Publisher’s version / Version de l'éditeur:
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à [email protected].
Questions? Contact the NRC Publications Archive team at
[email protected]. If you wish to email the authors directly, please see the first page of the publication for their contact information.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
Technical Translation (National Research Council of Canada), 1975
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
NRC Publications Archive Record / Notice des Archives des publications du CNRC :
https://nrc-publications.canada.ca/eng/view/object/?id=8a76e596-24d3-4ab2-98dc-f20e1b6fd675 https://publications-cnrc.canada.ca/fra/voir/objet/?id=8a76e596-24d3-4ab2-98dc-f20e1b6fd675
NRC Publications Archive
Archives des publications du CNRC
For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
https://doi.org/10.4224/20377922
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
New basement wall designs for below-grade living space
Elmroth, A.; Hoglund, I.; National Research Council of Canada. Division of
Building Research
CANADA INSTITUTE
FOR SCIENTIFIC AND TECHNICAL
IIVFORMATION
INSTITUT CANADlElV
DE L'INFORMATION SClENTlFlQUE
ET TECHNIQUE
N R C / C N R TT-
1801 TECHNICAL TRANSLATION TRADUCTION TECHNIQUENEW BASEMENT WALL DESIGNS
FOR BELOW-GRADE LIVING SPACE
TRANSLATED BY
1
TRADUCTION D E H. R. HAYESTHIS IS THE TWO HUNDRED AND SEVENTEENTH I N THE SERIES OF TRANSLATIONS PREPARED FOR THE DIVISION OF BUILDING RESEARCH
TRADUCTION N U M ~ R O 217 D E LA s ~ R I E P R ~ P A R ~ E POUR LA D I V I S I O N DES RECHERCHES EN BATIMENT
OTTAWA 1975
National Research
Conseil national
PREFACE
The increasing utilization of house basements for habitable space and the consequent desirability of improved performance of such subgrade structures are factors coni- mon to both Canada and the Scandinavian countries. A previous translation, TT-1603, described a "New Method of Drainage of Basement Walls" which was based on laboratory
studies by Knut
I.
Edvardsen in Norway. This presenttranslation of an article by Arne Elmroth and Ingemar H6glund describes further developments in Sweden in which mineral fibre insulation is utilized on the outside of basement walls to provide both a drainage layer and thermal
insulation. This technique could well have wide applica- tion in Canada, both in connection with house basements and with other subgrade structures where significant economies may result from the replacement of granular fill by the mineral fibre drainage layer.
The Division is most grateful to Mr. H.
R.
Hayes of theTranslation Services of N.R.C. for translating the paper,
and to Mr.
G.
0 . Handegord ofDBR
for reviewing the manuscript.The Division anticipates that further publications describing the Swedish experience in this regard will be made available in this way. Ottawa, April 1975. C. B. Crawford, Director, Division of Building Research,
NRC.
NATIONAL RESEARCH COUNCIL
OF
CANADA
CONSEIL NATIONAL DE RECHERCHES
DU CANADA
TECHNICAL TRANSLATION
lsOlTRADUCTION TECHNIQUE
New basement wall designs for below-grade living space
(Nya kgllaryttervaggar ger bostadsklimat under mark)
Authors/Auteurs:
A. Elmroth and I. ~oglund
Reference/RgfGrence:
Stockholm, ~yggforlaget,
1971.
35pp.
Translator/Traducteur: H. R. Hayes, Translation Services/Service de traduction
Canada Institute for
Institut canadien de
Scientific and Technical
l'information scientifique et
Information
technique
Ottawa, Canada
K1A
O S 2T a b l e o f C o n t e n t s I n t r o d u c t i o n by O l l e Bengtzon Foreword A new t y p e o f basement f o r s i n g l e - f a m i l y h o u s e s S t r u c t u r a l d e s i g n w i t h s p e c i a l r e f e r e n c e t o m o i s t u r e problems - G e n e r a l p o i n t s o f view C o n v e n t i o n a l methods o f m o i s t u r e p r o t e c t i o n i n t h e c o n s t r u c t i o n o f e x t e r n a l basement w a l l s - M o i s t u r e r a t i o s R e c e n t l y d e v e l o p e d methods o f m o i s t u r e p r o t e c t i o n i n e x t e r n a l basement w a l l s O b j e c t i v e and t e s t program T e s t methodology and s c o p e Some examples o f t h e r e s u l t s o b t a i n e d S t r u c t u r a l d e s i g n s C o n c l u s i o n F i g u r e s Page 4 5 6
- 4 -
Introduction
F o r a long t i m e t h e b a s e m e n t s of Swedish single - f a m i l y h o m e s have been neglected. Randomly c o n s t r u c t e d p a r t i t i o n w a l l s have
divided a r e a s into nooks and c r a n n i e s without any functional j u s t i f i c a - tion. M a n y bungalows and t e r r a c e h o u s e s a r e s t i l l being c o n s t r u c t e d with t r a d i t i o n a l b a s e m e n t r o o m s , which a r e m o r e of a h i n d r a n c e t h a n a help.
However, in m o r e r e c e n t y e a r s an i n c r e a s i n g n u m b e r of a r c h i - t e c t s , m a n u f a c t u r e r s , and c o n s t r u c t i o n c o m p a n i e s have d i s c o v e r e d t h a t , without any a c t u a l additional c o s t , the b a s e m e n t a r e a can be con-
v e r t e d into a valuable addition t o the h o u s e . Another g r e a t advantage i s t h a t c a r s a r e no l o n g e r kept in b a s e m e n t s t o the e x t e n t t h a t t h e y u s e d t o be.
The p i o n e e r s of the new a p p r o a c h t o b a s e m e n t d e s i g n a r e t h e a r c h i t e c t s U l l a - B r i t a B r a n d t ( M y r e s j o h u s ) and Reed A n d e r s s o n
( G u l l r i n g s h u s ) a n d , above a l l , Hans F o g and B e r t Sahlin with the " K i r s t i " h o u s e , a p r e f a b r i c a t e d dwelling which, unfortunately, i s no l o n g e r being p r o d u c e d . The b a s e m e n t a r e a , f r e e of u n n e c e s s a r y w a l l s , c o n t a i n s a T V - f a m i l y r o o m , a T u r k i s h bath, a r e c r e a t i o n r o o m and, in s o m e c a s e s , even a bedroom.
Such a new and f u l l e r utilization of the b a s e m e n t n a t u r a l l y
e n t a i l s a higher d e g r e e of technical s k i l l in i t s d e s i g n and construction. Until now t h i s a s p e c t h a s been n e g l e c t e d , and i t i s now t i m e t o introduce a new b a s e m e n t technology. T h i s , then i s the subject m a t t e r of the p r e s e n t w o r k , which will be i l l u s t r a t e d with a p r a c t i c a l e x a m p l e . I t i s hoped t h a t t h i s will c o n t r i b u t e t o l e s s expensive and b e t t e r u t i l i z a t i o n of t h e a v a i l a b l e land.
Stockholm, 16th D e c e m b e r , 1971 Olle Bengt zon
F o r e w o r d
The basement a r e a in single-family h o u s e s w a s a t one t i m e costly in r e l a t i o n t o i t s s e r v i c e a b i l i t y , since i t could only be used t o a l i m i t e d extent. It i s against t h i s background t h a t we have sought t o introduce m o r e up-to-date construction p r i n c i p l e s f o r e x t e r n a l
b a s e m e n t w a l l s , with p a r t i c u l a r r e f e r e n c e to m o i s t u r e and heat i n s u l a - tion, i n o r d e r t o achieve a n improved indoor c l i m a t e . Such m e a s u r e s would m a k e i t possible t o enjoy b e t t e r and w i d e r u s e of b a s e m e n t a r e a s , i. e.
,
a higher s t a n d a r d of living space.T h i s booklet i s p a r t i a l l y a d i s c u s s i o n of the r e s u l t s of investiga- tions of s u c h b a s e m e n t d e s i g n s , and p a r t i a l l y a suggestion f o r suitable designs.
D i r e c t economic a s s i s t a n c e f o r the r e s e a r c h work w a s provided by the National Council f o r Building R e s e a r c h . Lattbetong AB and Rockwool AB have given valuable economic support, p r i m a r i l y in the f o r m of m a t e r i a l and a s s i s t a n c e in obtaining a building f o r field i n v e s t i g a - t i o n s .
The w o r k w a s done a t the Institute of Building Technology, The Royal Institute of Technology. C i v i l e n g i n e e r s Hakan Lindkvist and B e r t i l M a t t s s o n a l s o p a r t i c i p a t e d in t h i s work.
