Development of a Tornado Safe 

Room Door from Wood Products

Door Design and Impact Testing

Robert H. Falk

James J. Bridwell

United States Department of Agriculture

Forest

Service

Forest Products

Laboratory

Research Paper

FPL–RP–686

September

2016
Abstract

In this study, a tornado safe room door built from wood 

products and steel sheeting was developed and impacttested according to tornado safe room standards. Results 

indicate that an door constructed from as few as two 

sheets of 23/32-in. (18.26-mm) construction-grade 

plywood and overlaid with 18-gauge (0.05-in.- (1.27-

mm-) thick) steel can pass the required impact test.

Keywords: tornado, tornado shelter, wood, impact testing, 

door

September 2016

Falk, Robert H.; Bridwell, James J. 2016. Development of a Tornado 

Safe Room Door from Wood Products: Door Design and Impact 

Testing. Research Paper FPL-RP-686. Madison, WI: U.S. Department of 

Agriculture, Forest Service, Forest Products Laboratory. 17 p.

A limited number of free copies of this publication are available to the 

public from the Forest Products Laboratory, One Gifford Pinchot Drive, 

Madison, WI 53726-2398. This publication is also available online at 

www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of 

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The Forest Products Laboratory is maintained in cooperation with the 

University of Wisconsin.

The use of trade or firm names in this publication is for reader 

information and does not imply endorsement by the United States 

Department of Agriculture (USDA) of any product or service.

Contents

Introduction .................................................................1

Materials and Methods ................................................1

Results .........................................................................2

Discussion....................................................................5

Conclusions .................................................................5

Acknowledgements .....................................................5

References ...................................................................5

Appendix—Door Test Results.....................................6

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Development of a Tornado Safe Room

Door from Wood Products

Door Design and Impact Testing

Robert H. Falk, Research Engineer

James J. Bridwell, General Engineer

Forest Products Laboratory, Madison, Wisconsin

Introduction

An important component of a tornado safe room is the entry 

door, and like the safe room itself, it must be designed and 

constructed to withstand the wind and impact forces 

produced by the tornado. Although many safe room doors 

exist in the marketplace, they are usually constructed solely 

of steel. This study was conducted to determine if a tornado 

safe room door could be produced from wood and other 

commodity building products. This study is an extension of 

research to develop a tornado safe room from commonly 

available wood building products (Falk and others 2015).

Materials and Methods

Standardized Testing of Safe Room Doors

Like the safe room itself, a safe room door must withstand 

the loads generated by both high winds from tornados and 

impact of windblown debris. Large missile impact testing is 

used to assess the performance of these assemblies and the 

materials used in safe room design (ICC/NSSA 2014). In 

these tests, the safe room door was subjected to the impact 

of a nominal 2- by 4-in. (standard 38- by 89-mm) lumber 

stud weighing 15 lb (6.8 kg) traveling at a speed of 100 mph

(160 km/h). For a door to meet the requirements of the 

previously mentioned standard, impact testing is required at 

several locations (that is, within 6 in. (140 mm) of an 

interface hinge joint, an upper latch point, and center 

primary latches or operators). The door must also be tested 

for its ability to resist positive and negative pressure forces 

produced by the high winds of the tornado.

Door Design

Tornado safe room doors are typically constructed of steel 

and, much like conventional home entry doors, are inset in 

the door frame, hinged on one side, and fitted with a lockset 

on the other. This allows the door to be swung either inward 

or outward. An inset tornado storm door relies on the 

lockset and addition deadbolts to resist the forces generated 

by debris impact and the tornado wind loads (both pressure 

and suction).

Experts have not come to a clear consensus if a tornado door 

should swing inwards or outwards. The Federal Emergency 

Management Administration (FEMA) states: “A common 

misconception about safe room doors is that they must 

swing in a particular direction – inward or outward. 

