Fibrous plaster for interior finish

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NATIOIIAL RESEARCII COUl7CIL C J W A

D I V I S I O N OF BUILDING ILESEARCH

FIBROUS PLASTER FOR INTERIOR F E T I S H

A

J o i n t

R e p o r t R. W. Muncey (D.B.R., C.S.I.R.O., A u s t i a l i a ) and R.

F.

L e g g e t ( D , 3 . R , , N.R.C.,

Canada)

Internal R e p o r t No. 220 o f t h e D i v i s i o n

of

B u i l d i n g

Research

OTTAWA

March 1 9 6 1

P a r t One F i b r o u s P l a s t e r by R. F. L e g g e t ( m e t e x t of a s h o r t p a p e r p u b l i s h e d , i n t h e February 1 9 6 1 i s s u e o f The N a t i o n a l B u i l d e r , T o r o n t o , b e i n g a s h o r t g e n e r a l d e s c r i p t i o n , w r i t t e n i n r e s p o n s e t o i n q u i r i e s a b o u t t h i s A u s t r a l i a n development. ) P a r t Two

The N a n u f a c t u r e and Use of F i b r o u s P l a s t e r by R.

IV.

_Muncey

( A p a p e r e s p e c i a l l y p r e p a r e d by t h i s s e n i o r member o f t h e D i v i s i o n o f B u i l d i n g R e s e a r c h , C.S. I.R.O., A u s t r a l i a , a n d i l l u s t r a t e d by p h o t o g r a p h s s u p p l i e d by his o r g a n i z a t i o n . ) P a r t !lhree Some A d d i t i o n a l N o t e s by R. F. L e g g e t (Based on o b s e r v a t i o n s made d u r i n g a v i s i t t o A u s t r a l i a i n 1956. )

PART ONE

FIBROUS PLASTER WALL FINISH

A t y p e of w a l l f i n i s h t h a t combines t h e a d v a n t a g e s of dry-wall f i n i s h and of t h e u s u a l t y p e of p l a s t e r c o a t has l o n g been i n wide u s e i n A u s t r a l a s i a . It i s s p e c i a l l y s u i t a b l e f o r house c o n s t r u c t i o n b u t can be u s e d i n a n y t y p e of small b u i l d i n g . There a p p e a r s t o b e no r e a s o n why

i t

c o u l d n o t be u s e d i n Canada w i t h s a t i s f a c t o r y a n d economical r e s u l t s .

The w r i t e r

w a s

s o i m p r e s s e d by w h a t h e saw of t h e method i n u s e i n A u s t r a l i a t h a t h e has mentioned

it

t o many f r i e n d s i n t h e Canadian b u i l d i n g i n d u s t r y . T h e i r i n t e r e s t has s u g g e s t e d t h e d e s i r a b i l i t y of p u b l i s h i n g t h i s s h o r t d e s c r i p t i o n .

B a s i c a l l y , t h e system c o n s i s t s i n making u n d e r

f a c t o r y c o n d i t i o n s t h i n s h e e t s o f p l a s t e r r e i n f o r c e d i n a n i n g e n i o u s way s o t h a t t h e y a r e s t r o n g enough t o be h a n d l e d a s l o o s e s h e e t s

a s

soon as t h e p l a s t e r has s e t . The d r y i n g - o u t p r o c e s s can t h e r e f o r e be c a r r i e d o u t u n d e r c o n t r o l l e d c o n d i t i o n s . When t h e s h e e t s a r e r e a d y f o r u s e , t h e y can be c u t t o e x a c t s i z e

-

a s l a r g e a s t h e whole s i d e o f a room

-

t r a n s p o r t e d from f a c t o r y t o b u i l d i n g , s i t e by t r u c k , e a s i l y h a n d l e d a n d s e t i n f i n a l p o s i t i o n by s i m p l e a t t a c h m e n t s . To t h o s e u n f a m i l i a r w i t h " f i b r o u s p l a s t e r " (as t h e system i s known), t h i s summary a c c o u n t p r o b a b l y sounds t o o good t o be t r u e . The w r i t e r may t h e r e f o r e u s e f u l l y r e c o r d t h a t h e s a w s h e e t s measuring 24 by

9

f t b e i n g made i n a

small six-man p l a n t o u t s i d e Melbourne, V i c t o r i a ,

a t

t h e r a t e of e i g h t s h e e t s i n one working s h i f t from one machine. He

saw

s h e e t s b e i n g t r a n s p o r t e d economically a n d w i t h o u t a n y d i f f i - c u l t y f o r d i s t a n c e s u p t o 50 m i l e s from t h e m a n u f a c t u r i n g p l a n t . And he

saw

f i n i s h e d h o u s e s , t h e i n n e r w a l l s of which were b e t t e r f i n i s h e d t h a n many c o n v e n t i o n a l l y p l a s t e r e d w a l l s , g i v i n g no i n d i c a t i o n t h a t t h e p l a s t e r had been c a s t i n a p l a n t many m i l e s away. Key t o t h e system i s t h e u s e of a m a t t e d r e i n f o r c e - ment c o n s i s t i n g o f v e r y c a r e f u l l y p r e p a r e d f i b r e s of sisal. T h i s

i s

a v e g e t a b l e p r o d u c t o b t a i n a b l e i n I n d o n e s i a a n d E a s t A f r i c a . S u b s t i t u t e m a t e r i a l s have been t r i e d i n A u s t r a l i a , e s p e c i a l l y d u r i n g t h e w a r y e a r s when s i s a l w a s i n s h o r t s u p p l y . C o i r and omat o b t a i n e d from t h e h u s k s of cocoanut were f o u n d t o be t h e b e s t s u b s t i t u t e s b u t t h e y a r e "harsh" i n u s e .

