NBSIR 73-141

Fire Endurance Tests of Plywood on

Steel Joist Floor Assemblies, With and

Without Ceiling

(Test Numbers 492, 497)

H. Shoub, B. C. Son

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

March 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

NBSIR 73-141

FIRE ENDURANCE TESTS OF PLYWOOD OU

STEEL JOIST FLOOR ASSEMBLIES, WSTH AND

WITHOUT CEILING

(Test Numbers 492, 497)

H. Shoub, B. C. Son

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

March 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

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

MATIOMAL BUREAU OF STANDARDS, Richard W. Roberts, Director

FIRE ENDURANCE TESTS OF PLYWOOD ON STEEL JOIST

FLOOR ASSEMBLIES, WITH AND WITHOUT CEILING

(TEST NUMBERS 492, 497)

by

H. Shoub

and

B. C. Son

ABSTRACT

Fire endurance tests were conducted on two floor/ceiling assemblies

intended for use in modular housing. One assembly simulated the combination of the floor of an upper story module with the ceiling assembly of

the module beneath; the other assembly, the floor of a first floor

module over a ceilingless crawl or foundation space.

The floors were of plywood deck with vinyl or carpet overlay on

light gage steel "C" joists. In the floor-ceiling assembly, the ceiling

was separately supported on its own joists, contained simulated HVAC*

duct work and a layer of glass fiber batt insulation. During the tests

which were conducted generally in accordance with the requirements of

ASTM E 119-71, Fire Tests of Building Construction and Materials,

the floors were loaded to represent the dead weight of structural parts

bearing on them and a live load application of 40 psf. The test results

are valid only for floors of similar construction loaded at or below the

stress level developed by this loading.

Failure of the floor with the protective ceiling assembly occurred

by flame-through to the unexposed surface at 29 min. , with extensive

structural failure (collapse under load) following at 33 min. The

*HVAC - Heating, Ventilation and Air Conditioning

i
unprotected floor over the crawl space had a flame-through at 3 1/A min . ,

and structural failure following at 3 3/4 min.

Key Words: Fire test; Floor assembly; Floor-ceiling assembly ^ Housing

systems; Modular construction; Operation BREAKTHROUGH; Steel

framing; Steel joist floor
TABLE OF CONTENTS

Pa_ge

ABSTRACT i

1.0 INTRODUCTION 1

2.0 DESCRIPTION OF TEST SPECIMENS 2

2.1 Floor Assemblies , 2

2.2 Ceiling 3

3.0 TEST METHOD AND INSTRUMENTATION . 4

4.0 RESULTS OF TESTS 6

4.1 Floor Over Foundation Space 6

4.2 Floor-Ceiling Space 7

5.0 DISCUSSION OF RESULTS 9

6.0 SUMMARY AND CONCLUSIONS 10

APPENDIX I 12

APPENDIX II 13

LIST OF ILLUSTRATIONS 14

iii

1.0 INTRODUCTION

The fire endurance of two plywood and steel joist floor assemblies,

one designed for the first floor module of a low-rise multifamily residential structure, the other as an upper story floor over a ceiling

covering a module below, was investigated in tests conducted by the

Fire Research Section of the National Bureau of Standards.

Although the use of stacked factory-built modules for residential

occupancies is becoming more prevalent, there have been very few fire

tests made on structural elements of two living unit modules positioned

one above the other. This type of construction is illustrated in

figure 1. These tests were conducted to examine the effect of several

innovative features of modular floor structures on the overall fire performance of the assemblies. The structural steel members of the floors

were of a type not widely used for joists in residential construction and

the performance under fire conditions of their method of attachment to

the perimeter framing of the floors was unknown.

The tests, which were conducted generally in accordance with the

requirements of ASTM Standard E 119-71, Fire Tests of Building Construction

and Materials—^, were sponsored by the Department of Housing and Urban

Development in an evaluation program of housing systems submitted under

Operation BREAKTHROUGH.

