studies and by the school administrators.

What Are “Best Available Refuge Areas”?

The term best available refuge areas refers to areas in 

an existing building that have been deemed by a qualified architect or engineer to likely offer the greatest safety for building occupants during a tornado. It is important 

to note that, because these areas were not specifically 

designed as tornado safe rooms, their occupants may be 

injured or killed during a tornado. However, people in the 

best available refuge areas are less likely to be injured or 

killed than people in other areas of a building.

Chapter 1: Tornado Profile

Tornado Profile

The National Weather Service defines a tornado as a violently rotating 

column of air pendant from a thunderstorm cloud that touches the ground.

From a local perspective, a tornado is the most destructive of all atmospheric-generated phenomena. In an average year, a little more than 800 

tornadoes hit various parts of the United States, though the number has 

varied from 500 to 1,400 in a given year. More tornadoes are recorded in 

the months of May and June than in any other month (Figure 1-1). Figure 

1-2 shows the distribution of tornadoes by month in the United States.

Figure 1-1 Tornado occurrence by month in the United States.

Determining Tornado Risk

Detailed guidance for determining the magnitude of the 

tornado risk in a specific area of the United States is 

presented in FEMA 361, Design and Construction Guidance for Community Safe Rooms, Second Edition (for 

more information, see the section of this booklet titled 

Information Sources).

FEMA
Chapter 1: Tornado Profile

 Tornado Protection: Selecting Refuge Areas in Buildings

Summary of Recorded F3, F4, and F5 Tornadoes **

Per 2,470 Square Miles (1950-2006)

* Based on NOAA, Storm Prediction Center Statistics

** Refer to a discussion on Fujita (F) or Enhanced Fujita (EF) Scale 

 on page 4.

Number of Recorded 

F3, F4, and F5 Tornadoes 

Per 2,470 Square Miles

Figure 1-2 Tornado occurrence in the United States based on historical data.
Chapter 1: Tornado Profile



Tornado Characteristics

The time of day when tornadoes are most likely to occur is the mid-afternoon, between 3:00 p.m. and 6:00 p.m. (Figure 1-3). Occasionally, severe 

tornadoes have been recorded in the early morning or late evening.

The direction of movement is predominantly from the southwest to the 

northeast. However, tornadoes have been known to move in any direction 

along with the parent thunderstorms.

The length of path averages 5 miles, but some tornado paths have exceeded 100 miles.

The width of path averages 300 to 400 yards, but may reach up to 1 

mile.

The travel speed (translational) averages 25 to 40 miles per hour (mph), 

Figure 1-3 Tornado occurrence by time of day. but speeds from 5 to 60 mph have been recorded. FEMA FEMA

FEMA
Chapter 1: Tornado Profile

 Tornado Protection: Selecting Refuge Areas in Buildings

The rotational speed is assumed to be symmetrical. The maximum rotational velocity occurs at the edge of the tornado core. The speed reduces 

rapidly as the distance from the edge increases.

The intensity of damage from a tornado is related to wind speed, windborne debris, and type of construction. The atmospheric pressure drop in 

the center of a tornado does not destroy buildings, because pressures inside and outside of buildings equalize through broken windows and doors 

or through openings that result when sections of the roof are removed.

Tornadoes are rated by the National Weather Service according to the

tornado damage scale* developed by Dr. Theodore Fujita, a professor 

of meteorology. Ratings vary from F0, for light damage, to F5, for total 

destruction of a building (Figure 1-4). Ninety percent of the tornadoes 

recorded over the past 45 years have been categorized as F0, F1, or F2 

(Figure 1-5).

Figure 1-4 The Fujita Tornado Damage Scale.

F1

28%

F3

3%

F2

9%

F5

Less

than 1%

F4

Less

than 1%

F0

60%

Figure 1-5

Percentage of recorded tornadoes by Fujita Tornado 

Damage Scale ranking.

* Since February 2007, the National Weather Service has used the Enhanced Fujita Scale (EF Scale). This 

new scale ranges from EF0 to EF5. See http://spc.noaa.ov/efscale for further information on the EF scale.
Chapter 1: Tornado Profile



Rotation is generally counterclockwise in the northern hemisphere (Figure

1-6). About 10 percent of tornadoes have been known to rotate clockwise.

Wind speed is the sum of rotational speed and translational speed. The 

rotational speed decreases as the distance from the center of a tornado 

increases. With a counterclockwise rotation, the wind speed on the right 

side of the tornado is higher because the translational speed adds to the 

rotational speed.

Because of the unpredictability of tornado paths and the destruction of 

commonly used instruments, direct measurements of wind speeds have 

not been made in tornadoes. Rather, wind speeds are judged from the 

intensity of damage to buildings. Engineering assessment of damage puts 

the maximum wind speed at 200 mph in most destructive tornadoes, and 

the speed is not likely to exceed 250 mph near ground level.

FEMA

FEMA

Figure 1-6

Typical tornado rotation.

Chapter 2: Effects of High Winds



Effects of High Winds

In buildings hit by tornadoes, the threat to life is due to a combination of 

effects that occur at almost the same time. To understand the tornado damage that can occur in a building, the following must be considered:

• wind-induced forces

• changes in atmospheric pressure

• debris impact

Wind Effects on Buildings

The wind speeds generated by some tornadoes are so great that designing for these extreme winds is beyond the scope of building codes and 

engineering standards. Most buildings that have received some engineering attention, such as schools, and that are built in accordance with sound 

construction practices can usually withstand wind speeds specified by 

building codes. Meeting these code-specified wind speeds can provide 

sufficient resistance to tornadic winds if the building is located on the outer 

edge of the tornado vortex. In addition, if a portion of the building is built 

to a higher tornado design standard, then both building and occupant survival are improved.

Wind creates inward- and outward-acting pressures on building surfaces, 

depending on the orientation of the surface (e.g., flat, vertical, low-slope). 

As the wind moves over and around the building, the outward-acting 

pressure increases as the building geometry forces the wind to change 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 2: Effects of High Winds



direction. These pressure increases create uplift on parts of the building, 

forcing the building apart if it is too weak to resist the wind loads. When 

wind forces its way inside or creates an opening by breaking a window or 

penetrating the roof or walls, the pressures on the building increase even 

more. Figure 2-1 shows how wind affects both an enclosed building and a 

building with openings.

Heavy building materials (e.g., reinforced masonry or concrete) that are 

well tied to all other building components often survive extreme winds. The 

weight of these materials helps resist uplift and lateral loads, and heavy 

materials often stop windborne debris that can increase damage to the 

building. However, heavy concrete roof panels and heavy masonry walls 

that are not adequately connected or reinforced have failed during severe 

winds. Lightweight roofing and siding materials such as gravel, insulation, 

shingles, roofing membranes, and brick veneer can also be a problem.

Building shapes that “catch” the wind, such as overhangs, canopies, and 

eaves, tend to fail and become “sails” in extreme winds. Flat roofs can be 

lifted off when the wind flows over them and increases the uplift pressure 

at the corners and edges of the roofs.

Atmospheric Pressure Changes

Initially, the pressure outside a building during a tornado is very low compared to the pressure inside. In most buildings, however, there is enough 

air leakage through building component connections to equalize these 

pressures. Also, windborne debris is likely to break windows and allow wind 

to enter.

The explosion of buildings during a tornado due to atmospheric pressure 

differences is a myth. In reality, the combination of internal pressure and 

outward pull on the building from suction pressure has caused building 

failures that have forced the walls outward and given the building the 

FEMA

Figure 2-1

Effects of wind on a fully enclosed building and on a 

building with openings.
Chapter 2: Effects of High Winds



appearance of having exploded. During an event, doors and windows 

should remain closed on all sides of the building in order to minimize the 

entry of wind into the building.