Teased condemned rope was

_{a l s o}

_{u s e d b u t any g r e a s e remaining}

on

i t caused s t a i n i n g

o f

t h e r e s u l t i n g p l a s t e r s h e e t s . F l a x

t o w ,

t h e d i s c a r d e d f i b r e

f r o m

t h e p r o d u c t i o n

o f

f l a x , h a s a l s o been u s e d b u t

i s

t h e l e a s t s a t i s f a c t o r y of t h e a l t e r n a t i v e s .

E s s e n t i a l t o t h e manufacturing p r o c e s s i s a w e l l - founded, f l a t s t e e l c a s t i n g bed, t h e f a c e o f which i s

p e r f e c t l y smooth and t r u l y l e v e l . Dimensions may v a r y u p t o

35

f t l o n g , 9 f t wide, and a b o u t 2

f t

6 i n . h i g h . A s t e e l l i p , s l i g h t l y t h i n n e r t h a n t h e r e q u i r e d thichmess of t h e f i n i s h e d s h e e t s , s u r r o u n d t h e s t e e l p l a t e t h u s forming t h e mould i n which a s h e e t w i l l be c a s t . The n e c e s s a r y s u p p l y of s i s a l i s p r e p a r e d on a n a d j a c e n t t a b l e . I t i s u s u a l t o cu-t t h e f i b r e s t o a l e n g t h of a b o u t 18 i n . from t h e i r normal l e n g t h of from

3

t o 4 f t .

The sisal

m u s t

t h e n be " f l u f f e d up" s o a s t o g i v e it a

uniform t e x t u r e , w i t h t h e i n d i v i d u a l f i b r e s completely i n t e r - twined s o a s t o g i v e a c o n t i n u o u s m a t - l i k e s t r u c t u r e when compressed. The f i n a l p r e p a r a t i o n s a r e t h e c l e a n i n g and c a r e f u l g r e a s i n g of t h e s t e e l c a s t i n g bed, and t h e mixing

of

t h e n e c e s s a r y b a t c h of p l a s t e r w i t h w a t e r i n a b u c k e t t h a t can be t r a v e r s e d a l o n g t h e

f u l l

l e n g t h o f t h e mould,

d i s c h a r g i n g a s it moves.

I n t h e p r o c e s s w i t n e s s e d by t h e w r i t e r , t h e p l a s t e r

w a s poured o u t of i t s b u c k e t , q u i c k l y s p r e a d i n g o v e r t h e s t e e l p l a t e t o a uniform thick.ness. Withou-t any d e l a y , t h e s i s a l

f i b r e s were dropped on t o t h e p l a s t e r from a n i n g e n i o u s p l a t f o r m of w i r e n e t t i n g immediately above. The s i s a l f i b r e s were

q u i c k l y f o r c e d i n t o t h e wet p l a s t e r , u s i n g l i g h t wooden l a t h r o l l e r s , edges and c o r n e r s b e i n g f i n i s h e d by hand. Expert

s c r e e d i n g by f i n i s h e r s working a l o n g t h e two s i d e s

o f

t h e working t a b l e q u i c k l y f i n i s h e d o f f t h e s h e e t i n a m a t t e r of minutes. A f t e r t h e n e c e s s a r y p e r i o d f o r t h e p l a s t e r s e t , t h e s h e e t s a r e removed w h i l e h e l d by wooden c l i p s . A i r d r y i n g i s u s u a l l y c a r r i e d o u t by hanging t h e s h e e t s , by means of t h e c l i p s , from s u i t a b l e d r y i n g frames. When d r y , t h e s h e e t s can be c u t t o e x a c t s i z e f o r t h e i n t e n d e d w a l l . . Openings f o r d o o r s , f i r e p l a c e s and even

e l e c t r i c a l r e c e p t a c l e s can be c u t w i t h p r e c i s i o n i n t h e f a c t o r y , t h e s h e e t b e i n g r e a d y f o r i n s t a l l . a t i o n a s a f i n i s h e d m a l l

when it l e a v e s t h e p l a n t i n a s p e c i a l l y designed t r a n s p o r t t r u c k . Although awkward i n s i z e , t h e s h e e t s a r e r e l a t i v e l y l i g h t and s o a r e e a s y t o h a n d l e w i t h a minimum of manpower provided t h e n e c e s s a r y s p e c i a l taclcle i s a v a i l a b l e . The s h e e t s

m u s t

u s u a l l y be i n s t a l l e d i n a r e l a t i v e l y incomplete house frame b u t t h i s merely c a l l s f o r c o - o r d i n a t i n g d e l i v e r y

o r by t h e u s e of c l i p s a t t a c h e d t o t h e b a c k s of t h e s h e e t s , g r i p p i n g w i t h companion c l i p s on t h e s t u d s .

