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Fire tests of protected wood floor assemblies
FIRE TESTS OF PROTECTED WOOD FLOOR ASSEMBLIES b Y
M . G a l b r e a t h and W.W. S t a n z a k
PREFACE
The f i r e r e s i s t a n c e o f wood beams, j o i s t s and f l o o r s can b e c o n s i d e r a b l y improved when t h e y a r e p r o t e c t e d by a membrane o f gypsum b o a r d . C o r r e c t s p a c i n g and p e n e t r a t i o n o f screws o r n a i l s i s t h e most i m p o r t a n t f a c t o r a f f e c t i n g t h e l e n g t h o f time t h e membrane can r e t a i n i t s i n t e g r i t y u n d e r f i r e e x p o s u r e . A s e r i e s o f t h r e e f i r e t e s t s on p r o t e c t e d wood f l o o r a s s e m b l i e s r e p o r t e d h e r e shows t h a t w a l l b o a r d d i r e c t l y a t t a c h e d t o wood j o i s t s w i t h n a i l s i s u n l i k e l y t o a c h i e v e a f i r e endurance r a t i n g o f one h o u r u n d e r e i t h e r p o s i t i v e o r n e g a t i v e f u r n a c e a t m o s p h e r e . The a u t h o r s recommend t h a t o t h e r a t t a c h m e n t methods b e i n v e s t i g a t e d t o o b t a i n a one-hour r a t i n g f o r t h i s t y p e of c o n s t r u c t i o n . M . G a l b r e a t h i s an a r c h i t e c t and W . W . S t a n z a k a mechanical e n g i n e e r . Both a u t h o r s a r e r e s e a r c h o f f i c e r s a t t h e F i r e Research S e c t i o n . Ottawa A p r i l 1978 C . B . Crawford D i r e c t o r , DBR/NRC
NATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH
DBR INTERNAL REPORT NO. 446
FIRE TESTS OF PROTECTED WOOD FLOOR ASSEMBLIES by M . G a l b r e a t h and W.W. S t a n z a k
Checked by: G
.
W . S. Approved by: L.
W.
G.
Prepared for: Record P u r p o s e sDate: A p r i l 1978
S t u d y o f membrane p r o t e c t i o n f o r c o m b u s t i b l e and noncombustible c o n s t r u c t i o n h a s been c a r r i e d on by D B R 1 s F i r e Research S e c t i o n f o r w e l l o v e r a d e c a d e . To improve u n d e r s t a n d i n g o f t h e many v a r i a b l e s
i n v o l v e d , b o t h s m a l l and f u l l - s c a l e f i r e t e s t s have been c a r r i e d o u t . T h i s p r e s e n t r e p o r t d e s c r i b e s t h r e e f u l l - s c a l e f i r e t e s t s on
p r o t e c t e d wood f l o o r a s s e m b l i e s .
A r e v i e w o f f i r e t e s t s o f framed f l o o r and c e i l i n g a s s e m b l i e s (1) was made d u r i n g t h e p r e p a r a t i o n o f F i r e Performance R a t i n g s 1965, Supplement No. 2 o f t h e N a t i o n a l B u i l d i n g Code o f Canada ( 2 ) . A t t h a t t i m e i t was o b s e r v e d t h a t i n wood and l i g h t s t e e l - f r a m e d f l o o r s t h e l e n g t h o f t i m e t h a t t h e c e i l i n g remained i n p l a c e was c o n s i d e r a b l y more s i g n i f i c a n t t h a n t h e i n s u l a t i n g p r o p e r t i e s o f t h e c e i l i n g m a t e r i a l . I t f o l l o w s , t h e n , t h a t t h e f a s t e n i n g o f t h e membrane i s t h e c r i t i c a l f e a t u r e t h a t d e t e r m i n e s t h e performance o f t h e assembly i n f i r e .