According to ICC-500, the pressure testing on a door must 

be conducted away from the door stop, meaning that the 

door is pressure-tested in the weakest condition regardless 

of being in-swinging or out-swinging. Additionally, a door 

must undergo the missile impact resistance testing in the 

configuration that will be used for installation. Beyond code 

requirements, both inward- and outward-swinging doors 

have benefits. For example, inward-swinging doors are less 

likely to be blocked by debris, while outward-swinging 

doors provide more space within the safe room. In some 

states or communities, the applicable building code may 

require that doors swing in a particular direction. For 

information on code requirements for your jurisdiction, 

contact a local building official or licensed design 

professional in your area.” (FEMA 2015).

In this study, an overlaid outward-swinging door was 

evaluated. This configuration was chosen because the 

impact forces may be more effectively transferred into the 

safe room wall through the overlaid door edges rather than 

through deadbolts, which must resist the greatly

concentrated forces of impact.

Three wood products were evaluated as potential wood door 

materials. Laminated strand lumber (LSL), laminated veneer 

lumber (LVL), and plywood were used as core materials for 

the doors. Initial tests evaluated the impact resistance of the 

wood product itself. Subsequent tests evaluated the impact 

performance with an added steel skin (14, 18, and 22 gauge) 

(0.07, 0.05, and 0.03 in. (1.8, 1.27, and 0.76 mm) thick)

fastened to the faces of the door with either nails or bolts.

Test Setup, Data Collection, and Test Parameters

The impact tests were performed at the USDA Forest 

Service, Forest Products Laboratory (FPL), in Madison, 

Wisconsin, using a missile cannon built by Spudtech, LLC 

(spudtech.com, New London, Minnesota). The cannon used
Research Paper FPL-RP-686

2

compressed air to propel the missile, and the pressure of the 

compressed air could be adjusted to control the speed of the 

missile. Each missile was a surface dry (moisture content 

between 16% and 19%) Southern Pine stud, selected such 

that no knots appeared within 12 in. (286 mm) of the 

leading edge. The trailing edge of each missile was affixed 

with a plastic sabot to facilitate launching. Details of this 

test cannon can be found in Falk and others (2015).

Each door was tested across a 36-in. (0.91-m) clear span,

which represented the actual span of the door in a safe room 

designed for the American Disabilities Act (ADA) 

compliance. The door was supported in the same test frame 

used to test the wall sections described in Falk and others

(2015). Similar to the wall testing, load and deflection of the 

door were recorded in real time.

Both high-speed and normal-speed videos were recorded for 

each test. High-speed video was recorded using two highspeed cameras (Phantom V710, Vision Research, Wayne, 

New Jersey). These high-speed videos were recorded at a 

resolution of 800 × 800 and speed of 7,000 frames per

second.

Each door was impacted at the geometric center of the door. 

Observational data were also collected after each test and 

included the missile speed, type and extent of damage, and 

amount and size of debris generated. These data are

provided in the Appendix for all door tests.

ICC/NSSA (2014) requires the impact testing of doors near 

hinges and latches (chapter 8, section 804.9.6). Because the 

focus of this study was to develop a workable wood-based 

tornado safe room door, specific testing of hinges and 

latches were not performed here. Latch and hinge impact 

resistance (as well as door pressure testing) is ongoing.

Door Construction

Each door was 42 by 86 in. (1.07 by 2.08 m), which 

provided an overlap on the sides and top of the door 

opening. Some doors were constructed from wood only 

(plywood, LVL, or LSL), although most included a sheet of 

hot-rolled steel (22, 18, or 14 gauge) attached to the front 

face (impact side) or both faces of the door. Nails or bolts, 

and in some cases, construction adhesive, were used to 

secure the layers together. For door configurations thicker 

than about 2.5 in. (63.5 mm) and faced with the thinner 

gauges of steel (18 and 22), a pneumatic nail gun and 16d 

wood framing nails were used to fasten the layers together. 

For doors thinner than this, 1/4-in. (6.35-mm) bolts were 

used to secure the layers together. Figures 1 and 2 show the 

layered construction of the tested doors, and Figures 3 and 4

indicate the fastener spacing used for all doors tested.

