FIRE ENDURANCE OF CLA Y BRICK VENEER

Walter L. Dickel

1. ABSTRACT

In order to provide for the excellent fire resistance of clay brick veneer in the balanced occupancy vs risk design, tests were made for assurance of joint bonding, unit bonding, and fire endurance ratings. The fire tests were in the pattern of A TSM E 119 for I hour and 2 hour endurance ratings.

The various equivalent thicknesses performed well and the typical instaJlations, with equivalent alternates, were subsequently developed and included in a Uniform Building Code Evaluation Report for use in ICBO jurisdictions. These included combinations of gypsum wallboard , gypsum plaster, adhered veneer, anchored veneer, reinforced veneer.

2. SUMMARY DISCUSSION

2.1 Code Fire Endurance Requirements

The Uniform Building Code, and others, contain requirements for Fire Endurance Ratings of various portions of TYPE OF CONSTRUCTION as shown in Table, Fig. I. These are based on considerations of; relation of risks of various occupancy type, with areas of building, height of building, 10cation on property, and Fire Zone, etc. This then determines the required fire endurance for various portions and clay brick veneer had no code rating.

2.2 Brick Fire Endurance Ratings

Design of early construction was not greatly concerned with fire endurance ratings of brickwork because normal clay brick walIs provided walls of over four or six hour ratings, far more than required for safety or code compliance, not only because of the superb fire resistive properties but also because of the wall thickness. However,

Key words: Masonry; Brick Veneer; Fire Rating; Veneer Bond

lConsulting Engineer, Higgins Brick Co., 1014 Fortune Way, Los Angeles, CA., 90042; Past Instructor in Masonry, Cal-Poly, Pomona

1079

2

improved engineering design of brickwork, such as required for economy, introduced use of thinner, lighter walls, including hollow brick, as introduced into UBC design by Western States Clay Products Association in the 60's, and later by ASTM after successful use in seismic areas of the Western USA. The well established fire resistance "Equivalent Thickness" method was applied by WSCPA to Hollow Brick tirst in UBC Research Approvals and then in to the code body including various moditications by fill or coating application.

There was a need for provision to use the highly fire resistant clay brick veneer in TYPES OF CONSTRUCTION, as indicted by the circled items of UBC Fig. 1. There are also the 1 and 2 hour ratings as required by location on property in T ABLE 5-A, and separations in TABLE 5-B of UBC.

_o. .0 TYPE' TYPEn TYPE~ TYPEIV TYPEV

HONCOMBUSTISLE COMIWST18LE 8WlDlHG ELEMEKT F~lttve

_ ...... , ..... "

,_o H H.T. , ..... H

L Exterior 8earing Walls 4

Sec. 4 J 4 4 4

18031') 1903(0) I N .200..2:l.a) 2003 (,) 2103 (a) r;.l. N

2. Interior Bearing Walb ) ( 2) (I) N " N ( I.J I \. I..) N

3. Exterior Nonbearing 4

Wall~ Su 4 (0 4 4 4

Ci) IRO) (a) 1903 (,) 1903 (.) N 2003 (a) 2003 (a) 2103 (a) N

4. Structural fume I 3 (2 ) 1:1) N I. I) N lorH.T. ( U N

, 5. Partilloos--Pennanenl -( I "'l I I, N I N lorH.T. I N ' .

6. Shaft Enclosures) -:tO) 0" __ f I) ( I') ( I) ( I.J ( I) ( U (. I...) , - . .. -

FIGURE I. E~cerpt trom use TASLE 17-A. The items in which rated veneer

may be used are marked with <:)

3. PURPOSE OF THIS PROGRAM

The goal of the program was to provide for use of clay brick veneer where 1 and 2 hour tire rated construction was required and to verify adequate attaching or bonding for assurance of performance.

This included tests of unit bond to backing, mortar joint bond and tire tests. The tire tests were for 1 hour and 2 hour ratings. Since the panel assemblies were asymmetrical, two of each type were made and tested, one for testing with the brick face exposed and one with the other face exposed.

