Good practice in masonry wall construction

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S er TW 392 no. 22 c . 2

-mT:

GOOD W,ACTICE

IN

FASOmY WALL

C

OPJSTRUCTION

by

B.3, Dickens

n u l l d i n g P r a c tic^ T-rousing

S e c t i o n

There i s a t endencg to r e g m d t h e exterior w a l l s of a house c h i e f l y a s suguorts f o r t h e f l o o r znC roof of t h e

s t r u c t ~ r r e 8nd to un6ercstirnate o r even neglect

o t h e r

f a c t o r s

which contribute t o the main Z u n c t i o n o f the w u E l

-

t h e en- c l o s ~ a r e of m a c e .

I n practice t h e s e other : r a c t o r s often p l a y

a

v i t a l

r o l e in t h e over-all p ~ r f o r r ~ . , n c e o f t 3 e v a l l a n d it r-rould. b e

7 -

-.rortI-._?.rhila to c o n s l & e r ~-:'2rr.

t

t !zcs5 ' a c t o r s

are,

?.owever,

they

a r p ?:ore e 3 s i l y assessd if' 7;re t h i n k

o f

an exterior

l:rnLI n o t as s t r u c t u r c l s u c n o r t a l o n e b u t r a t h e r 2 s a l a s ~ e n:en%rane s e p a r n t i n g i n d o o r f r o m outfioor con?.itions. A l i s t o f t h e major r e q u i r e m e n t s o f such a w a l l s h o u l d include the f o l l o r l r i n g : 1. S t r e n g t 3 e n d d u r a b i l i t y ; 2 , R e s i s t a n c e t o h e a t f l o w a n d the r e l a t e e p r o b l e m

o r

c o n d e n s a t i o n ;

3.

i l e s i s t a n c e t o fire;

&.

S a t i s f a c t o r y a p e a s a n c e ;

5.

K e s s o n a b l e c o s t ,

At

l e ~ s t 5Llrsn of t h e s e f a c t o ~ s

-

s t r e n g t h 3 h e 2 t f l o w , 2 n d xcnenrance, a r c v w f r closel:: r e l a t e d

t o

t h e ability

of

2

J ! 7

r.ral3

to

=!;a;, - I , .

,

~;?::t is

to

e x c l u d e r n T r < , ~ r y d E t i s e a s y t o r e l . r t e t 1 ? c : 7 e ~ i - i n i : - ! : ; tt;:m " " a c t o r s

-

f i r e r e s i s t a n c e a n d c o s t

-

to

% h i s cronertq r l s o .

I&t.ny c a s e s havo occurred in wl:iclz t h o 'strength

and

d u r a b i l i t y sf a w a l l

have

s t ? . f f e r ~ d o w i n g to '.:r:~ber genetration and frost a c t i o n , rzrhero insula-t;ion has been s ~ o 5 l ~ A 57 getting v e t , mil iwhepe a7neerance

h2s

been arfected by e f f l o r s s c e n c e .

'Satextightness of w a l l s i s imgnrtant t o t h e l r ovcr-all ? e r r o r -

mEncc znC l e a ! q r rnasonpy

is

still

c r e v a l s n t , rs evi?.cncec!

Sy

tlie t e c h n i c a l inquiries On t5e s u b j e c t referrod t o t h i s

D i v i s i o n , The r " o l l o i . ~ i n ~ , t;hereforle, d e z l s w i t h I ' a c t o ~ s t h 9 t x e i m p o r t z n t in d e t e r m i n i n ~ t h e abTlitg o f masonry w a l l s t o exclude r a S n .

[ ' 3 ~ i c k ~ . i o r k is t 5 e -cost com.mn T o r n

o f

u n l t

masonry

Sue

the

f o l l o r l r i n ~ rclmnxlks ?.lso 2rrnlg z e n e r a l l y to other

rosms

oC masonry construction i n q l ~ t d i n g b l o c k and s t o n e . )

A f i s s t requirement for a r a s t e r t i y h t w z l l i s tslat t h e buf l d i n - should be eroncrlg rlsaLmned. IYIrach can be d o n e at t h e

" s i p s t a ~ e t o e s s i a t

i n

o b t a i n i n g goo?. - r z r f o r m a n c e

in

t ' z e T u t u r e , D e t a i l s stlc5 c s : s6equato f l n ::kin? anZ c ~ . u l l r i n ~ ; ~ ) P O ? F F 9 1 - o t e c t i o n of n a r a p e t v a l l s ; a r o v i s l ~ n

o f

p o o r a v c r -

'7qaz

:$'-ere ~ o s s i b l e ; Lsola-bion o f t h e h u i l 6 i n . r P r o a

y ~ o u n 6 .