Debris Impact

The extreme winds in tornadoes pick up and carry debris from damaged 

buildings and objects located in the path of the winds (see Figures 2-2 and

2-3). Even heavy, massive objects such as cars, tractor trailers, and buses 

can be moved by extreme winds and cause collateral damage to buildings. 

Light objects become flying debris, or missiles, that can penetrate doors, 

walls, and roofs; heavier objects can roll and cause crushing-type damage. 

Figure 2-2 

Example of damage from a windborne missile. A 2-inch 

by 6-inch board penetrated a refrigerator.

Figure 2-3

Example of severe damage from a windborne 

missile. This metal door was pushed inward by 

the impact of a heavy object.

FEMA

FEMA
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 2: Effects of High Winds

10

Missiles can travel vertically as well as horizontally (see Figure 2-4). Therefore, safe rooms and refuge areas should provide protection overhead as 

well as on the side. Building walls and roofs can be designed to withstand 

the impacts of these missiles. Protection can be provided at the exterior 

building wall, or interior barriers can be constructed to provide protection 

for a smaller area within the building. 

Selecting Refuge Areas

Wind effects on buildings have been studied sufficiently to predict which 

building elements are most likely to successfully resist the extreme wind 

pressures caused by tornadoes and which are most likely to fail. Sufficient 

material testing and design work has been performed for large safe rooms 

to develop a refuge area selection guide for any building in which such areas are needed. Many buildings contain a small interior area or areas that 

could serve as the best available refuge area or possibly be converted or 

reinforced for refuge area use.

Figure 2-4

Example of damage from windborne missiles. 

Medium and small missiles penetrating through the 

roof of a high school. The missile protruding from the 

roof in the foreground is a double 2-inch by 6-inch 

wood board. The portion sticking out of the roof is 13 

feet long. This missile penetrated a ballasted ethylene 

propylene diene monomer (EPDM) membrane, 

approximately 3 inches of polyisocyanurate roof 

insulation, and the steel roof deck. The missile lying on 

the roof just beyond it is a 2-inch by 10-inch, 16-footlong wood board. The missile protruding from the 

roof in the background is a 2-inch by 6-inch, 16-footlong wood board. 

FEMA
Chapter 3: Case Studies

11

Case Studies

A large number of schools have been destroyed or heavily damaged by 

tornadoes, and there have been many injuries and deaths. The three 

school buildings presented as case studies in this booklet were selected 

for the following reasons:

• All were hit by different, but intense storms.

• The three structures varied in size, age, and type of construction.

• All were designed by different architects and engineers to national 

building codes.

• All had to be partially or totally destroyed later because of the extent of 

the tornado damage.

The building damage was examined by teams of structural engineers, 

building scientists, specially trained members of engineering and architectural faculties and firms, building administrators, and representatives of the 

architectural firms that designed the buildings.

The determination of the best available refuge areas in the three buildings 

(shown on floor plans presented later in this chapter) was based on three 

sources of information, in the following order of importance:

• persons who were in each building during the tornado

• building examinations by engineers and architects

• aerial photographs taken shortly after the storms

Guidance for Refuge Area Selection

Detailed evaluation checklists for selecting the best available refuge areas in existing buildings and guidance for designing and constructing safe rooms are presented in FEMA 

361, Design and Construction Guidance for Community Safe 

Rooms, Second Edition (for more information, see the section 

of this booklet titled Information Sources).

FEMA
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

12

The identified refuge areas in these buildings are the best that were available in each of the three buildings when the storms occurred.

These case studies are presented here with two goals:

• to help building designers and administrators locate accurately the 

parts of a building that would likely be left standing after a tornado—

before the tornado strikes

• to help architects and engineers design buildings that offer occupants 

excellent tornado protection
Chapter 3: Case Studies

13

Figure 3-1 Xenia Senior High School, Xenia, Ohio.

Xenia Senior High School

Xenia, Ohio

Building population:1,450, including staff

 12 students, 3 staff in building during tornado

Tornado direction: From southwest

Damage intensity: F5

Time: 4:45 p.m.

Date: April 3, 1974

WERC, TEXAS TECH UNIVERSITY 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

14

Xenia Senior High School (Figure 3-1) was a two-story, slab-on-grade 

building without a basement located on the north side of Xenia, Ohio. It 

faced Shawnee Park to the west.

The massive tornado hit 1 hour and 45 minutes after school dismissal. It 

was spotted by a student who was leaving the school. She alerted drama 

students who were rehearsing in the auditorium. The students ran and 

dove for shelter in a nearby corridor.

The tornado passed directly over the school. Two school buses came to 

rest on the stage where the students had been rehearsing. Some of the 

students were treated for injuries at a nearby hospital.

The building was found to be unsafe to enter and was demolished.

Construction

The construction types varied among the main parts of the school—original building, three additions (A, B, and C):

Original building and addition B: Lightweight steel frame, open-web steel 

joists, 2-inch gypsum roof deck.

Addition A: Loadbearing masonry walls, hollow-core precast concrete roof 

planks.

Addition C: Precast concrete frame, concrete double-tee floor/roof beams.

Girls’ gym: Loadbearing masonry wall, precast concrete tee beams.

Auditorium and boys’ gym: Loadbearing masonry walls, steel trusses.
Chapter 3: Case Studies

15

Tornado Damage

The tornado passed directly over the school, engulfing the entire building 

and the adjacent fieldhouse to the south (Figure 3-2).

The enclosure walls failed on the west and south sides, allowing the winds 

to enter the building. The roofs collapsed over the three large spans—the 

auditorium, the boys’ gym, and the girls’ gym. The lightweight roof over the 

original two-story building was torn off by the extreme winds.

Figure 3-2 Xenia Senior High School, Xenia, Ohio.

WERC, TEXAS TECH UNIVERSITY 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

16

Hazardous Elements

All windows on the west and south sides were blown into the interior. The 

high single-story, loadbearing masonry walls of the long-span rooms 

failed, allowing the roofs to fall in. The unbaffled west entrances allowed 

the east-west corridors to become wind tunnels.

Debris from nearby houses, vehicles, and Shawnee Park became missiles, many of which hit and entered the school. The 46-foot-high masonry 

chimney collapsed. A non-loadbearing second-floor wall on the north 

side collapsed onto a lower roof.

Protective Elements

The only portion of the original building that offered refuge was the lowest 

floor (first floor). The completely interior spaces remained intact, especially the smaller spaces. Most of the corridors that were perpendicular to 

the storm path offered considerable protection (Figures 3-3 and 3-4).

The concrete structural frame of addition C remained intact. As a result, 

interior portions of the second floor provided refuge for some custodians.

The heavy concrete roof remained in place, wherever the supports were 

rigid frames. It also remained intact in addition A, with its loadbearing 

walls.

The concrete block interior partitions stopped incoming missiles from 

reaching adjacent interior spaces.

As a result of combinations of the above protective elements, extensive 

refuge space existed in scattered locations throughout the building (Figure 

3-4). Figure 3-3

Surviving interior hallway. This is an example of the 

type of area that may provide refuge for building 

occupants during a tornado. 