4. BOND TESTS

4.1 Joint Bond Test

Fire resistance assurance is an essential property of construction and since there had been cases, some extensive, of adhered veneer failure the bond aspects were viewed. It is recognized that oadhered veneer is a hand placed material and there might hence be occasional points of imperfection, and range or scatter of results. Therefore, the

1080

3

treatment of joint bond was considered as an item for assurance of performance. (Figure 3)

4.2 Tests Of Unit Bond To Backing

The tests were made on 3" square specimens bonded to 4" square concrete backing units , as shown in drawing Figure 2.

5. 1 Method of Bonding

The UBC specifies an adhesive method step by step, and also that a minimum shear strength of 50 psi be developed. This is conservative because the units to be bonded weigh less than 15#/pft., i.e., . 1 psi. However, apparently, the ear1y value was based on judgment to provide for good field value. When a method provided 50 psi , the workmanship was good, if less it might be poor.

The units were bonded to the backing blocks with various methods. Basic was the UBC step by step, and then by methods that omitted one or more steps. AIso some by alternate bonding or adhesive agents were used. Alternate bond methods may be specified if proven.

5.2 Load Applications

The shearing load was applied as shown in the diagram by standard calibrated loading machines designed for the purpose and used extensively for testing of bond of tiles.

5.3 Test Indications

There was considerable scatter of results as expected for hand placed material. The UBC Method developed over 180 psi. Comparable values were also developed if any one of the steps were omitted . However, if 2 or more steps were omitted the values were considerably lower.

Bond developed by latex and by "thin-set" were markedly greater, some over 300 psi . Although the thin-set method developed high values under laboratory conditions it was more subject to field problems.

6. MORT AR JOINT BOND TESTING

The validity of the requirement for tooling joints was demonstrated. This was in view of the fact that most of the examples of field failures did nol have tooled joints.

If mortar joints bond the units to the backing in addition to providing water penetration , they will also provide an attachment factor of safety , similar to the use of two coats of painL A failure in one will probably not occur at the same place as a failure in the other. The factor of safety is desirable in hand placed construction.

1081

4

There are many items that may cause local bond failures to backing, e.g., dust or other bond inhibitors on the surface of backing or of unit, improper placing of units or bond coat, movement after initial placing, severe temperature at time of placing, etc.

6.1 Test Procedure

A test was made of the bond of tooled mortar joints to backing and bond to units. The specimen were prepared by different methods of placing and tooling in joints between typical veneer unit material , which was unbonded by paper separation.

6.2 Results

There was considerable scatter of the resulting values of bond strength, not only because of different methods , raking, etc., but due to the use of unpracticed personnel to place the joint mortar. However, the strengths were adequate to support the weight of the units by bond, either to the backing or to other units to provi de the assurance of attachment.

6.3 Logical Conc1usion of Bonding Tests

Joints should be tooled.

Bonding of units may be accomplished in several differing alternate methods.

7.0 FIRE TEST PROCEDURE

7. 1 Panel Construction

The panels were constructed similar to those for the past large programs of gypsum board fire evaluation tests and by fire test lab personnel experienced in similar large programs. Type X gypsum board was applied to one face of standard steel stud construction . Typical backing and adhered veneer units applied "according to UBC Chapter 30" was installed on the opposite face by masons experienced in such work, as shown in drawing Figure 5.

The UBC actually states:

VENEER is nonstructural facing of brick, concrete, stone, tile, metal, plastic or other similar approved material attached to a backing for the purpose of ornamentation, protection or insulation.

Adhered Veneer is veneer secured and supported through adhesion to an approved bonding material applied over an approved backing.

(b) Adhered Veneer. With the exception of ceramic tile, adhered veneer and its backing shall be designed to have a bond to the supporting element sufficient to withstand a shearing stress of 50 psi.

1082

5

(d) Application. In lieu of the design required by Section 3004(a) and (b), adhered veneer may be applied by one of the following application methods:

1. A paste of neat portland cement shall be brushed on the backing and the back of the veneer unit. Type S mortar then shall be applied to the backing and the veneer unit. Sufficient mortar shal1 be used to create a slight excess to be forced out the edges of the units. The units shall be tapped into place so as to completely fill the space between the units and the backing. The resulting thickness of mortar in back of the units shall not be less than 1/2 inch or more than 1-114 inches. See also note on Fig. 4.