~ o F s t , u r e pickup; zmf s u l t a h l e v a x w

g~otsction. -431

t : - c s e

h e l u t o j7roGuce a t . r r l l of r o o d qu;zlity RRC' shou11' T~C:+IVB due c o n s i d ? . t r f l t i n n ilerorc c a n s - t r u c t i o n i n bc-un. These i t e n s

?rc

yell

f l t t z i l e C : Ln t ' - c t e c h n i c a l l i t c r a t u - ; . e sn6- so, v i t h o u t

mtniniziny

t!:eLr trL.lnartr?nce t"lq - r i l l

n o t

br, g c a l t : : t * . t 1 i h . ~ : s o .

I l a t ' - e r consic?c ;.E t.j_on :: :I-1- .c - i v e n to t 'zc

~ ~ 2 1 1

i t s e l f . :,iesonr>y construction i s 4x2.co a? o.? brLcar r r d ::rtnr,

'+?re

i s arlgle e v t d s n c e f r o m both f Lead ~ n ? l ~ l o o r a t ; o r y s t u d i e s *hat w h e n leakzyn l;nlcqs ?l;.lce in 5 r i c l r w o r k it : : o e s s o r n n i n l g n t t h e j u n c t i o n o f t h a b r i c k m 2 . ;;lortar. The way in l.blic1.1 the 5rTck and mo;.t :lr a r e com?->ineil, t!>crefsx*e, 'is cx:;reme ly im?ort-

ant

t o t h e 3ur::bilitg ol" t h e whole w a l l .

At

t : 7 ~

risk of

o v e r sil;:ylifyFn 5 t h e -?roblorn :..re :

.icht

s t a t e that our

m i n

c o n c e r n I s to s e l e c t bricks and m o r k s r !-r'nhch a r e clureble a n d ~ b i c h , ?'-fen combine? u n d e r a w e r a j e jo3 c n ~ d i t ions, rill b e well b o n d e d t o t ~ e t h e r .

It

i s n o t dif."iculft

to name

t h e p r o n e ~ t i e s i m p o r t m t

in

'oric1.r: i t s r a o i s t u r e a?

m ~ t i o n

is c;ne and n _{second is}

strength.

It

i~ t 5 f t s g t w o properties t h z t a r c u s e d in t h e s t a n d a r d s p e c i f i c a t i o n for clay '>rLck as a me.?L::ul*e o f iks

r l u r ? ' ? l l i t y o r i t s r ~ : ; i s t z n c e t e fi5ast a c t i o n .

There is one p r o ~ s r t J-\-, .l-lowev~r, t h s t r z q v . i i ' e s

z r l c c l a l . , . o n t i o n since

it

is r , o t i n c l u d e d

In

t h e stanl;.~rd.

s p c c i f ' i c a t i o n

and

: e t ?as a marked efi'ect o n t ! l c

son fin^

ol"

h r i c l : t o r:lortzr3. "i'hi is s u c t i c n " an3 :na:- be tcfined a s t h e r n t a at which a briick t e36.s t o -' PEI-J or svck *:c7ter or1.t o r t3-e f - e s h r n o r t z r

i n

u'7ich it _ts Laid. rouplz

measuTe o f s u c t i o n is y i v m by t h e number o f - - P P . S o f

wzter

absarSec? 5 9 a bricl.; v h c n I g i r ! in water

118

i n c h ? . c e ~ , ST- g n f r - i n u t e , T t i s F T O ~ ? F T ~ : - i s i w m r t ~ n t

i~

' ; u i l d i n g * r : : l l s

since,

if

a h r l c k i*!ith .j ' ~ i y ! ~ s u c t i o n r & e i s t l s e d ,

it

t 7 ? . L 1 1

t e n d t o r?rzT+? t o o muc'? -.:2tsr Z r o r n t h e . ~ i o r t c r rlnd

~ x - :

7 r o v e n t

t h e n o r t a r f r o m s e t t i n g up, T h i s results in -9or bonr: and

7 ~ 3 3 ~ m o ~ ) t ~ ; n . ~ ~

If,

on l ; ' ~ r f o-Lbzr 5 ~ ~ 6 , e Cerise briclr i s used ( o n e h a v i n g a v c r g

low

s r l c t i o n p r a t e ) t h e n it :t:-Ia;:r n o t ~ X J X - J

311-ri'icient ua t e r em? S J . n e t ~ z t e r i a l s into t

he

' n r f ck !?o17es

~ n d

a , l a i n

re?uce

the h ~ n f l *

Yx7crience i n ? i c a t e s t t - a t the b e s t results a1.e

o h t a i n e ? w i t h c l a y S r i c k s h a v i n ~ a suction r p - t e of b e t w ~ ~ n