A s wood i n f i r e t e s t s i s known t o c h a r s t e a d i l y a t a r a t e o f a b o u t 1 / 4 0 i n . (0.63 mm) p e r m i n u t e , i t may b e e x p e c t e d t h a t t h e t i m e t o p a n e l d r o p o u t w i l l v a r y l i n e a r l y w i t h t h e d e p t h of n a i l p e n e t r a t i o n i n t o t h e wood. To o b t a i n q u a n t i t a t i v e d a t a t o s u p p o r t t h i s t h e s i s , many s m a l l -
s c a l e , a s w e l l a s t h e f u l l - s c a l e t e s t s o f t h i s r e p o r t , were c a r r i e d o u t and t h e r e l a t i o n s h i p d e t e r m i n e d from t h e s e s t u d i e s (3) i s shown i n F i g u r e 1. I t s h o u l d b e n o t e d t h a t 5 / 8 i n . i s t h e minimum p e n e t r a t i o n c o n s i d e r e d p r a c t i c a l .
The f u l l s i z e t e s t specimens were i n t e n d e d t o v e r i f y , by s t a n d a r d f i r e t e s t s , t h e r e l a t i o n s h i p shown i n F i g u r e 1, and t h e most r e c e n t l y t e s t e d assembly (8 December 1977) was i n t e n d e d a s a 1 - h r r e f e r e n c e
specimen t o s t u d y t h e e f f e c t s o f p e n e t r a t i o n o f t h e membrane by p a r t i a l l y p r o t e c t e d s e r v i c e o p e n i n g s .
DESIGN OF THE ASSEMBLIES
A t y p i c a l f i r e t e s t assembly i s shown i n F i g u r e 2 . The o u t s i d e dimensions were 1 3 x 16 f t ( a r e a : 2 0 8 f t 2 ) ; t h e f o l l o w i n g numbers c o r r e s p o n d t o t h o s e on t h e F i g u r e : 1. 2 by 10 i n . e a s t e r n s p r u c e j o i s t s . 1 A . A s i t e m 1, t o s e r v e a s e x t e r i o r frame and f i r e s t o p p i n g . 2 . S u b - f l o o r , 1 / 2 - i n . unsanded s h e a t h i n g g r a d e f i r plywood, i n s t a l l e d w i t h f a c e g r a i n p e r p e n d i c u l a r t o j o i s t s and j o i n t s s t a g g e r e d , n a i l e d w i t h 2 - i n . common n a i l s , 12 i n . O . C .
2A. B u i l d i n g p a p e r , commercial waxed, 0 . 0 1 i n . t h i c k .
3 . F i n i s h f l o o r , 5 / 8 - i n . t o n g u e and g r o o v e , s e l e c t s h e a t h i n g g r a d e f i r plywood, f a c e g r a i n p a r a l l e l t o j o i s t s and j o i n t s s t a g g e r e d , n a i l e d w i t h 2 - i n . common n a i l s , 12 i n . O . C .
4 . 5 / 8 - i n . "TYPE X" gypsum w a l l b o a r d ( s e e Appendix B) a t t a c h e d w i t h 2 - i n . common n a i l s s p a c e d 7 i n . o . c . , a c c o r d i n g t o r e f l e c t e d c e i l i n g p l a n o f F i g u r e 3 (Spec. # 3 o n l y )
.
5 . B r i d g i n g ( n o t shown), 1- x 3 - i n . c r o s s - b r i d g i n g a t mid-span o f j o i s t s .
The specimens were d e s i g n e d t o comply, i n e s s e n t i a l f e a t u r e s , w i t h ULC Design No. M500 ( b a s e d on a ULI t e s t and l i s t e d by U L I a s Design No. L501)
.
( 4 , s ) N a i l s were 2 - i n . common n a i l s s p a c e d 7 i n . o . c . and 3/4 t o 1 / 2 i n . from s i d e and end j o i n t s o f t h e w a l l b o a r d , r e s p e c t i v e l y . Because i t i s t h e most commonly u s e d and most a v a i l a b l e i n e a s t e r n Canada, t h e wood chosen f o r t h e j o i s t s was e a s t e r n s p r u c e , r a t h e r t h a n t h e Douglas f i r u s e d i n t h e U L I t e s t . ( E x p e r i e n c e h a s i n d i c a t e d t h a t t h e o n l y common wood s p e c i e s t h a t would e x h i b i t worse f i r e performanceis cedar, which, because of current higher prices, is used primarily for exterior constructions.)