Results

The Appendix provides details of all test results, whereas

Table 1 provides a general summary. The first four impact 

tests were performed on wood products with no steel 

sheeting reinforcement (Doors 1–4). Door 1 was 1-3/4-in.-

(44.5-mm-) thick LSL. The door was pierced by the missile 

and failed the test. To test if added plywood would improve 

impact resistance, 23/32-in. (18.26-mm) plywood was 

nailed to each face (Door 2). Again, the missile pierced the 

wood door. As indicated in Table 1 and the Appendix, both 

LVL and plywood (four layers) doors also failed the test,

with the missile piercing the door in both cases.

As indicated in Table 1, the addition of sheets of 18-gauge 

hot-rolled steel to the faces of the wood door core 

dramatically improved impact performance. When sheathed 

with steel, the LSL, LVL, and plywood doors (Doors 5–8) 

passed the test and did not excessively deform nor create 

debris.

To investigate if steel might be used on only one side of the 

door, four sheets of 23/32-in. (18.26-mm) plywood were 

nailed together with a sheet of 18-gauge steel only on the 

front (impact) side (Door 9). As indicated in Table 1, the 

door failed the test because large splinters of wood 

protruding more than 3 in. (76.2 mm) from the back of the 

door were produced (minimal flying debris was created, 

however).

To investigate if thinner steel might be used, four sheets of 

23/32-in. (18.26-mm) plywood were nailed together with a 

sheet of 22-gauge steel on the front and back (Door 10). 

This door also passed the test but had slightly more 

deformation (1.4 in. (35.56 mm)) than Door 9. No further 

door tests were conducted with 22-gauge steel because the 

cost savings of this thinner steel were not significant enough 

to warrant using it.

Significant cost savings could be realized, however, if 

sheets of plywood sheathing could be eliminated from the 

core of the door. For this reason, tests were conducted using 

successively fewer sheets of plywood (Doors 11, 12, and 

13). Because these doors were too thin to be nailed with 

commonly available 16d nails, 1/4-in. (6.35-mm) bolts were 

used to fasten the sheathing layers together.

As indicated in Table 1, doors with four, three, and two 

layers of plywood (but still retaining 18-gauge steel on both 

sides) passed the test. However, Door 13, with two layers of 

plywood, resulted in rather large (but acceptable) permanent 

deformation (2.1 in. (53 mm)). Using two sheets of plywood 

and 14-gauge steel (Door 14) significantly decreased the 

deformation (0.9 in. (22.86 mm)) but at the cost of thicker 

(and more expensive) steel sheeting.

As indicated in the Appendix, all doors (with the exception 

of Doors 1–4 and 6) were impacted twice and passed the test 

in each case. Door 9 failed the first test but passed the 

second.
Development of a Tornado Safe Room Door from Wood Products

3

Figure 1—Layered construction of nailed door

(1 in. = 25.4 mm).

Figure 2—Layered construction of bolted door

(1 in. = 25.4 mm).

Figure 3—Fastener pattern for nailed door

(1 in. = 25.4 mm).

Figure 4—Fastener pattern for bolted door

(1 in. = 25.4 mm).
Research Paper FPL-RP-686

4

Table 1. Summary of test resultsa

Door 

number

Door core 

construction

Wood sheathing 

type

Steel sheet 

placementb

Adhesive 

placement

Passed test 

(Y/N) Further information

1 1-3/4-in. LSL - - - N Wall pierced by 

missile

2 1-3/4-in. LSL 23/32-in. plywood, 

both sides

- Between 

plywood and 

LSL

N Wall pierced by 

missile

3 Two sheets of 1-1/4-

in. LVL glued and 

nailed

- - Between LVL 

layers

N Wall pierced by 

missile

4 Four sheets of 23/32-

in. plywood, nailed

- - - N Wall pierced by 

missile

5 1-3/4-in. LSL - 18-gauge steel, 

both sides

- Y Permanent 

deformation 2.3 in.

6 Two sheets of 1-1/4-

in. LVL, center layer 

of 3/4-in. plywood, 

glued and nailed

- 18-gauge steel, 

both sides

Between LVL 

and sheet metal 

layers

Y Permanent 

deformation 0.6 in.