8.0 TEST PANEL DESIGN

8.1 Principie

The basic design was acceptance of proven panel assemblies and modifying them according to proven alternatives, e.g., a basic wall panel with 1-5/8" thick Type X board each face for 1 hour and two such panels each face for 2 hour resistance, and then substituting 1.5 times that thickness of masonry for one or both faces.

That relative evaluation of thickness is expressed in a long standing footnote to TABLE 43-B of UBC. It had been indicated in very early studies and confirmed graphically in a Structural Engineers Association of California 1962 "Research Committee Report," Walter L. Dickey, Chairman.

The panel design was for symmetrical resistance as required by UBC and other codes as shown in Fig . 8. However, if one designed for a situation in which fire exposure were on 1 face only the resisting thickness could all be on one side as shown in alternate Fig. 9.

8.2 Interior Thermocouples

Additional thermocouples were installed during construction in order to provide information on the thermal gradient through the section. This gives information to help revise design alternates with assurance.

9.0 FIRE TESTING

The panels were exposed according to the procedures of ASTM E 119, i.e., Standard furnace temperature rise; thermocouples on the unexposed face to show temperature rise; verification that there were no cracks that would allow passage of flame or hot spots; resistance to hose stream exposure without penetration .

10.0 RESULTS

All panels passed the three basic ASTM requirements with considerable margin, i.e., as to temperature rise on unexposed face, resistance to cracking and penetrations, and to hose stream test. Although the results were somewhat conservative, indicating that

1083

6

slightly thinner veneer might be used, no further refinements or reduction of the design thicknesses was attempted . Precise refinements are not justified in variable hand placed materials, especially if no great cost benefits would resulto

The maximum temperature rise on the unexposed face is permitted to be a maximum of 3250 for a single point and 2500 for an average, at the specified time period.

The test panels showed the following maximum and average rise.

Panel IA; 1620 and 1580 Panel lB, 145" and 135"

Pane12A; 1290 and 1100 Panel 2B, 1070 and 1040

11.0 APPLICATlON, CODE lNTRODUCTlON

After verification that stud walls, either wood or steel, will provide 1 and 2 hour fire endurance ratings when covered, each face, with either 5/8" Type X gypsum or I inch of brick veneer for 1 hour, or either 2 Type X boards or 2 inches of veneer and backing application was made to provi de for code usage. First step was Research Evaluation approval , and inclusion into the code body to follow. Some of the alternates were drawn to illustrate and clarify the details and methods in the application as shown in Fig. 8.

12. ANCHORED BRlCK VENEER

It is also recognized that brick units may be anchored, as in Veneer Chapter 30, in lieu of attached by bonding. Therefore, 1 inch of masonry for 1 face could be provided by I inch of anchored brick units, except for the fact such units would be impractical to lay as masonry, hence units of about 2 inches thick are indicated as anchored .

Other types of masonry may be laid to provide adequate thickness for fire endurance, as indicated on the reproduction of the section drawings of the WSCP A-lCBO Evaluation Report, Fig . 8. That gives studied approval of examples for use of items acceptable for Code compliance.

13 . RElNFORCED BRlCK VENEER

Two of the sections shown on the Research Evaluation are for reinforced Hollow veneer. This is veneer which complies with the excellent performance design provisions of Chapter 30 (as written and adopted in 1967). Such veneer carries no load other than itself, including the imposed wind or seismic lateral load. The amount of reinforcing and spacing of ties or supports is as required by design of any structure to resist those forces of gravity, wind and seismic (in compliance with design of Chapter 23 and 24).

The fire ratings of those items are based on equivalent thickness in accordance with TABLE 43-B, items 1-5.1 and 1-5.2 (1991 edition).

1084

7

14. CONCLUSION

There was a need for fire rating of brick veneer in order that it be used in the ordered pattern of balanced occupancy risk and fire resistance. Such recognition was not in the UBC.

Load tests were made to verify the validity of methods of joint and unit bonding to backing by several methods.

Fire tests were conducted to verify the equivalent thickness principie application to veneer thickness required, and to verify the performance when exposed to a standard fire and hose stream.