Structural design considerations for the specimens, which were intended to allow the specimens to withstand the minimum National
Building Code (NBC) design load of 40 psf, are discussed in Appendix A. Assembly No. 1 was a so-called "split-frame" assembly, divided into equal quadrants. It also differed from the typical assembly shown in Figure 2 in that only the main frame was of 2- x 10-in. joists, with the filler joists being 2 x
4
in. The protection was two layers of 3/8-in. standard wallboard nailed to the joists with 1 1/4-in. lath nails. A different kind of wallboard was used in each quadrant. According to NBC Supplement No. 2 Tables 2.3.A. and 2.3.C. with application of Article 2.3.9., this assembly would be assigned a fire resistance rating of 1/2 hr.Assembly No. 2 incorporated 5/8-in. "TYPE X" gypsum wallboard and conformed to the details shown in Figure 2, as did Assembly No. 3. A reflected ceiling plan for the latter Assembly is shown in Figure 3; none is on record for Assembly No. 2. Figure l*, Table 2.3.C., and Supplement No. 2 Article 2.3.9. indicate that the fire endurance of these assemblies should be slightly over 50 minutes.
CONSTRUCTION OF TEST SPECIMENS
The specimens were constructed by DBR staff members. When applying the dry-wall they attempted to achieve a quality of workmanship equal to the average commercial grade.
FIRE TESTS
The specimens were subjected to fire tests in accordance with the provisions of ULC-SlUl-1977(6).
Gas flow into the furnace was controlled automatically so as to follow closely the temperature time curve prescribed by the standard. Furnace temperature was measured by nine symmetrically distributed thermocouples enclosed in 13/16-in. 0.d. inconel tubes having a wall thickness of 0.035 in. and equipped with a carbon steel cap at the top. The hot junction of the thermocouple was placed 12 in. from the exposed surface of the specimen. Both the individual temperatures at the nine points and their average were recorded during test.
*Because Table 2.3.A. does not apply to "TYPE X" wallboard, the
During the tests of Assemblies 1 and 2, the furnace was operated at slightly negative pressure, as are most other fire test furnaces. Before the test on Assembly No. 3, however, the furnace was altered to be operated at slightly positive pressures (7), a condition that more realistically represents the actual fire situation. An operating
pressure of 0.1 in. (2.5 nun) of H20 was chosen as being representative of severe but not maximum possible pressures during a fire in low-rise buildings (with insignificant stack action) (8,9).
Although the falloff time of the wallboard was the main interest in the tests, significant temperatures through the specimens were also measured. Figure 4 shows plots of average stud space and unexposed surface temperatures for Assembly No. 3. Figure 5 shows the deflections resulting from the applied live load of 40 psf during fire exposure.
Significant observations during the fire tests are recorded in Tables 1 to 3.
RESULTS
All Assemblies failed by flame penetration (burn-through) at the unexposed surface, rather than by measured temperature rise. The fire
endurance times according to the failure criteria of ULC SlOl were: Assembly No. 1 38 min
Assembly No. 2 53 min Assembly No. 3 47 min
On
termination of the test all assemblies were close to structural collapse. In Assembly No. 3 the rate of deflection just prior to unloading was 0.1 in. (2.5 nun) per minute. According to the Robertson- Ryan criteria* the rate of deflection just prior to collapse would be 0.27 in. per minute and the total deflection 3 in.*In order that fire tests might be terminated before, but reasonably close to, ultimate collapse Robertson and Ryan (10) proposed that the
7 7
R
point at which both 6c - -
- 800d
"
should be regarded as anand
Ac
= - 150dindication of load failure. In these expressions 6 = maximum C
deflection, in.;
6
= rate of deflection, in./hr; R = clear span of Cprincipal structural element(s), in.; d = distance between the upper and lower extreme fibres of the principal structural element(s).