7 Two sheets of 1-1/4-

in. LVL nailed

- 18-gauge steel, 

both sides

- Y Permanent 

deformation 0.6 in.

8 Four sheets of 23/32-

in. plywood, nailed

- 18-gauge steel, 

both sides

- Y Permanent 

deformation 1.4 in.

9 Four sheets of 23/32-

in. plywood, nailed

- 18-gauge steel, 

front side only

- N Large splinters of 

plywood extended 

more than 3 in. from 

back of wall. Minimal 

debris created.

10 Four sheets of 23/32-

in. plywood, nailed

- 22-gauge steel, 

both sides

- Y Permanent 

deformation 1.4 in.

11 Four sheets of 23/32-

in. plywood, bolted

- 18-gauge steel, 

both sides

- Y Permanent 

deformation 1.2 in.

12 Three sheets of 

23/32-in. plywood, 

bolted

- 18-gauge steel, 

both sides

- Y Permanent 

deformation 0.9 in.

13 Two sheets of 23/32-

in. plywood, bolted

- 18-gauge steel, 

both sides

- Y Permanent 

deformation 2.1 in.

14 Two sheets of 23/32-

in. plywood, bolted

- 14-gauge steel, 

both sides

- Y Permanent 

deformation 0.9 in.

a1 in. = 25.4 mm; LSL, laminated strand lumber; LVL, laminated veneer lumber.

b14, 18, and 22 gauge = 0.07, 0.05, and 0.03 in. (1.8, 1.27, and 0.76 mm) thick.
Development of a Tornado Safe Room Door from Wood Products

5

Discussion

At the thicknesses tested, a tornado safe room door 

constructed of wood cannot withstand a standard impact 

missile without the addition of steel sheeting applied to the 

door faces. A thicker wood door without steel might pass 

the test. However, the thickness required would probably be 

impractical from a construction, usage, and cost standpoint.

The necessity for steel sheeting is affected by both door

thickness and span. The 6-in.- (0.15-m-) thick wood walls 

tested in Falk and others (2015) survived the impact tests 

without steel sheeting not only because the walls were 

thicker but also because the longer span of the walls allowed 

for more deflection (and acceleration of mass), which 

helped dissipate the impact energy.

A door is thinner and has a shorter span, therefore requiring

reinforcement to prevent punch-through and to allow the 

impact force to be distributed into the wood core. A door or 

wall subjected to impact must resist the dynamic energy of 

the missile and its tendency to punch through while 

distributing and dissipating the high forces through 

deflection, mass acceleration, and damping.

A door is stiff relative to a wall (mostly because of its 

shorter span) and as a result, the missile has a tendency to 

punch through because the forces cannot be effectively 

transferred from the impact area into adjacent areas. Steel 

sheeting has enough stiffness to prevent punch-through and 

allows the forces caused by impact to be transferred into the 

wood core.

Conclusions

Several conclusions can be drawn from the results of this 

study:

1. A tornado safe room door can be constructed of wood but 

requires steel sheeting on both faces.

2. Steel sheeting of at least 18 gauge in thickness is 

recommended for door faces.

3. Laminated veneer lumber (LVL), laminated strand 

lumber (LSL), and plywood all perform well as door core 

materials as long as steel sheeting is applied to the door 

faces.

4. Although as few as two sheets of plywood can be used in 

a tornado safe room door, three sheets are recommended 

(with applied 18-gauge steel on both faces).

5. Nails or bolts work well to tie the steel door faces to the 

wood core. No adhesive is required.

Acknowledgments

The authors acknowledge the generous support of the 

Louisiana-Pacific Corporation, Schaumburg, Illinois, for the 

donation of laminated veneer lumber and laminated strand 

lumber materials used in this study. Thanks also to the staff 

of the Engineering Mechanics and Remote Sensing

Laboratory at the Forest Products Laboratory.

References

Falk, R.H.; Bridwell, J.J.; Hermanson, J.C. 2015.

Residential tornado safe rooms from commodity wood 

products: Wall development and impact testing. Res. Pap. 