WERC, TEXAS TECH UNIVERSITY 

Selecting Refuge Areas

An understanding of the effects of hazardous and protective elements allows the best available refuge areas in an 

existing building to be identified. The checklists in FEMA 

361 should be used to confirm that the selected refuge 

areas are the best available.
Chapter 3: Case Studies

17

Figure 3-4 Best available refuge areas in Xenia Senior High School.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

18

Comments

“The cast had just done the big dance number from the show. They had done 

a sloppy job and I was just getting ready to tell them to do it again when a 

girl yelled, ‘Hey, you want to see a tornado? There’s a funnel cloud outside.’ 

I came very close to telling everyone to forget it and do the dance again. 

That would have been a fatal mistake.

“Instead, I jumped off the stage and told everyone to follow me so that we 

could get a view of it. We ran out the front doors of the school nearest the auditorium. It looked like a lot of dirt or smoke swirling around. We couldn’t see 

anything that looked like a clearly defined funnel cloud. We were looking out 

at the park across from the school. The mass of wind, dirt, and debris was 

everywhere. I would say between 100 and 200 yards away. Cars parked in 

front of the school started to bounce around a bit from the force of the winds. 

It was really beyond belief.

“Someone said we’d better take cover, so we turned around and ran from 

the hallway we were in into the center hall that ran north and south. Before 

we could reach the center hall, the lights went out.

“I only opened my eyes a couple of times. When I did, I saw large pieces 

of dirt and wood flying through the air. Lockers clanged open and shut, and 

several sections of lockers were actually pulled from the wall and thrown 

onto the floor. One section barely missed some of my students when it 

came out of the wall.

“I was sitting directly across from one of the restrooms, and a metal door 

kept flying open and shut constantly during the time that the tornado was 

on us. That was my greatest fear.”

Figure 3-5

Loss of lightweight roof over the original two-story 

building.

WERC, TEXAS TECH UNIVERSITY 
Chapter 3: Case Studies

19

English/Drama Teacher

“I was watching the sky, and the lightning seemed to get worse. The 

minutes went by, and it at first had been going vertically, and slowly it 

started to go on angles.

“The black cloud looked like it was about 2 miles away from the school. As 

I watched, the lightning came concentrated into the middle of the cloud 

and began going on angles until it was horizontal.

“For a few seconds, I didn’t know that the shrinking cloud was forming a 

tornado funnel. The funnel was a whitish-grey color more in the shape of a 

column than it was a funnel. I realized it was a tornado when I saw air currents begin to swirl. At first I was not afraid. Instead, I was fascinated that 

you could really see air currents in it.

“I went to the main office to get the principal, but the office was locked and 

everyone was gone. Just as I started to move, the drama cast started to 

rehearse a song in the auditorium

“I walked down the aisle past 24 rows of seats to one of my friends in the 

second row and said, ‘Hi Paul, have you ever seen a tornado?’ He said ‘Ya’ 

and put his arm up on the back of a chair like he’s getting ready for a long 

conversation. I said ‘Neat, there’s one across the street.’ He looked up at 

me. Then they all stood up and started to walk out. They got about halfway 

out and started running.

“All the kids were yelling, ‘Hey, neat, look at that’ and things like that. All of 

a sudden everyone was dead silent for about 4 seconds. Then everyone 

started screaming and yelling at once. Julie yelled, ‘Get to A-1.’ I said, ‘Get 

to the southwest corner.’ Mr. Heath turned around and yelled, ‘Go to the 

main hall.’ So all the cast started to rush out of the doors and promptly got 

stuck, so they had to wait and go slow and go out one or two at a time.”

Figure 3-6

Collapsed hollow-core precast roof panels in the 

classroom area.

WERC, TEXAS TECH UNIVERSITY 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

20

Student (spotter)

“When we were warned about the tornado, we all ran to the door to look at 

it. I was about the last one to arrive there, and I stood there very long until 

someone yelled from around the corner to get over there. The last thing I 

saw the tornado doing was picking up my car which was parked out on the 

street.

“I then ran around the corner and found everyone already lying along each 

side of the wall and some around the corner. I then ran to the intersection 

of the two halls and laid alongside the wall.

“When it was all over, I was buried from the waist down in little pieces of 

gravel, boards, and a lot of water from the lake across the street in the 

park.”

Student

“The first place I ran to was this little cubbyhole right in front of the girls’ 

restroom door. If I had stayed there, I would have been splattered across 

the hall, because it blew so hard it almost came off its hinges. For some 

reason, which I cannot account for, I dived across the hall right after the 

lights went out and got to the other side of the hall just as the front doors 

were breaking.

Figure 3-7

Collapsed gymnasium walls and roof, where openweb roof joists were supported on unreinforced 

masonry walls.

WERC, TEXAS TECH UNIVERSITY 
Chapter 3: Case Studies

21

Figure 3-8 St. Augustine Elementary School, Kalamazoo, Michigan.

St. Augustine Elementary School 

and Gymnasium Kalamazoo, Michigan

Building population:Approximately 400, including staff

 One staff person in the building during tornado

Tornado direction: From west

Damage intensity: F2-F3

Time: 4:09 p.m.

Date: May 13, 1980

WERC, TEXAS TECH UNIVERSITY 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

22

Figure 3-9

Collapsed second floor of St. Augustine Elementary 

School building.

St. Augustine Elementary School Building

The St. Augustine Elementary School was a two-story, 17-classroom 

building constructed in 1964. Classes had been dismissed when the tornado struck. Only the facility engineer remained in the building. He took 

refuge in a janitor’s closet on the first floor and escaped injury.

Construction

The structural system consisted of 3-foot-wide masonry piers constructed 

of 8-inch concrete masonry units and 4-inch face bricks. The piers were 

8.7 feet apart. Steel beam lintels spanned the window openings between 

the piers. Steel open-web joists at 2 feet on center supported the 1.5-inch 

steel roof deck, which was welded to joists. The top chords of the joists 

were extended to provide a 2-foot overhang.

Tornado Damage

The tornado winds lifted part of the roof and collapsed the second-floor 

piers in one wing of the school building (Figures 3-8, 3-9, and 3-10). The 

wind and windborne debris blew in most of the windows, and windborne 

debris was found in the classrooms (Figure 3-11). The exterior solid-core 

wood doors stayed in place and kept the debris out. Wired glass windows 

near the exterior doors remained intact. The interior doors to the classrooms remained in place although the hinges were damaged. The school 

was damaged to an extent where demolition was required.

Hazardous Elements

The structural system of unreinforced masonry piers collapsed and almost one-third of the second-floor lightweight roof structure was lifted. 

Roof removal occurred over the classrooms as well as over the corridor. 

Most of the skylights in the corridors were removed by wind or broken 

by windborne debris. Almost all the windows on both floors were broken. 

Windborne debris and broken glass were found in the classrooms.

WERC, TEXAS TECH UNIVERSITY 
Chapter 3: Case Studies

23

Figure 3-10

Floor plan of second floor of St. Augustine Elementary School showing 

locations of roof removal.

Figure 3-11

Broken windows and debris in classroom of St. 

Augustine Elementary School building.

WERC, TEXAS TECH UNIVERSITY 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

24

Protective Elements

The structural system of the first floor remained intact. The exterior solid-core wood doors stayed in place and kept the debris out. The interior 

walls and doors were able to prevent debris from entering the corridors. 

The corridors, offices, and toilet areas on the first floor, which had two or 

more walls to the exterior, would have protected the occupants from serious injury (Figure 3-12).

Figure 3-12

Best available refuge areas in the St. Augustine 

Elementary School building.

