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Damage to Basement Floors, Great West Development Limited Project, St. James, Manitoba
N a t i o n a l R e s e a r c b C o u n c i l Canada
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
DAMAGE TO BASEMENT FLOORS,
GREAT WEST DEVELOPMENT LIMITED PROJECT, ST. JAMES9 MANITOBA
by
A. B a r a c o a ANALYZED:
( P r e p a r e d f o r C e n t r a l Mortgage and Housing C o r p o r a t i o n , )
R e p o r t No,
6 1
o f t h eD 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
P r e f a c e
T h i s i s a b r i e f Report on an unusually severe e a s e of damage t o basement f l o o r s i n Winnipeg, prepared by P r o f , A. Baracos of t h e Department of C i v i l Engineering, U n i v e r s i t y of Manitoba, who works w i t h t h e D i v i s i o n of Building Research d u r i n g summer p e r i o d s on s p e c i a l r e s e a r c h p r a j e c t a , i n t h e Winnipeg a r e a .
The w r i t e r a g r e e s w i t h
Mr,
Baracosl c o n c l u s i o n s and comments, a l t h o u g h h e s u s p e c t s t h a t a major f a c t o r i n t h e damage h e r e i n r e p o r t e d was t h e b a c k f i l l i n g of t h e basement e x c a v a t i o n s w i t h c l a y , Unless t h e s e e x c a v a t i o n s were very c a r e f u l l y b a c k f i l l e d , t h e y would form n a t u r a l sumps, t h ec o l l e c t i o n of water i n which could be expected t o cause e x c e s s i v e s w e l l i n g i n t h e c l a y b a c k f i l l .
The Report o n l y touches upon a major problem i n house d e s i g n and c o n s t r u c t i o n . S o i l c o n d i t i o n s i n Winnipeg make t h e m a t t e r of good basement d e s i g n u n u s u a l l y d f f f i c u l t , The D i v i s i o n of Building Research t h e r e f o r e hopes t o develop f u r t h e r s t u d i e s of t h i s problem with s p e c i a l r e f e r e n c e t o t h e Winnipeg a r e a , i n 1955,
Robert
F,
Legget, D i r e c t o r .Ottawa,
DAMAGE TO BASEMENT FLOORS,
GREAT WEST DEVELOPMENT LIMITED PROJECT, S T , JAMES MANITOBA
by A, Baracos
On August
14
and 1 6 , 1954 i n s p e c t i o n s were made of h o u s e s i n t h e Great West Development Limited P r o j e c t i nS t . James, Manitoba, These h o u s e s had s u f f e r e d e x t e n s i v e basement f l o o r damage due t o s o i l volume changes,
The i n s p e c t i o n s were made a t t h e r e q u e s t of t h e Winnipeg O f f i c e of C e n t r a l Mortgage and Housing C o r p o r a t i o n , on t h e i r r e c e i p t of a l e t t e r from t h e a r c h i t e c t s o f t h e p r o j e c t , Messrs. Green, B l a n k s t e i n , R u s s e l l , and A s s o c i a t e s of Winnipeg, T h i s l e t t e r p ~ o p o s e d c e r t a i n changes i n CMHC S p e c i f i c a t i o n s which t h e a r c h i t e c t s b e l i e v e d would a l l e v i a t e basement f l o o r heaving c o n d f t i o n s (Appendix A ) ,