\J Standard Methods of Fire Tests of Building Constri:c.''lrii and Materials , American Society for Testing and Materials DesigUciti oi. E 119-71,

available at 1916 Race Street, Philadelphia, Pa. 19103

1
2.0 DESCRIPTION OF TEST SPECIMENS

2.1 Floor Assemblies

The floors for the two tests were of similar construction and will

be described together with a separate section to present the ceiling

assembly used in one of the tests.

The details of the floors are shown in figures 2, 3a and 3b, the

latter two including the attached ceiling. The floor framing was factorybuilt, each in three sections, which were assembled with splice plates

and covered with pljwood and finish flooring at the NBS test facility.

This was necessary due to size and handling constraints in the test

furnace building. The overall floor size was 11 ft 9 in. by 17 ft 11 in.

The 3/4-in* thick tongue-and-groove , Douglas fir underlayment grade plywood flooring, was attached at 12-in. spacing along the perimeter and in

the field with 1 1/8-in. long hi-lo bugle head screws. Half the plywood

surface of each floor was covered with vinyl roll flooring, half with pad

and carpet. The vinyl flooring was 5/64 in. thick. The carpeting, 3/8-

ina Nylon pile on 1/8-in. jute backing, was laid over a 1/4-in. rubberized

hair pad.

The floors were built into perimeter channels of 6 1/8-in. by 1 3/4-

in. 18 ga. galvanized cold rolled steel. Floor joists, 6-in. by 1 3/4-

in. 18 ga. cold rolled steel "C" sections, were welded to the perimeter

channels at 24-in. on centers with 20 gage clip angles. The assembled

framing can be seen in figure 4. On the foundation space (or crawl space)

floor a steel reinforcing strap, 3-in. wide, 24 ga, , was welded transverse

to the bottom of the joists at the midspan.

2
As a means of simulating the floor and walls, stub walls of 5/8-in.

Type X gypsum board attached to 3-in. "C" studs to an overall height of

18-in. from the bottom of the joists to the top of the wall were erected

on the perimeter of the floor. Further, reinforcement was provided in

the form of cross-bracing members at the top of the stud walls (figures

2 and 3a) in simulation of the rigidity provided by a ceiling structure.

2.2 Ceiling

The ceiling assembly as shown in figures 5 and 6 was also constructed

with simulated perimeter walls to reduce the conditions at the top of

a housing module above. The stub walls were 24-in. in height with the

ceiling joists placed to allow about a 6-in. space above them for duct

work and batt insulation.

The ceiling joists, 3-in. by 1 3/4-in. 18 ga. cold rolled steel "C"

sections, similar to the floor joists, were spaced on 24-in. centers and

welded to the perimeter channel. A 3-in. wide 24-ga. continuous bracing

strap was welded to the top of the joists at their midspan. A 2-in. glass

fiber blanket was placed over the joists, passing over the duct work and

ceiling diffuser as shown in figures 3a and 3b. The ceiling surface was

5/8-in. Type X gypsum boards attached with 1-in. S-12 bugle head screws

spaced at 6-in. on centers on the perimeter of the boards and 12-in. on

centers in the field.

As with the floor assemblies , the ceiling assembly frame was fabricated by the housing system producer in three sections, and was joined

by splice plates at the test facility. The specimen for the fire test

3
was assembled by joining the floor and ceiling assemblies with bolts

through bearing plates on the abutting ends of the stub wall studs. The

bolts were on 24-in. centers, and were located adjacent to the studs.

3.0 TEST METHOD AND INSTRUT^NTATION

The floor and floor-ceiling assemblies were tested in the NBS floor

furnace with the underside of the floor or the ceiling exposed to a fire

controlled to give an average temperature in the furnace in accordance

with the time-temperature schedule specified in the ASTM E 119 standard.

The temperature within the furnace was determined from the readings of

12 thermocouples protected and positioned in the furnace chamber as

required by the test standards.

According to the standard, the fire endurance of a floor ar floorceiling assembly is the time required to reach the first occurrence of

any one of the following criteria of failure:

1. Inability to sustain the 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 degrees F (139 degrees C) average or

325 degrees F (181 degrees C) at one point above the initial

temperature on the unexposed surface.