According t o S e c t i o n 15 o f ULC-S101-1977 a s o - c a l l e d " f i n i s h r a t i n g " i s a s s i g n e d t o t h e p r o t e c t i o n o f c o m b u s t i b l e Assemblies i n conformance w i t h t h e c r i t e r i a o f A r t i c l e 1 5 . 3 . 3 . The f i n i s h r a t i n g f o r Assembly No. 3 was 15 m i n u t e s .
DISCUSSION
A l l Assemblies behaved a c c o r d i n g t o p r e d i c t i o n s b a s e d on
Supplement No. 2 o f t h e NBC. A s i s s e e n , t h e p r e d i c t e d f i r e e n d u r a n c e o f 30 min f o r Assembly No. 1 was exceeded by 8 m i n u t e s , and t h e
p r e d i c t e d f i r e e n d u r a n c e t i m e o f 50 m i n u t e s f o r Assemblies 2 and 3 was a c h i e v e d e x a c t l y , i f one a v e r a g e s t h e f i r e e n d u r a n c e t i m e s o f t h e two i d e n t i c a l a s s e m b l i e s . I t i s n o t e w o r t h y t h a t t h e two Assemblies d i d n o t a c h i e v e a f i r e r e s i s t a n c e r a t i n g o f 1 h r , a s i s i n d i c a t e d by t h e UL
l i s t i n g s . The 10-min d i s c r e p a n c y c a n b e a t t r i b u t e d m a i n l y t o t h e s p e c i e s o f wood used i n t h e f i r e t e s t . A s p r e v i o u s l y s t a t e d s p r u c e i s
one o f t h e p o o r e s t p e r f o r m e r s . C e i l i n g f a i l u r e o f Assemblies 1 and 3 c o u l d have been d e l a y e d by a b o u t 5 min i f s m a l l p i e c e s o f w a l l b o a r d had n o t been u s e d . A c c o r d i n g l y , t h e a u t h o r s recommend t h a t no p a n e l s s m a l l e r t h a n 4 f t s q u a r e s h o u l d b e u s e d i f optimum f i r e e n d u r a n c e t i m e i s t o be a c h i e v e d . I t s h o u l d b e n o t e d a g a i n t h a t t h i s optimum t i m e would n o t r e s u l t i n a 1 - h r f i r e r e s i s t a n c e r a t i n g . The optimum f i r e e n d u r a n c e t i m e f o r Assembly No. 3 would b e a b o u t 52 m i n u t e s , which a g r e e s v e r y c l o s e l y w i t h t h e r e s u l t o b t a i n e d i n t h e t e s t o f Assembly No. 2.
Furnace o p e r a t i o n a t p o s i t i v e p r e s s u r e d i d n o t s i g n i f i c a n t l y r e d u c e t h e f i r e e n d u r a n c e t i m e o f Assembly No. 3 . T h i s was b e c a u s e t h e steam t h a t was r e l e a s e d b y t h e h e a t e d gypsum remained i n t h e j o i s t s p a c e s and d e l a y e d i g n i t i o n o f t h e wood by t h e h o t g a s e s l e a k i n g t h r o u g h t h e open j o i n t s . Burn-through o f t h e assembly o c c u r r e d o n l y 8 m i n u t e s a f t e r t h e f i r s t p a n e l d r o p o u t , which i s two m i n u t e s l e s s t h a n a n t i c i p a t e d by T a b l e 2.3.C. o f Supplement No. 2 . T h i s was a b o u t 3 m i n u t e s l e s s t h a n w i t h Assemblies 1 and 2 , and c a n p r o b a b l y b e a t t r i b u t e d t o t h e p o s i t i v e p r e s s u r e o p e r a t i o n . A s t h e o p e r a t i n g p r e s s u r e was a r e l a t i v e l y h i g h o n e , however ( 8 ) , it would a p p e a r t h a t t h e t i m e a s s i g n e d t o wood f l o o r j o i s t s i n T a b l e 2.3.C. r e m a i n s a p p r o p r i a t e , s i n c e t h e j o i s t s d i d n o t c o l l a p s e .