The p o t e n t i a l of t h e method w i l l be obvious. It i s

c a p a b l e o f many v a r i a t i o n s , even t h e simple c a s t i n g p r o c e s s p r e s e n t i n g c h a l l e n g e s t o t h e i n g e n u i t y of machinery d e s i g n e r s . The l i t t l e p l a n t v i s i t e d by t h e w r i t e r was a " g a d g e t e e r f s

dream", t h e owner h a v i n g d i s p l a y e d remarkable i n g e n u i t y i n t h e development o f h i s c a s t i n g and h a n d l i n g procedures.

F i b r o u s p l a s t e r seems t o o f f e r p o s s i b i l i t i e s f o r

i n t r o d u c i n g f u r t h e r economies (and convenience ) i n t o Canadian house b u i l d i n g f o r t h o s e who want t h e a d v a n t a g e s o f p l a s t e r w a l l f i n i s h .

PART TWO

TIIE IWACTITRE

AND

_{USE OF FIBROUS PIJASTJ~R}

R. Vt. Muncey

D.B.R., C.S.I,R.O., A u s t r a l i a

( A paper s p e c i a l l y p r e p a r e d a t t h e r e q u e s t of D.B.R.

,

N.R,C. )

F i b r o u s p l a s t e r s h e e t , made from f i b r e - r e i n f o r c e d gypsum p l a s t e r , h a s l a r g e l y superseded l a t h and p l a s t e r a s

an i n t e r n a l l i n i n g f o r t h e wa1l.s and c e i l i n g s of timber-framed d w e l l i n g s i n A u s t r a l i a and New Zealand. So f a r a s i s known t h e manufacture a n d u s e of f i b r o u s p l a s t e r i n s h e e t form i s c o n f i n e d t o t h e s e bvo c o u n t r i e s b u t i n c r e a s i n g i n t e r e s t i n it

h a s r e c e n t l y been shown o v e r s e a s . It i s cheap, s t r o n g and e a s i l y f i x e d , and can be more s a t i s f a c t o r i l y f l u s h - j o i n t e d than most o t h e r w a l l boards.

mis

paper d e s c r i b e s b r i e f l y

i t s manufacture and a p p l i c a t i o n . Raw M a t e r i a l s

The p l a s t e r used i s t h e hemihydrate of calcium s u l p h a t e

( c ~ s o ~ . & H ~ o )

commonly h o w n a s p l a s t e r of p a r i s , p r e p a r e d by p a r t l y d e h y d r a t i n g calcium s u l p h a t e d i h y d r a t e

(CaS04. 2H20 ) which o c c u r s a b u n d a n t l y a s t h e m i n e r a l gypsum. Although t h i s m i n e r a l h a s many p h y s i c a l forms r a n g i n g from

f i n e llsugarll c r y s t a l s t o s o l i d " r o c k u i t s chemical c o n s t i t u t i o n a p a r t from i m p u r i t i e s i s c o n s t a n t .

I n A u s t r a l i a t h e workable d e p o s i t s of gypsum, which o c c u r a l m o s t e n t i r e l y i n t h e s o u t h e r n p a r t s of t h e mainland, form beds o r r e e f s r a n g i n g i n t h i c k n e s s from one f o o t t o 20 f t w i t h an over-burden r a r e l y exceeding a few i n c h e s . A f t e r removdl of t h e t o p s o i l , t h e gypsum i s e x c a v a t e d ,

g i v e n a p r e l i m i n a r y wash and t r a n s p o r t e d t o t h e p l a s t e r m i l l .

Here it i s washed, c r u s h e d i f n e c e s s a r y , c a l c i n e d i n a

s t a t i o n a r y k e t t l e o r r o t a r y c a l c i n e r , ground and bagged. The p r o d u c t i s s u p p l i e d i n b a g s a t a b o u t

EA14

p e r t o n (of 25 b a g s ) ex m i l l . S i s a l f i b r e , o b t a i n e d from J a v a o r E a s t A f r i c a where t h e p l a n t Aqave s i s a l a n a i s c u l t i v a t e d , i s used a s r e i n f o r c e - ment. When h a r v e s t e d t h e l e a v e s of t h e p l a n t a r e m e c h a n i c a l l y d e c o r t i c a t e d t o s e p a r a t e t h e f i b r e from t h e f l e s h y p a r t s and most of t h e j u i c e . The f i b r e i s t h e n washed t h o r o u g h l y ,

d r i e d a n d s h i p p e d i n b a l e s t o A u s t r a l i a , where it i s s o l d a t a b o u t