Stockholm, D e c e m b e r 1971 A r n e E l r n r o t h , I. Hoglund
NEW BASEMENT W A L L DESIGNS
FOR BELOW GRADE LIVING SPACE
A. E l m r o t h and I. Hoglund
A new type of basement f o r single-family houses
The conventional b a s e m e n t in both s i n g l e - f a m i l y and m u l t i - f a m i l y h o u s e s w a s , a s a r u l e , only used f o r allocating the b o i l e r
r o o m , l a u n d r y and s t o r e r o o m s , e t c . The r e q u i r e m e n t s f o r the i n d o o r t e m p e r a t u r e of t h e s e p r e m i s e s a s well a s the s t r u c t u r a l
solution t o t h e i r heat and m o i s t u r e insulation have, i n i t i a l l y , been r a t h e r m o d e s t .
Today, s i n g l e - f a m i l y h o u s e s in Sweden a r e , however, i n c r e a s - ingly c o n s t r u c t e d with a new type of b a s e m e n t . T h u s h o b b y - r o o m s , t e l e v i s i o n r o o m s , e t c .
,
a r e now placed in the b a s e m e n t s . In m u l t i - f a m i l y h o u s e s the e n t r a n c e and b a s e m e n t f l o o r - s p a c e m a y well be u s e d in f u t u r e f o r d i f f e r e n t s e r v i c e f a c i l i t i e s f o r t h e r e s i d e n t s . T h e changed and m o r e v e r s a t i l e utilization of the b a s e m e n t f l o o r - s p a c e c a l l s f o r a h i g h e r s t a n d a r d a s r e g a r d s indoor c l i m a t e . G r e a t e r c o n - s i d e r a t i o n m u s t be paid t o q u e s t i o n s p e r t a i n i n g t o m o i s t u r e and h e a t i n s u l a t i o n of the e x t e r n a l w a l l s , b e t t e r ventilation and a p e r m a n e n t heating s y s t e m .The conventional b a s e m e n t c o n s t r u c t i o n s with o u t e r w a l l s o f , only c o n c r e t e o r hollow c o n c r e t e blocks do not m e e t the i n c r e a s e d r e q u i r e m e n t s . During the l a s t few y e a r s t e c h n i c a l and economically r a t i o n a l solutions t o b a s e m e n t c o n s t r u c t i o n s and foundation d e s i g n have been sought which p e r m i t utilization of the b a s e m e n t . New s t r u c t u r a l
d e s i g n s and m a t e r i a l combinations have been t e s t e d f o r b a s e m e n t s . T h i s i n c r e a s e d i n t e r e s t in the b a s e m e n t s h a s a l s o been s t i m u l a t e d by the d e s i r e t o develop quick and "dry" m e t h o d s suitable f o r p r e - f a b r i c a t e d s y s t e m s and w i n t e r c o n s t r u c t i o n .
S t r u c t u r a l d e s i g n with s p e c i a l r e f e r e n c e t o m o i s t u r e p r o b l e m s
-
g e n e r a l points of viewIn t h e c o n s t r u c t i o n of b a s e m e n t s above the ground w a t e r t a b l e , the following m o i s t u r e p r o b l e m s have t o be taken into account ( F i g . 1 ) -
S u r f a c e w a t e r i n the f o r m of r a i n o r m e l t i n g w a t e r should, a s f a r a s p o s s i b l e , be p r e v e n t e d f r o m p e n e t r a t i n g into the s o i l n e a r a h o u s e . T h i s c a n be achieved by g r a d i n g t h e s o i l n e a r the house in
s u c h a way t h a t i t s l o p e s away f r o m it. In c a s e t h e s o i l i s not s e l f - d r a i n i n g and the e x t e r n a l b a s e m e n t w a l l s a r e not w a t e r p r o o f , back -
filling a g a i n s t the w a l l s i s u s u a l l y effected with g r a n u l a r m a t e r i a l ( e . g. u n g r a d e d g r a v e l ) . The d r a i n a g e
-
often the m o s t i m p o r t a n t m e a s u r e f o r obtaining a d r y b a s e m e n t-
c a n n o r m a l l y be placed on a bed with a m i n i m u m t h i c k n e s s of 5 c m with a 30 c m backfill of ungraded g r a v e l . With a view t o the r i s k of silting-up, u n g r a d e d g r a v e l i s c o n s i d e r e d asuitable m a t e r i a l .
C a p i l l a r y w a t e r in the ground (and p o s s i b l y a l s o s u r f a c e w a t e r which p e n e t r a t e s down t o the foundation w a l l ) m u s t be p r e v e n t e d f r o m being d r a w n i n t o the e x t e r n a l w a l l s and the b a s e m e n t f l o o r . T h i s a i m i s u s u a l l y achieved by placing u n d e r the b a s e m e n t f l o o r a l a y e r of c o a r s e g r a v e l , m a c a d a m o r s h i n g l e , which d e s t r o y s c a p i l l a r y a c t i o n and
-
a t the s a m e t i m e-
functions a s a d r a i n a g e l a y e r . E x t e r n a l b a s e m e n t w a l l s , p a r t i c u l a r l y m a s o n r y w a l l s , a r e u s u a l l y p r o t e c t e d with a s p h a l t coating s.
The m a i n p u r p o s e of the a s p h a l t coating i s t o obtain a h i g h e r d e g r e e of w a t e r p r o o f n e s s which m a y be d e s i r a b l e in connection with l o c a l e x c e s s w a t e r p r e s s u r e due t o , heavy s p r i n g and autumn r a i n - f a l l s . The a s p h a l t coating i s , h o w e v e r , e a s i l y d a m a g e d d u r i n g back-filling, e t c , and i t s value can t h u s be questioned.
The i n h e r e n t m o i s t u r e in b a s e r i ~ e n t s follow-ing c o r ~ s t ~ u c t i o n m u s t be allowed t o d r y out sufficiently. In heated b a s e m e n t s , with an e x t e r n a l m o i s t u r e b a r r i e r applied t o the b a s e m e n t w a l l s , the e x c e s s i v e i n h e r e n t m o i s t u r e m u s t , a s a r u l e , d r y out t o w a r d s the i n s i d e . In t h e s e c a s e s t h e r e i s a r i s k t h a t s o m e p a r t of t h i s m o i s t u r e r e m a i n s in the o u t e r p a r t of the w a l l .
In w i n t e r t h e r e i s u s u a l l y a r i s k of condensation within t h o s e s e c t i o n s of e x t e r n a l b a s e m e n t w a l l s above ground level o r n e a r e s t t o i t . T h i s i s due t o diffusing w a t e r vapour f r o m the i n s i d e t o the outside. F u r t h e r down into the ground the r i s k b e c o m e s s m a l l e r , p a r t i c u l a r l y a f t e r a y e a r o r s o , when the ground outside the wall h a s been w a r m e d up.
An e x t e r n a l b a s e m e n t wall h a s , a s a r u l e , a d e n s e r s u r f a c e l a y e r on t h e cold s i d e than on the w a r m s i d e t o w a r d s the i n s i d e . Owing t o t h i s f a c t and taking into account t h e vapour p r e s s u r e
g r a d i e n t in heated b a s e m e n t s , t h e r e i s h a r d l y any diffusion f r o m t h e outside t o the inside. (In the m a j o r i t y of foundation w a l l s , a c e r t a i n humidity t r a n s f e r c a n , h o w e v e r , t a k e p l a c e t o w a r d s the i n s i d e due t o c a p i l l a r y s u c t i o n , )
A s a r e s u l t of c r a c k f o r m a t i o n and p e r v i o u s c o n n e c t i o n s , m o i s t u r e t r a n s f e r m a y a r i s e t h r o u g h m o i s t a i r i n f i l t r a t i o n .