The data was put in form for use in a UBC Evaluation Report, i.e., for use under UBC jurisdictions. It may then be put into the body of the Code, as was the data for Hollow Brick equivalent thickness.

This was a program designed to determine if Brick Veneer could be used to provide 1 and 2 hour fire endurance as required by UBC. The results were successful, and put to use.

1085

FIRE RATINGS OF BRICK VENEER WALLS l-H OU R WALL SECTIONS 2-HOUR WALL SECTIONS

1" masonry or s/a" gypsum ea. lace 2" masonry or 1'/'" gypsum ea. face

S/a"

Adhered vencer A-----'-- unilS & backing ------L

1" 2"

--f-p,Lf----- Sluds---------f71F71---

f-----t'7"1----- Wall board --------b""'~7_"_j----I

1"1/1-----Adhered veneer _____ --r bolh laces 1" 2"

I:oj-----5Iuds----------b""j,,..f;j

....+-----Adhered veneer -----_1/ 1" 2"

--tit":t-----Sluds----------Ir"::!-"

hr-"'J----- Gypsum plasler ------'b"'97-<-i -----1

~i=---;;>'7'''_- Anchored veneer ---~p::~:r-I

-2" 2" - Brick unils------í

______ Ancl10rs spOI bedding ________ LA--<'---'" oplional

FIGURE .(~) FIGURE (b)

F I Gur~E 8

1086

1'/'"

-2"

1'/'"

"_1'/'"

Plasler board

~ (

~ ..

I / ' ; ','

" 'i-

'.

( ,1'\ (

1 " -, , ,,,,v . '

i j;' t

-\ í )

...

\ ' \ UNIT' IJOINT

I ; PAPER BOND BREAI<ER

BI\CKING

8KI<INO· SIlKl$

Figure 2 , Test specimen

for Joint bonds

--- 3. "'-10 l':o-MORTAS! TnOVlEllEO TO Utllr AAO~I(ItIC

5. JOIIH$ POINTEO ANO lOOUO

on 5. rOtllrEO. RAAEO ANO l00lEO

BOND

BRICI< UNIT

BI\CKING

Fiyure 3, Test specimen

for un i t bono '/'0 back i ng

1. Clean lhe 3u.foco of dusl, di,t ar olhor """'bla bond Inh{biIO(5, mOlslDn and brush wllh slurryol cemonl. ar comen! and OQuol part3 fino sendo

2. Apply ,'urry lo bnck of unll:5. or d lp onlo morta, lo wofk "Julce" onlo back.

3. Apply monar lo bock lno end lo uolts. 4. Pross unil.5 In 10 p/ace topplng for propar

allgnmenl ond locarian.

5. Mortor pre.ssed ar polnled Inlo lolols and too/sd. ar rakod .nd lootod.

6 . $00 olher dOlall, lor 9upports. expan510n o tc.

Sect i on Bas i c- me'l'hod Figure ~ _ SAction and I isfing of bas i c Ul'lC method , '. ,

1087

l 19" I

/.4"

l 6;>" ---_ .-- -- ----

+10

1,2,3,4,5,6,7

-----"'+ thermocoup I ~s .

( ~ +9

2;" x 0.0 19 stee l U track /

19"

c-S

c-V

r\ \ .. , 2, x O.lJ/9

StAp.1 ,: <:tuus

Figure 5 Panel construct ion. This shows the detai Is for the 2 hour exposure

Anchor -+-+---- ---~§~~~ Stud

g> ~ -"

U V>

'" ~ D

u U

C Q)

ro ., U

L · ro

" D Q) C L

" Q)

> . a.

'" -" a. U

L D

N

exposure

Figure 7. example of assymetr i cal panel if tire exposure is I imited to one direct ion

Altarnata

" Lal...: Idd"l ... k) be ~ a«Ofdlno lo ma nvfaC1v""'. Inslrvc:liont

1088

u O

~ N

<li 1 , QJ L U

"' U O) O "-LA

" I N

"' ~ , .- " L

U

i' "' ro ~ O I Q) :: L

u. , L L·

Q) " >- >-

'" '" Q) Q)

u "' '" '" D

~