E

~ 1 6 0

_{p e r t o n . B e f o r e u s e it r e q u i r e s t e a s i n g t o make} it; f l u f f y . During t h e l a s t w a r s i s a l w a s e x t r e m e l y s c a r c e a n d v a r i o u s s u b s t i t u t e f i b r e s h a d t o be u s e d . C o i r a n d omat o b t a i n e d from t h e h u s k o f t h e c o c o a n u t were g e n e r a l l y c o n s i d e r e d t h e most s a t i s f a c t o r y s u b s t i t u t e s a l t h o u g h t h e y a r e v e r y h a r s h . Teased condemned r o p e a l s o w a s u s e d b u t a n y g r e a s e r e m a i n i n g on i t d i s c o l o u r e d t h e p l a s t e r s h e e t s . A t h i r d b u t l e s s i m p o r t a n t s u b s t i t u t e was f l a x tow, t h e d i s c a r d e d f i b r e i n t h e p r o d u c t i o n o f f l a x . Manufacture

The t'-two-gauge" method o f m a n u f a c t u r e i s g e n e r a l l y c o n s i d e r e d t o produce t h e b e s t t y p e o f s h e e t . !he s h e e t s a r e c a s t on c o n c r e t e t a b l e s ( F ~ G . 1) t h e s u r f a c e s o f which have been t r o v l e l l e d t o a h i g h g l o s s . The t a b l e s a r e u s u a l l y

36

f t l o n g , from

3

f t t o 6 f t 8 i n . wide a n d a b o u t 2 f t 8 i n . h i g h . I n r e c e n t y e a r s b e n c h e s w i t h p l a s t i c s u r f a c e s have become p o p u l a r . S t e e l bench b a r s , 1/16 i n . t h i n n e r t h a n t h e s h e e t t h i c k n e s s r e q u i r e d , a r e l a i d a t t h e e d g e s of t h e t a b l e t o r e t a i n t h e p l a s t e r w h i l e it i s s e t t i n g . To p r e v e n t t h e s h e e t s t i c k i n g , t h e t a b l e i s g r e a s e d a f t e r e v e r y two o r t h r e e c a s t s . The t a b l e s shown a r e f o r c a s t i n g s h e e t s w i t h g r o o v e s t o r e p r e s e n t t i l e s ( t h e s e a r e f o r u s e i n k i t c h e n s a n d b a t h r o o m s ) . P l a i n t a b l e s a r e u s e d f o r c a s t i n g o r d i n a r y wall s h e e t s . F o r

t h i s most o i l companies make a s p e c i a l p r e p a r a t i o n o f s o l ; ~ b l e o i l , which s h o u l d be d i l u t e d w i t h from t e n t o t w e n t y , p a r t s of w a t e r . A m i x t u r e o f p u r ' j f i e d mu,tton f a t and k e r o s e n e i s a l s o u s e d . The f a c e gauge, c o n s i s t i n g of a m i x t u r e of a b o u t 1$ l b of w a t e r and 2$ l b o f p l a s t e r p e r s q u a r e y a r d , f o r m s a l a y e r s l i g h t l y l e s s t h a n 1/16 i n . t h i c k . For t h i s a t h i n l a y e r of p l a s t e r i s poured o r thrown on t h e t a b l e a n d s p r e a d e v e n l y w i t h a wide h a i r b r u s h ( F i z . 2 ) . !Jhis i s a l l o w e d t o s e t p a r t l y b e f o r e t h e r e m a i n i n g p l a s t e r i s poured, and i s

o f t e n l i g h t l y d u s t e d w i t h d r y p l a s t e r . The main g a u g e , made from a b o u t 8& l b of w a t e r and 1 2 4 l b of p l a s t e r , h a s t h e c o n s i s t e n c y o f t h i n cream. R e t a r d e r s s u c h a s c i t r i c a c i d , a n i m a l g l u e , b l o o d a l b u m e ~ o r p r o p r i e t a r y p r o d u c t s , a r e added t o t h e w a t e r t o modify t h e s e t t i n g t i m e t o 25 o r

3 0

_{m i n u t e s .} T h i s gauge i s poured o v e r t h e p a r t l y s e t f a c e c a u g e ( F i g . 3 ) and s p r e a d e v e n l y . The t e a s e d s i s a l f i b r e

-

a b o u t 11 ounces p e r s q u a r e y a r d

-

i s t h e n r a p i d l y shaken o v e r t h e whole

s u r f a c e ( F i g . 4 ) ; t h i s f i b r e l a y e r s h o u l d e x t e n d a b o u t 2 i n . beyond t h e edge of t h e t a b l e . The f i b r e n e a r t h e edge i s

p r e s s e d i n t o t h e p l a s t e r by hand a n d t h e r e s t i s t h e n f o r c e d i n t o t h e body of t h e p l a s t e r w i t h r o l l e r s of v a r i o u s t y p e s ( F i g .

5 ) .