5

m?. 25 g ~ a n l s . Since manv ?L:~ic?r"ian b r i c k s are a b o v e t h i s

-an,ce

it i s nscessopy to control the r:ropert;;ii

of

s : ~ . c t i o n

on t'- E j o b , ancT t:-!is is c:.nne 37 t ~ e t t i n g t h e b r l r k ~ : n c e s u c t i o n d c c r e a s e s as m o i s t u r o c=s!l++,ei?t ei' the ' ~ r i c l i 5:ocs 1 7 p .

Accurately

c o n t r o l l e d

wetting

on t h e j o b is n o t always p r a c t l c a ' s l e and a compromise is usnally made

in

which

the

bricks are hosed

Gown

a f t e r

b e i n g s t a c k e d

in

such a way as

to e n s u r e

uniform

w e t t l n g , Wetting s h o u l d b e done several

h o u r s

p r i o r t o u s i n g t h e bricks s o t h a t t h e i r s u r f a c e

i s

riry

when p l a c e d

i n

t h e

wxll,

o t h e r w i s e t h e l r s u c t i o n

may

be

reduced t o o

much

and t h e Srlcks may t h e n f l o a t o r s l i d e on

the mortar,

The

c o n t r o l o f

suction

is f u r t h e r

compllcaked

d m i n p c o l d w e a t h e r because I t i s t h e n undesirable t o e r e c t a w a l l u s i n g materials t h a t a r e relativalg damp and thus t h e wettlng o f u n i t s may have

t o

b e L T r n i t e d d u r i n g p e r i o d s of

low

temperature.

GOFlCRETE A I D SAND-LINE B R I C K

T h e r e is one problem in connection w i t h t h e use o f

c o n c r e t e o r s a n d - l i m e b r i c k s which should b e mentioned, This is t h e dImensiona1 s t a b i l i t y or t h e change o f l e n g t h

o f

t h e

brick with

c h a n g e s

in its

moristure c o n t e n t . The problem

with

these b r i c k is t h a t t h e y

exhibit

a

relatively

much g r e a t e r d l -

mensional change 7 ~ l ~ e n v e t t e d a p d r i e d than do c l a y

units.

If

c o n c r e t e or sand-lime b ~ i c k s

are

b u i l t into t h e w a l l in a wet

and g r e e n c o n d i t i o n t h e y are a p t

to

c a u s e severe shrinkage cracklng i n the wall.

S h r i n k a ~ e o c c u r s

most

often d u r i n g t % e i n i t i a l d r y -

Zng p r o c e s s f l t e r t h e b ~ i c l r s

are

made. The shrinkage : % r i l l

vary with such f a c t o r s a s t h e c r o p o r t i o n s

o f

t h e m a t e r L a l s

used

I n

making t h e units,

the

nature of

t h e c u r i n g treatment;, and t h e c e n t r a l exercised d u r i n g t h e manufacture, High-

pressure s t e m c u r i n g w i l l g r e a t l y reduce t h e amount

o r

such

shrinkage

b u t this may add s u b s t a n t i a l l y 5 0

the

c o s t of the

unit

and i s therefore

n o t usually done.

To try to educe t h i s p r o b l e m 5n England,

the

B ~ i t i s h S t a n d a r d . 3 S p e c i f i c a t i o n

for Concrete

Units has

imposed a l i r n i t o n t h e d r y i n g s h r i n k a g e of units meeting this

specification. U n f o r t u n a t e l y no similar

limits

have been s e t

in

s p e c f f i c a t i o n s f o r c o n c r e t e producks in t h i s country.

In

t h e absence o f c o n t r o l

o f

drying s h r i n k a ~ e at

the

manufacturerrs level

it

is necessary for b u i l d e r s t o t a k e

particular p r e c a u t i o n s when b u i l d i n g these units i n t o t h e

w a l l .

It;

i s i m p o r t a n t t h a t b o t h c o n c r e t e and sand-lime units be

reasonably

d r y when u s e d and, unlsss

it

i s known w i t h

certainty that these u n i t s have been d e l i v e r e d i n a p r o p e r l y

c u r e d a n d d r i e d c o n d i t i o n , t h e n they s h o u l d be stacked for as

l o n g as possible ( p r e f e r a b l y s e v e r a l weeks or m o n t h s ) u n d e r c o n d i t i o n s

of

goad a i r c t r c u l a t i o n and protected from r a i n , They should

n o t

b e i n Cirect c o n t a c t w i t h the ground or t h e y will absorb moisture f r o m t h e s o i l by c a p i l l a r i t y .