When positioned for the test, the 17-ft 11 in. -long floor specimens

had only nominal clearance in the 18-ft long furnace opening. The floor

width of 11 ft 9 in. , however, was 15 in. less than the furnace width.

To provide for this, the floor assemblies were installed to one side of

the opening at the top of the furnace, with an .-beam for support of the

4
side not against the furnace wall. Suitable fire resistive material was

placed to protect the beam and provide closure of the space. As the

auxiliary beam and filler were not part of the test structures, they

were designed so as not to contribute to, or be affected by, the fire

exposure.

Loading of both floors was the same, applied with concrete blocks

to a weight of 51.4 psf. This represented a design live load of 40 psf

,

and a dead weight of supported structure of 11.4 psf (not including the

3.6 psf weight of the floor itself). The actual construction dead load

on the ceiling assembly was approximated by the installation of ductwork

and insulation.

Deflections of the floors during the test were measured along the

longitudinal centerline, at the midpoint of the assembly and at the

quarter points. Wires with suitable pointers and scales were attached

at the three check points to provide visual indication as well as automatic recording (through potentiometers) of the movement of the floor

surfaces

.

For the floor over the foundation space, temperature measurements

were made on the unexposed surface only. This was accomplished with 12

Chromel-Alumel (Type K) thermocouples disposed in an almost symmetric

pattern over the vinyl and carpet coverings, as shown in figure 7. Each

thermocouple was covered with an asbestos pad (6- by 6- by 0.4-in.) as

specified in the ASTM E 119 standard. Temperature readings indicated by

the thermocouples, including those in the furnace, were recorded at 2-inin.

intervals for subsequent processing and plotting by computer.

5
The floor-ceiling assembly had thermocouples on the interior members

of the structure and under the covering material as well as on the unexposed surface, although the failure by temperature rise is determined only

by the condition on the unexposed surface. Thirteen thermocouples placed

on the floor covering were distributed as indicated in figure 8, which

also shows the disposition of the thermocouples under the covering and in

the structure, a total of 62 for the assembly. Those on the unexposed

surface were covered with asbestos pads as described above. The remainder

were uncovered, and were attached with screws to the adjacent structural

parts or ductwork.

4.0 RESULTS OF TESTS

4.1 Floor Over Foundation Space

Failure of the floor structure over the foundation or crawl space

was observed at 3 min. 15 sec. after start of the test when flames penetrated the unexposed surface. At 3 min. 45 sec. the entire floor collapsed

into the furnace under the superimposed load of concrete block, probably

as a result of failure of the welded joints at the perimeter framing.

The ASTM E 119 fire test standard requires compensation for fire

exposures deviating from the standard time-temperature relation only if

indicated failure times are 1/2-hr. or greater. As the fire exposure

severity in this case was appreciably greater than that required by the

standard (figure 9) , it was appropriate to apply corrections for the times

to the two modes of failure despite their brevity. Applying these corrections estimates to the results, the end point times become 3 min. 30

sec. and 4 min. 5 sec. for flame through and failure to sustain load,

respectively.

6
Maximum and average temperature rises on the unexposed surface (over

vinyl floor covering, figure 10; over carpeting, figure 11) were low, and

did not approach the limits defining failure by transmission of heat. The

recorded data indicated little or no effect of the flame penetration,

probably because this occurred at one end of the floor, somewhat away

from the thermocouples.

At 2 min. after start of the test the exposed plywood surface was

charred, with general flaming at 2 1/2-min. Significant bowing of the

floor was noted as early as 1 min. of test time, and increased rapidly

until final collapse. Deflections were measured as follows:

Time (South) Center (North)

(min) 1/4 Pt (in.) 1/4 Pt

(in.) (in.)

Initial 0 0 0

1 1.2 1.8 1.4

2 2.6 3.6 2.5

3 6.0 7.6 5.5

3:45 Collapse

A view of the top or unexposed surface of the collapsed floor is presented

in figure 12.