The o v e r h a n g i n g p a r t i s t u r n e d back i n t o t h e s h e e t w i t h e i t h e r the _{h a n d s o r a s t e e l l a y i n g t r o w e l a n d} f i n a l l y , b e f o r e t h e s e t t i n g h a s advanced a p p r e c i a b l y , t h e p l a s t e r i s l e v e l l e d w i t h a s c r e e d i n g b a r ( F i g . 6 ) . Sometimes, t o i n c r e a s e t h e r a t e o f s e t t i n g , t h e s u r f a c e (which f o r m s t h e back of t h e s h e e t ) i s d u s t e d w i t h p l a s t e r which i s t h e n t r o w e l l e d i n . It i s customary t o c a s t a n o t h e r s h e e t on a second t a b l e w h i l e t h e f i r s t i s s e t t i n g . It g e n e r a l l y t a k e s 8 0 o r 90 m i n u t e s t o c a s t two s h e e t s and r e q u i r e s one t o f o u r o p e r a t i v e s , depending on t h e s i z e o f t h e t a b l e a n d t h e c h a r a c t e r i s t i c s of t h e m a t e r i a l s .

Some m a n u f a c t u r e r s s p r e a d t h e f i b r e between t h e two g a u g e s , b u t t h i s i s c o n s i d e r e d u n w i s e , b e c a u s e t h e r e i s

f r e q u e n t l y no bond between t h e g a u g e s i n some p a r t s of t h e s h e e t ; r e l i a n c e h a s t h e n t o be p l a c e d on t h e f i b r e f o r h o l d i n g them t o g e t h e r . T h i s n e a r l y a l w a y s l e a d s t o damage t o t h e

f a c e gauge a n d t h e c o n s e q u e n t n e e d f o r s u r f a c e p a t c h i n g . O t h e r s v a r y t h e method o f m a n u f a c t u r e . S i n g l e - g a u g e s h e e t s , cotmonly u s e d i n Ilew S o u t h Wales a n d Queensland, a r e produced by a t e c h n i q u e similar t o t h a t f o r t h e two-gauge, e x c e p t t h a t t h e whole o f t h e p l a s t e r m i x t u r e ( 1 0 l b w a t e r w i t h r e t a r d e r i f n e c e s s a r y a n d 1 5 l b p l a s t e r ) , i s poured a t

t h e one t i m e , T h i s method i s f a s t e r t h a n t h e two-gauge method b u t i s c o n s i d e r e d by some t o have d i s a d v a n t a g e s .

S h e e t s a r e u s u a l l y c u t t o t h e s i z e s r e q u i r e d f o r a p a r t i c u l a r h o u s e , A b a c k i n g s t r i p of wood i s p l a c e d u n d e r t h e s h e e t t o r a i s e i t n e a r where i t i s t o be c u t , a n d t h e r e q u i r e d p i e c e i s c u t w i t h a l i n o h i f e . More b a c k i n g s t r i p a r e i n s e r t e d a n d t h e s h e e t i s t i e n l i f t e d i n t o a v e r t i c a l p o s i t i o n a n d c a r r i e d t o t h e d r y i n g r a c k s ( P i g .

7 ) .

The p e r i o d n e e d e d f o r a i r d r y i n g v a r i e s from a c o u p l e of d a y s i n summer t o weelrs i n w i n t e r . F i r e p l a c e s , c e i l i n g c e n t r e - p i e c e s , and c o r n i c e s a r e moulded from f i b r o u s p l a s t e r i n s u i t a b l y s h a p e d moulds by

t e c h n i q u e s s i m i l a r t o t h o s e d e s c r i b e d f o r f i b r o u s s h e e t s . Large a r t i c l e s n e e d r e i n f o r c e m e n t by wood l a t h a n d h e s s i a n s c r i m a s w e l l a s by f i b r e , a n d t h i s must b e s p e c i a l l y d e s i g n e d t o talce t h e s t r e s s e s o c c u r r i n g d u r i n g h a n d l i n g a n d f i x i n g , F i x i n g F i b r o u s p l a s t e r w a l l s h e e t s a r e made t o e x t e n d t h e

whole of a w a l l (maximum 2 0 f t ) o r frorn w a l l t o d o o r , t o a h e i g h t of 6 f t 8 i n . , a second shee-t

be in^

u s e d between t h i s h e i g h t a n d t h e c e i l i n g . P o u r s h e e t s , a r r a n g e d s o t h a t t h e i r j o i n t s meet a t t h e c e n t r e ( P i g . 8 ) a r e u s e d f o r a c e i l i n g u p t o 24 f t by 1 3 f t . C e i l i n g , w a l l a n g l e a n d v e r t i c a l w a l l j o i n t s a r e g e n e r a l l y f l u s h - j o i n t e d : t h e h o r i z o n t a l j o i n t between t h e l o w e r a n d u p p e r w a l l s h e e t s i s u s u a l l y c o v e r e d w i t h a p i c t u r e r a i l a n d t h e vial1 c e i l i n g j o i n t w i t1-1 d e c o r a t i v e f i b r o u s p l a s t e r c o r n i c e s . Wall s h e e t s a r e n a i l e d d i r e c t l y t o t h e s t u d s , a n d c e i l i n g s h e e t s t o 2 i n . by 1 i n . b a t t e n s w i t h 1$ i n . by 1 0 - gauge g a l v a n i z e d i r o n c l o u t s s p a c e d a t 1 8 - i n . c e n t r e s ( F i g . 8 ) . 'The b a t t e n s a r e f i x e d a t 1 8 - i n . c e n t r e s , e x c e p t a t t h e c e n t r e of t h e c e i l i n g where a b a t t e n i s f i x e d a t each s i d e o f t h e c e i l i n g j o i n t w i t h a n i n t e r v e n i n g s p a c e o:f a b o u t

3

i n . ; t h i s p r o v i d e s enough s t i f f e n i n g f o r t h e e d g e s o f t h e s h e e t s .

