Residential Tornado Safe Rooms 

from Commodity Wood Products

Wall Development and Impact Testing 

Robert H. Falk

James J. Bridwell

John C. Hermanson

Research Paper

FPL–RP–681

United States Department of Agriculture

Forest 

Service

Forest Products

Laboratory

October

2015
Abstract

In the United States, tornadoes cause significant damage and 

result in many injuries and deaths. Although the development and use of tornado safe rooms and shelters have 

helped reduce the human toll associated with these events, 

the cost of these structures is often too high for many that 

could benefit from their use. The development of a residential tornado safe room constructed from commodity wood 

building products, buildable by a local contractor or do-ityourselfer, and adaptable to existing homes could lower the 

cost of these structures and result in more widespread use. 

In this study, impact tests were performed on a series of 8-ft 

by 8-ft wood wall sections according to the standard test 

criteria of ICC-500. Results indicate that a nailed and glued 

wall section constructed of three layers of 2 × 8 lumber and 

sheathed with 23/32-in. CDX plywood can consistently pass 

the impact test. Included in the test results are the effects 

of wall construction, sheathing and lumber type, and added 

adhesive on impact performance.

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

walls 

Contents

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

Objectives and Scope.......................................................1

Stacked 2 × 4 Wall........................................................2

Nail Laminated 2 × 4 Wall............................................3

Variables Evaluated..........................................................3

Test Setup and Data Collection........................................4

Results..............................................................................6

Discussion........................................................................6

Future Testing ..................................................................7

Conclusions......................................................................7

Acknowledgments............................................................7

References........................................................................8

Appendix—Wall Test Results..........................................9

Conversion table

English unit

Conversion

factor SI unit

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

miles per hour (mph) 1.609 kilometers per hour (kph)

pound (lb) 0.4535 kilogram (kg)

pounds force (lbf) 4.448 newton (N)

October 2015

Falk, Robert H.; Bridwell, James J.; Hermanson, John C. 2015. Residential 

tornado safe rooms from commodity wood products: wall development and 

impact testing. Research Paper FPL-RP-681. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 15 p.

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

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

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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 

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Residential Tornado Safe Rooms 

from Commodity Wood Products

Wall Development and Impact Testing

Robert H. Falk, Research General Engineer

James J. Bridwell, General Engineer

John C. Hermanson, Research General Engineer

Forest Products Laboratory, Madison, Wisconsin

Introduction

A significant portion of the United States is susceptible to 

the dangerous winds of tornadoes (Fig. 1). Every year, these 

events cause injury, death, and billions of dollars of property 

damage (FEMA 2014). Improved weather forecasting, increased lead-in times for tornado warning, and the development of reinforced safe rooms has helped reduce the human 

toll from these events.

The principal aspect of a tornado safe room is that it must 

be able to withstand the loads generated by the high winds 

of a tornado (FEMA 2015). Tornado severity is categorized 

by the Enhanced Fujita Scale (EF Scale) and an EF-5 tornado is considered the most severe (wind speed greater than 

200 mph).

In addition to high wind loading, the tornado safe room 

must also withstand the impact of the windblown debris 

(identified as missiles) associated with these events (NIST/

TTU 2006). According to the ICC-500 (International Code 

Council Standard for the Design and Construction of Storm 

Shelters), large missile impact testing is an accepted way 

of assessing the performance of assemblies and materials 

used in safe room design (ICC/NSSA 2014). In these tests, 

the safe room is subjected to the impact of a 2 × 4 lumber 

stud weighing from 9 to 15 lb traveling at a speed of 34 to 

100 mph. The range of standard tests is given in Table 1. 

The tornado test (highlighted yellow) imparts the most 

energy and thus can be considered the most severe. 

According to the ICC-500, paneled or framed walls are to 

be impacted in the center of the roof or wall section, at interface joints, or other locations of weakness. A successful 

impact test requires the wall meets three basic criteria. The 

performance criteria for impact testing places limits on the 

permanent wall deflection (3-in. max), the creation of significant debris, and any penetration of the missile into the 

room. 