4.2 Floor-Ceiling Assembly

For the floor-ceiling assembly, failure occurred at 29 min. after

start of the test by passage of flame through to the unexposed surface.

At 33 min. , local collapse of the assembly was observed at the end away

from the ductwork and diffusers. As can be seen in ligure 13 the actual

fire exposure severity was slightly greater than that specified in the
standard and a correction of approximately 1 min. should be added to the

noted failure.

Average and maximum temperature rises on the unexposed surface were

not significant, with the maximum rise not exceeding 50 degrees C on the

carpet at the end of the test, as can be seen in figure 14. Surface

temperature rises in the area covered with vinyl flooring did not approach

those over the carpet. As before, the flame through occurred in an area

away from the thermocouple locations.

Temperature rises on the steel joists and adjacent structure are

illustrated in figure 15 (average) and figure 16 (maximum) . Similar

rises in the area of the ceiling duct are shown in figure 17, giving the

average temperature changes. Maxima in this location were not significantly

higher. Temperature rises through the assembly at locations not at

joists were noted to be somewhat lower than those indicated for the

thermocouples at sections through the joists.

No significant deflection of the floor surface was noted until 26

min. after start of the test, when a downward movement of 0.7 in. occurred

at one of the quarter points. This rapidly increased so that a 30 1/2-

min. , prior to complete collapse, the deflection at this point was approximately 8 in. At the same time, the deflection at the midpoint was

2 in., at the other quarter point, 1 in.

A log of the observations made during the test on the floor-ceiling

assembly is given in Appendix I.

8
5.0 DISCUSSION OF RESULTS

The dimension of the shorter side of the floor assemblies tested,

11 ft 9 in. , was slightly less than the 12 ft required by the ASTM E 119

standard. However, the size tested was representative of that to be used

in the actual modules.

The uniform distribution of heat in the furnace is reflected in the

temperature gradients measured at the five steel joist locations. At

these points, the maximum and average ten5)erature rises were of a similar

pattern, with the maxima only moderately higher than the averages, indicating the absence of wide variations of exposure. If large differences

in furnace temperature had been present these would have been reflected

in the temperatures on the test structure.

For the unprotected floor assembly over a foundation space, failure

occurred at less than 5 min. with the indicated furnace temperature considerably less than 1000°F. This can be explained by a lag in the furnace

teii5)erature readings which are based on thermocouples in heavy iron

pipes. The actual furnace temperature was considerably higher during the

early stage of the test. Of greater significance than the loss in yield

strength of the structural elements at elevated temperature was their

rapid expansion which caused the welded attachment to the perimeter

framing to break within a few minutes after start of the test.

In floor-ceiling assembly, the gypsum board ceiling provided

protection to the ceiling and floor joists, the latter being further

shielded by the insulating blanket over the cei''tng. Failure in this

test depended upon heat penetration of the protective layers. Opening

9
of the gypsum board ceiling may have been precipitated by torsional

buckling of the asymmetrical "C" ceiling joists.

The loading applied to the floor assemblies in these tests was based

on calculated dead loads for the structure and an estimated occupancy

live load, but did not necessarily develop the maximum allowable working

stresses in the structural members. Thus, the results of these tests

may be made applicable only to similar floor assemblies with spans and

loads such that the stresses developed do not exceed those developed in

these cons truetions

6.0 SUMMARY AND CONCLUSIONS

Inafire test of a floor assembly consisting of 3/4-in. plywood on

unprotected steel "C" section joists, failure by flame through occurred

at 3 1/4 rain, and failure by inability to sustain an applied load occurred

at 3 3/4 min. after start of the test. A primary cause of the failure

was the breaking of the weld joints between the joists and their supporting perimeter frame. Failure of a similar floor assembly, but with a

protective gypsum board ceiling, was noted at 29 minutes by flarae through

and at 33 minutes by load failure following destruction of the ceiling

and its insulating overlay.

