2T

NBSIR 73-170

Fire Endurance Test of an Interdwelling

Double Wall Constructed of Polyurethane

Foam-Filled Sandwich Panels

B. C. Son

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D, C, 20410

NBSIR 73-170

FIRE ENDURANCE TEST OF AN INTERDWELLING

DOUBLE WALL CONSTRUCTED OF POLYURETHANE

FOAM-FILLED SANDWICH PANELS

B. C. Son

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director
1
Fire Endurance Test of an Interdwelling

Double Wall Constructed of Polyurethane

Foam-Filled Sandwich Panels

by

B. C. Son

Building Fires and Safety Section

Center for Building Technology

ABSTRACT

As a part of the evaluation of housing systems of Operation

BREAKTHROUGH, a standard ASTM E 119 fire endurance test was performed

on a double wall assembly comprising a loadbearing interdwelling (party)

wall for single family attached housing.

The test was generally in accordance with the requirements of

ASTM E 119, Fire Tests of Building Construction and Materials. The

applied live load was 678 pounds per linear foot (plf) per wall and the

test results are valid only for walls of similar construction loaded

at or below the stress level developed by this loading.

The fire endurance of the first (fire-exposed) wall, based on

structural load failure, was 1 hr. and 4 min. The test was discontinued

at 1 hr. 06 min. because of untenable conditions in the test building

resulting from smoke and combustion gases released by the polyurethane

foam insulation in the wall.

Key Words: Fire endurance; fire test; housing systems; interdwelling

wall; load failure; modular construction; Operation

BREAKTHROUGH; polyurethane foam; toxic gases

i
Table of Contents

Page

Abstract . . ............ i

1 . Introduction . . . - . .... .... . . ... . . 1

2. Construction ..... . 2

3. Instrumentation . ......... . 3

4. Description of Test ......... ... 4

4.1 Loading .................... 4

4.2 Furnace Conditions 4

4.3 Fire Performance Criteria 5

5.. Test Results 5

6. Discussion 7

Table I

.

8

Appendix I 10
1. INTRODUCTION

A standard fire endurance test was conducted to measure the fire

endurance of a loadbearing interdweiling double wall assembly. The test

was performed at the Fire Test Laboratories of the National Bureau of

Standards, Washington, D.C., on January 20, 1972. It was part of the

evaluation of housing systems under Operation BREAKTHROUGH sponsored by

the Department of Housing and Urban Development.

The double wall, which is required to be a fire barrier between two

adjacent living units, was made up of two identical sandwich panels

erected parallel to each other. Each panel consisted of two layers of

gypsum board over a layer of plywood, a polyurethane foam insulation core,

and a layer of cement asbestos board. The gypsum board formed the interior (room) side of each unit, while the cement asbestos board formed

the opposite or what would normally be the exterior side of a unit. The

construction was innovative to the extent that available data from existing fire tests were not applicable. Although the fire performance of

conventional walls composed of gypsum board and plywood sheets has been

long established, the characteristics of an assembly of panels with plastic

foam cores and the behavior of the aluminum extrusion joints under severe

fire conditions required investigation. The construction and assembly

of this test specimen was representative of actual construction used in

the field.

1
The fire exposure followed the requirements of Standard Methods of

Fire Tests of Building Constructions and Materials ASTM E 119—^ for

loadbearing walls.

2. CONSTRUCTION

The assembly consisted of two identical 8 foot high by 16 foot long

walls parallel to each other and separated by a two inch air space. Each

wall consisted of 1/8 inch cement asbestos board as an exterior surface

and 5/16 inch C-D interior grade plywood covered with two layers of 1/2

inch type X gypsum board as a interior (room) side finish. The three

inch space between the exterior and interior surface had been filled

with foamed- in-place rigid polyurethane insulation to provide thermal

insulation.

Each wall was received as an assembly made up of four-4 foot wide

by 8 foot high panels. The panel joint consisted of an aluminum spline

engaging the channels of the aluminum extrusion surround on the edges of

each panel. Epelene propylene—dyehe monomer (EPDM) resilient wedges

(filler strip), which ran the full height of the panel, had been driven

in each side of the joint. The top and bottom edges of the panel were

closed with the same extruded aluminum surround which was used on the

sides of the panels. The plywood and asbestos boards were force fit

within channels of the aluminum extrusion shape. The details of the

construction are shown in Figures 1, 2 and 3.