The w r i t e r o b t a i n e d from CMHC, and t h e a r c h i t e c t s , t h e a d d r e s s e s of h o u s e s where t h e S p e c i f i c a t i o n s were f o l l o w e d and where e x c e s s i v e f l o o r heave had been observed. It was l e a r n e d from CMHC t h a t damage had o c c u r r e d i n t h e r e c e n t l y c o n s t r u c t e d Great West Development h o u s e s , CPlIHC had a l s o been asked t o a c t a s r e f e r e e i n d e t e r m i n i n g whether damage was due t o u n u s u a l s o i l c o n d i t i o n s o r whether t h e c o n t r a c t o r o r
d e s i g n was a t f a u l t , T h i s i n f o r m a t i o n was r e q u i r e d i n o r d e r t o d e c i d e who would b e a r r e p a i r c o s t s ,
2, S p e c i f i c a t i o n s , Municipal Code Requirements
CMHC s p e c i f i c a t i o n s c a l l f o r t h e u s e of weeping t i l e d r a i n s p l a c e d a l o n g t h e e x t e r i o r p e r i m e t e r of t h e f o u n d a t i o n w a l l f o o t i n g s i n h o u s e s w i t h basements, These d r a i n t i l e s a r e c o n n e c t e d t o t h e basement f l o o r c a t c h b a s i n by weeping t i l e l e a d e r s p a s s i n g t h r o u g h t h e f o u n d a t i o n w a l l f o o t i n g s and u n d e r t h e basement f l o o r s , F i v e i n c h e s of g r a v e l a r e s p e c i f i e d under t h e basement f l o o r . The weeping t i l e l e a d e r s a l s o s e r v e a s d r a i n s f o r t h e g r a v e l ,
The M u n i c i p a l i t y of S t . James d o e s n o t p e r m i t r a i n w a t e r l e a d e r s from t h e r o o f t o be connected t o t h e s a n i t a r y
sewer, a s i s t h e e a s e i n Winnipeg, Rain w a t e r c o l l e c t e d on t h e r o o f i s d i s c h a r g e d on t o t h e lawns around t h e h o u s e s ,
3.
A r c h i t e c t s ' P r o p o s a l sThe a r c h i t e c t s c l a i m t h a t t h e g r a v e l u n d e r t h e basement f l o o r s a c t s a s a r e s e r v o i r f o r w a t e r which e n t e r s t h r o u g h t h e t i l e d r a i n s , It i s thought t h a t t h e w a t e r cauaea t h e u n d e r l y i n g c l a y s t o s w e l l and r e s u l t i n basement f l o o r heave. They t h e r e f o r e proposed t h e f o l l o w i n g :
(a) R e d u c t i o n of t h e amount of g r a v e l from
5
i n c h e s t ol/4
t o 1/2 i n c h e s t o e l i m i n a t e t h e r e s e r v o i r of w a t e r ; ( b ) The weeping t i l e d r a i n s t o be moved from t h e e x t e r i o r
of t h e f o u n d a t i o n w a l l f o o t i n g s t o t h e i n t e r i o r ;
( c ) A s i n g l e weeping t i l e d r a i n , one t o e a c h w a l l , t o p a s s t h r o u g h t h e f o o t i n g s w i t h g r a v e l b l o c k i n g t h e e x t e r i o r open end; t h i s t i l e would be connected t o t h e weeping t i l e s on t h e i n t e r i o r o f t h e f o o t i n g ;
( d ) The l e a d e r s from t h e p e r i m e t e r weeping t i l e t o t h e c a t c h b a s i n t o be l a i d i n "a t h i n l a y e r of cementn; t h e s e l e a d e r s would be p l a c e d i n e x c a v a t i o n 8 so t h a t t h e t o p of t h e t i l e would be l e v e l w i t h t h e t o p of t h e basement f l o o r e x c a v a t i o n , A copy of t h e a r c h i t e c t ' s l e t t e r w i l l be found i n t h i s r e p o r t i n Appendix A,
4.