The p r e f e r r e d method of making t h e f l u s h j o i n t i n c e i l i n g s i s t o p l a c e a l a g e r of p l a s t e r a n d s i s a l on t h e back o f t h e j o i n t ( i n t h e c e i l i n g s p a c e ) a n d when t h i s i s a l m o s t s e t a s t o p p i n g of p l a s t e r i s f o - r c e d i n t h e j o i n t fro12 below. When t h i s l a t t e r i s i n i t i a l l y s e t , i t i s r o u g h l y

s c r a p e d w i t h t h e edt:e o f t h e t r o w e l and a seconti c o a t of v e r y t h i n p l a s t e r s p r e a d o v e r t h e j o i n t and t r o w e l l e d srnooth. I n f l a t - r o o : ? d w e l l i n g s where t h e r e i s no c e i l i n g s p a c e t h e e d g e s of t h e s h e e t s a r e roughened ( s o t h a t t h e exposed f i b r e w i l l p r o v i d e a cood k e y ) , a m i x t u r e o f

p l a s t e r and s i s a l i s f o r c e d u p from below and t h e n t h e whole i s s t o p p e d and s c r e c d e d smooth. Wall j o i n t s a r e s t o p p e d by r o u g h e n i n g t h e e d g e s of -the shee-t a n d f i l l i n g t h e j o i n t w i t h n e a t p l a s t e r which i s t h e n s c r e e d e d smooth. N a i l h e a d s a r e c o v e r e d w-ith p l a s t e r . Because of t h e s r n s l l d i m e n s i o n a l change of f i b r o u s p l a s t e r i n v a r y i n g a-t:n,ospheric c o n c l i t i o n s no c r a c k i n g o c c u r s a t t h e j o i n t s a n d f l u s h j o i n t s made a s d e s c r i b e d c a n n o t be s e e n . D e c o r a t i o n F i b r o u s p l a s t e r can be d e c o r a t e d w i t h v a r i o u s f i n i s l i e s t h e most common p r o b a b l y b e i n g l a - t e x p a i n t s . A s w i t h a l l p a i n t e d s u r f a c e s o c c a s i o n a l c a s e s of p e e l i n g , s t a i n i n g a n d mould growth h a v e o c c u r r e d w i t h f i b r o u s p l a s t e r s u r f a c e s .

PART EIRXE

SOME ADDITIOTJA.T, TJOTES by

A s w i l l be e v i d e n t from Part One of t h i s R e p o r t , t h e w r i t e r was g r e a t l y i m p r e s s e d by what h e savi of t h e

m a n u f a c t u r e a n d u s e of f i b r o u s p l a s t e r when i n A u s t r a l i a ( t o a t t e n d t h e f i v e - y e a r l y m e e t i n g of t h e D i r e c t o r s of B u i l d i n g Research of t h e E n g l i s l l - s p e a k i n g w o r l d )

.

M r . _{I a n Langlands,} Chief of t h e A u s t r a l i a n D.B.R., a r r a n g e d f o r h i s v i s i t o r s when i n Melbourne t o examine t h e p l a n t o f M r . _{Alan Donald a t}

Greensborough. L a t e r , a n o p p o r t u n i t y w a s p r o v i d e d f o r s e e i n g f i b r o u s p l a s t e r i n p l a c e , a n d b e i n g t r a n s p o r t e d t o a n on

t h e job, d u r i n g a v i s i t t o a development o f t h e V i c t o r i a n Housing Commission. The r e p o r t by M r . RTuncey w a s p r e p a r e d

a t t h e w r i t e r ' s r e q u e s t , t o a m p l i f y d e t a i l s t h a t h e d i d n o t have t i m e t o p r o c u r e f o r h i m s e l f when i n A u s t r a l i a .

The d e f e c t s which M r . l'v!luncey m e n t i o n s a t t h e end of h i s p a p e r o c c u r o n l y i n f r e q u e n t l y a n d a r e n o t r e s t r i c t e d t o

f i b r o u s p l a s t e r . Some l o c a l i z e d t r o u b l e s of t h e k i n d s

n o t e d were c a r e f u l l y s t u d i e d by C.S. I . R . 0 . i n t h e immediate post-war y e a r s . I n 1 9 4 8 , f o r example, a number o f c a s e s of s t a i n i n g o c c u r r e d i n a new h o u s i n g e s t a t e a t E a s t Geelong. I n v e s t i g a t i o n s u g g e s t e d t h a t t h e p r o b a b l e c a u s e w a s t h e