S u r f a c e condeilsation m a y , f o r e x a m p l e , o c c u r on w a l l and f l o o r s u r f a c e s of b a s e m e n t s c o n s t r u c t e d in w i n t e r d u r i n g the f i r s t
s p r i n g a f t e r c o n s t r u c t i o n . In s u m m e r , s u r f a c e c o n d e n s a t i o n m a y o c c u r in unheated b a s e r n e n t s when w a r m a i r i s t r a n s p o r t e d i n t o t h e b a s e m e n t a s a r e s u l t of ventilation e t c . C o n v e n t i o n d m e t h o d s of m o i s t u r e ~ r o t e c t i o n in t h e c o n s t r u c t i o n of e x t e r n a l b a s e m e n t w a l l s
-
m o i s t u r e r a t i o s M a s o n r y w a l l s In t h e c o n s t r u c t i o n of conventional m a s o n r y w a l l s of hollow c o n c r e t e b l o c k s , a e r a t e d c o n c r e t e b l o c k s o r lightweight c l i n k e r c o n - c r e t e , t h e m o i s t u r e p r o b l e m s have u s u a l l y been d e a l t with a s i n d i c a t e d in F i g 2. T h i s m e t h o d i m p l i e s t h a t t h e w a l l i s p r o t e c t e d a g a i n s tw a t e r f r o m t h e o u t s i d e with t h e h e l p of a d r a i n e d backfill a t t h e o u t s i d e of t h e w a l l t o g e t h e r with a l a y e r on t h e o u t s i d e of t h e w a l l which d e s t r o y s c a p i l l a r y a c t i o n . The l a t t e r m a y c o n s i s t , of a coating with cold a s p h a l t and one o r t w o c o a t i n g s with hot a s p h a l t on a b a s e of thin p r i m e r and
a p a r g i n g of m o r t a r r i c h in c e m e n t , A s t h e s u r f a c e t r e a m e n t on t h e
o u t s i d e a l s o e x e r c i s e s a c o n s i d e r a b l e diffusion r e s i s t a n c e , p a r t of t h e r e s i d u a l m o i s t u r e in t h e c o n s t r u c t i o n and the c o n d e n s a t i o n w a t e r ( a s a r e s u l t of m i g r a t i o n o i w a t e r v a p o u r t o r e g i o n s of l o w e r t e m p e r a - t u r e ) m u s t m a i n l y d r y out t o w a r d s t h e i n s i d e of t h e b a s e m e n t . The
s u r f a c e t r e a t m e n t on the i n s i d e should t h e r e f o r e not be t o o d e n s e . T h e r e i s t h u s a h i g h e r m o i s t u r e content a t t h e o u t s i d e of t h e b a s e - m e n t w a l l s t h a n on t h e i r i n s i d e . T h i s c a n be s e e n f r o m i n v e s t i g a - t i o n s c a r r i e d out on n l a s o i l r y w a l l s of a e r a t e d c o n c r e t e . Below t h e ground s u r f a c e , t h e m o i s t u r e content w a s , on t h e a v e r a g e , about
21 p e r c e n t b y weight in t h e o u t e r l a y e r of t h e w a l l s a s c o m p a r e d w i t h about
9
p e r c e n t in t h e i n n e r l a y e r . The a v e r a g e m o i s t u r e content w a s about 1 5 p e r c e n t by weight. T h i s m o i s t u r e content f o r m s t h e b a s i s of t h e c o e f f i c i e n t s of t h e r m a l conductivity a p p l i c a b l e i n p r a c t i c e f o rm a s o n r y of a e r a t e d c o n c r e t e below g r o u n d l e v e l . The c o r r e s - ponding m o i s t u r e r a t i o f o r m a s o n r y of a e r a t e d c o n c r e t e above g r o u n d l e v e l i s 6 p e r c e n t . A s r e g a r d s blocks of lightweight c l i n k e r , the c o e f f i c i e n t s of t h e r m a l c o n d u c t i v i t y a r e b a s e d on a m o i s t u r e c o n t e n t of 4 p e r c e n t b y weight above g r o u n d and 7 p e r c e n t by weight below ground. T h u s t h e S w e d i s h Building Code of P r a c t i c e r e c k o n s with
z
r l i o i s t u r e c o n t e n t o i a p p r o x i m a t e l y t w l c e t h i s value f o r m a s o n r y of both t h e s e m a t e r i a l s if t h e y f o r m p a r t of t h e b a s e m e n t wrtil below g r o u n d l e v e l a s c o m p a r e d t o c a s e s when t h i s m a t e r i a l i s u s e d above g r o u n d l e v e l ,R e c e n t l y d e v e l o p e d m e t h o d s of m c i s t i l r e p r o t e c t i o n i n e x t e r n a l
-
b a s e m e n t w a l l sT h e c o n v e n t i o n a l p r i n c i p l e s of c o n s t r u c t i o n e a r l i e r a c c o u n t e d f o r , p a r t i c u l a r l y with a view t o m a s o n r y foundation w a l l s , c a u s e
c e r t a i n t e c h n i c a l d i f f i c u l t i e s i n p r o d u c t i o n . T h u s i t i s , a m o n g s t o t h e r t h i n g s , t i m e - c o n s u m i n g a n d e x p e n s i v e t o p l a c e t h e d r a i n a g e m a t e r i a l a d j a c e n t t o t h e foundation w a l l in a c o r r e c t way. F u r t h e r m o r e , t h e c o n s t r u c t i o r l c a n , i n p r i n c i p l e , be c o n s i d e r e d t o function l i k e a f l a t roof w i t h a d e n s e s u r f a c e l a y e r on t h e cold s i d e ( i n t h e c a s e of t h e foundation w a l l t h e r e m u s t be added the h e a t r e s i s t a n c e and t h e r m a l c a p a c l t y of the g r o u n d on the o u t s i d e ) r e s u l t i n g i n a d r y i n g - o u t p r o c e s s w h i c h i s r e n d e r e d m o r e difficult. F o r t h i s r e a s o n , a n u m b e r of m o r e m o d e r n s t r u c t u r a l d e s i g n s f o r w a l l s and r o o f s have b e e n t e s t e d w i t h t h e a i m of finding a s i m p l e r solution t o t h e m o i s t u r e p r o b l e m s i n t h e c o n s t r u c t i o n of foundation w a l l s . At p r e s e n t a m e t h o d i s being t e s t e d w h i c h i n v o l v e s t h e foundation w a l l being p r o v i d e d w i t h one o r two l a y e r s of m i n e r a l wool ( c f . F i g . 3) o r a ( v e n t i l a t e d ) a i r s p a c e ( F i g . 4)
on the s i d e f a c i n g t h e s o i l i. e . a t y p e of t w o - s t a g e w a t e r p r o o f i n g ("the open s c r e e n p r i n c i p l e " ) .
- 11
-
T h e m e t h o d s r e q u i r e t h e following m e a s u r e s :
a ) The ground m u s t be g r a d e d in s u c h a way t h a t a p r o p e r slope leading away f r o m the house i s f o r m e d .
b) The w a t e r f r o m the roof m u s t be d r a i n e d d i r e c t l y into the s t o r m s e w e r
c ) The house m u s t be provided with effective t i l e d r a i n a g e . It i s c o n s i d e r e d that a l a y e r of m i n e r a l wool c a n
-
f o r m a sufficiently effective l a y e r t o b r e a k c a p i l l a r y a c t i o n ,-
f o r m a n additional insulation which c a n , f i r s t l y , bring about a higher t e m p e r a t u r e in the w a l l , r e s u l t i n g in a d r i e r c o n s t r u c t i o n with b e t t e r insulating p r o p e r t i e s a n d , consequently, with a l o w e r l o s s of heat a n d , secondly, a h i g h e r t e m p e r a t u r e on the i n s i d e of the wall.-
f o r m a f r o s t b a r r i e r with a view t o reducing, if p o s s i b l e , the depth of the foundation,-
s i m p l i f y and l o w e r the c o s t of back-filling, a s i t i s f r e q u e n t l y p o s s i b l e t o u s e a v a i l a b l e excavated m a t e r i a l ,-
p r o t e c t the foundation wall and a s p h a l t coating (if any) a g a i n s t m e c h a n i c a l d a m a g e in connection with t h e back-filling w o r k , ground m o v e m e n t sc a u s e d by f r o s t - h e a v i n g , r o c k b l a s t i n g , e t c and a c t a s a p r o t e c t i o n a g a i n s t f r o s t a c t i o n i n the s u r f a c e l a y e r ,
- provide a "dry" c o n s t r u c t i o n method ( f o r w i n t e r c o n s t r u c t i o n ) .
One of the r e s u l t s of t h i s c o n s t r u c t i o n m e t h o d would s e e m t o be t h a t the a s p h a l t coating of the foundation wall c a n be simplified and p o s s i b l y o m i t t e d . It c a n e v e n be c o n s i d e r e d a disadvantage in t h a t it p r e v e n t s m o i s t u r e diffusion f r o m coming out into the m i n e r a l wool, which, of c o u r s e , h a s no diffusion r e s i s t a n c e t o s p e a k of.
The s i m p l e s t and be s t way of a s s e m b l i n g t h e m i n e r a l wool b a t t s would, h o w e v e r , s e e m t o be t o p r e s s t h e m into a l a y e r of a s p h a l t . The
l a t t e r d o e s not have t o s a t i s f y a n y g r e a t r e q u i r e m e n t s of d e n s i t y . T o p r e v e n t w a t e r p e n e t r a t i o n in connection with t e m p o r a r y e x c e s s w a t e r p r e s s u r e ( a s a r e s u l t of h e a v y r a i n o r c o n s i d e r a b l e
snow m e l t i n g ) , t h e foundation w a l l should be p a r g e d and a s p h a l t - c o a t e d on t h e o u t s i d e about d . 5 n-i above t h e fo:~ting. T h i s i m p l i e s a g r e a t e r d i f f u s i o n r e s i s t a n c e , but i s of l i t t l e disadvantage a s t h e v a p o u r p r e s s u r e d i f f e r e n c e i s s m a l l s o d e e p below t h e g r o u n d .