In both tests, torsional buckling of the "C" sections was apparently

a contributing, and perhaps the principal, factor in the failures. This

movement probably accelerated destruction of the welds. The uneven movement of the structural elements could have opened the ceiling in the

assembly so constructed, allowing early heat penetration, and acted

similarly on the pljwood floors, producing flame through conditions in

10
both tests at times less than ordinarily experienced with the given thick

ness of wood.

The load applied to the floors was 40 psf and the results should be

applied only to floors of similar construction loaded to develop stresses

not exceeding those developed in this assembly.

11
APPENDIX I

Log of Fire Test of Floor - Ceiling Assembly

Time Observaliion

Min:Sec

01:00 Considerable smoke in furnace, probably from pyrolysis of

paper on the gypsum board.

05:00 Gypsum board paper on exposed side consumed.

07:00 Sheet metal diffusers warping slightly.

08:00 Smoke on top at one corner, indicating possible combustion

of the binder in the glass fiber insulation.

10:00 Some smoke at all edges adjoining stub walls.

12:00 Diffusers appear to have dropped about 1-in.

16:00 Diffuser near end of ceiling still moving down; gypsum

board panel at same end moving out.

21:00 Diffuser nearer to center descended about 1 1/2-in. Apparent

flaming on gypsum board on fire side, from joints and cracks;

joint spackling falling out.

23:00 Smoke mainly at edges on unexposed side.

24:00 A gypsum board panel opening, and appears ready to fall.

25:00 Gypsum board panel fell into furnace, exposing the glass

fiber insulation blanket.

29:00 Furnace full of flames; gypsum board ceiling falling in;

glass fiber insulation melting; much smoke coming through

top of specimen. Flame through.

32:00 Considerable flaming at one end of floor; fire exposure

terminated

.

33:00 One end of floor assembly fell into furnace.

12
APPENDIX II

SI Conversion Units

In view of present accepted practice in this country in this

technological area, common US units of measurement have been used

throughout this paper. In recognition of the position of the United

States as a signatory to the General Conference on Weights and

Measurements which gave official status to the metric SI system of

units in 1960, we assist readers interested in making use of the

coherent system of SI units by giving conversion factors applicable

to US units used in this paper.

Length

1 in = 0.0254 meter

1 ft = 0.3048 meter

Mass

1 lb = 0.45 Kilograms

Stress

2

1 psf = 47.88 newton/meter2

1 psi = 0.332 newton/meter

1 plf = 13.45 newton/meter

Temperature

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

13
LIST OF ILLUSTRATIONS

Fig. 1 - Sketch of Module Positioning

Fig. 2 - Floor over Foundation Space - Details of Construction

Fig. 3 - Floor-Ceiling Assembly - Construction

a. Floor Plan

b . Ceiling Plan

Fig. 4 - Floor Framing - Showing construction of stub walls, and

ceiling insulation blanket.

Fig. 5 - Floor-Ceiling Assembly - Ceiling framing, showing duct

Fig. 6 - Ceiling Assembly - View of framing, partially covered

ceiling, and stub wall

Fig. 7 - Floor over Foundation Space - Thermocouple locations on unexposed surface

Fig. 8 - Floor-Ceiling Assembly - Thermocouple locations

Fig. 9 - Floor over Foundation Space - Average furnace temperature

compared with standard E 119 curve

Fig. 10 - Floor over Foundation Space - Maximum and average temperature

rise on unexposed surface (vinyl)

Fig. 11 - Floor over Foundation Space - Maximum and average temperature

rise on unexposed surface (carpet)

Fig. 12 - Floor over Foundation Space - View of unexposed surface of

collapsed floor

Fig. 13 - Floor-Ceiling Assembly - Average furnace temperature compared

with standard E 119 curve

Fig. 14 - Floor-Ceiling Assembly - Maximum and average temperature rise

on unexposed surface (carpet)

Fig. 15 - Floor-Ceiling Assembly - x\verage temperature rise on steel

joists

Fig. 16 - Floor-Ceiling Assembly - Maximum temperature rise on steel

joist

Fig. 17 - Floor-Ceiling Assembly - Average temperature rise on the

ceiling ducts

14
PLYWOOD FLOOR

WITH VINYL OR

CARPET RNISH

'C' FLOOR

JOIST

GLASS RBER

BATT INSULATIO*

'C FLOOR

JOIST

GYPSUM BOARD

CEILING

PLYWOOD floor!