I n summary,

the g r e a t e s t s h r i n k a z e r n q b e e x p e c t e d

from

units laid

in

a F e e n a n d m o i s t c o n d i t i o n , A d d i t i o n a l p r e c a u t T o n s c a n b e t a k e n to c o n t r o l t h e e f f e c t s o f shrinkage

in

a

w a l l by

c a r e f u l s ~ l e c t i o n of n o r t a r

to

b e used

in

t h e s e b r i c k s .

Mortar consf s t s of a c e r n e n t i n ~ a g e n t , sand, and water, The

c e m e n t i n g ngent rnaF b e p o r t l a n d cernont, l i m e , masonry cement or a

mixture

af t h e s e ,

The

proportions

in

which t h e m o r t a r i n p r e d i e n t s are comb5ned 2eternTne t h e properties o f t h e ort tar which,

in

4-

_burn,

have a significant effect

on

t h e performance of a w a l l .

Th@

p e r f e c t m o r t a r f o r any job o f b r i c k - l a y i n , 5 would

probabk: have the T o 1 1 3 ~ ~ ~ i n g properties : 1, It shoulc w o r k e n s 4 l y ;

2 . S t i r f e n qufckly e~ou@;

3a

Rave ceeqsxnta s t r e n g t h ;

4.

Bond r i e l 1

to

t h e b r i c k s ;

5.

Be

d w a b l a ,

Vnfortunately a l l o f these propertics w i l l n o t be found to

the highest

degree

Ln

one and t h e same m o r t a r

nix.

Another camplica-

tion is the

d i f f e r e n c e s

which

e x i s t

in

t h e properties of t h e b r i c k s themselves, F o r cash job, t h e r e f o r e , it i s

necessary t o

d e c i d e which of t h e s e p r o p e r t i e s i s t h e m o s t i m o o r t a n t znd t!aen to d esf gn a s u t t -

a 3 l e m Z x ,

To do t h i s we must understand t h e e f f e c t t h a t each

i n g r e -

dFent hes upon t h e p r o p e r t i e s of the m o r t a r . !.5ortars which consist essentially o f p o r t l a n d

ceasnt

as t h e cementing a g e n t e r e charac-

t e r i z e d by t h e f o l l o w i n g :

1.

Harsh working properties; 2 . Law w a t e r ratentiveness;

3.

S h r i n k a p ;

4.

HPgh s t r e n g t h ;

F- RapEd sbiff en in^;

6

F r o s t r e s i s t a n c e ,

On t h e o t h e r bane, rnortara in which limo i s the principal

cementing sgent e x h i F t t t h e r o l l o w i n g c h a r ~ c t ~ r i s t i c s :

I.

Plasticity

znd

~ ~ o r k a ' u f l i t y ; 2. High w a t e r retentiveness;

3.

Reduced shrinkage;

4.

Low strength;

5 .

Slow s t l f f a n f n g ;

6 .

Reduced resistance t o S r o s t .

To

o b t a i n some o f t h e d s s f r a b l e c h a r a c t o r i s t i c s of b o h h

types, mortars a r e almost a l ~ ~ ~ a y s

made

w i t h a m i x t w e of both lime

and portland cement. As a r e s u l t

of

b o t h l a b o r a t o r y and f i e l d s t u -

d i e s t h e following nixes

are

s u g z e s t e d as a g e n e r a l gu5de to m o r t a r s

High s u c t i o n bIe

t

1:3:6 *1:2:9

Medium

s u c t i o n

D o

n o t

w e t

~ ; ~ : h ? -

:--

1:1:6

+1:2:9

LOW s u c t i o n 5.0 n o t w e t

_l:-k:k2-

f

.rT ,. 1": 1: 6

Do ~ ? a t

wet

Do

not wet

These m r t z r s a r c only y e n n r a L recorr,ren-n t l s n s and :'_? ~ 2 7

b

2 nscesssr:i .to r,~:ju.r,t r : . o p o r t i o n s s l i g h t l y _to

z u i t t h e ?articular c o ~ ~ i t i o r r s

of

:I fob.

In

~ e l i i n g t h o s e

c . ; ! ? u ~ ' ; r e n t s I;!?r~..r xJc- r n c r IFF.^^ r n i n 5 s I h a t s'laulZ! bc k e p t in

A

:11 .it

3cn6..