a p p l i c a t i o n of p a i n t t o s h e e t s of' f i b r o u s p l a s t e r b e f o r e t h e y were d r y ( 1 ) . A few c a s e s of mould on p l a s t e r s h e e t s were

i n v e s t i g a t e d l a t e r i n t h e same y e a r ( 2 ) . The c o n c l u s i o n w a s r e a c h e d t h a t l a c k of a d e q u a t e v e n t i l a t i o n , c o u p l e d w i t h u n u s u a l l y high' n a t u r a l r e l a t i v e h u m i d i t i e s , w a s r e s p o n s i b l e

a s

had e a r l i e r been found t o be t h e c a s e i n Hew Zenland when

similar

t r o u b l e developed, The normal w i n t e r h e a t i n g of Canadian h o u s e s would n o t n o r m a l l y be conducive t o t h i s type

of t r o u b l e . The D i v i s i o n d o e s know of one c a s e of t h e development of mould i n t h e j o i n t i n g m a t e r i a l of d r y vrall

c o n s t r u c t i o n which w a s d e t e c t e d i n H a l i f a x some f i v e y e a r s a g o ,

a s

a r e s u l t of c o n t i n u i n g damp c o n d i t i o n s . O t h e r i n v e s t i g a t i o n s by A u s t r a l i a n b u i l d i n g r e s e a r c h w o r k e r s have been c o n c e r n e d w i t h d e f e c t s i n f i b r o u s p l a s t e r s h e e t s ( 3 ) a n d a few c a s e s of b u l g i n g o f f i b r o u s p l a s t e r s h e e t s a f t e r a p p l i c a t i o n ( 4 ) . The r e f e r e n c e s s o f a r n o t e d a r e a l l t o p r i v a t e ( a n d s o u n p u b l i s h e d ) r e p o r t s of t h e A u s t r a l i a n b u i l d i n g r e s e a r c h o r g a n i z a t i o n , of which UBR/luli~ i s p r i v i l e g e d t o have c o p i e s f o r p r i v a t e u s e o n l y . One p a p e r on t h e s e

(who h a d v i s i t e d DBR/NRC i n 0-btawa). T h i s r e p o r t s t h e s t u d y of d e f e c t s i n p a i n t f i l m s on f i b r o u s . p l a s t e r which o c c u r r e d when s h e e t s were s e a l e d w i t h a n o i l - b a s e p i n t c o n t a i n i n g l e a d and, o t h e r heavy m e t a l d r i e r s , t h e s h e e t s b e i n g f i n i s l i e d w i t h a w a t e r - b a s e p a i n t a s f i n a l d e c o r a t i o n .

!I!tze s t a i n s were c a u s e d by t h e m e t a l r a d i c a l o f -the d r i e r r e a c t i n g w i t h t h e s u l p l i i d e r a d i c a l produced by b a c t e r i a l d e c o m p o s i t i o n o f t h e w a t e r - b a s e p a i n t . I n view o f t l i e t y p e s of p a i n t n o ~ n a l l y u s e d i n Canada f o r i n t e r i o r f i n i s h , t r o u b l e of t h i s k i n d i s n o t t o be e x p e c t e d i n t h i s c o u n t r y . F u r t h e r d i s c u s s i o n r e g a r d i n g t h e d e c o r a t i o n a n d u s e of f i b r o u s p l a s t e r i s t o b e found i n r e f e r e n c e s 6 , 7 , 8 , 9 , a n d 1 0 . There i s a n A u s t r a l i a n S t a n d a r d S p e c i f i c a t i o n f o r F i b r o u s P l a s t e r S h e e t s (A44 and C1\20-1960) which s p e c i f i e s r e q u i r e m e n t s f o r t h i c k n e s s , a p p e a r a n c e , s u r f a c e h a r d n e s s , a n d r e s i s t a n c e t o a t r a n s v e r s e b e n d i n g t e s t .

I t w i l l be s e e n t h a t , l i k e a l l b u i l d i n g m a t e r i a l s , f i b r o u s p l a s t e r i s n o t e n t i r e l y f r e e from t r o u b l e s . Even i n A u s t r a l i a , however, t h e number o f c a s e s i s almos*

n e g l i g i b l e . B e y h a v e been l i s t e d h e r e , however., t o sllow t h a t t h e y a r e g e n e r a l l y o f

a

t y p e t h a t s h o u l d n o t n o r m a l l y be e n c o u n t e r e d i n Canadian b u i l d i n g p r a c t i c e , s h o u l d f i b r o u s p l a s t e r come i n t o u s e i n t h i s c o u n t r y .