F o r t h i s new f i e l u of a p p l i c a t i o n f o r d e n s e m i n e r a l wool b a t s -
about which t h e e x p e r i e n c e gained s o f a r i s r a t h e r l i m i t e d - t h e
m i n e r a l wool q u a l l t y t o be u s e d f o r t h e t i m e being ( h i g h c h e m i c a l and b i o l o g i c a l r e s i s t a n c e ) should r e s i s t tile c h e m i c a l s p r e s e n t in t h e g r o u n d ( e . g . , h u m u s c o n t a m i n a t i o n ) which in t h e f o r m of w a t e r - soluble s a l t s c a n be expected t o p e n e t r a t e t e m p o r a r i l y i n t o t h e o u t e r l a y e r of t h e m i n e r a l wool i n s u l a t i o n , F u r t h e r m o r e , t h e m i n e r a l wool s l a b s should, a m o n g s t o t h e r t h i n g s , have s u c h s t r e n g t h p r o p e r t i e s a s t o r e s i s t t h e e a r t h p r e s s u r e in connection with t h e r e - f i l l i n g w o r k . It should a l s o be o b s e r v e d t h a t t h e m i n e r a l wool s l a b s m u s t not be c o a t e d . In a d d i t i o n , i t i s i m p o r t a n t f o r t h e h e a t - i n s u l a t i n g c a p a c i t y t h a t t h e e x t e r n a l m i n e r a l wool i n s u l a t i o n i s kept a s d r y a s p o s s i b l e ,
An e x t e r n a l a i r s p a c e , " T w o - s t a g e c o n s t r u c t i o n " , i s c o n s i d e r e d t o
-
f o r m a l a y e r which e f f e c t i v e l y clestroys c ~ p i l l a r y a c t i o n ,-
d r a i n any p o s s i b l e p e n e t r a t i n g s u r f a c e w a t e r and g r o u n d w a t e r and any p o s s i b l e c o n d e n s a t i o n w a t e r c o m l n g f r o m the i n s i d e ,-
t r a n s p o r t a w a y w a t e r v a p o u r c o m i n g f r o m the i n s i d e ,-
m a k e p o s s i b l e d r y i n g - o u t t o w a r d s t h e o u t s i d e ,-
s i m p l i f y and m a k e c h e a p e r r e -filling,-
prcjte ct t h e foundation w a l l a g a i n s t m e c h a n i c a l a c t i o n ,-
be a "dry" c o n s t r u c t i o n m e t h o d .F o u n d a t i o n w a l l s w i t h a n a i r s p a c e on t h e o u t s i d e should not be p r o v i d e d w i t h a s p e c i a l s u r f a c e t r e a t m e n t on t h e o u t s i d e with t h e e x c e p t i o n of a s e c t i o n a p p r o x i m a t e l y 0 . 5 m above the footing. Such w a l l s d o not r e q u i r e a n y s p e c i a l ( w a l l ) d r a i n a g e m a t e r i a l . It i s , h o w e v e r , n e c e s s a r y t h a t t h e d r a i n a g e s y s t e m i n g e n e r a l f u n c t i o n s s a t i s f a c t o r i l y .
Objective a n d t e s t p r o g r a m
At t h e D i v i s i o n of Building T e c h n o l o g y , f u n c t i o n a l t e s t s with m o d e r n e x t e r n a l b a s e m e n t w a l l c o n s t r u c t i o n s have been conducted d u r i n g t h e p a s t few y e a r s , The p u r p o s e of t h e s e i n v e s t i g a t i o n s h a s been t o s t u d y the d i f f e r e n t t y p e s of c o n s t r u c t i o n with a view t o h e a t i n s u l a t i o n a n d m o i s t u r e p r o b l e m s , s o a s t o a r r i v e a t t e c h n i c a l l y and e c o n o m i c a l l y c o r r e c t s o l u t i o n s w h i c h m a k e p o s s i b l e a b e t t e r i n d o o r c l i m a t e i n b a s e m e n t s . T h e s e s t u d i e s h a v e , a m o n g s t o t h e r t h i n g s c o m p r i s e d t h e new t y p e s of c o n s t r u c t i o n a c c o u n t e d f o r a b o v e . The t e s t p r o g r a m included a l a r g e n u m b e r of i t e m s , i n t e r a l i a , t h e d e t e r m i n a t i o n of m o i s t u r e r a t i o s a n d t e m p e r a t u r e s i n d i f f e r e n t m a t e r i a l s and i n t h e g r o u n d , t h e d e t e r m i n a t i o n of t h e h e a t f l u x t h r o u g h t h e c o n s t r u c t i o n s , t h e e f f e c t of, f o r e x a m p l e , f l o a t i n g ( p l a s t e r m o r t a r ) with o r without a d d i t i v e s and of a s p h a l t c o a t i n g s on t h e m o i s t u r e c o n t e n t of t h e b a s e m e n t c o r ~ s t r u c t i o n s . The e f f e c t of m o i s t u r e 011 t h e c o e f f i c i e n t of t h e r m a l c o n d u c t i v i t y of t h e m a t e r i a l s
h a s a l s o b e e n s t u d i e d .
T e s t methodolorrv a n d s c o p e
T h e i n v e s t i g a t i o n s have been c a r r i e d out p a r t l y in t h e f o r m of l a b o r a t o r y t e s t s a n d p a r t l y a s f i e l d s t u d i e s .
T h e l a b o r a t o r y i n v e s t i g a t i o n s have m a i n l y comprised the following :
a ) T e s t s with f u l l - s c a l e m o d e l s of b a s e m e n t w a l l c o n s t r u c t i o n s have been c a r r i e d out. The m o d e l s w e r e d e s i g n e d i n s u c h a way t h a t t h e i r function c o r r e s p o n d s
-
a s f a r a s p o s s i b l e - t o t h a t of a c t u a l c o n s t r u c t i o n s 111 p r a c t i c e . T h e w a l l s w e r e e r e c t e d in p a i r s , T h es p a c e i n b e t w e e n t h e m w a s f i l l e d wrth s o i l w h i c h w a s ~ c t t e ~ i w l t h t h e h e l p of a s p r i n k l e r z i r r a ~ g e m e n t . The n ~ o i s t u r e content oi the c o n s t r u c t i o n s w a s d e t e r m i n e d s y s t e m a t i c a l l y , p a r t l y a t two diffcr?ilt m o i s t u r e c o n t e n t s of the s o i l m a t e r i a l ( 2 0 and 2 5 p e r c e n t b y weight r e s p e c t i v e l y ) jild p a r t l y with a ~ e m p e r a t u r e g r a d i e n t between t h e ground and the r o o m t e m p e r a t u r e c o r r e s p o n d i n g t o p r a c t i c a l c o n d l - t i o n s in w i n t e r .
b ) The h e a t f l u x and t e m p e r a t u r e c o n d i t i o n s of a n u m b e r of c o n s t r u c t i o n s have been i n v e s t i g a t e d with t h e h e l p of e l e c t r i c a l a n a l o g u e m o d e i s .
T h e f i e l d s t u d i e s c o m p r i s e d : a ) The d e t e r m i n a t i o n of m o i s t u r e r a t i o s of c o m p l e t e d e x t e r n a l b a s e m e n t w a l l c o n s t r u c t i o n s b y m e a n s of s a m p l e e x t r a c t i o n below g r o u n d f r o m f i n i s h e d h o u s e s . b) Systematic i n v e s t i g a t i o n s w i t h t h e h e l p of s p e c i a l t e s t h o u s e s . .lChese s t u d i e s i n c l u d e d , i n addition t o t h e d e t e r m i n a t i o n of t h e m o i s t u r e content i n e x t e r n a l b a s e m e n t w a l l s , the d e t e r m i n a t i o n of t e m p e r a t u r e s i n t h e g r o u n d adjoining t h e h o u s e and u n d e r it a s w e l l a s the a i r tern- p e r a t u r * s , the deterrrliriation of t h e h e a t t r a n s f e r t h r o u g h t h e e x t e r n a l b a s e m e n t w a l l s a t d i f f e r e n t l e v e l s , e t c .