WITH VINYL OR

CARPET FINISH

'C* FLOOR

UOIST

GYPSUM

BOARD

C' SHAPE

STUD

GYPSUM

BOARD

C SHAPE

STUD

GROUND

Figure 1 - Sketch of Module Positioning

15
140"

4 8"

-THIS HALF COVERED

WITH VINYL ROLL GOODS.

APPLIED BY THE NATION- AL BUREAU OF STArOARDS

'4 T&G PLYWOOD SITE APPLIED.

-THIS HALF COVERED WITH CARPET AND PAD- APPLIED BY THE NATION- AL BUREAU OF STAhJDARDlS

I o

I si3

i

FLOOR PLAN FLOOR OVER CRAWL SPACE BUILT AND

SHIPPED TO THE NATIONAL BUREAU OF STANDARDS

IN ( 3)THPFE SECTIONS

NOTE" X" DENOTES 1 '4 STAPLE USED TO

MECHANICALLY ATTACH TWO

BOARDS TOGETHER.

T

19/2 t

:i <

a

>- o

SECTION \ "BB"

TYPE X GYPSUM SHEATHING

FIG. 2 FLOOR OVER FOUNDATION SPACE DETAILS OF CONSTRUCTION

16
141"

140"

38" 48"

NOTE.- FLOOR-CEILING ASSEMBLY BUILT AMD SHIPPED TO THE NATIONAL BUREAU OF

STANDARDS IN SIX (6 ) SECT/ONS.

48"

-THIS HALF COVERED

WITH VINYL ROLL GOODS.

APPLIED BY THE NATION- AL BUREAU OF STAND

ARDS,

1/

-THIS HALFCOVERED WITH CARPET AND PAD. APPLIED BY THE NATIONAL BUREAU OF STANDARDS.

NOTE: ALL SPLICE jOiNTS APPLIED AT N.B.S. ATTACH- ED WITH TEK 2 TYPE SCREWS.

4

'i T&G PLYWOOD MATIONAL BUREAU OF STAND] ARDS APPLIEDFLOOR PLAN SECTION "AA" -WALL STUr a 24 "OC

"

FIG. 3a FLOOR-CEILING ASSEMBLY CONSTRUCTION

17
141"

140

TYPE"X" GYPSUM SHEATHING

-^a TYPE"X-' GYPSUM

27

'X--- , DIFFUSERS ; FACTORY INSTALLER

60

CEILING PLAN

/a TYPE"X" GYPSUM -

^ : in

2 TYPE"X" GYPSUM SHEATHING

FIG. 3b FLOOR-CEILING ASSEMBLY CONSTRUCTION

18

4-1 u

W)C

•H -i iX 05 CO »< bOC C e

•H CO

1—1

u

•Hu CO 1 c

>-l •H o r-l o •H

OJ o

1-1

20

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e

(

)

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(

) ^ )

^

^ ^

(:

<:

CO

-IftI

rolO

t

22
<_X

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CsJ UJ

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(BB2

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CD

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CD XBBI 11

Jjj

UJX f x_

i^x-,8 y<

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23
Figure 9 - FLOOR 0¥ER FOUNDATION SPACE - A¥E.SAGE F0EKACE TafPERAXIME CSKPiy^ES

MITl STA^JDARD E 119 CURVE

24
zoo fir , ta^'

® BVE. 3UR. TEMPA MRX. 3UR. TEMP150_

O

^ iaa_

25
0 BVE. 3UR. TEMP

A MAX. 3UR. TEMP

ISO.

t_3 a

100

UJ

8—

CEUJ

a.