-

.% ~ o o e S~onr: between t h e

?ort2r

anri thLe hr5c:c is

-

- . e s e n t i r ; l . ; t h l s n , - . o ~ c Y t j ~ i s ~ ~ - 1 z t e < Z irccJ61y

to

t'?e s u c t i o n

1

-

? r o ~ ~ . r t y O T thr! brick, :;ifice our c o n c r r n w i t h ~ o s t :~r;.ck? i. Y ~ a t i;'~e:- h s v e t o o T ? I X C ~

s u . c t i o n

s n d t e n ? 'ia i q tGlc nor-t;ar 3 u t q u i c ' r l g

a

r n n r t z r > : i t k h i z h w t n r retqntiv2ncss sboul6 56

~ t - ~ t T ~ T ~ , c + o r g . T k i z ~ - ~ . - e s ' ; s 2 h i g : ~ lint c o n t c - t , Qcly in a - pew c 2 s ~ s :rhere the - j r i c l ; s u s e d '21-e ::nosdn t r he . ~ . i - y dense,

m e

"i"l~ref'ore h e v e vcsg Z O ~ C s l x c t i o n , i s it necessary t o use

z n o r t n - o f l o w : , r ~ ~ i s r r c t e ~ t i v c n e s s

or

Low lTme c o n t e n t . . : o r l c n b i l i t g .

-

9 h92h l i m e c o n t e n t :yives, in e d l r ' i t i o n ,

-~lasticitg tc t h e -IT~x :!hich ae.211~ i ~ c r e a ~ e d r n ! o r k a S i l l t ~ r

-

an

:'..,:~ortr:nt i'ectos? in a s

istins

a ricklager to a c h i e v e t h e ~ o o d ~ r c l r k r n a ~ s!>i? s s s e n t i z l i n

abtainln?

a scl tisf a c t o r 7 j o t . S1lrinkar.c Crael:inr.

-

There i s a s p e c i a l nrablem w i t 5 u c i t s -

t z v i n ; a !11-;1 C r y i n n . shr.inlc;jye s u c h zs c o ~ c r - e t ? 2nd

~2nd-Itme

b r i c l c s .

20

f u r t h e r rer?uce t h e

serious

c r n c l z i n ~ t h ~ t r n q r ~ s u l t f r o m u n F t s 0 2 t r \ . i z ?;;-TC l t i n : ~ s u c l 30 z r e c 5 i ' y a v e r y :-.-eelr n : o r t a r s u c h as 1:2:9 ( z c ~ e n t : l l m e : s a n d ) in or?-er

to

c ~ c . C i ~ o Z P ~ : c : ~ ~ c J c Z ~ T th.q.t oljz ;.:.l-e ~-.?-sce t o ';hg r 1 1 0 ~ t 2 . r

j o z n t s

;-?ere it is n o r e s:1sily r e ~ ? i r e d . J i t h a si;ronn R o r t P r t \ e r e T s a ~'--n,zc-r oi' <;:;'~r u v L t ',>~i;?-- +,ye f - i r n ? 4 - r ~ l w t e r i ~ l r n d

of' c r ~ . c l c i n r r o c c u ~ r i ~ r : _- t';roup*h t h e

u n i t

rat9er

t % a n

t h r g u - h

-;-I a l o r t a r ,

~t

is b.o?c.' cP c r ; ~ ~ r s z t l - r t

b:

u s i n ' ? -:7a?:~ly c u r c S ar,d r!ry u n i t s

in

the

f i r s t

p l a c e that, s h r i n k a g e crack-

in? 7 - r i l l ?3e k e p t t o a s l F n 5 r . r ~ ~ ~ : znci w i l l n o t be s e r f ous.

'..tronqth.

-

.:Lno.t;her f a c t o r o.bout : a ? ' i i c h t t ; z e ~ e

is

s r r e a t r l e a l

-

. - 1 ~ s c r ? p r , ~ 7 t L o n

.

2r: t.' ::>::/IFLPCC: si;j:(:?ny-;;:~ _{~ f '}

t1-,0 : : : o r t a r . T h i s : a c t o r h a s

S x n

I c f t un81;ri,l tl- e l a s t bsc!.~use

it

5 s _{o f t e n ~+rlrr~cn.ylg}

c7

S E ,!le s t r c n y t r z 3-f b r i c k ! o r > S u i l t of' E V C X ~b r i c k s ~ ~

L 1

of r i n t e ~ m e c ? i a t c s t r c n y , ? ~ is

n n t

30 I;~uc!? in?lu~nce.? 11:- ~ ~ 7 . e

- - ' - ~ ~ . q r . + j 0'7 t:-.?