Tile r e s e a r c h w o r k w a s planned i n s u c h a w a y t h a t e x p e r i e n c e gairLed and r e s u l t s obtained f r o m a s u b -inve s t i g a t i o n could b e u t i l i z e d i n t h e w o r k w i t h a n o t h e r p a r t of t h e i n v e s t i g a t i o n p r o g r a m . T h u s
e x p e r i e n c e g a i n e d f r o r n t h e e x c a v a t i o n s and s a m p l e e x t r a c t i o n s frcjn: f i n i s h e d h o u s e s w a s u s e d in t h e planning of t h e t e s t s w i t h w a l l n ~ o d e l s in t h e l a b o r a t o r y , T h e r e s u l t s o b t a i n e d f r o m t h e t e s t h o u s e s w e r e u s e d in t h e analogical inve s t l g a t i o n s
.
S o m e exarrlules of t h e r e s u l t s obtained In F i g s . 5 and 6 , t h e v a r i a t i o n i n t h e m o i s t u r e c o n t e n t with t r n l c in t h e d i f f e r e n t ! a y e r s of foundation w a l l s e r e c t e d of e n t i r e l y u n t r e a t e d a e r a t e d c o n c r e t e o r i i g h t w e i g h t c l i n k e r c o n c r e t e r e s p e c t i v e l y i s a c c o u n t e d f o r . A s c a n b e s e e n f r o m F i g . 4 , t h e u n t r e a t e d a e r a t e d c o n c r e t e w a l l s showed a f t e r only a b o u t 2 0 d a y s a v e r y c o l ~ s l d e r a b l e i n c r e a s e w h i c h r e s u l t e d in a r i s e of t h e n ~ o i s t u r r c o n t e n t i n t h e e n t i r e w a l l f r o m about 10 t o a l m o s t 65 p e r c e n t of d r y w e i g h t . T h e u n t r e a t e d lightweight c l i n k e r c o n c r ~ t e , w i t h a n i n i t i a l m o i s t u r e c o n t e n t of m o r e t h a n 10 p e r c e n t , d i d not s h o w a n y i n c r e a s e a n d t h e m o i s t u r e r a t i o r e m a i n e d p r a c t i c a l l y c o n s t a n t t h r o u g h o u t t h e e n t i r e t e s t i n g p e r i o d , T n e s e t e s t s h a v e shown t h a t a e r a t e d c o n c r e t e h a s a c o n s i d e r a b l y g r e a t e r c a p i l l a r y s u c t i o n c a p a c i t y t h a n l i g h t w e i g h t c l i n k e r c o n c r e t e , In c o n n e c t i o n w i t h t e m p o r a r y e x c e s s w a t e r p r e s s u r e a g a i n s t t h e f o u n d a t i o n w a l l i t h a s , h o w e v e r , b e e n shown t h a t t h e w a t e r r u n s p r a c t i c a l l y r i g h t t h r o u g h t h e w a l l of u n t r e a t e d l i g h t w e i g h t c o n c r e t c c l i n k e r . T h e s e t e s t s t h u s p r o v e t h a t , when u s e d below g r o u n d l e v e l , a e r a t e d c o n c r e t e m u s t be p r o v i d e d w i t h a p r o t e c t i v e l a y e r w h i c h effectively g i v e s a c a p i l l a r y b r e a k . F i g . 7 s h o w s t h e v a r i a t i o n i n t h e m o i s t u r e c o n t e n t w i t h t l m e in a n a e r a t e d c o n c r e t e w a l l p r o v i d e d w i t h m i n e r a l wool b a t t s o n t h e s i d e f a c i n g t h e g r o u n d , but o t h e r w i s e without a n y s u r f a c e t r e a t m e n t . .In t h i s t e s t , no wetting of the w a l l h a s b e e n o b s e r v e d , i n s t e a d , t h e m o i s t u r e c o n t e n t d e c r e a s e d . The d r y i n g - o u t w a s somewhat q u i c k e r i n connectiorl with a t e m p e r a t u r e d i f f e r e n c e b e t w e e n the i n n e r and o u t e r s i d e of t h e w a l l . A comparison of t h e m o i s t u r e c o n t e n t In
t h e w a l l i n t h i s t c s t w i t h the r e s u i t a5 g i v e n i n F i g . 5 s h o w s th;rt the r n i n e r a i wool c o , ~ s i ituteci a l a y e r , which effectiveiy i r o t k J c t a g a i n s t capillary a c t i o n .
T h e variaticjn or' t h e m o i s t u r e c o n t e n t w i t h t i m e in a n a e r a t e d collcretta w a l l p r o v i d e d wlth a n i n s u i a t i o n c o n s i s t i n g of a cold a s p h a l t coating and m i n e r a l w o o l b a i t s on t h e s i d e f a c i n g t h e g r o u n d i s show r l
in F i g , 8. A s i n t h e p r e v i o u s t e s t s , a t e m p e r a t u r e g r a d i e n t of a t o u t
1 5 ° C w a s e s t a b l i s h e d a f t e r about t h r e e m o n t h s between the i n n e r and o u t e r s i d e of t h e c o n s t r u c t i o n .
In t h i s c o n n e c t i o n i t c a n be o b s e r v e d t h a t t h e d r y i n g - o u t - c o n t r a r y t o t h e p r e v i o u s c a s e of a c o r r e s p o n d i n g c o n s t r u c t i o n without a n y s p e c i a l a s p h a l t coating - t a k e s p l a c e a t a c o n s t a n t and s o m e w h a t s l o w e r p a c e due t o t h e s e a l i n g s u r f a c e t r e a t m e n t ,
T h e m o i s t u r e c o n d i t i o n s i n a n a e r a t e d c o n c r e t e w a l l provicitd with a v e r t i c a l a i r s p a c e on t h e o u t s i d e of the w a l l
-
thc s i d e f a c i s gt h e g r o u n d - a r e i l l u s t r a t e d i n F i g , 9. The c o n s t r u c t i o n c o n s i s t , of an u n t r e a t e d a e r a t e d c o n c r e t e w a l l which i s p r o v i d e d with a s b e s t o s ce~rieril,
s h e e t s on the s i d e f a c i n g the g r o u n d . At t h e t o p , the a i r s p a c r i s in c o n t a c t w i i h the a i r . At t h e beginning of t h i s t e s t , the m o i s t u r t .
content oi t h e a t - r d t e a c o n c r e t e w a s r e l a t i v e l y h i g h , about 30 p e r c e n t , w h i c h r o u g h l y c o r r e s p o n d s t o the m o i s t u r e content on d e l i v e r y of t h e m a t e r i a l . A s c a n be s e e n from F i g . 8, t h e w a l l d r i e d c o m p a r a t i v e l y q u l c ~ i y . The a v e r a g e m o i s t u r e content f e l l f r o m about 30 p e r c e n t t o about 1 0 p e r c e n t i n s i x m o n t h s . T h e e q u i l i b r i u m m o i s t u r e r a t i o
-
about 5 p e r c e n t-
w a s obtained a f t e r about one y e a r .The m o i s t u r e contents d e t e r m i n e d f o r e x t e r n a l l y applied m i n e r a l wool batts below ground level have been v e r y low, usually l e s s than 1 p e r cent by weight, i. e . the m i n e r a l wool w a s p r a c t i c a l l y d r y . In t h i s connection i t should be noted t h a t the d e t e r m i n a t i o n s of the m o i s t u r e contents w e r e m a d e i m m e d i a t e l y a f t e r the snow-melting period when the ground i s c o n s i d e r e d to be a t i t s wettest.
In F i g . 10 the d e t e r m i n e d m o i s t u r e contents of a e r a t e d c o n c r e t e with a n e x t e r n a l protection comprising the parging of the wall and
the application of m i n e r a l wool batts against the foundation w a l l s a r e shown. The batts w e r e glued t o the w a l l s with asphalt. The p l a s t e r used contained a sealing compound. On the inside the wall r e m a i n e d untreated. 'Ihe inside of the a e r a t e d c o n c r e t e w a l l d r i e d v e r y quickly, f r o m a m o i s t u r e content of m o r e than 25 p e r cent by weight t o about
5 p e r cent within the c o u r s e of approximately s e v e n months. To s t a r t with, the o u t e r l a y e r r e t a i n e d i t s higher m o i s t u r e content a s
r e c o r d e d on d e l i v e r y , but subsequently d r i e d considerably. After about 2 1/2 y e a r s , the a v e r a g e m o i s t u r e content of the e x t e r n a l basement wall f e l l f r o m about 30 p e r cent t o about
9 p e r cent. T h i s f i g u r e t e n d s
t o d e c r e a s e even f u r t h e r . Thus the construction shows a favourable drying -out p r o c e s s . The a v e r a g e m o i s t u r e content would s e e m tobecome considerably lower than t h a t d e t e r m i n e d f o r s o - c a l l e d conventional s t r u c t u r a l d e s i g n s .