Objectives and Scope

The primary objectives in developing a safe room from 

commodity wood products were to use materials that are 

commonly available at local building material outlets, buildable by an advanced do-it-yourselfer (DIYer) or local contractor, and easily retrofitted into an existing home. Because 

commodity lumber is commonly sold in 8-ft lengths and 

wood sheathing materials are 4-ft by 8-ft, the walls tested 

were designed to represent walls from a safe room 8-ft by 

8-ft in plan with a height of up to 8 ft. This size makes this 

space suitable for other uses (e.g., bathroom, sauna) during 

non-event periods and still accessible and useable when a 

wind event occurs.

The walls evaluated in this study were designed such that 

the components can be built on-site for new or existing construction, making it feasible to construct all or part of the 

safe room in a basement or other suitable area over a properly designed concrete slab. 

Two basic wall designs were investigated in this study. The 

following provides an overview of the two basic designs. 

The Appendix provides more specific details. Figure 1—Tornado activity in the United States from 

1950–2013 (Source: Storm Prediction Center 2014).

Table 1—Missile testing criteria (NIST/TTU 2006)

Test Missile

Missile

size

(lb)

Missile

speed

(mph)

Basic hurricane 2 by 4 wood stud 9 34

Hurricane enhanced-A 2 by 4 wood stud 15 50

Hurricane enhanced-B 2 by 4 wood stud 15 60

Tornado 2 by 4 wood stud 15 100

Hurricane shelter 2 by 4 wood stud 9 0.4 × wind 

zone speed
Research Paper FPL–RP–681

2

Stacked 2 × 4 Wall

The first wall type investigated was constructed by stacking 

and nailing 2 × 4s (stud grade, SPF species) into a solid slab 

of wood. This slab was then covered with oriented strandboard (OSB) sheathing on the exterior faces (Fig. 2). To 

fasten each 2 × 4 layer, 16d smooth shank round head nails, 

3 in. long, were nailed vertically using a pneumatic framing 

nailer in the nailing pattern shown in Figure 3. The sheathing was nailed to the stacked 2 × 4s as shown in Figure 4 

using 16d, 2-3/8-in.-long nails. These were also driven with 

a framing nailer.

Figure 4—Sheathing nailing pattern for stacked 2 × 4 walls.

Figure 3—Repetitive nailing pattern for stacked 2 × 4 wall.

Figure 2—Stacked 2 × 4 wall design. (a) Stacked and nailed 

2 × 4s prior to attachment of wood sheathing. (b) Side view of 

wall before testing.

(a) (b)
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

3

Nail Laminated 2 × 8 Wall

The second wall type evaluated was a wall constructed of 

nail laminated 2 × 8s (Fig. 5). Three 2 × 8s (No. 2 grade, 

SPF species) were nailed together (16d smooth shank nails, 

round head, 3 in. long) to form a beam with a tongue and 

groove configuration (Fig. 6a). The beams are then stacked 

and interlocked to create a wall (Fig. 6b). For most wall 

configurations, OSB or plywood sheathing was then nailed 

(or nailed and glued) to one or both faces of the wall (Fig 7). 

To nail the sheathing, 16d smooth shank nails, round head, 

2-3/8 in. long, were used.

Variables Evaluated

This study was intended to be an initial evaluation of the 

impact resistance and constructability of a wood safe room 

wall option and not a rigorous statistical evaluation of a 

wide set of variables or performance evaluation of a completed safe room design. That said, in addition to the two 

types of wall designs investigated, several variables, including sheathing type, sheathing placement, and use of adhesive, were investigated. Two types of sheathing were used: 

1/2-in. OSB and 23/32-in. flooring grade plywood (CDX 

grade). Depending on the wall, sheathing was (1) not used, 

(2) nailed to the back side of the wall, or (3) nailed to both 

sides of the wall. A series of tests was also performed on the 

nail laminated 2 × 8 wall design investigating the effect of 

using a commonly available construction adhesive, Liquid 

Nails (PPG Architectural Coatings, Cranberry Township, 

Pennsylvania). The adhesive was placed (1) between the 

plywood and the 2 × 8s (Fig. 8), and/or (2) between the 

2 × 8 beams (Fig. 9), and/or (3) between the 2 × 8 layers 

of the beams (Fig. 10). Table 2 summarizes the variables 

investigated. Figure 5—Nail laminated 2 × 8 wall beam.