- , a !:ort:.r ?-v -.rl-:ich

it i s lard

as is o f t e n a u e ~ n s e d . ; - ( : . s t s s!"<.o- >!la+, !:,picl,-,:oi.l: ,;cfi:;j.s";n:: 01 k p i c l ; s i-!;,t?-i 1. ca.:-~j;:essivc

s t r e n ~ t h 3300 lb. Ter s q u a r e

inch,

l n f d in a s t r o n p

m

i

:

:

1:3

( c c m ~ n t : sand r n o r t : : ~ ) t h e r f i o ~ t a r h a v l n z

a

s t r e n g t h of

ovcr 2 0 0 0 lb,

per

square i n c h g c n e r e l l g hag o n l y

4

p a r

cent

mere

str~ncth

than

7,ihcn the snme b r i c k

Is

~ l a c e r ?

in a

1:1:6

mi; (cement : l i m e : sand : n o r t a r ) , r n d o n l y

15-

t o 20 p e r cent

n o r e

strongth t h g n :.!hen l a i d

in

a m i x

1:2:$

(cement:lime:sand

m o r t a r ) , th5s lnttcr :r,ortar h a v i n p a s t r c n g t h of

only

5 0 0

Ib.

z e r square Lnch.

Fox* any ~ a ~ t i c u l a r s t r c n y t h of brick there is a

c o r r e s o o n r ! i ~ z ~ ~ o r t e r s t r e n g t h whZch g i v e s a

maximm~

s t r c n g t h

t o thr: b.rick-mrk. 'J?>cTc i s no g c i n

in

strength if'

more

cevent i s u s e d t h a n Ys needcd

t a

~ 9 v e t h i s n a x i m u w . The l n o r t e r s y i v l n p t h i s maxitmsl z r e r6uchkg as f o l l o w s :

a ) F o r Low-strength b r i c k (1500 p . s . i . )

-

1 : F : q ; c e m e n t : l i m e : s m d .

b ) F o r

medl-~m-strength

b r i c k ( 3 0 0 0

to

4000 p . s . i . ) -

1:1:6;

cenent: lime: sand

c ) F o r hich-strength b r i c k ( L O O 0 p.s.i. or over)

-

1:3;

c e r n e ~ t : s m d

with

a srr,?ll a f ? . i t i c n of l i m e ,

In

house censtructlon w h e r e the loac?.s c r e comp:=17a-

J- , ~ v e l ~

.

1lrh-b o v e n

the

>aea!:est m o r t a r n o r n a l l y c o n s i d e r e d w 113.

provide v & l l s

OP

suf

r i c l e n t

s t r e n g t h .

A second :nisconccption ;;!:at h a s c r e z t e d p r o b l c ~ s w i t h r e g a r d t o wakes penetration oP rnp-sonry w a l l s i s t h a t - o r t a r

s t r e n g t h i s o f t e n taken

a s

a criterion of bonc'. which

it is not.

I n ?act tt;e n s c of a ye!Latf vel:r s t r a n ? ; r;ni Cerise : o ~ t ! - r si:.ch. 2s one ~ i c h in ceiilent bas o r t e n l c f ; t o ,s?r:i.nka~e cracl-s 'let:-~ccn

L ' b+;~: fi:ortar and the h r 5 c k throu-11 > C ~ i c b r a T n c cmeasily ~ e n o t r z t e ,

Th.0 onl;: j a s t % f f c ~ t i o n for the use sf a n o r t a r w i t h n h i c h s r cement

c o n t e n t

i s t o csntri5uto t o i t s f r o s t

2.1-si s t a n c c , nee6 l o r i n c r e c s o c frost r c s i s t a v c e ;-rill

vnrz

;..?it+

the exposure, t h e temperature rJurfn2 laying o f t h e

3 r i c k

encl the metl?od o r ~ r a t e c t l o n o r t h o b r i c l ~ w o r 3 , but

one

sho~rb?. ; g a r 8 a , - a l n s t ; rislcTnp t o o m?llrch on n o o r bond z n ? ss'7ri?1r?-e c r n c l c s i r r a k t e ~ p t i n ? to o b t a i n b e t t e r fTost resistance by e??- in? cement,

L c t

us

now asstme that t h e b u i l d i n g has Seen ;:rap-

srl7 d e s i g e r ' ; the b r k l c s rrieet t h e r e q u i r e m c n - 5 ~

o f

t h e

~ . ? p r c ~ r i a t e s l ~ e c i f i c a t i o n ; t h e i r suction is pl-operlg a d j u s t e d

on t l - e ;job; t : ? e r i g h t mortar has been s e l e c t ~ d ; ailequate cocinc, f l a s b i n g and c n u l l c i n g are p r o v i d e d ; ~ a u n d w a t e r *