— S tandard Methods of Fire Tests of Building Construction and Materials , American Society for Testing and Materials Designation E 119-71,

available at 1916 Race St., Philadelph-i a , Pa. 19103

2
The two wal Is were mounted in tlie furnace frames separated by a

2 inch air space. Two layers of 1/2 inch type X gypsum board were fastened

to the plywood face of the walls using type S, bugle head screws spaced

as shown in Figure 4. The panel joints and gypsum board joints were

staggered. Each complete wall assembly weighed 57 pounds per linear

foot and its thickness was 4-7/16 in.

Since the 8 foot height of the specimen was less than 10 foot high

opening of the test frame, a filler piece was placed at the top of the

specimen. The filler piece was made up of 2 x 12 (nominal) pine wood,

protected on the fire side with two layers of 5/8 inch Type X gypsum

board and sprayed fire protective vermiculite plaster on metal lath, and

on the unexposed side, with a single layer of 5/8 inch Type X gypsum

board. The filler piece was expected to have sufficient fire endurance

and rigidity during the test so as not to affect the test results.

3. INSTRUMENTATION

The instrumentation consisted of thermocouples, deflection measuring

devices and loading equipment. A total of 52 Chrome 1-Alumel (type K)

thermocouples were installed as follows: 40 thermocouples internally

in the panels and air space, and 12 surface thermocouples on the unexposed

surface of the second wall panel. The surface thermocouples uere placed

under standard 6 inch by 6 inch by 0.4 inch felted asbestos pads. Figure

5 shows the locations of the thermocouples. Thermocouples between foam

insulation and plywood, and between foam insulation and asbestos boards,

were installed by the panel manufacturer during plant assembly. The

remainder were installed by NBS personnel.
The temperatures measured by the thermocouples were printed out at

2 minute intervals on a data logger Crom which they were punched onto

cards for processing and plotting by computer. The lateral deflection

indicator consisted of a wire which was stretched horizontally in front

of the specimen at mid-height. At the start of the test the wire was

3-1/4 inches from the unexposed surface; the distance from the wire to

the wall surface was measured periodically during the test by a ruled

measuring device.

The vertical movement of each wall during the test was measured by

four mechanical extensometers which were placed at the mid-points under

the bottom of each wall. The photograph in Figure 6 shows the unexposed

surface of the specimen, the connections of the thermocouples, the

loading jacks and the mechanical extensometers.

4. DESCRIPTION OF TEST

4.1 Loading

Five minutes prior to the start of the test, a load of 735 plf

(678 plf live load + 57 plf dead load) was applied to each wall independently though four hydraulic jacks at the bottom of the specimen.

The total applied load per wall was 11,760 lb.

The applied load of 678 plf corresponded to representative loading

for the intended residential occupancy and was not necessarily the load

required to develop the working stresses in the assembly.

4.2 Furnace Conditions

The average temperature inside the furnace was measured by 12

Type K thermocouples enclosed in sealed 1/2 inch diameter wrought iron

4
pipe whlcli were equally distribuLed Lnslde the furnace. The ends of the

thermocouples were placed six inches from the exposed face of the specimen. The average furnace temperature was regulated to follow the standard

ASTM E 119 temperature-time curve by manual control of the gas flow to

the burners. The actual furnace time temperature curve is shown in

Figure 7.

The pressure measurement within the furnace was made with a dish

shaped probe connected to a pressure difference meter with tubing. The

pressure probe consisted of 1/8 inch inside diameter stainless steel

tubing attached to the edge of a 1-1/8 inch diameter flat metal disk

connected to a small hole in the center of the disk. The disk was

positioned normal to the upward flow of gas. The test was run with the

furnace neutral pressure point located at one-third height of the specimen

above the bottom of the specimen.

4.3 Fire Performance Criteria

The fire endurance of a wall according to ASTM E 119 is the time

required to reach the first occurrence of the following criteria of

failure

:

1. Inability to sustain the applied load.

2. Passage of flame or gas through the structure to the unexposed

surface hot enough to ignite cotton waste.