Figure 6—Nail laminated 2 × 8 wall design. (a) 2 × 8 wall 

prior to attachment of wood sheathing. (b) Side view of wall 

before application of sheathing.

Figure 8—Adhesive placement between plywood 

and 2 × 8s in nail laminated wall.

Figure 9—Adhesive placement between 2 × 8s 

in nail laminated wall.

Figure 7—Sheathing nailing pattern for 

nail laminated 2 × 8 wall design.

7.25"

1.5" 1.5"

16" typ

(a) (b)
Research Paper FPL–RP–681

4

Test Setup and Data Collection

The impact tests were performed at the Forest Products 

Laboratory using a missile cannon (Fig. 11) built by 

Spudtech, LLC (New London, Minnesota). The cannon used 

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

compressed air could be adjusted to control the speed of the 

missile. Missile speed was measured using a photoelectric 

timing device.

Each missile was a surface dry (moisture content between 

16% and 19%) southern pine stud, selected such that no 

knots appeared within 12 in. of the leading edge. The trailing edge of each missile was affixed with a plastic sabot to 

facilitate launching. 

The ends of the walls were supported by heavy wooden 

beams, which were themselves attached to a steel framework bolted to a massive concrete strong wall. Each wall 

was tested over a 7-ft 3-in. clear span, which represented 

the actual span of the wall in an 8-ft by 8-ft safe room.

Sensotec Model 41 load cells (10,000-lb capacity) 

(Sensotec, Jabbeke, Belgium) installed between each 

wooden support beam and the steel framework measured 

Figure 10—Adhesive placement between 

2 × 8 beams in nail laminated wall.

Table 2—Variables investigated

Wall

ID

Wall 

construction

Sheathing

type

Sheathing

placement

Adhesiveb

placement

1 2 × 4 stacked 1/2-in. 

OSB

Both sides None

2 2 × 8 beams None None None

3 2 × 8 beams 1/2-in. 

OSB

Back side 

onlya None

4 2 × 8 beams 1/2-in. 

OSB

Back side 

onlya None

5 2 × 8 beams 23/32-in.

subfloor 

grade

plywood

Both sides None

6 2 × 8 beams 23/32-in. 

subfloor 

grade 

plywood

Both sides Only on 

plywood

7 2 × 8 beams 23/32-in.

subfloor 

grade 

plywood

Both sides Between

2 × 8s 

and on 

plywood

8 2 × 8 beams 23/32-in.

subfloor 

grade 

plywood

Both sides Between 

2 × 8s 

on plywood

and between

beams

a

Back side indicates wall face away from missile impact.

b

Liquid Nails Heavy Duty Construction Adhesive, 

LN-901/LNP-901 (www.liquidnails.com).

Figure 11—Test cannon and 2 × 4 missiles.

Figure 12—One of four load cells used to monitor 

force of impact.

Figure 13—Two of four displacement 

transducers used to monitor wall 

displacement. 
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

5

the impact force transmitted to each corner of the impacted 

wall (Fig. 12). Four TRANS-TEK Model 0244, ±1.00 in. 

displacement transducers (TRANS-TEK, Inc., Ellington, 

Connecticut) were also connected to the back side of each 

wall to record the deflection of the wall during impact 

(Fig. 13). Location of these devices is shown in Figure 14.

Data from the load and displacement devices were captured using National Instrument NI-9205 and NI-9401 input 

modules (National Instruments Corporation, Austin, Texas) 

connected to an NI cDAQ-9172 chassis. LabVIEW software (National Instruments Corporation) was used to collect these data at 7,000 Hz, with recording triggered as the 

missile passed by the timing system in the barrel. Dynamic 

load versus time and displacement versus time plots from 

an impact test are shown in Figure 15. These data are being 

collected for use in ongoing studies to create design models 

for wood walls subject to impact.

Figure 14—Location of load cells and displacement transducers (LVDTs).

Figure 15—Load (top) and displacement (bottom) data from typical impact test.

Load (lbf)

–3000

–2000

–1000

0

1000

2000

3000

4000

5000

Displacement (in.)