Selecting Refuge Areas

An understanding of the effects of hazardous and protective elements allows the best available refuge areas in an 

existing building to be identified. The checklists in FEMA 

361 should be used to confirm that the selected refuge 

areas are the best available.
Chapter 3: Case Studies

25

Figure 3-13 St. Augustine Elementary School Gymnasium, Kalamazoo, Michigan.

St. Augustine Elementary School Gymnasium

An 80-foot by 100-foot, 23-foot-high gymnasium building was adjacent to 

the school building.

Construction

The structural system consisted of loadbearing masonry walls constructed 

of 12-inch concrete masonry units and 4-inch face brick. The walls were 

not reinforced in the vertical direction. The roof structure consisted of longspan steel joists spanning 80 feet between the walls and spaced 6 feet 

apart. The steel roof deck was connected to the joists with puddle welds.

WERC, TEXAS TECH UNIVERSITY 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

26

Tornado Damage

The building was destroyed (Figures 3-13 and 3-14). The loadbearing 

west wall collapsed inward, and the east wall fell outward. The roof fell in 

the building when the walls collapsed.

Hazardous Elements

Slender unreinforced masonry walls and long-span roof structure.

Protective Elements

None

Observations: School Building and Gymnasium 

The unreinforced masonry walls combined with the lightweight roof structure in the building as well as the gymnasium building were vulnerable to 

collapse in windstorms. Gymnasium buildings are not considered suitable for occupant protection because they usually include tall walls and 

long-span roofs. Lightweight roof structures that are not adequately anchored can be lifted in windstorms. Except in violent (F4 and F5 in the 

Fujita scales or EF4 and EF5 in the Enhanced Fujita scales*) tornadoes, 

the lower floor (in two-story or higher buildings) generally provides good 

protection for occupants when there are two or more walls between the 

refuge area and the outside.

Figure 3-14

Collapsed St. Augustine Elementary School 

Gymnasium building.

WERC, TEXAS TECH UNIVERSITY 

* Refer to page 4 for a discussion on Fujita (F) or Enhanced Fujita (EF) Scale.
Chapter 3: Case Studies

27

Kelly Elementary School

Moore, Oklahoma

Building population:490, including staff

Tornado direction: From southwest

Damage intensity: F4

Time: 7:25 p.m.

Date: May 3, 1999

Figure 3-15 Kelly Elementary School, Moore, Oklahoma.

CLEVELAND COUNTY, OK
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

28

The Kelly Elementary School was a one-story slab-on-grade building, 

without a basement, located in Moore, Oklahoma.

The tornado hit after school hours and passed just to the north of the site. 

Damage to the school building was both severe and extensive (Figure 3-

15). As discussed in the Lessons Learned section in this case study, the 

remaining structure was demolished and the school was rebuilt. The new 

school includes structural elements designed to provide increased wind 

resistance.

Construction

Three basic wall types were used in the construction of the school:

• reinforced masonry

• unreinforced masonry topped by reinforced bond beams

• lightweight steel frame with masonry infill

The roof system consisted of open-web steel roof joists, metal decking, 

and a built-up roof. Wall and roof construction of this type is common to 

many schools in the United States.

Hall corridors were the designated areas of refuge (see Figure 3-16). The 

corridor walls were of lightweight steel frame with masonry infill. The infill 

extended to a height of approximately 7 feet. Above this height were clerestory windows that extended to the tops of the walls. Had the halls been 

occupied during the tornado, many injuries and deaths would have occurred (see Figure 3-20, later in this chapter).
Chapter 3: Case Studies

29

Figure 3-16 Designated refuge areas in the original Kelly Elementary School.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

30

Figure 3-18

Corridor area. Separation of reinforced bond beam 

(indicated by circles) from supporting wall.

Figure 3-17

Interior and exterior unreinforced masonry walls were damaged when 

reinforced bond beams failed.

Tornado Damage

Wall and roof structures, including those of designated areas of refuge, 

failed under the combination of uplift and lateral loads caused by the tornado winds. Connections between bond beams, joists, and walls were 

adequate for gravity loads, but could not resist the high uplift loads caused 

by the wind.

Unreinforced masonry walls failed when the roof system was lifted or 

removed by tornado winds (Figures 3-17, 3-18, and 3-19). Figures 3-17 

and 3-19 show failed interior and exterior walls, respectively. Figure 3-18 

shows the separation of the reinforced bond beam (indicated by circles) 

from the upper part of a corridor wall. The inclusion of clerestory windows 

in some corridor walls contributed to their failure under loads imposed by 

tornado winds (Figure 3-20).

FEMA

FEMA
Chapter 3: Case Studies

31

Figure 3-19

Collapsed roof structure and exterior wall.

Figure 3-20

Failed interior corridor walls. These walls consisted 

of unreinforced brick masonry infill between steelframe members. The brick masonry extended to a 

height of approximately 7 feet. Clerestory windows 

extended from the top of the masonry to the tops of 

the walls. 

FEMA FEMA
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

32

Inspection of the roof damage revealed that the roof decking failed at the 

points where it was welded to the tops of the steel trusses. Although the 

spacing of the welds appeared to be consistent with standard practice, 

the welds were not strong enough to resist the wind uplift forces (Figure 

3-21).

Damage was also caused by the impact of windborne missiles. Figure 2-

3, in Chapter 2, shows a steel door that appeared to have been opened 

by the impact of a heavy object. This door led into an area where the 

roof was missing. The opening created by this breached door may have 

allowed wind to enter the building and create internal pressure that increased the load on the building envelope. Figure 3-22 shows damage 

to a laminated glass window hit by a table.

Figure 3-21

Failed roof structure showing broken welds between metal roof deck 

and tops of joists (upper circle) and lack of vertical reinforcement 

(bottom circle).

FEMA

FEMA

Figure 3-22

Impact performance of laminated glass. The corner 

of a table penetrated this laminated glass window, 

but the glass remained in its frame.
Chapter 3: Case Studies

33

Hazardous Elements

Walls with clerestory windows, such as the corridor walls of the designated areas of refuge, have limited capacity to resist lateral forces.

Unreinforced masonry walls failed when the reinforced bond beams at 

the tops of the walls failed.

Welds between the roof decking at the tops of the metal joists failed because they were not strong enough to resist the uplift.

Unprotected doors and windows can be breached by windborne missiles. The resulting openings allow wind to enter the building, where it 

causes increased pressures on the building envelope.

Protective Elements

None

Lessons Learned

Because the damage to Kelly Elementary School was so great, the 

school was demolished and completely rebuilt. The new building, although constructed on the same footprint, incorporated several structural 

improvements specifically designed to provide improved resistance to 

extreme winds and create refuge areas for the school’s occupants. As in 

the original building, the central corridors of the three wings are the designated refuge areas (Figures 3-23 and 3-24).

The creation of refuge areas in the new school involved, among other 

improvements, the design and construction of stronger loadbearing walls, 

roofs, roof-to-wall connections, and wall-to-foundation connections. Figure 3-25 is a typical cross-section of the top of a safe area (corridor) 

wall in the new school. As shown in this figure, the wall is constructed 

of reinforced concrete masonry. Note the continuous, closely spaced (8 

inches on center) vertical reinforcement bars, fully grouted block cells, 
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 3: Case Studies

34

Figure 3-24

Corridor (designated safe area) in reconstructed 

Kelly Elementary School.

Figure 3-23

Designated refuge areas in the reconstructed Kelly Elementary School.

CITY OF MOORE, OK
Chapter 3: Case Studies

35

6-inch-thick reinforced concrete roof slab, and strong connection between 

the roof slab and wall. The new ceilings over the corridors are constructed 

of poured reinforced concrete, which will provide nearly ultimate resistance to winds and damaging missiles.