The f i n i s h r a t i n g w i t h Assembly No. 3 was r a t h e r l e s s t h a n would b e e x p e c t e d w i t h 5 / 8 - i n . w a l l b o a r d . A 30-minute f i n i s h r a t i n g i s s t a t e d i n t h e UL d e s i g n s . P r o b a b l y t h e lower f i n i s h r a t i n g c a n b e a t t r i b u t e d t o t h e p o s i t i v e p r e s s u r e o p e r a t i o n , a s a l l j o i n t f i l l e r had f a l l e n o u t b y 10 m i n u t e s . A c u r s o r y s t u d y o f a v a i l a b l e d a t a by t h e a u t h o r s i n d i c a t e s t h a t t h e f i r e r e s i s t a n c e t i m e o f a p r o t e c t e d wood assembly i s a p p r o x i m a t e l y 3 t i m e s t h e f i n i s h r a t i n g t i m e .
I t was mentioned t h a t Assembly No. 3 was i n t e n d e d a s a r e f e r e n c e f o r a s t u d y o f t h e e f f e c t o f p e n e t r a t i n g t h e c e i l i n g b y p a r t i a l l y p r o t e c t e d a i r h a n d l i n g o p e n i n g s . O b v i o u s l y s u c h a p e n e t r a t i o n would r e d u c e t h e f i r e e n d u r a n c e of t h e s e c o n s t r u c t i o n s t o below 3 / 4 h r , which
i s t h e minimum f i r e r e s i s t a n c e r a t i n g r e c o g n i z e d i n t h e NBC. I t i s
s t i l l n e c e s s a r y , t h e r e f o r e , t o produce a r e f e r e n c e specimen t h a t h a s a f i r e endurance t i m e o f a t l e a s t 1 h r . Study of UL f i r e t e s t r e p o r t s and d i s c u s s i o n s w i t h w a l l b o a r d m a n u f a c t u r e r s i n d i c a t e t h a t a 1 - h r f i r e r e s i s t a n c e r a t i n g can b e achieved by screwing t h e 5 / 8 - i n . "TYPE X"
gypsum w a l l b o a r d t o r e s i l i e n t s t e e l f u r r i n g c h a n n e l s n a i l e d i n t o t h e j o i s t s w i t h 2 - i n . common n a i l s .
CONCLUSIONS
1. The f i r e endurance time of a wood f l o o r assembly p r o t e c t e d w i t h two l a y e r s o f s t a n d a r d 3 / 8 - i n . gypsum w a l l b o a r d was 38 m i n u t e s ; t h e c o n s t r u c t i o n h a s a f i r e r e s i s t a n c e c l a s s i f i c a t i o n o f 1 / 2 h r a c c o r d i n g t o t h e c r i t e r i a o f ULC-S101-1977.
2. The f i r e endurance t i m e o f a wood f l o o r assembly p r o t e c t e d by 5 / 8 - i n . "TYPE X" gypsum w a l l b o a r d was about 50 m i n u t e s ; t h e c o n s t r u c t i o n h a s a f i r e r e s i s t a n c e c l a s s i f i c a t i o n o f 3/4 h r a c c o r d i n g t o t h e c r i t e r i a o f ULC-S101-1977.
3 . P o s i t i v e f i r e g a s p r e s s u r e s do n o t s i g n i f i c a n t l y r e d u c e t h e f i r e endurance t i m e o f p r o t e c t e d wood c o n s t r u c t i o n when t h e h e a t e d
,
p r o t e c t i o n g e n e r a t e s c o n s i d e r a b l e q u a n t i t i e s o f m o i s t u r e .4. Openings a s allowed by NBC 1977 A r t i c l e 3 . 1 . 5 . 6 . cannot b e p e r m i t t e d i n t h e s e a s s e m b l i e s .
REFERENCES
G a l b r e a t h , Murdoch. F i r e endurance o f l i g h t - f r a m e d and m i s c e l l a n e o u s a s s e m b l i e s . T e c h n i c a l Paper No. 222, D i v i s i o n o f B u i l d i n g Research, N a t i o n a l Research Council o f Canada, Ottawa, J u n e 1966. (NRC 9085) Fire-performance r a t i n g s 1965. Supplement No. 2 t o t h e N a t i o n a l Building Code o f Canada. (NRC 8330)
Unpublished f i r e t e s t d a t a on f i l e a t DBR/NRC.