–0.6

–0.4

–0.2

0

0.2

0.4

0.6

0.8

Time (s)

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Time (s)

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Load 1

Load 2

Load 3

Load 4

Displacement 1

Displacement 2

Displacement 3

Displacement 4
Research Paper FPL–RP–681

6

Two high-speed Vision Research V710 cameras (Vision 

Research, Wayne, New Jersey) were used to capture the 

dynamic out-of-plane displacement response of the wall for 

each test. Using Phantom Camera Control software (Vision 

Research), the cameras were triggered to start coincidently 

with the LabVIEW data collection and recorded the movement of a 23 × 23 array of 0.5-in.-diameter black dots painted 2 in. on center (Figs. 6a and 16). These high-speed videos 

were recorded at a resolution of 800 × 800 and speed of 

7,000 frames per second. The out-of-plane displacement of 

the walls was determined using the mesh-free random grid 

method (Iliopoulos et al. 2012).

In addition to notes about wall construction, observational 

data were also collected after each test and included the missile speed, type, and extent of damage, maximum permanent 

wall deflection, and amount and size of debris generated. 

These data are provided in the Appendix for all wall tests. 

Walls were tested more than once if they did not fail the test 

after the first impact. For all wall tests, the first shot was 

aimed at the geometric center of the wall. For most walls, 

subsequent shots were aimed 12 in. away from the first shot 

(either left, right, above, or below). Shot location information is given in the Appendix.

Results

The Appendix provides details of all test results; Table 3 

provides a general summary.

As indicated in the photographs of the Appendix, Wall 1 

showed little resistance to the impact and the 2 × 4 easily 

pierced the wall in all three tests. Wall 2 failed the test because the permanent wall deformation was 3 in., the maximum allowed by the test standard. No significant debris was 

generated. 

The first impact test of Wall 3 (Wall Test 3a) resulted in a 

permanent deflection of 0.5 in. and no significant debris; 

however, a second shot on the same wall (Wall Test 3b) resulted in the 2 × 4 piercing the wall and a large permanent 

deflection. Unlike Wall 3, Wall 4 failed on the first shot 

(8.9 in. of deflection) because of a failure of the sheathing.

The first shot on Wall 5 (Wall Test 5a) resulted in 1.5 in. of 

permanent deflection and no debris was generated. A second shot (Wall Test 5b) also resulted in 1.5 in. of deflection; 

however, two small pieces of plywood veneer were dislodged and the test deemed a failure.

As indicated in the Appendix, Wall 6 was impacted four 

times and the first three impacts resulted in permanent wall 

deformation less than 2 in. and only slight cracking of the 

plywood. The fourth shot resulted in failure because the permanent deflection was 3.1 in., slightly greater than allowed. 

No debris was generated in this series of tests.

Wall 7 was constructed the same as Wall 5; however, construction adhesive was added between the 2 × 8s making up 

the wall beams as well as between the plywood sheathing 

and the 2 × 8 beams (see Figs. 10, 11). This wall was shot 

four times, and the first three impacts resulted in permanent 

wall deformation less than 1.5 in. and only slight cracking 

of the plywood. The fourth shot resulted in failure with a 

permanent deflection of 3.9 in. No debris was generated in 

this series of tests.

The final series of impact tests were performed on Wall 8. 

Also constructed the same as Wall 5, this wall included construction adhesive between the 2 × 8s making up the wall 

beams, between the 2 × 8 wall beams, and between the plywood sheathing and the 2 × 8 beams (see Figs. 9–11). This 

wall was shot six times. The first four impacts resulted in 

permanent wall deformation less than 2 in. and only slight 

cracking of the back side plywood face. The fifth shot resulted in a permanent deflection of 2.6 in. and the sixth shot 

resulted in failure with a permanent deflection of 5.9 in. 

No debris was generated in this series of tests, although the 

last test resulted in the separation of the plywood from the 

2 × 8s in the area of impact.

Discussion

Resisting dynamic loads, such as wind, earthquake, or impact, can be achieved by either building a structure so stiff 

and massive that the loads have little effect on the structure 

or by building a structure that can dampen and dissipate the 

applied loads. Wood and wood construction are lower in 

mass compared with other building materials, such as steel 

or concrete, but have good damping characteristics and can 

dissipate load through deformation of and slippage between 

wood components, crushing of the wood, and deformation 

of fasteners. These characteristics were used in the design of 

the wood walls evaluated here.