Figure 3-26 is a typical cross-section of the bottom of a safe area wall. 

Note that the wall is securely tied to the floor slab with L-shaped reinforcing bars placed 24 inches on center. As shown in Figures 3-23 and 3-24, 

the corridor walls do not include the clerestory windows that increased the 

vulnerability of the corridor walls in the original school building. 

The improvements discussed here are designed to prevent the types of 

damage to interior corridor walls and roofs shown previously in Figures 

3-17, 3-18, 3-20, and 3-21. The reconstruction of the Kelly Elementary 

School is a good example of how refuge areas can be incorporated into 

new construction.

Figure 3-25

Typical cross-section of top of safe area wall in the 

reconstructed Kelly Elementary School.

Figure 3-26

Typical cross-section of bottom of safe area wall in the reconstructed Kelly 

Elementary School.

Chapter 4: Selection Procedure

37

Selection Procedure

The procedure presented in this chapter is designed to assist in a systematic review of a building for the purpose of selecting the areas within the 

building that are likely to be the most resistant to tornadoes, referred to 

in this booklet as the best available refuge areas. When used for refuge 

during tornadoes, these areas do not guarantee safety; they are, however, 

the safest areas available for building occupants. This selection procedure 

does not apply to structures such as lightweight modular houses and offices and relocatable classrooms. Such structures are presumed to fail, 

and they must be evacuated.

Most buildings, unless specifically designed as shelters or safe rooms, will 

sustain catastrophic damage if they take a direct hit from a Violent Tornado (i.e., a tornado ranked F4 and F5 in the Fujita scales or EF4 and EF5 

in the Enhanced Fujita scales*—see Chapter 1). Because the maximum 

wind speeds associated with a Violent Tornado greatly exceed the wind 

speeds that the buildings were designed to withstand, complete destruction will usually occur during these extremely rare events.

In reality, most tornadoes do not produce the winds of a Violent Tornado, 

and some areas of many buildings can survive these lesser events without catastrophic damage or collapse. Placing building occupants in the 

best available refuge areas within a building greatly reduces the risk of 

injury or death. However, unless the refuge area was designed as a safe 

room, its occupants are vulnerable to injury or death.

Guidance for Refuge Area Selection

Detailed evaluation checklists for selecting the best available refuge areas in existing buildings and guidance 

for designing and constructing shelters are presented in FEMA 361, Design and Construction Guidance for 

Community Safe Rooms, Second Edition (for more information, see the section of this booklet titled Information 

Sources.)

FEMA

* See page 4 for a discussion on Fujita (F) or Enhanced Fujita (EF) Scale or http://spc.noaa.ov/efscale for 

further information.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

38

Selecting the best available refuge areas involves three main steps:

• determining how much refuge area space is required to house 

building occupants 

• reviewing construction drawings and inspecting the building to 

identify the strongest portion(s) of the building

• assessing the site to identify potential tree, pole, and tower fall-down 

and windborne missiles

Determining the required refuge area space and assessing the site are 

relatively straightforward tasks that can be completed by many people. 

The drawing review and building inspections are more technical in nature. Qualified structural engineers or architects should be consulted for 

those tasks.

Determine the Required Amount 

of Refuge Area Space

Refuge areas must be large enough to provide space for all occupants 

who may be in the building when a tornado strikes. In schools, space must 

be provided for all students and faculty, maintenance and custodial workers, and any parents or other visitors who may be present.

Refuge area space requirements vary according to the age of the occupants and any special needs they may have. FEMA 361 recommends that 

shelter space determinations be based on the following guidelines:

Occupants, Standing and seated 5 square feet per person

Wheelchair Users 10 square feet per person

Bedridden Children or Adults 30 square feet per person

Example Calculation of Required 

Refuge Area Space

Consider an elementary school that has 560 students, 

2 of whom use wheelchairs; 28 faculty members; and 

3 custodial and maintenance workers. Calculating the 

required refuge area space involves identifying all groups 

of occupants and their refuge space needs:

589 Occupants @ 5 sq ft each = 2,945 sq ft

2 Wheelchair users @ 10 sq ft each = 20 sq ft

Total = 2,965 sq ft

In this instance, the required refuge area space could be 

provided by a total of 375 feet of 8-foot-wide corridor or 

by a combination of smaller areas.
Chapter 4: Selection Procedure

39

In larger buildings, several dispersed refuge areas should be selected 

when possible so that travel times for building occupants are minimized. 

Keep in mind that building occupants with special needs, such as wheelchair users, may require additional time to reach the refuge area.

Review Construction Drawings and 

Inspect the Building

As there are stronger and weaker tornadoes, there are stronger and 

weaker portions of any building. The construction drawing review and 

building inspection help identify the stronger areas that are most resistant 

to damage from high winds and windborne missiles.

Selecting the best available refuge areas involves predicting how a building 

may fail during an event that produces complex winds and unpredictable 

missiles. The failure modes in a building are numerous, complex, and progressive. The complex nature of tornadoes and the variations in as-built 

construction limit the effectiveness of even detailed engineering models in 

accurately predicting failure of an existing building. However, experience 

and subjective judgment can help identify areas that are less prone to failure during a tornado.

Protective Elements

The lowest floor of a building is usually the safest. Upper floors receive 

the full strength of the winds. Occasionally, tornado funnels hover near the 

ground but hit only upper floors. Belowground space is almost always 

the safest location for a refuge area. If a building has only one floor and 

no basement, look for building elements that can improve the chances for 

occupant survival:

1. Interior partitions that provide the greatest protection are somewhat 

massive, fit tightly to the roof or floor structure above, and are securely 

Why Are Individual Building 

Inspections Needed?

This section describes the role of different building elements in providing safety from extreme winds. However, 

individual buildings can vary considerably; therefore, individual building assessments based on the guidelines 

of FEMA 361 are always recommended. For example, 

although the lowest floors in a building are usually the safest, an individual evaluation of a school building may find 

that second-story areas are safest in a particular instance. 

Another example, shown previously, is the performance 

of Kelly Elementary School. Although interior corridors are 

often one of the safer areas, the corridors in Kelly Elementary School, as originally constructed, were unsafe during 

the F4 tornado that struck Moore, Oklahoma. An individual 

evaluation of Kelly Elementary School using the checklists 

in FEMA 361 would reveal these weaknesses.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

40

connected to the floor or roof. Avoid interior partitions that contain windows.

2.Short spans on the roof (see sidebar) or floor structure are more 

likely to remain intact. This is because short spans limit the amount of 

uplift on connections caused by winds. Although short spans are best, 

small rooms, even those with walls that do not support the roof, may 

be the best available refuge areas. If the roof rises and then collapses, 

the interior walls may become supporting walls and thereby protect the 

occupants, although there is the risk that the walls will also collapse or 

be blown away. 

3.Buildings with rigid frames usually remain intact. Buildings with heavy 

steel or reinforced concrete frames rigidly connected for lateral and 

vertical strength are superior to buildings that contain loadbearing 

walls. On the other hand, wood-framed construction used in residences and in light commercial buildings can be extremely vulnerable 

to damage from high winds. Wood-framed and pre-engineered metal 

buildings should not be used as tornado shelters.

4.Poured-in-place reinforced concrete, fully grouted and reinforced 

masonry, and rigidly connected steel frames are usually still in 

place after a tornado passes. However, in either type of construction, 

the floor or roof system must be securely connected to the supports. 