Nature o f DamageThe f o l l o w i n g damaged houses were v i s i t e d :
384
Davidson S t r e e t388
Davidson S t r e e t 300 S t r a t h m i l l a n Road 292 S t r a t h m i l l a n RoadThese were examples of t h e most s e v e r e l y damaged h o u s e s , and i n a l l f o u r t h e damage was s i m i l a r , The basement f l o o r s had heaved r e l a t i v e t o t h e basement w a l l s a s much a s
4
i n c h e s(292 S t r a t h m i l l a n Road), a s d e t e r m i n e d by r u n n i n g l e v e l s , Heaving was most s e v e r e n e a r t h e c e n t r e o f t h e f l o o r and
f o r c e d t h e a i r f u r n a c e a g a i n s t t h e f l o o r j o i s t s c a u s i n g damage t o t h e f u r n a c e and t o t h e s h e e t m e t a l ducts. The s o i l s t a c k and w a t e r p i p e s were a l s o damaged. The chimney of t h e house had l i f t e d c a u s i n g t h e f l a s h i n g s on t h e r o o f t o r i s e above t h e roof s h i n g l e s
(19
b r i c k c o u r s e s a t 384 Davidson S t r e e t ) . Basement f l o o r s had c r a c k e d and f l o o r d r a i n a g e was s e v e r e l yF o r t u n a t e l y t h e houses have no i n t e r i o r f o o t i n g s and s t e e l beams t r a n s m i t t h e s u p e r s t r u c t u r e l o a d s t o t h e f o u n d a t i o n w a l l s . They had been c o n s t r u c t e d d u r i n g 1953-54 and appear g e n e r a l l y w e l l b u i l t and designed, The c o n c r e t e basement f l o o r was a t l e a s t
3
i n c h e s t h i c k and had beensmoothly f i n i s h e d ,
On t h e second v i s i t , t h e basement f l o o r had been broken and p a r t l y removed i n p r e p a r a t i o n f o r r e p a i r s a t
300 S t r a t h m i l l a n Road and 384 Davidson S t r e e t , The u n d e r l y i n g g r a v e l was found t o be a p i t r u n m a t e r i a l having s t o n e s up t o about 1 1/2 i n c h e s diameter and c o n s i d e r a b l e sand. It appeared q u i t e permeable a s i n d i c a t e d by t h e r a t e a t which water flowed i n t o a shallow excavation, ( F i g * l ) , T h e t o t a l t h i c k n e s s of g r a v e l was up t o
6
o r7
i n c h e s , c o n s i d e r a b l y more t h a n t h e s p e c i f i e d5
i n c h e s , The weeping t i l e d r a i n s waren e a r t h e t o p of t h e g r a v e l , F r e e water was found i n t h e g r a v e l up t o t h e i n v e r t of t h e t i l e . Under t h e g r a v e l was found a t h i n l a y e r of decaying s t r a w u n d e r l a i n by a n o l i v e brown,
h i g h l y p l a s t i c c l a y , From a v i s u a l examination of t h i s c l a y i t was i d e n t i f i e d a s being s i m i l a r t o t h e Winnipeg c l a y s whioh have h i g h s w e l l i n g and s h r i n k i n g p r o p e r t i e s ,
Some of t h e t i l e d r a i n s under t h e basement f l o o r were broken ( F i g , 2 ) , It was n o t p o s s i b l e t o determine whether t h e y had been broken p r i o r t o , o r when t h e basement f l o o r w a s removed,
59
I n t e r v i e w w i t h OwnersI n t e r v f e w s w i t h t h e owners r e v e a l e d t h a t t h e basement f l o o r heaving had o c c u r r e d d u r i n g t h e s p r i n g and summer of
1954, A t 292 S t r a t h m i l l a n Road, t h e owner mentioned t h a t he had watched t h e c o n s t r u c t i o n of t h e basement, He had noted t h a t r u b b l e f i l l was used t o b r i n g t h e basement e x c a v a t i o n
t o t h e proper e l e v a t t o n b e f o r e p l a c i n g t h e g r a v e l f o r s u p p o r t i n g t h e basement f l o o r , The weeping t i l e d r a i n s were p l a c e d near t h e t o p of t h e g r a v e l , S i m i l a r i n f o r m a t i o n was g i v e n independ- e n t l y and u n s o l i c i t e d a t
384