Figure 16—High-speed camera setup.
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

7

The dissipative characteristics described above are evident if 

one compares the missile impact performance of the stacked 

2 × 4 wall design with the nail laminated 2 × 8 wall design. 

The stacked 2 × 4 design did not result in effective transfer of the impact energy from one 2 × 4 to the next, nor into 

and across the sheathing. The relatively high stiffness of 

this wall combined with the lack of energy transfer resulted 

in the punch-through of the missile witnessed in the tests. 

In contrast, the nail-laminated 2 × 8 wall design was much 

more effective in dampening and transferring the energy of 

impact. The layering of the 2 × 8s with the face of the lumber perpendicular to the impact load tended to flex, dissipating energy through bending and through the yielding of the 

nails and adhesive. 

The performance criteria for impact testing places limits on 

permanent wall deflection, creation of debris, and penetration of the missile into the room. While permanent deflection can often be minimized by increasing the thickness of 

the wall cross section, the wall may still fail because of the 

generation of wood debris. These and previous unpublished 

testing (Murphy 2013, personal communication) indicate 

that the addition of sheathing material, especially on the 

inside of the wall (or room), is effective in reducing the 

amount of debris generated. As indicated in the test results 

of the Appendix, plywood is an effective sheathing material for impact resistance. The OSB was less effective and 

tends to fail more locally as compared with plywood, likely 

because of the small flake size used in its manufacture (relative to the size of the panel). 

The results also indicate that the addition of construction adhesive is effective in stiffening and tying together the components of the wall as well as reducing the amount of debris. 

This is indicated in the performance of Walls 6–8. 

Table 3—Summary of test results

Wall

ID

Wall

construction

Sheathing

type

Sheathing

placement Adhesive placement

Passed test

(Y/N)

Reason 

for failure

1 2 × 4 stacked OSB Both sides None N Wall pierced by 

missile

2 2 × 8 beams None None None N Deformation

3 2 × 8 beams OSB Back side onlya None Y

4 2 × 8 beams OSB Back side onlya None N Deformation

5 2 × 8 beams Ply Both sides None Y

6 2 × 8 beams Ply Both sides Only on plywood Ya

7 2 × 8 beams Ply Both sides Between 2 × 8s and

on plywood

Yb

8 2 × 8 beams Ply Both sides Between 2 × 8s, on plywood,

and between beams

Yc

a

Wall 6 withstood three impacts before failing.

b

Wall 7 withstood three impacts before failing. 

c

Wall 8 withstood five impacts before failing.

Future Testing

Research is ongoing to evaluate the lateral wind load and 

impact performance of an 8-ft by 8-ft safe room constructed with the nail laminated beam design discussed above. 

Construction methods and cost estimates for construction 

are also being evaluated and will be published in a subsequent report.

Conclusions

Several conclusions can be reached regarding the impact 

tests performed in this study:

• The nail laminated 2 × 8 wall design presented in this 

study can effectively resist the standardized impact loads 

required for residential tornado safe rooms.

• The stacked 2 × 4 wall design presented in this study cannot effectively resist the standardized impact loads and is 

not recommended for use in safe rooms.

• Though not evaluated here, the use of a 2 × 6, 2 × 8, or 

2 × 10 stacked wall configuration may better resist impact 

loads.

• The use of construction adhesive is effective in enhancing 

the impact performance of the nail laminated 2 × 8 wall 

design presented here.

Acknowledgments

The authors acknowledge the generous support of the 

Engineering Mechanics and Remote Sensing Laboratory 

at the Forest Products Laboratory. The technical support of 

Dave Simpson, Marc Joyal, and Sara Fishwild in testing and 

data collection was invaluable. Thanks also to Dr. Joseph 

Murphy (retired FPL scientist) whose previous impact cannon development work and safe room research paved the 

way for this study.
Research Paper FPL–RP–681

8

References

FEMA. 2014. Taking shelter from the storm: building a safe 

room for your home or small business. FEMA P-320, fourth 

edition. 

FEMA. 2015. Safe rooms for tornadoes and hurricanes: 

guidance for community and residential safe rooms. FEMA 

P-361. Available at http://www.fema.gov/media-library/

assets/documents/3140. 

Iliopoulos, A.P.; Michopoulos, J.G.; Andrianopoulos, N.P. 