3. A temperature rise of 250°F (139°C) average of all the

thermocouples, or 325°F (181°C) maximum at any one point above

the initial temperature on the unexposed surface.

5
5. TEST RESULTS

The average and the maximum temperature rises on the unexposed surface

during the test are shown in Figure 8. The average and maximum temperature

rise across the assembly are shown in Figures 9 and 10. It is clear that

very little heat was transmitted through the double wall assembly during

the 66 min. test.

Structural failure of the first (fire-exposed) wall occurred at 64

minutes, as evidenced by a sudden rapid deflection and inability to maintain the applied hydraulic load. Immediately prior to the failure of the

first wall, its measured vertical deflection was 3/4 inch.

The second wall did not fail during the test. Lateral and vertical

deflections on the second wall were barely perceptible during the test.

The test results were inconclusive with respect to the fire endurance of

the double wall assembly, since the test was terminated prematurely because

the smoke generated by the test assembly made conditions untenable for the

personnel involved. Most of the smoke was coming out between the bottom

edges of the assembly and furnace frame. See "Test Observations."

Figure 11 shows the fire side of the wall assembly immediately after

removal from the furnace. Note buckling (and melting) of the aluminum frame

in the first wall. The buckling of the vertical aluminum frame occurred at

the time of load failure of the first v;all . The flaming at the joint is

from the resilient wedge behind the joint. The asbestos boards of the first

fire side wall were also buckled and cracked but no large holes were observed.

6
6. DISCUSSION

'J'lic c-ons L rue tion of the s pec i iiion was syniiiietr lea I , so LliaL the .same

fire resistance would have been expected if the opposite side of the

assembly had been exposed to fire.

Based on results of several different loaded double wall tests

performed under Operation BREAKTHROUGH, the second (unexposed) wall of

a double wall assembly may provide, on the average, an additional 75

percent fire endurance time relative to the first (fire-exposed) wall.

This relation may apply when the construction of each wall in the double

wall configuration is similar, when the wall surfaces that face the

internal air space are not combustible, and when failure or collapse of

the fire-exposed wall does not structurally damage the second wall.

In accordance with the above, the fire endurance of the double

wall assembly may be estimated as 1 hr:52 min (64 x 1.75 = 112).

A load of 678 plf was applied to each wall and the result of this

test is applicable only to similar wall structures loaded to develop

stresses not exceeding those developed in this structure.

7
TABLE I

Log of Test Obseirvations

Time Observations

mxn : sec

0:00

1:30

4:00

11:00

12:00

14:00

17:00

19:00

Start of test

Paper on exposed gypsum board burning.

All the paper on the exposed gypsum board consumed.

The spackling on exposed vertical joints peeling off.

There appears to be an opening in the south end

horizontal joint.

There is blackening at top of specimen (exposed side

south end) . Flaming at the intersection of horizontal

and south vertical joint. (See Figure 12.)

There are cracks and flaming at the center of the

horizontal joint.

There is increased flaming at the south end joint

probably the paper on the second layer of gypsum board

is burning. Quite a bit of steam being emitted at the

center bottom on the room side.

20:00

27:00

28:00

43:00

49:00

There is flaming at the horizontal joints both north and

south. Burning smell noticed.

Very little burning at north center horizontal joint,

but considerable burning at south end of horizontal

j oint

.

At the south end there is a crack at the top of the

specimen. Quite a bit of flaming whole length of the

vertical joint. Some localized buckling on the fire

side at mid-center.

Possible opening at top of upper south side (exposed

side)

.

Joints on fire side have opened up 1/2 inch. Smoke

coming out at the edges of the assembly.

8
Time

min : sec

50:00

51:00

53:00

58:00

59:00

61:00

62:00

64:00

66:00

68:00

Observations

Increased flaming at north horizontal and center lower

(vertical) joints. (Apparently plywood is burning.)

Rapid rate of flaming at south upper section and halfway

across north (upper) section and halfway down

south section vertically.

Dark brown Irritating smoke coming out lower south* and

center portions of the assembly on room side.

One inch openings in the north end horizontal joint

(exposed side)

.

Thick brown smoke from specimen filling room. Mostly

smoke coming out between bottom edges of the assembly and

and furnace frame. Black smoke and flames are coming

out of stack. Visibility in building is very poor.