Davidson S t r e e t , A t t h i s l a t t e r a d d r e s s , t h e ownerss w i f e mentioned t h a t workmen had t o l d h e r t h a t t h e basement had been excavated t o a g r e a t e r d e p t h t h a n r e q u i r e d and had t o be f i l l e d i n , It was n o t p o s s i b l e t o confirm t h e s e s t a t e m e n t s a s t h e basement f l o o r s were n o t removed,60 Discussion
The s o i l heaving a t t h e houses examined h a s been u n u ~ l u a l l y s e v e r e , T h i s c o n d i t i o n h a s been a i d e d t o a l a r g e e x t e n t by water c o l l e c t i n g i n t h e g r a v e l under t h e basement f l o o r , I n t h e two houses where t h e examination of t h e g r a v e l under t h e f l o o r was p o s s i b l e , adequate d r a i n a g e of t h e g r a v e l was n o t p o s s f b l e , The e l e v a t i o n of t h e i n v e r t of t h e t i l e
d r a i n s d i d n o t permit d r a i n a g e of t h e g r a v e l below t h e t i l e . It i s conceivable t h a t t h e t i l e d r a i n s supply water t o t h e g r a v e l r a t h e r t h a n provide d r a i n a g e ,
Adequate d r a i n a g e does n o t p r e c l u d e s o i l heaving a s s o i l m o i s t u r e v a r i a t i o n s can s t i l l occur i n t h e c l a y , however, t h e heaving would be l e s s s e v e r e and much more g r a d u a l ,
Regarding t h e a r c h i t e c t s c l a i m s f o r t h e changes t o t h e CMHC S p e c i f i c a t i o n s t h e f o l l o w i n g may be s a i d :
( a ) The d r a s t i c r e d u c t i o n of t h e amount of g r a v e l under a basement f l o o r would n o t reduce 8011 heaving, What
i s more important i s t h a t t h e g r a v e l should be a b l e t o d r a i n , T h i s would r e q u i r e p l a c i n g t h e i n v e r t of t h e t i l e s u f f i c i e n t l y deep t h a t water i n t h e r a v e l w i l l d r a i n
f
i n t o t h e t i l e . The d r a i n e d g r a v e l w 11 a c t as c a p i l l a r y c u t - o f f and keep t h e u n d e r s i d e of t h e basement f l o o r away from f r e e moistuye;
( b ) The weeping t i l e s a r e p r e f e r a b l e on t h e e x t e r i o r of t h e f o o t i n g s where t h e y i n t e r c e p t seepage i n t o t h e ground b e f o r e p a s s i n g under t h e f o o t i n g s ;
( c ) Laying of t h e t i l e l e a d e r s " i n cementn under t h e f l o o r would n o t permit d r a i n a g e of t h e g r a v e l . There i s m e r i t i n t h e s u g g e s t i o n t h a t t h e weeping should be dug i n t o t h e u n d e r l y i n g c l a y . T h i s would a s s u r e b e t t e r f l o w of water
downwards i n t o t h e d r a i n ,
7 *
ConclusionThe a u t h o r h a s t r i e d t o determine t h e cause of
e x c e s s i v e s o i l heaving i n t h e Great West Development, Limited p r o j e c t i n S t , James, Manitoba, and t o comment on t h e proposed changes t o t h e CMHC S p e c i f i c a t i o n s suggested by t h e a r c h i t e c t s f o r t h e p r o j e c t ,
It i s recommended t h a t no a c t i o n be t a k e n on t h e s e s u g g e s t i o n s , The f o l l o w i n g p r e c a u t i o n s a r e recommended i n making r e p a i r s and i n f u t u r e i n s t a l l a t i o n s :
( a ) The weeping t i l e under t h e basement f l o o r should be p l a c e d a t an e l e v a t i o n t o permit complete d r a i n a g e of t h e g r a v e l ; ( b ) The g r a v e l should be f r e 6 of e x c e s s i v e f i n e s t o permit
f r e e d r a i n a g e ;
( e ) Rain water l e a d e r s should be i n s t a l l e d i n such a manner
t h a t t h e water i s d i s c h a r g e d away from t h e f o u n d a t i o n w a l l s ; ( d ) Grading of t h e y a r d s around t h e houses should be such
APPENDIX A
GREEN BLANKSTEIN RUSSELL AND ASSOCIATES
.