U n d e r w r i t e r s ' L a b o r a t o r i e s o f Canada, L i s t o f Equipment and M a t e r i a l s , Volume 11, B u i l d i n g C o n s t r u c t i o n , September 1976.
U n d e r w r i t e r s ' L a b o r a t o r i e s I n c . , F i r e R e s i s t a n c e Index, J a n u a r y 1977. ULC-S101-1977: S t a n d a r d methods o f f i r e endurance t e s t s o f b u i l d i n g c o n s t r u c t i o n and m a t e r i a l s . U n d e r w r i t e r s ' L a b o r a t o r i e s o f Canada, Scarborough, O n t a r i o .
McGuire, J . H . A method o f a c h i e v i n g p o s i t i v e p r e s s u r e i n a f i r e r e s i s t a n c e f u r n a c e . Submitted f o r p u b l i c a t i o n .
McGuire, J . H . P r e s s u r e s developed by f i r e . T e c h n i c a l Note No. 320, D i v i s i o n o f B u i l d i n g Research, N a t i o n a l Research Council o f Canada, Ottawa, J a n u a r y 1961.
Wilson, A . G . , and Tamura, G.T. S t a c k e f f e c t i n b u i l d i n g s . Canadian B u i l d i n g D i g e s t No. 104, D i v i s i o n o f B u i l d i n g Research, N a t i o n a l Research Council o f Canada, Ottawa, August 1968.
Ryan, J . V . , and Robertson, A.F. Proposed c r i t e r i a f o r d e f i n i n g l o a d f a i l u r e o f beams, f l o o r s and r o o f c o n s t r u c t i o n d u r i n g f i r e t e s t s . J o u r n a l o f Research o f t h e N a t i o n a l Bureau o f S t a n d a r d s , Vol. 63C, No. 2, Washington, 1959.
- 8 -
TABLE 1
OBSERVATIONS
-
ASSEMBLY NO. 1 Time(min)
2 Paper c h a r r i n g .
5 Charred paper glowing and f a l l i n g o f f . 12 J o i n t f i l l e r f a l l i n g o u t .
16 Some n a i l heads showing a s b l a c k d o t s .
2 0 Smoke coming from c e n t r e j o i n t of c e i l i n g . 2 2 J o i n t opening i n S.E. q u a d r a n t .
2 4 One edge o f wallboard i n N . E . quadrant down 1 / 2 i n . 2 5 One edge o f wallboard i n S.E. quadrant down 1/2 i n .
2 6 One p i e c e o f wallboard 16 i n . by 4 f t i n S.E. quadrant dropped o u t . T h i s was t h e f i l l e r p i e c e r e f e r r e d t o p r e v i o u s l y i n t e x t . 2 8 J o i s t No. 5 where wallboard dropped o u t shows a s h e a r c r a c k .
Another p i e c e o f wallboard i n S.E. quadrant s t a r t i n g t o f a l l .
30 Another p i e c e o f wallboard between S.E. and S.W. q u a d r a n t s s t a r t i n g t o f a l l .
32 Corner of wallboard i n N . W . quadrant down 1/2 i n .
38 Two j o i s t s i n S.E. quadrant s e v e r e l y c h a r r e d and f a i l e d i n s h e a r . The d e f l e c t i o n of t h e f l o o r i n g a t t h i s p o i n t caused an opening through which flames passed.
T e s t t e r m i n a t e d .
F a i l u r e o f t h e f i r s t p i e c e o f wallboard o c c u r r e d a t 26 min. T h i s p i e c e o f wallboard was o n l y 16 i n . by 4 f t and was t h e r e f o r e supported by n a i l i n g on two edges a d j a c e n t t o j o i n t s .