Although A u s t r a l i a and Canada a r e such d i s s i m i l a r c o u n t r i e s i n s o many r e s p e c t s , t h e g r e a t c o n c e n t r a t i o n s of p o p u l a t i o n i n s u c h m e t r o p o l i t a n a r e a s a s t h o s e o f Sydney a n d ~ ! l e l b o u m e have c r e a t e d u r b a n b u i l d i n g p r a c t i c e s n o t t o o d i f f e r e n t from t h e Canadian p a t t e i - n . A c c o r d i n g l y , t h e w r i t e r can s e e no i n s u p e r a b l e d i f f i c u l t y i n t h e wide u s e of f i b r o u s p l a s t e r i n Canada, p a r t i c u l a r l y i n r e s i d e n t i a l c o n s t r u c t i o n . And t h e p o t e n t i a l f o r r e a l econoniy i n i n t e r i o r f i n i s h k g p r o c e d u r e i s w e l l shown by t h e a c t u a l m a n u f a c t u r i n g p r o c e s s w i t n e s s e d by t h e w r i t e x -

-

a small p l a n t , w i t h i t s e n t i r e machine i n s t a l l a t i o n c o s t i ~ g l i t % l e more t h a n

f

_A2,000

( e x c l u s i v e of t h e s i m p l e e n c l o s i n g b u i l d i n g ) , p r o d u c i n g b e a u t i f u l l y f i n i s h e d s h e e t s u p t o 24 f t by

9

_{f t a t t h e r a t e}

R e f e r e n c e s

1. Holmes, B.M., R.W. hluncey,

E.H.

_{Viaters a n d J.E. B r i g h t .} The _{D e c o r a t i o n of F i b r o u s P l a s t e r Walls a n d C e i l i n g s .}

P r o g r e s s R e p o r t No. 1, P r o j e c t C.P. 1, B u i l d i n g Pclaterials R e s e a r c h , C o u n c i l f o r S c i e n t i f i c a n d I n d u s t r i a l R e s e a r c h , Commonwealth of A u s t r a l i a , May 1948.

2. Holmes, B.N. a n d R.W. Muncey. Mould Growth on F i b r o u s P l a s t e r Walls a n d C e i l i n g s i n C e r t a i n Houses. R e p o r t CP1-2, B u i l d i n g R e s e a r c h , C o u n c i l f o r S c i e n t i f i c a n d I n d u s t r i a l R e s e a r c h , Comnonv~ealth o f A u s t r a l i a , November 1948.

3 -

_{W a t e r s , E.H. F a i l u r e o f F i b r o u s P l a s t e r C e i l i n g s a t} Balgovtlah, N.S.W. R e p o r t G5.1-2, D i v i s i o n o f B u i l d i n g R e s e a r c h , Comrnonv~ealth S c i e n t i f i c and I n d u s t r i a l R e s e a r c h O r g a n i z a t i o n , Cornonwealth of A u s t r a l i a , 1955.

4.

W a t e r s , E.H. Sagging o f F i b r o u s P l a s t e r S h e e t , R e p o r t G5 .l-1, D i v i s i o n of B u i l d i n g R e s e a r c h , Commonwealth S c i e n t i f i c a n d I n d u s t r i a l R e s e a r c h O r g a n i z a t i o n , Commonv~ealth of A u s t r a l i a , 1955. 5. Holmes, B.K. The D e c o r a t i o n o f F i b r o u s P l a s t e r w i t h Water P a i ~ t s . J o u r n a l of t h e O i l a n d C o l o u r Chemists! A s s o c i a t i o n ( A u s t r a l i a ) , No. 407, Vol. 37, p. 221-247, May 1954.

6. Hoffmann, E. S u l p h i d e S t a i n i n g o f Allcyd P a i n t s . J . 0 . C. C.A.

,

Vol. 42, p.452, 1959.

7 . Hoffmam, E. Adhesion of L a t e x P a i n t s t o P l a s t e r u n d e r Humid C o n d i t i o n s . J . O . C . C . A . Val. 43, p.196, 1960. 8. Hoffmann, E. and

M.

_{J . Ridge. E f f e c t of R e l e a s e Agents}

a n d A d d i t i v e s on t h e Adhesion of L a t e x a n d Alkyd P a i n t s t o P l a s t e r , J . O . C . C . A . , Vol. 42, p.844, 1959.

9 , Hoffmann, E. and

M.J.

Ridge. The E f f e c t o f R e l e a s e Agents u s e d i n t h e F i b r o u s P l a s t e r I n d u s t r y on t h e Appearance of P a i n t F i l m s . C.S.I.R.O. D i v i s i o n of B u i l d i n g R e s e a r c h , R e p o r t No. F1-2, 1959. 1 0 . R i d g e ,

M.J.

_{!Ihe I l l u m i n a t i o n a n d D e c o r a t i o n o f F l a t} S u r f a c e s . C. S. I . R . 0. D i v i s i o n of B u i l d i n g R e s e a r c h , R e p o r t No. L 8 , 1957.

SUPl?LEI\IENTARY

NOTE

m e r e i s i n A u s t r a l i a a t r a d e a s s o c i a t i o n f o r m a n u f a c t u r e r s of f i b r o u s p l a s t e r . R e a d e r s who w i s h t o g e t i n f o r m a t i o n m i g h t w r i t e t o : !The A s s o c i a t e d F i b r o u s M a n u f a c t u r e r s o f A u s t r a l i a , 24 Bond S t r e e t , Sydney, X.S.W.

F i g u r e 2

F i g u r e 3

Main gauge b e i n g poured o v e r p a r t l y s e t f a c e gauge a n d s p r e a d e v e n l y