FPL-RP-681. Madison, WI: USDA Forest Service, Forest 

Products Laboratory. 15 p.

Federal Emergency Management Administration [FEMA].

2015. Frequently asked questions.

https://www.fema.gov/safe-rooms/frequently-askedquestions-tornado/hurricane-safe-rooms. (Aug. 1, 2016).

International Code Council/National Storm Shelter 

Association [ICC/NSSA]. 2014. Standard for the design and 

construction of storm shelters (ICC 500). 

http://shop.iccsafe.org/standards/icc-standards.html.
Research Paper FPL-RP-686

6

Appendix—Door Test Results

Definitions and unit conversions for this Appendix are as follows:

LSL, laminated strand lumber

LVL, laminated veneer lumber

1 in. = 25.4 mm

1 mph = 1.61 km/h

14 gauge = 0.07 in. (1.8 mm) thick

18 gauge = 0.05 in. (1.27 mm) thick

22 gauge = 0.03 in. (0.76 mm) thick

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N) Additional notes

1 1-3/4-in. LSL 103.5 Full - Y Wall 

pierced by 

missile

N 3-in. bearing on 

vertical edges, 

horizontal edges 

free

L to R: Impact damage to front of door, impact damage to back of door.
Development of a Tornado Safe Room Door from Wood Products

7

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

2 1-3/4-in. LSL, 23/32-

in. plywood both 

sides

102.3 Full - Y Wall 

pierced by 

missile

N 3-in.

bearing on 

vertical 

edges, 

horizontal 

edges free

L to R: Door prior to test, edge detail of door, missile embedded in front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

3 Two sheets of 

1-1/4-in. LVL 

glued and nailed

104.4 Full - Y Wall 

pierced by 

missile

N 3-in. bearing on 

vertical edges, 

horizontal 

edges free

L to R: Front of door after impact, damage to back of door.
Research Paper FPL-RP-686

8

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

4 Four sheets of 23/32-

in. plywood, nailed

102.0 Full - Y Wall 

pierced by 

missile

N 3-in. bearing 

on vertical 

edges, 

horizontal 

edges free

L to R: Door prior to test, edge detail of door, missile embedded in front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

5a 3-1/2-in. LSL with 18-

gauge steel sheeting

nailed both sides

102.2 2.6 2.3 Y Front steel

sheet torn at 

impact 

location

Y Rear steel 

sheet intact

L to R: Door prior to test, impact damage to front of door, impact damage to back of door.
Development of a Tornado Safe Room Door from Wood Products

9

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

5b 3-1/2-in. LSL with 

18-gauge steel 

sheeting nailed both 

sides

102.5 3.6 2.5 N Front steel 

sheet torn 

at impact 

location 

Y Second 

shot on 

door 5, rear 

steel sheet 

intact

L to R: Door prior to test, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

6 Two 1-1/4-in. LVL 

panels with one sheet 

23/32-in. plywood 

between, 18-gauge 

steel sheeting nailed 

both sides

101.5 0.8 0.6 N Front steel 

sheet torn 

at impact 

location

Y Rear steel 

sheet intact

L to R: Door prior to test, impact damage to front of door, impact damage to back of door.
Research Paper FPL-RP-686

10

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

7a Two 1-1/4-in. LVL 

panels with 18-gauge 

steel sheeting nailed 

both sides

101.1 0.5 0.6 N Front steel 

sheet torn 

at impact 

location

Y Rear steel 

sheet intact

L to R: Door prior to test, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

7b Two 1-1/4-in. LVL 

panels with 18-gauge 

steel sheeting nailed 

both sides

102.1 1.0 1.2 N Front steel 

sheet torn

Y Second shot 

on door 7, 

rear steel 

sheet intact

L to R: Door prior to test, impact damage to front of door, impact damage to back of door.
Development of a Tornado Safe Room Door from Wood Products

11

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

8a Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting nailed to 

both sides

102.3 1.0 1.4 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Rear steel 

sheet intact

L to R: Front of door prior to impact, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