First wall on furnace side buckling inward at south

horizontal and lower center vertical joints. (See

Figure 13)

.

There is a great amount of smoke filling the whole room. The first wall falling inward.

Black smoke both inside and outside the furnace. Unable

to maintain load. Load failure of the first wall.

END OF TEST - Untenable smoke conditions in building.

Black smoke and some flame coming out of furnace stack.

* For identifying the location of an occurrence, the two ends of the

assembly were differentiated according to this orientation.
Appendix I _j

SI Ccnverslou Units v

In view of present accepted practice in this country in this

technology caJ area, common US units of measurement have been used througl

out this paper. In recogndtDon of the position of the United States as

a signatory to the General Conference on Weigiits and Measurements whicii

gave official status to the metric SI system of units "in 1960, we assist

readers interested in mailing use of the coherent :r.ystcm of SI units by

giving conversion factors applicable to US units used in this paper.

Length

;

. 1 in = 0.025A meter

1 ft = 0.3048 meter

Mass

1 lb = 0.45 Kilograms

Stress .

•

1 psf - 47.88 newton/raeter^

1 psi = 0.332 newton/meter^

1 plf = 13.49 newton/meter

Temperature

Temperature in ''F = 9/5 (temperature in °C) + 32°F

10
11
12

SCREW PLACED AT INTERSECTION

-1/2'

, <-

12'

12" -h

12" -1-

12"

t

thl/2"

-16'^-16"-^

2

loy^ 1 2- Vl/2^*I2^.

II/2 '^•1/2

SA ME SAME

l-l>

JITU 1/2" FASTENER SCHEDULE FOR 1st LAYER OF 1/2 in TYPE X

•SCREW PLACED AT INTERSECTION

13-1/2"

1

i16" +14" t

14"

16" ^-

3-1/2"

-tir

n

2" 0. C. 12."o.c

FASTENER SCHEDULE FOR 2nd LAYER OF 1/2 in TYPE X

Figure 4. Fastener schedules for 1st and 2nd layers of gypsum board on each wall.

14
i

1 ^ !

1 1

1

1 'i 1

1 ll —M ^1—1

i

1

1

1

9 10 1 'i ] ° 1 ^

! ! 1

1 1

1 Ii 1

48"

-12"-- 48 •4'« 4

-'l2"*|-*-l2"* b" [*I2"* 48" ^

EXPOSED SIDE\

1 ^ ^

T/C's LX)CATED UNDER T/C's LOCATED UN

SURFACE T/C NO- SURFACE T/C NO

2aio 3ail

1/2 inch Gypsum Board,

5/16 C-D Interior grade

plywood

.

3 inch polyurethene insulation foam.

1 / 8 inch cement

asbestos board,

2 inch air space,

1/8 inch cement a asbestos board.

3 inch polyurethene

insulation foam . 5/16 C-D Interior

grade plywood , 1/2 inch gypsum board.

PANEL JOINTS

JOINTS OF FIRST LAYER OF GYPSUM BOARDS ^ of the second

JOINTS OF SECOND LAYER OF GYPSUM BOARDS/' wall

T/C UNDER PAD

• T/C INTERNALLY IN THE PANEL AND AIR SPACE

Figure 5. The locations of the interior and surface thermocouples.

15
r

01

C • U OJ to !-i M-l CD 0)

^1O 4-1 3 '-' <U

CO E - O

TD CO CO

1) c a

(0

O (U

O -r^ 4-1 a 4-1 X X o <u D C CDc

CD , oE ^ E CO 00 <u o

•H CO

16
1000^

TIME (MINUTE)

Fi guv

AVERAGE FURNArE TEMPERATURE COMPARED WITH STANDARD El 19-71 FOR TEST 505

17
200

O MHX . SUKf«CC TtPIP . A ftVC. 3URf«CE TfHP

181 . °C SPECIFIh'g LIMIT FOR MAXIMUM TEMPEPATUPvE RISE

150_

S 100.

Pi

PiH

H

50 -

139 °C SPECIFI bD LIMIT. FOR.-AVERAGE-IEMPIIRAJ.'URE.^RISK.