2012. Performance analysis of the mesh-free random grid 

method for full-field synthetic strain measurements. Strain. 

48(1): 1–15. doi: 10.1111/j.1475-1305.2010.00786.x

ICC/NSSA. 2014. ICC/NSSA Standard for the Design and 

Construction of Storm Shelters (ICC 500). Available at 

http://shop.iccsafe.org/standards/icc-standards. Lubbock, 

Texas: International Code Council/National Storm Shelter 

Association.

Murphy, J. 2013. Joseph Murphy, Retired FPL Research 

Scientist. October 2013, personal communication. 

NIST/TTU. 2006. Debris impact resistance of building assemblies. A compilation of testing performed by the Wind 

Science and Engineering Research Center Texas Tech 

University and Florida A&M University, Florida State 

University, and University of Florida. Summary report 

submitted to National Institute of Science and technology 

(N.I.S.T.). August 2006. 

Storm Prediction Center. 2014. NOAA National Weather 

Service. http://www.spc.noaa.gov/gis/svrgis/
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

9

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional 

notes

1a Stacked 2 × 4s. Nailed 16 in. on 

center (oc). Sheathing both sides 

with 1/2-in. OSB.

97.8 – – Y Missile completely 

pierced wall. 

Significant debris.

N First shot on 

Wall 1. Impact 

0 in. right, 3 in. 

below center.

Left to right: Wall before test, wall construction, impact damage to front of wall, impact damage to back of wall.

1b Stacked 2 × 4s. Nailed 16 in. oc. 

Sheathed both sides with 1/2 in. 

OSB.

102.2 – – Y Missile completely 

pierced wall. 

Significant debris.

N Second shot on 

Wall 1. Impact 

18 in. left, 10 in. 

above center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

1c Stacked 2 × 4s. Nailed 16-in. oc.

Sheathed both sides with 1/2-in. 

OSB.

103.0 – – Y Missile completely 

pierced wall. 

Significant debris.

N Third shot on 

Wall 1. Impact 

16 in. left, 13 in. 

below center.

Impact damage to back of wall.

Appendix—Wall Test Results

Note: All missiles targeted the geometric center of the wall panel unless otherwise noted.
Research Paper FPL–RP–681

10

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional

notes

2 Interlocking 3-ply sections of 2 × 8.

No sheathing.

99.4 1.6 3.0 N Wall displacement 

maximum allowable. 

No significant debris.

N Impact at seam 

between 2 × 8 

layers.

Left to right: Wall before test, impact damage to front of wall, impact damage to back of wall, side view of wall damage.

3a Interlocking 3-ply sections of 2 × 8. 

1/2-in. OSB sheathing nailed to back 

side.

97.0 1.5 0.5 N Cracking of OSB 

on back side. No 

significant debris.

Y Similar to Wall 2 

with added 1/2-

in. OSB. Impact 

3 in. right, 0 in. 

below center.

Left to right: Wall before test, impact damage to front of wall, impact damage to back of wall.

3b Interlocking 3-ply sections of 2 × 8. 

1/2-in. OSB sheathing nailed to back 

side.

100.5 2.8 4.1 Y Missile pierced wall. 

Significant debris. 

Severe cracking of 

OSB.

N Second shot on 

Wall 3. Impact 

1 in. left, 0 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

4 Interlocking 3-ply sections of 2 × 8. 

1/2-in. OSB sheathing nailed to back 

side.

97.0 1.8 8.9 N 8.9-in. defect is 

from a section of 

delaminated OSB. 

Lumber deflection 

is closer to 1.5 in.

N Same as Wall 3.

Left to right: Wall before test, impact damage to front of wall, impact damage to back of wall.
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

11

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional

notes

5a Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. No adhesive.

101.7 2.0 0.5 N Some permanent 

deformation and light 

cracking of plywood 

on back side of wall. 

No debris.

Y First shot on 

Wall 5. Impact 

0.5 in. right, 0 in. 

below center.

Impact damage to front of wall.

5b Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. No adhesive.

102.6 2.5 1.5 N Two pieces of 

plywood veneer, 

about 4 in. in length, 

dislodged from rear 

of panel.

N Second shot on 

Wall 5. Impact 

0.5 in. right, 

12 in. above 

center.

Left to right: Wall before test, impact damage to back of wall.