Some of the foundation w a l l s of two t e s t h o u s e s w e r e provided with a d e n s e s u r f a c e l a y e r and s o m e with a ventilated a i r s p a c e o r m i n e r a l wool b a t t s r e s p e c t i v e l y , Fig. 11
-
14. In one c a s e , the d e n s es u r f a c e l a y e r c o n s i s t s of a p l a s t i c sheeting (Bithuthene) e n t i r e l y glued t o the a e r a t e d c o n c r e t e , F i g s . 11
-
12, and i n the o t h e r c a s e of s o - called m e m b r a n e coating, F i g . 13. The drying-out of the a e r a t e dw a l l s w e r e provided with a s e a l on the outside. So f a r , the e x t e r n a l w a l l l a y e r h a s not d r i e d a t a l l o r only v e r y little ( s e e F i g s . 12 and 13). P e r h a p s t h i s l a y e r will d r y out a s t h e i n n e r l a y e r s c o m e even n e a r e r t h e v a l u e s of e q u i l i b r i u m . Although the a v e r a g e m o i s t u r e contents in t h e s e w a l l s have become somewhat s m a l l e r
-
m a i n l y a s a r e s u l t of thed r y i n g - o u t of the i n n e r wail l a y e r - t h e y a r e s t i l l c o n s i d e r a b l y h i g h e r t h a n t h o s e of c o r r e s p o n d i n g w a i l s without a sealing l a y e r .
In a e r a t e d c o n c r e t e walls with a ventilated a i r s p a c e o r m i n e r a l wool b a t t s on the outside i t c a n be noted t h a t the a v e r a g e
m o i s t u r e content of t h e w a l l s d e c l i n e s t o w e l l u n d e r 1 5 p e r c e n t d u r i n g t h e f i r s t y e a r . The e q u i l i b r i u m m o i s t u r e contents would s e e m t o become c o n s i d e r a b l y srrialler,
T h u s t h e field s t u d i e s p r o v e t h a t e x t e r n a l b a s e m e n t w a l l s of a e r a t e d c o n c r e t e with a d e n s e e x t e r n a l l a y e r of, f o r e x a m p l e , p l a s t i c sheeting c a n only d r y t o w a r d s the i n s i d e . A s a r e s u l t of t h i s t h e d r y i n g -out of t h e e n t i r e wall i s v e r y slow. The o u t e r wall l a y e r r e m a i n s v e r y d a m p f o r a c o n s i d e r a b l e length of t i m e . However, in
t h e t e s t s no univocal tendency could be o b s e r v e d which would indicate t h a t a f u r t h e r accumulation of m o i s t u r e t a k e s p l a c e in the o u t e r l a y e r i n addition t o the i n h e r e n t m o i s t u r e on c o n s t r u c t i o n . When reducing the d e n s i t y of t h e o u t e r l a y e r by u s i n g , f o r e x a m p l e , a p l a s t e r p a r g i n g and a l a y e r of adhesive f o r m i n e r a l wool batt s , a c e r t a i n d r y i n g -out would s e e m t o be p o s s i b l e even t o w a r d s the outside. A c o n s i d e r a b l y
4
q u i c k e r d r y i n g - o u t p r o c e s s i s achieved with a ventilated a i r s p a c e
1
o r with m i n e r a l wool b a t t s a g a i n s t t h e foundation wall.
F i g u r e 1 5 shows the t h e r m a l r e s i s t a n c e of a n e x t e r n a l b a s e m e n t w a l l , i n s u l a t e d with m i n e r a l wool on the outside. The h e a t r e s i s t a n c e
(excluding s u r f a c e r e s i s t a n c e and the t h e r m a l r e s i s t a n c e of t h e ground) h a s been d e t e r m i n e d a t f o u r d i f f e r e n t l e v e l s . The i l l u s t r a t i o n c l e a r l y shows t h a t the m i n e r a l wool s l a b i n c r e a s e s t h e t h e c m a l r e s i s t a n c e c o n s i d e r a b l y .
In F i g . 15, the o v e r - a l l heat t r a n s m i s s i o n coefficients a r e given f o r the s a m e wall a s in F i g . 14, p a r t l y f o r the wall s e c t i o n above ground and p a r t l y f o r the s e c t i o n below ground level. In the s e c t i o n below ground l e v e l , the t h e r m a l insulating c a p a c i t y of t h e g r o u n d h a s a l s o been taken into account. As can be s e e n f r o m the
f i g u r e , t h e u-value f o r the wall s e c t i o n below ground l e v e l h a s been 2
"
d e t e r m i n e d t o slightly m o r e t h a n 0 . 3 k c a l / m h C , i. e . t h e t h e r m a l insulating c a p a c i t y of the wall i s a p p r o x i m a t e l y t h e s a m e a s that of a w e l l - i n s u l a t e d o u t e r w a l l above ground. The u-value of the b a s e m e n t
L
w a l l s e c t i o n above ground h a s been d e t e r m i n e d t o 0 . 8 5 kcal/m h
" C ,
i. e . the u-value i s a l m o s t t h r e e t i m e s a s big a s t h a t of the wall section below ground. T h i s value c a n be c a n s i d e r e d t y p i c a l f o r a conventionale x t e r n a l b a s e m e n t wall without additional insulation. A s a s t a n d a r d value i t c a n be reckoned that h = 0 . 0 5 kcal/m h
" C
f o r m i n e r a l wool below ground.S t r u c t u r a l D e s i g n s
1 ) In t h e forthcoming m o r e complete r e p o r t i t i s suggested t h a t a
calculation m e t h o d based on functional r e q u i r e m e n t s and i n r e l a t i o n t o d i f f e r e n t m o i s t u r e l o a d s be introduced.
2) F i g u r e s 17 and 18 show two s t r u c t u r e s with m i n e r a l wool s h e e t , which i s p r o v i s i o n a l l y approved by the G o v e r n m e n t De sign D e p a r t m e n t . When f i n e r g r a i n e d m a t e r i a l i s u s e d a s backfill, t h e m o i s t u r e loads on t h e foundation w a l l a r e r a t e d somewhat h i g h e r .
In t h i s c a s e , the vapour b a r r i e r should be applied t o p a r g i n g , which i s p r i m a r i l y intended t o a c t a s a n e x t r a b a r r i e r t o e x c e s s w a t e r p r e s s u r e . An efficiently applied b r u s h coating h a s been found t o i m p e d e even t h e high l e v e l of c a p i l l a r y action of a m a t e r i a l like p o r o u s c o n c r e t e ,
w h e r e a s we have not yet been able t o e s t a b l i s h t h a t the u s e of s o - c a l l e d w a l l - s e a l i n g compound r e s u l t s in a n y s u b s t a n t i a l i m p r o v e m e n t o v e r a b r u s h coating.
3) Two design solutions with e x t e r n a l a i r s p a c e s a r e shown in F i g s . 19 and 20. The one in F i g . 19 h a s a r e l a t i v e l y s m a l l a i r space (approximately
9 m m ) , which i s provided by a s p e c i a l p l a s t i c wall
s h e e t . The foundation wall s h e e t i s attached a t the t o p of a foundation wall using a d e t a i i s o t h a t the a i r space i s s e a l e d . In the o t h e rc a s e ( F i g . 20) the a i r s p a c e i s l a r g e r (approximately 2 5 mm) f o r which a s b e s t o s cement s h e e t s on wooden studs a r e used. The a i r space i s connected to the e x t e r n a l a i r space of the above g r a d e wall and t o the outside a i r a t the junction. T h u s , the foundation wall
a l s o h a s a cladding of a s b e s t o s cement s h e e t s . T h i s s c h e m e provides the e s s e n t i a l s f o r a completely "dry" building m e t h o d , which can be employed, r e g a r d l e s s of the outside climate.
4 ) F i g u r e 21 shows a n example of a design d e t a i l a t the top of the
foundation wall. The object h e r e i s t o d i v e r t the s u r f a c e w a t e r f r o m the i m m e d i a t e vicinity of the wall, during heavy r a i n , f o r example. A s we pointed out e a r l i e r , i t i s e s s e n t i a l t h a t the s o i l slopes away f r o m the house. Of c o u r s e , t h i s i s p r e s c r i b e d in the Swedish Building S t a n d a r d s , but, unfortunately, the recommendation i s not always
followed.