0 To 15 fo 5o Is 40 45

TIME (MINUTE)

Figure 8.

ko Si 60 65

MAXIMUM AND AVERACE TEMPERATURE RISE ON THE UNEXPOSED SURFACE TEST 505.

18
1000

© OEYMEEN CVr. LBYtK3 OF FiK3T WALL

A BETWEEN GYP. RNO PLYWOOD BOflRO IN 15T WALL

4- BETWEEN PLYWOOD RNO INSULATION fOfln IN 1ST WALL

X BETWEEN FOAM AND ASBESTOS BOARD IN 1ST WALL

900- « ON THE ASBESTOS BOARD OF 1ST WALL FACING AIR SPACE ^ ON THE ASBESTOS BOARD OF ZNO WALL FACING AIR SPACE

X BETWEEN ASBESTOS BOARD AND FOAtl IN 2ND WALL

Z BETWEEN FOAM AND PLYWOOD IN 2H0 WALL

Y BETWEEN PLYWOOD AND GYPSUM BOARD IN 2N0 WALL

800_ W BETWEEN GYPSUH BOARDS IN 2N0 WALL

TIME (MINUTE)

Figure 9.

AVERAGE TEMPERATURE RISE ACROSS THE ASSEMBLY TEST 505,

19
o

o

w

M

<

PiW

1000.

900_

800.

700.

600.

500«

400.

O BCYMECN

BETMCfN

THC

ON THE

BEfUtCN

BETWEEN

BETWEEN

BETWEEN

0N THE

4-X

^ ON

Z

Y

CYr . LAYERS OF riKST WBLL

CYr . fiND PLYWOOD BOflRO IN 1ST WRLL

rLYwooo nNo insulation roRn in isr wrll

FORH RNO RSBESTOS BORKO IN 1ST WRLL

R3BE3T0S BORKO OF 15T WRLL FRCING RIK 3PRCE

R3BEST0S BORKO OF 2N0 WRLL FRCING RIK 3PRCE

ASBESTOS SORRO RNO FORM IN 2ND WRLL

FORtI RNO fLYWOOD IN eND WALL

FLYWOOO RNO GYrSUH SORRO IN 2N0 WRLL

GYrSUrS BOARDS IN 2N0 WALL

UNEXrOSEO SURFACE

300_

200_

100_

0

TIME (MINUTE)

Figure 10,

MAXIMUM TEMPERATURE RISE ACROSS THE ASSEMBLY TEST 505,

20
21

23

FORM NBS-114A (1.71) U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. B'BL'OGRAPHIC DATA ^^^-^^ 73_;L70

2. Gov't Accession

No,

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Fire Endurance Test of an Interdwelling Double Wall

Constructed of Polyurethane Foam-Filled Sandwich Panels

5. Publication Date

6. Performing Organization Code

7. AUTHOR(S)

Bvune Chan Son

8. Performing Organization

NBSIR 73-170

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

10. Project/Task/ V['ork Unit No. A600443

11. Contract/Grant No.

IAA-H-16-70

12. Sponsoring Organization Name and Address

Department of Housing and Urban Development

Washington, D.C. 20410

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) As a part of the evaluation of housing systems for Operation BREAKTHROUGH, a standard ASTM E 119 fire endurance test was performed on a double wall assembly

comprising a loadbearing interdwelling (party) wall for single family attached

ho us ing.

The test was generally in accordance with the requirements of ASTM E 119, Fire

Test of Building Construction and Materials. The applied live load was 678

pounds per linear foot (plf) per wall and the test results are valid only for

walls of similar construction loaded at or below the stress level developed by

this loading.

The fire endurance of the first (fire exposed) wall, based on structural load

failure, was 1 hr and 4 min. The test was discontinued at 1 hr:06 min because

of untenable conditions in the test building resulting from smoke and combustion

gases released by the polyurethane foam insulation in the wall.

17. KEY WORDS (Alphabetical order, separated by semicolons) p^^g endurance; fire test ; housing systems;

interdwelling wall; load failure; modular construction; Operation BREAKTHROUGH;

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21. NO. OF PAGES

SUNLIMITED.

UNCL ASSIFIED

iZ': FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

20. SECURITY CLASS

(THIS PAGE)

22. Price

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