73 _;r::~133 !~r?[? rioi ,~kr.:.re c o n d e n s a t i o n

2 r e

b o t 5 cnr-l;rollcc':. E v e n

iC

211 t ! z z s e r = e c ; u i r s ~ - ~ e n t s ar*e . S i l l c d , t h e m o s t cor::on c u l p r i t

f o r Z c n k y mgsonq,r t ~ n l l s I s s t i l l at l a r g e

-

:-:o~knznshi?,

in

a

masonry

w a l l

will shed

water

n r o p e r l y .

There o;.e s e v o r a l 3ch.ooLs

of

thouwht o n v h a t constitut-s ,-ooil : : o r h i i n s h i n

i n masonry construati

on, S u t

one n o i n t on 1 ~ f ~ 5 c h t%ey

all^

acrer: _. . i s t i l a t

all

n o r t a r

j o i n t s

in masonrTj.

r u s t

be f i l l e 6 ,

The imyortnnce of this

f a c t

h a s 3-.en S r o u z h t

o u t

:77 t e s t s c o r n ~ l o t e C : at the U. 3 . l i l t i o n 0 1 3 w 0 a u of S t a n G a r C ~

on

l:c0 m r s o n r y u:all s e c t i o n s ;

39

kinds of u n i t s , and 10 types

of

m o r t a r . These t e s t s showed t h a t

it

w r s o n l y when t 5 c bed

joints w e p c s ? r e a d t o a u ~ i f o m thickness e n 6 t h e head j o i n t s -.-!n17e c o r ~ ? l e t e l y f i l l e d b - h e a v i l y b u t t c r k n g t h e heads of

s t r e t c h e r s s n d t h c ~ ~ B G s _{of h e a d e r s , t ! i o t o n l y} t h e n were t h e

t s s t w a l l s h i ~ h l y r e s d s t a n t to w a t e r ? c n e t r a t i o n .

7 s d J o i n t s .

-

To e n s u r e

full

b a d joints t h e m o r t a r s h o u l d be

S T P E ; L - . ~ t h i c k 2 n d n o t I'urpowed.

If

a furrot$ i s used it s h o u l d

be k s ~ t s h a l l o w and n o t deep. T 3 e r e w i l l t h e n bc enouzh e;-- c e s s o? n o r t e r

in

t b n b e 2 joints t o completal;

fill

t h e

m r o w

when

t h e

briclcs are bcdded t o line.

If

t h e

mortar for

the bed j o i n t is s p r e a d t o o t h i n l y

or if the f w r o w

in

t

h e ? ? o r t a r i s made t o o decp,

t

h e r e w i l l

be i n s ~ f l f i c i c n t m o r t a r in ti-e b e d joint to c o m p l e t e l y fill t h e f w ~ * a w when t h e next course of b r i c k I s l o i d . T h i s r \ r i l l l e a v e

a c h n n n o l 2 l o n . r ir'?ich ::a:-.or n_ntcr.ing

rrn:r.

zone open j o i n t -ay

t r a v e l u n t i l

it

f i n 6 . s a passare t o t h e i n s i d e of t h o wnll.

Yhen a b s o r b e n t b r i c k a r e used, e s p c e L a l l y

in

h o t

w e a t h e r , m o r ~ t a r

for

t h e b e d

j o i n t

shoulc? be snroat! o u t o v e r only a T E I + Srlclts at a t i m e , :il!le b r i c k should be p l a c e d

on

t o g

of

this T O T ~ ~ T i x v e c 5 a t e l p b e f o r e

it

h a s a c h ~ n c e t o stiffen,

If'

t h i s is

nct ::or2

aricl Y e hric!; f s n z t 1216 i - ~ % i l e t l ? o _{m o r t t ; e r} 5 s s k i l l soft

~2

ylsstic, tken a r;.ooC b o n d c ~ n n o t b e o b t a i n e d ,

--

I1

:.-,car7 J o i n t s .

--

-

lhe nason

may u s e s e v e r a l methods

to

o n f 1 I 3 . o n ;

.

- i izethoc! e omonl:, ~,ecomfrenC.ed

L s t o t ' f ~ r o n p l e n t y a f

mortar on

t h o e n d o f t h e brick to 5 e halc'

&id

t ' i e n t o

?ush

t % r ? brick i n t o place s o ':-:EL t h e m o r t a r o o z e s out

at

the I;op or t ? z c l i e a d jof ht.