5 ) The w a t e r f r o m the roof will be d i s c h a r g e d d i r e c t l y into the s t o r m s e w e r via the r a i n - w a t e r pipe. F i g u r e 2 2 shows how the l a t t e r c a n be connected to the s t o r m s e w e r t o e n s u r e s i m p l e and convenient a c c e s s f o r cleaning p u r p o s e s ,
6 ) Our e x p e r i e n c e shows that m o i s t u r e contents a r e usually
g r e a t e s t w h e r e the wall joins the footing. F i g u r e 23 i l l u s t r a t e s a suggested detail. The capacity of the d r a i n a g e s y s t e m m a y not always be adequate. T h i s m e a n s that occasional l o c a l w a t e r p r e s s u r e e x c e s s e s cannot be avoided a t the bottom, n e a r the joint. T h e r e f o r e , we suggest t h a t an o u t e r waterproof l a y e r be extended up about 0. 5 m above the footing. The waterproof l a y e r m a y c o n s i s t of a m e m b r a n e ( F i g . 24
shows how t h i s i s achieved with Bithuthene) o r parging and two applications of asphalt.
Conclusion
Investigations t o d a t e indicate that the t h e o r e t i c a l advantages of the new t y p e s of s t r u c t u r e s a r e r e a l i z e d i n p r a c t i c e . C o m p a r e d with t r a d i t i o n a l b a s e m e n t d e s i g n s , t h e s e afford, among o t h e r s , the following advantages:
the possibility of formulating d e s i g n s f o r different m o i s t u r e loads; f a s t e r drying of walls t o a lower m o i s t u r e level ( m o i s t u r e r a t i o
balance) and thus b e t t e r heat insulation;
t h e a l t e r n a t i v e with m i n e r a l wool sheeting provides a simple way of obtaining good s u p p l e m e n t a r y insulation;
the backfill r e q u i r e m e n t s can be reduced;
g r e a t e r protection against w a t e r penetration of c r a c k s in b a s e m e n t w a l l s
.
The new d e s i g n s e n s u r e a living s p a c e f o r the b a s e m e n t which i s c o m p a r a b l e t o the n o r m a l living space. The b a s e m e n t space can be utilized t o g r e a t e r advantage, s o that m u c h m o r e living s p a c e b e c o m e s available without enlarging the house a r e a . T h i s i m p l i e s s u c h a n i n c r e a s e in the quality of s m a l l h o u s e s t h a t t h e i r c o s t level in r e l a t i o n t o a p a r t m e n t houses i s enhanced.
Water penetration
a
1-
Moist a i r infiltration F i g u r e I . D i a g r a m m a t i c s k e t c h showing t h e relevant s o u r c e s of m o i s t u r e-
i n addition t o t h e inherent humidity on construction-
i n e x t e r n a l basement walls.Rendering-- Indoor s u r f a c e t r e a t m e n t , Coating with o r hot asphalt Thin p r i m e r and a c o a r s e float of c e lime m o r t a r KC 11 /4 Optional backfill 'Theoretical lint2 pp Drained backfill \ \ - Levelling with g r a v e l Polyethylene film I. F i g u r e 2. Example of m o i s t u r e protection in a c c o r d a n c e with the conventional method in m a s o n r y construction. The asphalt coating constitutes a r e l a t i v e l y thick c a p i l l a r y breaking l a y e r , which a l s o i m p e d e s t h e d r y i n g out of t h e foundation wall.
Bearing wall
M i n e r a l wool batts
Backfill
F i g u r e 3. E x t e r n a l basement wall insulated on t h e outside with m i n e r a l wool b a t t s . The backfill c o n s i s t s of g r a v e l o r sand, f o r example. If i t contains f i n e r m a t e r i a l , such a s c l a y - f r e e fine sand o r m o r a i n e , we would, until f u r t h e r r e s u l t s become available, suggest that the foundation wall be p a r ged. --7 7
1
I1.
. .
I Bearing wall Sheet m a t e r i a l ( a s b e s t o s c e m e n t s h e e t type on p r e s s u r e c r e o s o t e d wood s t u d s ) Backfilling ' d , 2F i g u r e 4. E x t e r n a l basement wall provided with air s p a c e on t h e o u t e r s i d e (for example, a s b e s t o s c e m e n t sheeting on t r e a t e d wood s t u d s ) . T h i s r e p r e s e n t s a f o r m of "two-stage s e a l . I ' The a i r s p a c e c a n
e i t h e r be ventilated o r unventilated. Available excavated material. m a y be used a s backfill.
M o i s t u r e content,
7'0
by d r y weight0 LO 80 120 160 200
Days
F i g u r e 5. Foundation wall of unprotected a e r a t e d c o n c r e t e . T h e m o i s t u r e content of t h e s o i l is about 20% by weight. The m o i s t u r e content of t h e a e r a t e d c o n c r e t e h a s i n c r e a s e d within a v e r y s h o r t period of t i m e
-
about 20 d a y s-
f r o m about 1070 t o about65% i. e. t h e a e r a t e d c o n c r e t e i s a l m o s t w a t e r - s a t u r a t e d .
0 LO 8 0 120 160 200 24 0 2 80 Days
F i g u r e
6.
Foundation wall of unprotected light -weight clinker c o n c r e t e . The m o i s t u r e content of the s o i l i s about 207'0. Initially, the m o i s t u r e content ranged between 10 and 15%. This m o i s t u r e r a t i o was maintained f o r the i n t e r m e d i a t e l a y e r and the l a y e r n e a r e s t the soil, while the i n n e r l a y e r d r i e d t o about 5%.(The m a t e r i a l i s on the other hand highly p e r m e a b l e in the p r e s e n c e of e x c e s s i v e w a t e r p r e s s u r e ) .
M o i s t u r e content,
%
by d r y weightT e m p e r a t u r e g r a d i e n t
1
1
-4
through t h e w a l l \Days F i g u r e 7. Foundation wall of a e r a t e d c o n c r e t e insulated with 5 c m
m i n e r a l b a t t s (density 150 kg/rn?. The m o i s t u r e content of t h e s o i l i s about 20%. After a p p r o x i m a t e l y 3 months, t h e t e m p e r a t u r e of t h e s o i l f e l l f r o m about t20 " C t o about $5 " C , i. e. t h e t e m p e r a t u r e difference between the i n n e r and o u t e r s i d e had been about 15 "C. During t h e f i r s t 3 months a slight d e c r e a s e in t h e m o i s t u r e content of t h e a e r a t e d c o n c r e t e was obtained. After t h e reduction in t h e t e m p e r a t u r e of t h e s o i l , the d r y i n g - o u t p r o c e s s took p l a c e m o r e quickly and the m o i s t u r e content would s e e m t o b e c o m e s t a b l e a t about 5%.
M o i s t u r e content,
OJo
by d r y weightI
I 'I I T e m p e r a t u r e g r a d i e n t
1
~
- II---
-t
through the wall
-)-- - - --
Days F i g u r e 8. Foundation wall of a e r a t e d c o n c r e t e insulated with an
e x t e r n a l cold a s p h a l t coating and 5 cm of m i n e r a l wool, d e n s i t y 150 k g / m 3 ( l a b o r a t o r y t e s t ) .
T h e e x p e r i m e n t a l conditions w e r e the s a m e a s t h o s e in F i g u r e 7. During the f i r s t 3 months t h e a e r a t e d c o n c r e t e d r i e d slowly. Following reduction of s o i l t e m p e r a t u r e , t h e a e r a t e d c o n c r e t e continued t o d r y out a t a p p r o x i m a t e l y t h e s a m e slow pace a s d u r i n g the f i r s t t e s t period. Cf. F i g u r e 7. The l a y e r of asphalt i s t h e r e f o r e shown t o p r e v e n t d r y i n g o u t w a r d s .
Moisture content,
70
by d r y weightDays
F i g u r e
9.
Foundation wall of a e r a t e d c o n c r e t e provided with a n e x t e r n a l a i r s p a c e and an a s b e s t o s cement s h e e t mounted on v e r t i c a l , p r e s s u r e - i m p r e g n a t e d woodenstuds ( l a b o r a t o r y t e s t ) . At the top, the a i r s p a c e was open t o the a i r in the room. T h e m o i s t u r e
content of the s o i l i n m o s t c a s e s amounted t o between 1 7 and 2 0 p e r cent by weight. T h e initial m o i s t u r e contents in the a e r a t e d c o n c r e t e have been r e l a t i v e l y high
-
c l o s e t o the n o r m a l m o i s t u r e content ond e l i v e r y . However, the drying-out p r o c e s s i s quick. Already a f t e r about 5 months, t h e a v e r a g e m o i s t u r e content i s lower than 10% by weight. The equilibrium m o i s t u r e content would s e e m t o r a n g e between 4 and 570 which i s obtained a f t e r approximately 1 y e a r .
M o i s t u r e content,
a/o
by d r y weight L3 1 u Mede varae I Days F i g u r e 10. V a r i a t i o n s in m o i s t u r e contents r e c o r d e d in field s t u d i e s conducted with e x t e r n a l b a s e m e n t wall c o n s t r u c t i o n s of 2 5 c m a e r a t e d c o n c r e t e . On t h e outside, t h e w a l l s w e r e p a r ged with p l a s t e r containing a wall s e a l i n g compound and provided with 3 c m m i n e r a l wool b a t t s (volume weight150 k g / m 3 ) glued t o t h e wall with a s p h a l t . T h e backfill c o n s i s t e d of c l a y e y m o r a i n e .