8b Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting nailed to 

both sides

102.2 1.3 1.4 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Second shot 

on door 10, 

rear steel 

sheet intact

L to R: Impact damage to front of door, impact damage to back of door.
Research Paper FPL-RP-686

12

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

9a Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting nailed to 

front face only

102.0 Full - Y Missile 

pierced 

steel sheet

N Large 

splinters of 

plywood

extended 

more than 3 

in. from back 

of wall,

minimal 

debris created

L to R: Front of door prior to test, back of door prior to test, missile embedded in front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N) Additional notes

9b Four sheets of 23/32-

in. plywood, 18-

gauge steel sheeting 

nailed to front face

101.2 N <3 in. N Steel sheet on 

front face 

torn, some 

steel sheet 

buckling at 

location of 

impact

Y Second shot to 

door 8, shot 10 

in. above 

previous impact 

location, no 

plywood 

splintering or 

debris created

L to R: Impact damage to front of door (top dent is second shot), impact damage to back of door.
Development of a Tornado Safe Room Door from Wood Products

13

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

10a Four sheets of 23/32-

in. plywood, 22-gauge 

steel sheeting nailed to 

both sides

105.6 2.5 1.4 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Rear steel 

sheet intact

L to R: Front of door prior to impact, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

10b Four sheets of 23/32-

in. plywood, 22-gauge 

steel sheeting nailed to 

both sides

102.3 - 1.5 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Second shot 

on door 9, 

rear steel 

sheet intact

L to R: Impact damage to front of door, impact damage to back of door.
Research Paper FPL-RP-686

14

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

11a Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting bolted to 

both sides

101.5 1.8 1.2 N Steel sheet on 

front face torn, 

some steel 

sheet buckling 

at location of 

impact

Y Rear steel 

sheet intact

L to R: Front of door prior to test, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

11b Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting bolted to 

both sides

101.8 1.5 1.3 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Second shot 

on door 11, 

rear steel 

sheet intact

L to R: Front of door prior to test, impact damage to front of door, impact damage to back of door.
Development of a Tornado Safe Room Door from Wood Products

15

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

12a Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting bolted to 

both sides

100.8 0.8 0.9 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Rear steel 

sheet intact

L to R: Front of door prior to test, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

12b Four sheets of 23/32-

in. plywood, 18-gauge 

steel sheeting bolted to 

both sides

101.3 1.8 1.3 N Steel sheet on 

front face torn, 

some steel

sheet buckling 

at location of 

impact

Y Second shot 

on door 12, 

rear steel 

sheet intact

L to R: Impact damage to front of door, impact damage to back of door.
Research Paper FPL-RP-686

16

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

13a Two sheets of 23/32-in.

plywood, 18-gauge steel 

sheeting bolted to both 

sides

102.1 2.0 2.1 N Steel sheet 

on front 

face dented

Y

L to R: Front of door prior to test, impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

13b Two sheets of 23/32-in.

plywood, 18-gauge steel 

sheeting bolted to both 

sides

101.3 1.6 2.4 N Steel sheet

on front 

face dented

Y Steel sheet

buckled but 

intact

L to R: Impact damage to front of door, impact damage to back of door.
Development of a Tornado Safe Room Door from Wood Products

17

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N)

Additional 

notes

14a Two sheets of 23/32-in.

plywood, 14-gauge steel 

sheeting bolted to both 

sides

102.7 1.0 0.9 N Steel sheet

on front 

face dented

Y Missile 

shattered on 

impact

L to R: Impact damage to front of door, impact damage to back of door.

Door 

number Door construction

Missile 

speed 

(mph)

Front 

penetration 

(in.)

Permanent 

door 

deflection 

(in.)

Door 

perforated? 

(Y/N)

Observed 

damage

Passed 

test? 

(Y/N) Additional notes

14b Two sheets of 23/32-

in. plywood, 14-

gauge steel sheeting 

bolted to both sides

101.9 0.9 0.5 N Steel sheet 

on front 

face 

dented

Y Missile shattered 

on impact. 

Permanent door 

deflection was a 

localized 

measurement in the 

area of the second 

shot.

L to R: Impact damage to front of door, impact damage to back of door.