TABLE 2
OBSERVATIONS
-
ASSEMBLY NO. 2 Time (min) Paper glowing on c e i l i n g . P l a s t e r j o i n t f i l l e r b e g i n n i n g t o s e p a r a t e . Charred p a p e r glowing. J o i n t f i l l e r f a l l i n g o u t . Char l i n e on j o i n t i n c e n t r e o f c e i l i n g about 6 i n . l o n g . Char l i n e on j o i n t extended t o second p a n e l .Char l i n e extended t o f u l l l e n g t h o f c e i l i n g E.W. J o i n t s between w a l l b o a r d g e n e r a l l y open and c h a r r e d . S l i g h t b u l g e s a t edge o f w a l l b o a r d .
C e n t r e p a n e l moving.
Large p i e c e o f w a l l b o a r d f e l l o u t , N.W. q u a d r a n t . Second p i e c e o f w a l l b o a r d f e l l o u t , N . W . q u a d r a n t . Smoke r i s i n g from c r a c k i n f l o o r i n g (non exposed f a c e ) . C h a r r i n g around c r a c k i n f l o o r i n g (non exposed f a c e ) .
Time (min)
TABLE 3
OBSERVATIONS - ASSEMBLY NO. 3
Paper on wallboard c h a r r i n g and p e e l i n g . J o i n t f i l l e r beginning t o f a l l .
"Clean" steam l e a k i n g from edges of unexposed s u r f a c e . Wallboard j o i n t s b a r e and opening due t o s h r i n k a g e .
"Clean" steam s t i l l l e a k i n g , p a r t i c u l a r l y from west edge of unexposed s u r f a c e .
Wallboard j o i n t s open about 1 / 8 i n .
Steam on unexposed s u r f a c e becoming mixed with p a l e yellow smoke (an i n d i c a t i o n o f " f i n i s h - r a t i n g 1 ' ) .
Wallboard j o i n t s open about 3/16 i n . , flames i s s u i n g from j o i n t s due t o burning o f g a s e s g e n e r a t e d i n j o i s t s p a c e s . J o i n t s open about 3 / 8 i n . , flames i s s u i n g f o r t h , heavy smoke i s s u i n g from edges o f unexposed s u r f a c e , m o i s t u r e s p o t s observed on unexposed s u r f a c e .
Steady l i c k i n g o f flames from a l l wallboard j o i n t s . Panel No. 11 coming l o o s e on e a s t e r n edge.
E a s t e r n edge down t o allow opening of about 5 i n . Dropout of panel No. 11.
Flames i n f u r n a c e t o o t h i c k f o r d e t a i l e d o b s e r v a t i o n s . Panel No. 4 dropped. (This should be considered a s an
i n d i c a t i o n o f c e i l i n g f a i l u r e f o r optimum f i r e endurance t i m e . ) Unburnt g a s e s i n f u r n a c e c a u s i n g flames t o shoot o u t a l l
f u r n a c e c r a c k s and openings.
Burnthrough on t h e unexposed s u r f a c e . T e s t t e r m i n a t e d
APPENDIX A
STRUCTURAL DESIGN (Assemblies 2 and 3)
The minimum j o i s t s i z e r e q u i r e d t o span t h e f u r n a c e i s 2 by 10 i n . a c c o r d i n g t o R e s i d e n t i a l S t a n d a r d s (NRCC 155631, which a r e p e r m i t t e d by Table B-2 t o span 14 f t 6 i n . w i t h a l i v e l o a d o f 40 p s f . A t
maximum span t h e l i v e load s t r e s s i s about 780 p s i . The t e s t assembly, loaded a t 40 p s f , r e s u l t e d i n a t h e o r e t i c a l s t r e s s o f about 630 p s i ; t h a t i s about 20 p e r c e n t l e s s t h a n would be p e r m i t t e d by e n g i n e e r i n g d e s i g n a c c o r d i n g t o CSA 086, 1976. The p r o p e r t i e s o f a wood s e c t i o n a r e given i n t h e 1972 e d i t i o n o f t h e Timber Design Manual (Laminated Timber I n s t i t u t e o f Canada) a s f o l l o w s :
Area 13.87 i n . 2 S e c t i o n Modulus 21.38 i n . 3
Lumber used was graded S-GRN, S e l e c t S t r u c t u r a l No. 2 . Measured m o i s t u r e c o n t e n t a t time o f t e s t was about 7 p e r c e n t . Live l o a d d e f l e c t i o n o f t h e assembly was 0.3 i n . (7.5 mm)
.