The i n n e r l a y e r of the a e r a t e d c o n c r e t e d r i e d quickly. After about 6 months t h e m o i s t u r e r a t i o f e l l f r o m about
2 5 % t o about
670.
The o u t e r l a y e r d o e s not d r y at thebeginning, but a slow d r y i n g p r o c e s s c a n be o b s e r v e d a f t e r s o m e t i m e . After a l m o s t 3 y e a r s , t h e o u t e r l a y e r h a s d r i e d f r o m 3 0 % t o about 147'0 and i t a p p e a r s t h a t t h e drying-out p r o c e s s s t i l l continues in that l a y e r . T h e a v e r a g e m o i s t u r e content in the wall dropped down t o about
970
d u r i n g the s a m e p e r i o d .M o i s t u r e content,
70
by d r y weightF i g u r e 11. In one and the s a m e house, the e x t e r n a l b a s e m e n t walls of a e r a t e d c o n c r e t e w e r e provided with two fundamentally d i f f e r e n t types of m o i s t u r e protection. In one section, a p l a s t i c sheeting was glued e n t i r e l y against the a e r a t e d c o n c r e t e thus yielding an a l m o s t completely d e n s e o u t e r l a y e r . In the o t h e r section, a ventilated a i r s p a c e was formed with the help of a s b e s t o s c e m e n t s h e e t s . T h e backfill in t h i s c a s e consisted of h a r d clay.
The drying-out p r o c e s s i s quicker if t h e r e i s a ventilated a i r s p a c e on the outside, even though the m o i s t u r e content of this wall s e c t i o n h a s in fact been somewhat lower than i n the p a r t of the a e r a t e d c o n c r e t e wall with a d e n s e o u t e r l a y e r . Already within one y e a r t h e a v e r a g e m o i s t u r e content i s lower than 15% by weight, while it i s m o r e than 20% in t h e p a r t of the wall w h e r e the a e r a t e d c o n c r e t e h a s a "dense" m o i s t u r e b a r r i e r on t h e outside.
M o i s t u r e c o n t e n t ,
70
by d r y weightF i g u r e 1 2 . T h e f i g u r e r e f e r s t o t h e s a m e c o n s t r u c t i o n s a s i n F i g u r e 11,
and i s i n t e n d e d t o i l l u s t r a t e t h e m o i s t u r e d i s t r i b u t i o n i n t h e r e l e v a n t w a l l a f t e r n d a y s c a l c u l a t e d f r o m t h e b e g i n n i n g of t h e t e s t when t h e foundation w a l l s w e r e n e w l y e r e c t e d . With a d e n s e o u t e r l a y e r o n t h e a e r a t e d c o n c r e t e w a l l , t h e w a l l d r i e s out m a i n l y t o w a r d s t h e i n s i d e . T h i s i m p l i e s t h a t t h e o u t e r l a y e r of t h e w a l l h a r d l y d r i e s a t a l l d u r i n g t h e f i r s t y e a r . An e x t e r n a l a i r s p a c e a l l o w s of t h e d r y i n g - o u t of t h e e n t i r e w a l l and t h u s t h e m e a n v a l u e b e c o m e s c o n s i d e r a b l y l o w e r .
Moi I I 0 1 I I 0 100 200 300 LOO 11/9-70 20112-70 3013-71 ElF-71 1611 0-71 Days F i g u r e 13. In t h i s c a s e , t h e m o i s t u r e p r o t e c t i o n of t h e a e r a t e d c o n c r e t e c o n s i s t s of a m e m b r a n e coating
-
the outside of t h e w a l l i s p r a c t i c a l l y watertighli. Also in t h i s c a s e t h e a e r a t e d c o n c r e t e could only d r y out t o w a r d s t h e i n s i d e , and a t t h e beginning t h e r e was h a r d l y a n y d r y i n g out in t h e o u t e r p a r t of t h e a e r a t e d c o n c r e t e wall.M o i s t u r e content, '$I by d r y weight
Days
F i g u r e 14. As an a l t e r n a t i v e t o the vapour b a r r i e r shown in F i g u r e 13, m i n e r a l wool b a t t s , spot-glued with a s p h a l t , w e r e a l s o used in t h e s a m e house. The backfill c o n s i s t e d of g r a v e l . As t h e m i n e r a l wool allows vapour t r a n s m i s s i o n , d r y i n g out w a s p o s s i b l e both t o w a r d s t h e i n s i d e and outside. After about
1 y e a r t h e a v e r a g e m o i s t u r e content had fallen t o a l m o s t 10% by weight f r o m an i n i t i a l value of a p p r o x i m a t e l y 25%.
Thermal r e s i s t a n c e m ' h ' ~
k cal
Fe
b Mar A p r i l May19 66
F i g u r e 15. Examples of t h e r m a l r e s i s t a n c e d e t e r m i n e d f o r an e x t e r n a l basement wall of a e r a t e d c o n c r e t e with an outside insulation of m i n e r a l batts (excluding s u r f a c e r e s i s t a n c e and heat
r e s i s t a n c e of the ground r e s p e c t i v e l y ) . T h e l a r g e difference between the t h e r m a l r e s i s t a n c e of t h e wall section above
ground and the p a r t below ground level, A and B respectively,
C and D i s mainly d u e to the t h e r m a l r e s i s t a n c e of the m i n e r a l wool batts in c a s e B, C and D. The v a r i a t i o n s between the t h e r m a l r e s i s t a n c e of the wall s e c t i o n s below ground level a r e , on the other hand, due t o v a r i a t i o n s in t h e m o i s t u r e r a t i o of the a e r a t e d c o n c r e t e . The r e s u l t s indicate that in foundation walls with v e r t i c a l insulation the s t a n d a r d value of the coefficient of t h e r m a l conductivity of t h e relevant m i n e r a l wool quality can, i n p r a c t i c e , be taken t o be about
k cal
O v e r -all heat t r a n s f e r coefficient
-
rn2h.c
Feb Mar April
1966
F i g u r e 1 6 . C o m p a r i s o n between the over- ail h e a t t r a n s m i s s i o n coefficients of a foundation wall ( 2 0 c m of a e r a t e d c o n c r e t e ) above ground l e v e l , A , and the "equivalent" u-value of a foundation wall
( 5 c m m i n e r a l wool b a t t s t 2 0 c m a e r a t e d c o n c r e t e t s o i l ) below ground level, C. The continuous l i n e s i l l u s t r a t e the values b a s e d on d i r e c t d e t e r m i n a t i o n s of h e a t flux and t e ~ n p e r a t u r e and t h e dashed l i n e s show t h e o r e t i c a l l y calculated v a l u e s . As c a n be s e e n f r o m the d i a g r a m t h e h e a t t r a n s m i s s i o n coefficients of t h e wall s e c t i o n below ground l e v e l i s c o n s i d e r a b l y s m a l l e r t h a n t h a t of t h e c o r r e s p o n d i n g wall s e c t i o n above ground level.
Gutter pipe which i s __ connected t o a w a t e r pipe Foundation wall
r e n d e r i n g ~ ~~
Backfill of g r a v e l o r sand, grain s i z e -- according to Swedish Building Standards
Min 5 c m ground sheet 8 1 7 of Rockwool with folded s e a m s . The s e a m s a r e
spot-cemented with cold asphalt.
Repair of chipped c o r n e r and edging with cement m o r t a r ~ 1 0 0 / 4 5 0 in a c c o r d a n c e
ding Standards 24: 2 3 2 1 Bearing Wall
5 cm c o n c r e t e floor. The floor should
Cement m o r t a r ~ 1 0 0 / 4 5 0
-
Swedish Draining m a t e r i a l Building Standards 24:2321(with low c a p i l l a r y
action) 2 coatings of cold asphalt
50 c m above footing
\ C e m e n t m o r t a r s c r e e d with
a
1:2 slope o v e r which the insulation is extendedF i g u r e 17. E x t e r n a l b a s e m ent wall t e m p o r a r i l y approved by t h e State Design Office. When t h e backfill i s composed of previous m a t e r i a l s u c h a s g r a v e l o r sand, we c o n s i d e r t h a t no e x t r a m o i s t u r e protection i s needed between the m i n e r a l wool and the brickwork, except on the lowest p a r t . Moisture p r e s s u r e s w e r e
observed t o be g r e a t e s t along the bottom of the footing, f o r which r e a s o n we suggest a s e p a r a t e o u t e r asphalt o r m e m b r a n e covering on this p a r t .