Gravity connection of the roof deck to the frame is inadequate. Generally, the heavier the floor or roof system, the more resistant it is to 

lifting and removal by extreme winds. Figure 4-1 shows typical fully 

grouted, reinforced masonry wall construction.

Hazardous Elements

The following building elements seriously diminish occupant safety. Areas 

that contain these elements should not be used as refuge areas.

1.Long-span roofs are almost always found on rooms with high ceilings 

(e.g., gyms, auditoriums, music and multipurpose rooms). The exterior 

What is a Short-Span Roof?

No single number defines a “short span.” The ability of 

any roof to resist wind uplift depends on several factors. 

The type of structural members used in the roof (e.g., 

steel joists vs. reinforced concrete frames), the weight of 

the roof (heavy for concrete decks vs. light for most metal 

decks), and the strength of the connections between the 

roof and the supporting structure all dictate how well a 

roof will resist high winds.

In FEMA 342, Midwest Tornadoes of May 3, 1999, FEMA’s 

Building Performance Assessment Team recommended 

that rooms with roof spans longer than 40 feet not be 

used as refuge areas. Similarly, the Red Cross limits roof 

spans to 40 feet for hurricane shelters. The 40-foot criterion should be considered an absolute maximum unless 

an engineering analysis determines that the roof system is adequate. Preferably, best available refuge areas 

should have roof spans that are 25 feet or less.
Chapter 4: Selection Procedure

41

walls of such rooms are higher than typical one-story walls and often 

collapse under the forces imposed by tornado winds. Occasionally, 

high walls collapse into a long-span room, and roofs that depend on 

the walls for support collapse. Building administrators must resist 

the temptation to gather many building occupants into a large space 

so that control will be easier. Often these spaces incur maximum 

damage; if a large group of people is present, many deaths and 

injuries are likely to result.

2.Lightweight roofs (e.g., steel deck, gypsum, lightweight insulating 

concrete, cement woodfiber, wood plank, and plywood) usually will be 

lifted and partially carried away while roof debris falls into the room below. The resulting opening then allows other flying debris to be thrown 

into the interior space. In addition, walls often collapse after loss of the 

roof deck.

3. Heavier roofs (e.g., precast concrete planks, channels, and tees) may 

be lifted, move slightly, and then fall. If supporting walls or other members have collapsed, the roof may fall onto the floor below, killing or 

seriously injuring anyone there. Cast-in-place concrete decks typically 

remain in place.

4.Windows are no match for the extreme winds or missiles of a tornado. Windows usually break into many jagged pieces and are blown 

into interior spaces. Even tempered glass will break, but usually into 

thousands of small, cube-like pieces. Windows in interior spaces also 

break, usually from missile impact. Acrylic or polycarbonate plastics 

are more resistant to impact than glass, but large panes may pop out, 

and the fumes given off when these materials burn can be toxic. Laminated glass can be quite effective, except when hit by very powerful 

missiles (see Figure 3-22, in Chapter 3). Windows at the ends of corridors are particularly dangerous because high winds can blow them 

down the corridor. (See window protection sidebar on page 42.)

Figure 4-1

Typical fully grouted, reinforced masonry construction.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

42

5.Wind tunnels occur in unprotected corridors facing oncoming winds. 

In post-event damage inspections, debris marks have been found covering the full height of corridor walls, indicating that the winds occupied 

almost the entire volume of the corridor. If entrances are baffled with a 

solid, massive wall, this effect is much less serious. 

6.Loadbearing walls are the sole support for floors or roofs above. If 

winds cause the supporting walls to fail, part or all of the roof or floors 

will collapse. In addition, walls often collapse after loss of the roof 

deck.

7. Masonry construction is not immune to wall collapse. Most masonry 

walls are not vertically reinforced and can fail when high horizontal 

forces such as those caused by winds or earthquakes occur. Masonry 

walls without vertical reinforcement are potentially hazardous. Such 

walls can also fail and create an additional hazard if the roof deck is 

lost.

Assess the Site

Inspect the site and identify trees in excess of 6 inches in diameter, poles 

(e.g., light fixture poles, flag poles, power poles), masonry chimneys, and 

towers (e.g., electrical transmission and communication towers). Those 

trees, poles, chimneys, and towers that are close enough to fall on the 

building should be marked on a site plan. Accurately locate those trees, 

poles, chimneys, and towers and note the approximate height of each on 

the plan. (An example of a site plan is shown in the refuge area selection 

example presented later in this chapter.)

In selecting the best available refuge areas, plot the tree, pole, chimney, 

and tower fall-down areas on the building plan. The best available refuge 

area should not be located within or adjacent to the fall-down areas, because fall-down of trees, poles, chimneys, and towers can cause localized 

A Note About Window Protection

Many facilities in hurricane-prone areas have provisions to protect vulnerable windows from high winds 

and windborne debris. Most window protection methods 

are designed for wind speeds much lower than those associated with tornadoes. Also, some window protection 

devices, such as shutters and storm panels, need to be 

installed or closed to offer any benefit. With tornadoes, 

there will generally not be sufficient warning time for this 

to be accomplished. Consequently, any refuge area with 

large windows should be avoided.

An evaluation of potential refuge areas may include areas 

with doors that contain small windows. After an evaluation has been completed, areas that include such doors 

could still be considered the best available refuge areas 

despite the vulnerability of the glass. However, known 

problems should be addressed to the extent possible. Examples of corrective actions that could be taken include 

replacing any doors that contain windows, replacing the 

existing glazing with more impact-resistant glazing, and 

ensuring that the occupants of the refuge area are not 

in the path of any debris that could be generated by the 

failure of these small windows.
Chapter 4: Selection Procedure

43

Figure 4-2

Two trees toppled by tornado winds damaged this 

house in Haysville, Kansas. 

Figure 4-3

Failure of brick chimney under tornado winds damaged 

the room of this house in Moore, Oklahoma.

FEMA FEMA
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

44

Figure 4-5

This photograph illustrates the importance of 

overhead protection in refuge areas. The missile 

shown here fell nearly straight down.

building collapse (see Figures 4-2 and 4-3). In addition to falling, these 

elements can also be blown a considerable distance (see Figure 4-4).

For most building locations, there will be many nearby sources of small 

and large windborne missiles. Missile examples include aggregate roof 

surfacing, rooftop HVAC equipment, components from nearby damaged 

buildings (e.g., roof decking, studs, joists, trusses, hot water heaters, 

kitchen appliances, building furnishings), tree limbs, trees, trash containers, propane tanks, poles, automobiles, buses, and trucks. Missiles can be 

propelled horizontally and vertically (see Figures 2-2, 2-3, 2-4, and 4-5). 

Therefore, in selecting the best available refuge areas, it is typically prudent to assume that the building being evaluated will be bombarded with 

both small and large missiles, traveling horizontally and vertically.

Figure 4-4

This power pole penetrated a window and extended several feet into the house 

after being blown 40 feet from its original location.

FEMA

FEMA
Chapter 4: Selection Procedure

45

Figure 4-6 Site plan for example facility.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

46

Example of Refuge Area Selection 

Process

The following example illustrates the methodology for assessing refuge 

area needs and identifying the best available refuge areas.

General

The example facility is a single-story elementary school built in the early 

1990s. In layout, design, and construction, it is typical of many schools 

in Florida. As shown by the site plan in Figure 4-6, the school consists of 

eight separate wings (Buildings 100–800) situated around a central courtyard. The school site includes parking areas to the west and south, several 

wood-framed portable classrooms near the library, a tall flagpole in the 

courtyard, and a trash container and aboveground propane tank near the 

kitchen.