F u l l

c r o s s

joints

a r e s e l d a r secured

on

t h e avcyage

;ob, ~ a r t 5 c u l n r l y

In

teo('er c o u r s c s .

In

hclsa6.e~ courlges t l ~ e :-m;-ter s'?oulrl 3 e S T Y Z ? o v e r t?tc c n t i r c side of

t

h e t?.:gdor

35 _{cl: mrl t%e} b r i c k shoulr3 be pushad

i n t o

> l a c e

a ~ a i n

so t h s t t 5 c m o r t a r oozes

out

c t t h e t o p o f

t

he joint.

jdhen

p l a c i n g

c l o s u r e b ~ i c k s , eithsr s t r e t c h e r s or !:ea3.ers, it is e s s ~ n t i a l

t o sp-eaf. nmor5lt2r

on

t h c encis

o r

t ke

s i d e s of b o t h t k b r i c k s ~

ia

3Lzcc z v d _{t ' l c}

_closure

_Sriclc.

m < 1 - 1 e o r S a r q ~ e t s Z l a c ? ~ ,

-

In

lay in^ hollow wits such es

-

full

head

j o i n t s

on

b o t h t h e

i n s i d e

m d t h e o u t s i d e edges

of

the unit, O f t e n c o n c r e t e b l o c k am l a i c

with

n o r t a r

o n l y

an

t h e or?.ge

sf

one web

-

t h i s cannot be expectec? t o pive a w a t -

e r t i p h t ';lall.

In

T ~ c t , s i n c e c o n c r e t e b l o c l r s do not ? r e s e n t

a

solid

r a c e a c r o s s t h o end of t h e b l o c k ,

it

i s o f t e n n e c e s -

s a q , even::

hen

ends of b o t h

webs are

c o v e r e d w i t h rnorter,

t o zpply a f u r t h e r p r o t e c t i v e c o a t i n g suc3 2 s a cernont-water p a i n t

or a

s t u c c o o v e r .t h e e x t e r i o r of the b l o c k .

Type of' J o i n t s .

-

joints a n t h o e x t e r i o r f a c e

of

masonry canstmaction s h o u l d be t o o l a d to rive a concave f i n i s h .

T h c r c i s rmch e v i d e n c e t e show t h a t joints s e a l e d in th-is marine? z r e t h c most e i ' r e c t i v e

in

? m e v e n t i n g w a t e r from s n t e r -

inc

t 3 e 'fall. T o o l i n f s h o u l d be done w l t 3 a rouncl tool, slishtly I n r r - o r than tile jcfnt,

with

s

_ufficlent

_{f o r c e to} press %kc n o r t a r t i s h t l y a 5 a i n s t t h e brick

an

b o t h s i d e s of %be m o r k r r , j o i n t , It s h o u l d

ncvrr

b e h n e b e f o r e t h e n o r t a r

has b e ~ m

to

s e t , On the o t h e r h m d

ft

must Se cornpleteC

b c r o r e t h e m o r t n r h a r d e n s .

An a t t e n p t hzs been vaCe in

the

foregoing - d i s-

cuss5on t o c a l l a t t e n t d o n t o some of t h e Z a c t o r s 1:~3ich

exer-

c i s e m i a ~ o r t n n - t ; i n f l u e n c e on _hc s;rntcrti:;htness 2 n d the euraSilit7 o f

mzsonry

wall-s . The requLremcnts for r a t i s - factory ~ u t e r i o l s czn b e met w i t h o u t : m e t expensc.

If,

in

n C r l i t i o n , adoquatc inspection is 9 r o v i 8 e d and good w o r h m a h i p i s o 3 t a i n e d , tlon qunlity brick i - ~ a l l s c a n b e

constructed

f o r

most t y p e s of exposures,

IT,

however, the t r o r h a n s h i p i s n e t

coot?, t h e structure is fllrnost c o r t a i n t o be permeable t o

c'

w a t e r 8,nd d c f i c f ~ n t

i n

r e s i s t z n c e Go weather.

T h e meth.ods of buildin,: masonry w a l l s t h a t r = ! i l l 7er.for;s r r c l l a r e r e l n 5 i v o l y s i m l e ,

It

is

not

so s-irnrlc t o

g e t t h e m h u i l t t h a t vay, and u n t i l the ir;lportancc of f o l l a w h g t . 7 ~ rules whrch a rc believec:

to

y o v i d e

water :;ish.tness

in

:Tasonry

i s r1ecg,?nized t - e n r c s e c r c l ~ and even s p e c i f i c a t i o n s ?:ill have v e r y l i t t l e e f f e c t .