UJ

so 1

—

"1 TIMEIMINUTE)

Figure 11 - FLOOR OVER FOUNDATION SPACE - MAXIMUM AND AVERAGE TEMPERATURE RISE

OVER CARPET ON THE UNEXPOSED SURFACE

26

1000_,

TIMEtniNUTE)

Figure 13 - FLOOR-CEILING ASSEMBLY - AVERAGE FURNACE TEMPERATURE COMPARED

WITH STANDARD E 119 CURVE/
500

40Q_

t_i ca 300.

O

UJto

ft: UJ

ft:

cc£ zoo.

o.

100_

10

^ To

TIME I MINUTE*

10

Figure 14 - FLOOR-CEILING ASSEMBLY

Maximum and Average Temperature

Rise on Unexposed Surface (Carpet)

29

xnax ^

ave
1000

IXl

9Q0_

800

700

^

600_

LU 500

a:I-<

a:

LU

o.

LU

400

300

200

100

(D 1 A 2 + 3

X 4 See Figure ^ 5 ^ 6- Section "B'

15 20

TIMEJMINUTEl

^0

Figure 15 - FLOOR-CEILING ASSEMBLY

Average Temperature Rise

on Steel Joists 30
1000_

900_

+

X

See Figure 8 - Section "B"

800.

700_

Tlf1ECniNUT£}

Figure 16 - FLOOR-CEILING ASSEMBLY

Maximum Temperature Rise on Steel Joists

31
Flgufe 17 - FLOOR-CEILING ASSEMBLY

Average Temperature Rise

on the Ceiling Ducts
FORM NBS-114A (1-71) U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA mtjcto -7 q i / i SHEET NBSIR 73-141

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Fire Endurance Tests of Plywood on Steel Joist Floor

AcicomK 1 T pQ wi And TJn t*}! nnt" Ppt lino (Tpcit"*? NiittiI^pt" ^^nd 4Q ,

5. Publication Date

1^. Performing Organization Code

7. AUTHOR(S)

Byung Chan Son and Harry Shoub

8 Performing Organization

NBSIR 73-141

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10, Project/Task/Work Unit No.

1 r r\r\ f I —i 4600447

11. Contract/Grant No.

J.riri—n— XU — / \J 12. Sponsoring Organization Name and Address Office of Research and Technology

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.)

Fire endurance tests were conducted on two floor/ceiling assemblies intended for use in modular housing. One assembly simulated the combination of the floor of

an upper story module with the ceiling assembly of the module beneath; the other

assembly, the floor of a first floor module over a ceilingless crawl or foundation space.

The floors were of plywood deck with vinyl or carpet overlay on light gage steel

"C" joists. In the floor-ceiling assembly, the ceiling was separately supported

on its own joists, contained simulated HVAC* duct work and a layer of glass fiber

batt insulation. During the tests which were conducted generally in accordance

with the requirements of ASTM E 119-71, Fire Tests of Building Construction and

Materials, the floors were loaded to represent the dead weight of structural

parts bearing on them and a live load application of 40 psf. The test results

are valid only for floors of similar construction loaded at or below the stress

level developed by this loading.

Failure of the floor with the protective ceiling assembly occurred by flame-through

to the unexposed surface at 29 min. , with extensive structural failure (collapse

under load) following at 33 min. The unprotected floor over the crawl space had

a flame through at 3 1/4 min. , and structural failure following at 3 3/4 min.

*HVAC - Heating, Ventilation and Air Conditioning

17. KEY WORDS (Alphabetical order, separated by semicolons)

Fire test; Floor assembly; Floor-ceiling assembly; Housing systems; Modular

construction; Operation BREAKTHROUGH; Steel framing; Steel joist floor

18. AVAILABILITY STATEMENT 19. SECURITY CLASS 21, NO. OF PAGES

(THIS REPORT)

Q UNLIMITED, 37

UNCLASSIFIED

1 1 FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE 20, SECURITY CLASS 22. Price TO NTIS. (THIS PAGE)

UNCLASSIFIED

USCOMM-DC 66244.P71