The school population comprises 1,146 students, 49 faculty and administrative staff, and 3 maintenance workers and custodians. One of the 

students uses a wheelchair.

Required Refuge Area Space

The following is a calculation of the required refuge area space for the 

population of this example school based on the guidelines in FEMA 361.

1,197 Occupants @ 5 sq ft each = 5,985 sq ft

1 Wheelchair user @ 10 sq ft each = 10 sq ft

Total = 5,995 sq ft

Architectural and Structural Characteristics

Building 100 is the main entrance to the school. It is much smaller than 

the other buildings and contains the administrative offices. Building 300 

contains the gymnasium, locker rooms, and the band and choir areas. The 

library, labs, and other large classrooms are in Building 500. The kitchen 
Chapter 4: Selection Procedure

47

Figure 4-7

Floor plan of Building 500.

Figure 4-8

Floor plan of Buildings 200, 400, 

600, and 800 (see Figure 4-10 for the 

wall cross-section at A-A).
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

48

and multipurpose room (a cafeteria that doubles as an auditorium) are in 

Building 700. Figure 4-7 shows the floor plan of Building 500. The general 

layouts of Buildings 100, 300, and 700 are similar to that of Building 500.

Buildings 200, 400, 600, and 800 contain typical classrooms. These 

classrooms are smaller than the library, labs, and large classrooms in 

Building 500 and, unlike the rooms in Buildings 100, 300, 500, and 700, 

are accessed from long, central, interior corridors. Figure 4-8 shows the 

floor plan of Buildings 200, 400, 600, and 800. One of the central corridors 

in these buildings is shown in Figure 4-9.

In each of the eight buildings, exterior and interior loadbearing concrete 

block masonry walls support the roof above. These walls are reinforced 

with vertical steel spaced at 2 feet 8 inches on center. Figure 4-10 shows 

a cross-section of one of the loadbearing corridor walls in Buildings 200, 

Figure 4-9

Interior central corridor – typical of the corridors in Buildings 200, 400, 600, and 800. FLORIDA DCA
Chapter 4: Selection Procedure

49

Figure 4-10

Cross-section A-A through corridor/classroom wall 

– Buildings 200, 400, 600, and 800 (see Figure 4-8 for 

location of A-A).

400, 600, and 800 (the location of this cross-section is shown in Figure 

4-8). The exterior walls include a brick veneer that is relatively resistant 

to the impact of small windborne debris. The interior partition (non-loadbearing) walls are unreinforced masonry, extend only 6 inches above the 

suspended ceilings, and are not laterally secured to the roof.

Note that a visual inspection of structure walls will not reveal whether 

or how they are reinforced. Construction drawings will show whether the 

wall design includes reinforcement and will provide details regarding the 

intended size and placement of reinforcing steel. However, only an inspection of the interior of a wall will reveal the actual construction. Such 

inspections can be made with nondestructive tests (e.g., magnetic, ultrasonic, or x-ray).

The roofs of the eight buildings are relatively lightweight and are constructed with open-web steel roof joists, metal decking, rigid insulation, 

and single-ply membrane roofing. In Buildings 300, 500, and 700, the roof 

framing typically spans 32 feet between the supporting loadbearing walls 

(Figure 4-11). The roof framing in Building 100 is similar.

In Buildings 200, 400, 600, and 800, the roof framing spans 34 feet 4 inches from the exterior loadbearing walls to the center loadbearing corridor 

walls. Separate roof joists span the 11-foot 4-inch-wide corridors (Figure 

4-12). In all eight buildings, the roof joists are fastened to the tops of the 

masonry loadbearing walls with welded base plates and anchor bolts (Figure 4-13).

The exterior windows in all eight buildings have aluminum frames and tempered glass. The exterior doors—including the exterior corridor doors in 

Buildings 200, 400, 600, and 800 (Figure 4-14)—are insulated metal-framed 

units with large windows. The doors from the corridors to the classrooms in 

these four buildings are wood with small windows (Figure 4-15).
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

50

Figure 4-12

Roof framing plan for 

Buildings 200, 400, 600, and 

800.

Figure 4-11

Roof framing plan for 

Building 500.
Chapter 4: Selection Procedure

51

Figure 4-13 Typical roof truss connection to exterior 

wall in the example school.

FLORIDA DCA

Figure 4-14

Exterior corridor doors in the example school.

FLORIDA DCA
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

52

Figure 4-15

Door connecting classroom to corridor – Buildings 

200, 400, 600, and 800.

FLORIDA DCA

Identifying the Best Available Refuge Areas

In the identification of the best available refuge areas, several locations 

were ruled out because of their limited strength, inherent weaknesses, or 

lack of usable space.

Buildings 300, 500, and 700 were ruled out for two reasons:

1.Vulnerability to debris impact and wind penetration. These buildings contain many large exterior windows that are extremely vulnerable 

to penetration by windborne debris. As noted in Chapter 2, once 

the building envelope is breached, wind enters the building and the 

pressures on the building increase. In addition, debris can enter the 

building through the window openings and may injure or kill building 

occupants. 

2.Long roof spans. As noted earlier, the roof spans in these buildings 

are 32 feet long. Long-span roofs are more susceptible to uplift, which 

can lead to the collapse of the supporting walls.
Chapter 4: Selection Procedure

53

Building 100 was also ruled out. In addition to sharing the vulnerabilities 

of Buildings 300, 500, and 700, Building 100 is relatively small, as are th 

rooms it contains. The available space in this building is further restricted 

by the large amount of furniture and office equipment normally found in an 

administrative building.

The interior corridors in Buildings 200, 400, 600, and 800 (Figure 4-16) 

offer the best available refuge areas in this example. The corridors have 

relatively short roof spans and relatively small percentages of exterior 

window glass. In addition, because the classroom doors open onto the 

corridors, the occupants of these buildings would have ready access to 

these refuge areas.

Each corridor is 10 feet 8 inches wide (11 feet 4 inches minus the 8-inch 

wall thickness) and 170 feet long, and provides approximately 1,800 

square feet of gross refuge area space. Assuming that a 2-foot-wide 

clear area must be maintained to allow students and staff to access the 

refuge area, each corridor can provide approximately 1,500 square feet of 

usable refuge area space. The four corridors provide 6,000 square feet 

of usable refuge area. While slightly less than the recommended total of 

6,047 square feet, the available usable refuge area space satisfies the 

intent of FEMA 361.

Although these corridors are the best available refuge areas in this 

example, they could be made more resistant by the construction of a 

wind-resistant alcove that would protect the exterior glass doors and help 

prevent the entry of wind and debris into the refuge area (Figure 4-17). 

An alternative would be to install solid, wind-resistant exterior doors that, 

although normally left open, could be closed when a tornado warning is 

issued. A less desirable option would be to add a double set of laminated 

glass exterior doors.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

54

Building administrators and school officials must weigh the protective 

benefits of such modifications against potential security problems, in the 

case of solid-wall alcoves, and the need for adequate warning time, for the 

operation of protective doors. An upgrade alternative for the interior corridor doors would be to replace them with stronger doors equipped with 

stronger hardware and small laminated glass windows.

Figure 4-16 Best available refuge areas in the example school – corridors in Buildings 200, 400, 600, and 800.
Chapter 4: Selection Procedure

55

Figure 4-17

Glass exterior doors can be protected from wind and 

debris with a wind-resistant alcove.