6a Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied to plywood 

only.

104.5 2.0 0.5 N Some permanent 

deformation and light 

cracking of plywood 

on back side of wall. 

No debris.

Y First shot on 

Wall 6. Impact 

2 in. left, 1 in. 

above center.

Left to right: Wall before test, impact damage to front of wall, impact damage to back of wall.
Research Paper FPL–RP–681

12

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional

notes

6b Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied to plywood 

only.

103.5 2.1 1.8 N Some permanent 

deformation and 

cracking of plywood 

on back side of wall. 

No debris.

Y Second shot on 

Wall 6. Impact 

0 in. right, 12 in. 

above center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

6c Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied to plywood 

only.

104.2 2.0 1.9 N Some permanent 

deformation and more 

severe cracking of 

plywood on back side 

of wall. No debris.

Y Third shot on 

Wall 6. Impact 

1 in. right, 

12 in. below 

center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

6d Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied to plywood 

only.

103.9 3.0 3.1 N Excessive permanent 

deformation and 

splitting of plywood 

on back side of wall. 

No debris.

N Fourth shot on 

Wall 6. Impact 

13 in. left, 1 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

13

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional

notes

7a Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies and on the plywood.

102.0 2.4 1.4 N Minor cracking of 

plywood.

Y First shot on 

Wall 7. Impact 

1 in. left, 0.5 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

7b Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies and on the plywood.

102.3 1.9 1.5 N Minor cracking of 

plywood.

Y Second shot on 

Wall 7. Impact 

2 in. left, 12 in. 

above center.

Impact damage to front of wall.

7c Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies and on the plywood.

101.2 2.3 1.5 N Minor cracking of 

plywood.

Y Third shot on 

Wall 7. Impact 

1 in. right, 13 in. 

below center.

Impact damage to back of wall.

7d Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies and on the plywood.

101.1 4.3 3.9 N Excessive permanent 

deformation and 

splitting of plywood 

on back side of wall. 

No debris.

N Fourth shot on 

Wall 7. Impact 

13 in. left, 0 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.
Research Paper FPL–RP–681

14

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional

notes

8a Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies, 2 × 8 sections, and 

between plywood and 2 × 8 sections.

101.0 2.1 0.6 N Minor cracking of 

plywood.

Y First shot on 

Wall 8. Impact 

1 in. right, 2 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

8b Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies, 2 × 8 sections, and 

between plywood and 2 × 8 sections.

104.6 3.0 1.6 N Minor cracking of 

plywood.

Y Second shot on 

Wall 8. Impact 

0 in. right, 11 in. 

above center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

8c Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies, 2 × 8 sections, and 

between plywood and 2 × 8 sections.

103.1 2.0 1.8 N Minor cracking of 

plywood.

Y Third shot on 

Wall 8. Impact 

1.5 in. left, 14 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

8d Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies, between 2 × 8 sections, 

and on plywood.

103.1 2.5 1.9 N Minor cracking of 

plywood.

Y Fourth shot 

on Wall 8. 

Impact 13 in. 

left, 0 in. above 

center.

Impact damage to front of wall.
Residential Tornado Safe Rooms from Commodity Wood Products: Wall Development and Impact Testing

15

Wall

ID Wall construction

Missile

speed

(mph)

Front

penetration

(in.)

Permanent

wall

deflection

(in.)

Wall

perforated

(Y/N) Observed damage

Passed

test?

(Y/N)

Additional

notes

8e Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies, between 2 × 8 sections, 

and on plywood.

104.5 3.5 2.6 N Minor cracking of 

plywood.

Y Fifth shot 

on Wall 8.

Impact 13 in. 

left, 10 in. 

below center.

Left to right: Impact damage to front of wall, impact damage to back of wall.

8f Interlocking 3-ply sections of 2 × 8. 

23/32-in. plywood sheathing both 

sides. Adhesive applied between 

2 × 8 plies, between 2 × 8 sections, 

and on plywood.

104.3 5.3 5.9 N Missile perforated the 

2 × 8 plies, though 

not the plywood. 

Back side plywood 

was separated from 

the 2 × 8s in area of 

impact.

N Sixth shot 

on Wall 8.

Impact 12 in. 

left, 11 in. 

above center.

Impact damage to back of wall.