ARCHITECTS AND CONSULTING ENGINEERS222 Osborne S t r e e t North, Winnipeg, Man, June 11, 19540 M r , J o A , KcFarlane, A s s i s t a n t Manager Winnipeg Branch O f f i c e C , M o H o C o Donalda Block Donald S t r e e t , WINNIPEG, Manitoba, Dear PIP, McFarlane:
A meeting was h e l d a t our o f f i c e on t h e morning of June l o t h , 1954, t h e r e s u l t s o f which we b e l i e v e you w i l l be i n t e r e s t e d i n , Those who a t t e n d e d t h e meeting were J , C , S c a i f e , B,Sc, ( C o E 0 ) , from t h e
M u n i c i p a l i t y of S t , James, P,H, D e m l e , B u i l d i n g I n s p e c t o r from S t , James, MP, A , Sandylands, Building I n s p e c t o r f o r C , M , H o C o , M r , I, Margolese, Great West Development Co,, and t h e w r i t e r ,
The problem under d i s c u s s i o n was "expansion of s o i l a under basement f l o o r s * , The i n f o r m a l meeting sought t o d i s c o v e r some means of a l l e v i a t i n g t h e c o n d i t i o n s which cause basement f l o o r s t o r i s e w i t h expanding s o i l s , It was g e n e r a l l y agreed by a l l t h o s e p r e s e n t t h a t i f t h e g r a v e l
5"
t h i c k was o m i t t e d f r o m t h e underside of t h e s l a b and i n i t s p l a c e a t h i n l a y e r of g r a v e l approximatelyl/hn
t o 1/2" t h i c k were i n s t a l l e d , t h e r e would t h e n be no r e s e r v o i r under t h e basement f l o o r which could c o n t r i b u t e t o t h e expansion of t h e s o i l , Itwas
f u r t h e r agreed t h a t t h e weeping t i l e should be p l a c e d on t h e i n s i d e of t h e f o o t i n g w i t h t i l e s p e n e t r a t i n g t h e f o o t i n g s one t o each s i d e w i t h t h e o u t e r e x t e r i o r f a c e blocked o f f by c o u r s e g r a v e l and connected
i n t o t h e weepers a t t h e i n s i d e edge of t h e f o o t i n g , The l e a d e r s from t h e p e r i m e t e r t i l e s should be l a i d i n a t h i n l a y e r of cement and t h e n covered over w i t h c o n c r e t e , f i r s t having been dug i n t o t h e bed a t l e a s t by a d e p t h s u f f i c e n t so t h a t t h e t o p of t h e t i l e would be l e v e l w i t h t h e bottom of t h e excavation, Than t h e f l o o r should be p u t over t h e t o p of t h a t , It was f e l t a s t h e w r i t e r mentioned, t h a t by so doing, t h e expansion of s o i l s under t h e f l o o r could be c u t down t o some degree, Would you be good enough t o d f s c u e s t h i s m a t t e r with M r , Sandylands and l e t t h e w r i t e r have your o p i n i o n a s t o whether o r n o t C,M.H,C,
would a c c e p t houses i n t h i s r e g i o n of G r e a t e r Winnipeg, and e l i m i n a t e t h e n e c e s s f t y of u s i n g t h e
5"
g r a v e l f i l l , Your k i n d a t t e n t i o n t o t h i s m a t t e r would be g r e a t l y a p p r e c i a t e d ,'- .
Yours vary t r u l y ,
GREEN BLANKSTEIN RUSSELL AND ASSOCIATES
L o J o Green LG/GB
F i g u 1
-
330 S t s s t h l ? ! i l l a n Road; showing .posit%sn of w e e p i n g t i l e Invert i n
relation to free water bn the grsvel under the ba ssrnent f l o o r .
Ffgu 2
-
368 Ftrathmfllan R o a d ; s h o v ~ i n gc r a c k e d tile drafn a n d position o f t i l e
drain w i t h r e s p e c t t o foundation w a l l f o o t i n g s , ("he t f P e drain may h a v e b e e n
damaged draring r e m o v a l of b a s e m e n t f l o o r , )