In many buildings, the size of the best available refuge area will be less 

than the required size determined according to the guidelines in FEMA 

361. In such buildings, the occupants will need to be housed in either 

smaller areas or more vulnerable areas. Although there are physical limits 

to the number of people a space can accommodate, housing more people 

in less space is preferable to locating them in more vulnerable areas.

Verifying the Best Available Refuge Areas

After refuge areas have been selected according to the methodology described in this chapter, the evaluation checklists in FEMA 361 should be 

used to verify that the selected areas are the best available in the building. 

FEMA 361 also includes information that can help building administrators 

improve the effectiveness of the selected refuge areas (e.g., guidelines 

concerning signage and operations plans). 

Selecting the Best Available Refuge 

Areas in Other Types of Buildings

Mid-Rise and High-Rise Buildings

In buildings with more than five stories, the building frames receive custom structural engineering analysis and design attention. Experiences of 

the past 50 years indicate that these buildings do not collapse under wind 

loads, but the outside walls and roof structure can receive major damage. 

The best available refuge areas in these buildings are in the lower floors 

(basement if available) and in the central part of the building. Stairwells 

(particularly those with reinforced concrete walls) typically provide the 

best available refuge. If the stairwells have inadequate capacity for the 

occupant load, restrooms typically provide the next best available refuge 

areas.

402

ENGLISH

403

SOCIAL STUDIES

CORRIDOR

SHELTER AREA 

PROTECTIVE ALCOVE

CONSTRUCTED WITH

MISSILE-RESISTANT

WALLS AND ROOF
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 4: Selection Procedure

56

Large Stores and Movie Theaters

In large stores and movie theaters, the best available refuge areas will typically be restrooms, closets, or narrow storage areas. For example, in 2002, 

in Van Wert, Ohio, 50 people in a movie theater took refuge in restrooms 

when warned about an approaching tornado. The building collapsed, but 

no one suffered significant injury. In grocery stores, if restrooms, closets, 

or narrow storage areas are not accessible, building occupants should 

crouch in narrow frozen food aisles between freezer cases and cover their 

heads. This tactic will reduce the likelihood of injuries from a falling roof. 

The aisles used should be as far as possible from exterior glass and masonry walls. Also, aisles with very tall storage racks should be avoided.

Again, the selection of refuge areas should always be verified with the 

checklists provided in FEMA 361.
Chapter 5: Conclusions

57

Conclusions

In regions of the United States subject to tornadoes, the identification 

of best available refuge areas within schools and other public buildings 

is essential for the safety of building occupants. Safe rooms specifically 

designed and constructed to resist wind-induced forces and the impact of 

windborne debris provide the best protection. However, findings from investigations of past tornadoes show that many buildings contain rooms or 

areas that may afford some degree of protection from all but the most extreme tornadoes (i.e., a tornado ranked F4 and F5 in the Fujita scales or 

EF4 and EF5 in the Enhanced Fujita scales*—see Chapter 1). In buildings 

not designed and constructed to serve as safe rooms, the goal should be 

to select the best available refuge areas—the areas that will provide the 

greatest degree of protection.

A building administrator, working with a qualified architect or structural 

engineer, can select the best available refuge areas within a building. 

As discussed in Chapter 4, the selection must account for the required 

amount of safe room space, the layout and structure of the building, and 

potential missiles at and near the building site. In general, the best available refuge areas will meet the following criteria:

Interior rooms. Rooms that do not depend on the exterior walls of the 

building are less likely to be penetrated by windborne debris.

* See page 4 for a discussion on Fujita (F) or Enhanced Fujita (EF) Scale or http://spc.noaa.ov/efscale for 

further information.
Tornado Protection: Selecting Refuge Areas in Buildings

Chapter 5: Conclusions

58

Location below ground or at ground level. Upper floors are more vulnerable to wind damage.

A minimal amount of glass area. Typical windows and glass doors are 

extremely vulnerable to high wind pressures and the impact of windborne 

debris.

Reinforced concrete or reinforced masonry walls. Reinforced walls are 

much more resistant to wind pressures and debris impact, but can fail if 

the roof deck is blown away.

Strong connections between walls and roof and walls and foundation. Walls and roofs will be better able to resist wind forces when they are 

securely tied together and anchored to the building foundation.

Short roof spans. Roofs with spans of less than 25 feet are less likely to 

be lifted up and torn off by high winds.

As illustrated in the case studies and selection procedure presented in 

this booklet, long central corridors often qualify as the best available refuge areas in a school building. In addition to having desirable structural 

characteristics (e.g., short roof spans, minimal glass area, and interior locations), corridors usually are long enough to provide the required amount 

of refuge area space and can be quickly reached by building occupants. 

Other potential refuge areas include small interior storage rooms, restrooms, and offices.

Building administrators should also consider increasing the resistance 

of existing rooms or areas within a building whenever repairs or reconstruction are necessary. In high-risk areas, it may be prudent to perform 

remedial work (such as that noted on page 54) without waiting for other 

repairs or reconstruction to become necessary. As discussed in Chapter 3, 
Chapter 5: Conclusions

59

the modifications made to the Kelly Elementary School during reconstruction after tornado damage are an excellent example of what can be done 

to improve the wind resistance of a school and provide safe room areas.

In conclusion, it is particularly important for building administrators and 

building occupants to be aware that the best available refuge areas do 

not ensure the safety or survival of their occupants. They are simply the areas of a building in which survival is most likely. To provide a high reliability 

of safety, a safe room area must be intentionally designed and constructed 

as a safe room. Refer to FEMA 361, for safe room performance criteria, 

sample construction plans, and other detailed information.

Information Sources

61

Information Sources

FEMA Publications

Taking Shelter From the Storm – Building a Safe Room For Your 

Home or Small Business

FEMA 320, Third Edition, August 2008

This illustrated, full-color booklet is intended for homeowners and contractors. It explains the hazards posed by severe winds associated with 

tornadoes and hurricanes, includes maps and charts for assessing 

tornado risk, presents safe room design criteria, and includes estimated 

costs and detailed construction drawings for several types of in-residence safe rooms.

Building Performance Assessment Team Report, Midwest Tornadoes 

of May 3, 1999

FEMA 342, October 1999

This illustrated, full-color report presents the observations and conclusions 

of the Building Performance Assessment Team (BPAT) deployed by FEMA 

after the May 3, 1999, tornadoes in Oklahoma and Kansas. The report 

describes the tornado damage; assesses the performance of residential 

and nonresidential structures, including tornado shelters; and presents 

recommendations for property protection, building code enforcement, and 

residential and group sheltering.

FEMA 320

FEMA

Additional information about tornado shelters is available from the 

Federal Emergency Management Agency (FEMA).

FEMA 342

FEMA
Tornado Protection: Selecting Refuge Areas in Buildings

Information Sources

62

Design and Construction Guidance for Community Safe Rooms

FEMA 361, Second Edition, August 2008

This illustrated manual is intended for engineers, architects, building officials, and prospective safe room owners. It explains tornado and hurricane hazards, presents safe room design criteria based on performance 

requirements and human factors, and outlines emergency management 

considerations for community safe rooms. Also provided are site assessment checklists that can be used in the selection of safe room areas in 

existing buildings; case studies that include wind load analyses, costs, 

and construction drawings; and the results of laboratory tests of safe room 

construction materials.

To view or download FEMA publications visit http://www.fema.gov/library. 

To order FEMA publication call 1-800-480-2520 or fax 240-699-0525 

(Monday – Friday 8:00 a.m. – 5:00 p.m., EST) or write to: 

FEMA Distribution Center, PO Box 430, Buckeystown, MD 21717.

FEMA 361

FEMA