APPENDIX B
GYPSUM WALLBOARD AND "TYPE X" GYPSUM WALLBOARD
The "TYPE X I 1 wallboard d e a l t w i t h i n t h i s r e p o r t i s produced by
s e v e r a l Canadian m a n u f a c t u r e r s . I t h a s t h e same g e n e r a l c h a r a c t e r i s t i c s a s s t a n d a r d gypsum wallboard, i . e . , d u r a b i l i t y , s t r e n g t h , h a r d n e s s ,
n a i l a b i l i t y and dimensional s t a b i l i t y w i t h o r d i n a r y changes i n temperature and humidity.
I t h a s g r e a t e r f l e x u r a l s t r e n g t h and dimensional s t a b i l i t y under f i r e c o n d i t i o n s , however, because o f c e r t a i n a d d i t i v e s t h a t improve t h e f i r e r e s i s t a n c e o f "TYPE X" w a l l b o a r d s . Small amounts of m i n e r a l f i b r e and unexpanded v e r m i c u l i t e o r p e r l i t e a r e added t o t h e gypsum c o r e d u r i n g manufacture. The a c t u a l amounts a r e i n f o r m a t i o n p r o p r i e t a r y t o t h e manufacturer and cannot be provided i n t h i s r e p o r t .
The r e a s o n t h a t o r d i n a r y gypsum board i s an e f f e c t i v e f i r e b a r r i e r i s t h a t gypsum c o n t a i n s about 21 p e r c e n t w a t e r o f c r y s t a l l i z a t i o n which, when s u b j e c t e d t o high t e m p e r a t u r e s , i s r e l e a s e d w i t h r e s u l t a n t a b s o r p t i o n o f h e a t . The t e m p e r a t u r e on t h e unexposed s i d e o f t h e board, t h e r e f o r e , cannot g r e a t l y exceed t h e b o i l i n g p o i n t o f w a t e r u n t i l a l l o f t h e gypsum h a s been c a l c i n e d . Once t h i s happens, however, t h e passage of h e a t i s r e l a t i v e l y f a s t because o f t h e h i g h thermal c o n d u c t i v i t y o f t h e remaining m a t e r i a l . Also, a s t h e gypsum i s c a l c i n e d , t h e r e i s a s h r i n k a g e o f t h e c o r e which r e s u l t s i n c o n s i d e r a b l e c r a z i n g . T h i s p e r m i t s f a s t e r passage o f h e a t through t h e board and l e a d s t o i t s e a r l y
subsequent l o s s of p h y s i c a l i n t e g r i t y .
The f i b r e s c o n t a i n e d i n t h e c o r e of a "TYPE X" board a r e incombustible and h o l d t h e c a l c i n e d gypsum c o r e t o g e t h e r t o p e r m i t c o n s i d e r a b l e f l e x u r e o f t h e panel without breaking and f a l l i n g . Raw o r unexpanded v e r m i c u l i t e o r p e r l i t e i n t h e c o r e expands under t h e h e a t of f i r e and compensates f o r t h e s h r i n k a g e o f t h e gypsum c o r e a s it l o s e s i t s combined w a t e r . A f t e r expansion t h e p r e s e n c e o f t h e expanded a d d i t i v e improves t h e thermal p r o p e r t i e s o f t h e c a l c i n e d board by reducing t h e thermal c o n d u c t i v i t y . Any "TYPE X I ' board, when p r o p e r l y f a s t e n e d , w i l l r e t a i n i t s p h y s i c a l
1 2 P E N E T R A T I O N , I N . F I G U R E 1 P A N E L D R O P O U T T I M E V S N A I L P E N E T R A T I O N I N T O S P R U C E J O I S T S F I G U R E 2 T Y P I C A L F I R E 'TEST A S S E M B L Y
1 3 ' - 0 W E S T
4
6 1 - 6 "
F I G U R E 3
