The National Research Council and Roofing Research

Texte intégral

(1)

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 Paper (National Research Council of Canada. Division of Building

Research), 1963-10

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=4d80a1fa-5fe6-439a-bf0b-6b8e56e992b4 https://publications-cnrc.canada.ca/fra/voir/objet/?id=4d80a1fa-5fe6-439a-bf0b-6b8e56e992b4

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/10.4224/20375410

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

The National Research Council and Roofing Research

(2)

Ser TH1 NzLT2 no" t51 e . 2 BLDG

(3)
(4)

NATIONAL RESEARCH COUNCIL CANADA

DIVTSION OI' BUILDING RESEARCH

THE NATIONAL RESEARCH COUNCIL AND ROOT'ING RESEARCH

by M. C. Baker

A N A I . Y Z E D

T e c h n i c a l P a p e r No. l5l of the

Divislon of Bulldlng Research

P a p e r p r e a e n t e d at the Fourth Annual Meetlng of the

Canadlan Rooflng Contractorgr Aasoclatlon, M o n t r e a l , 5 M a r c h 1 9 6 3 .

OTTAWA October 1963

(5)

THE NATIONAL RESEARCH COUNCIL AND ROOFING RESEAR-CH

b y M . C . B a k e r

T h e arnount of research done by Canadlan lndustrles has b e e n rapldly increaslng ln recent years as the lndustrles have grown, a n d a t t h e p r e s e n t t i r n e r e a e a r c h l s a c c e p t e d a s a n l n t e g r a l p a r t o f t h e lndustrial pattern. M a n y rooflng materlal r n a n u f a c t u r e r s , w h o f o r r n an lmportant part of the rooflng lndustry, h a v e r e s e a r c h

f a c l l l t l e s w h e r e work ls dlrected toward improvernent and developrnent o f p r o d u c t s . T h e d e v e l o p r n e n t of new and lmproved products ls

a l m o s t u n l v e r s a l l y a c c e p t e d b y l n d u s t r y a s n e c e s s a r y f o r b u e l n e s s p r o g r e s s a n d t h e e x t e n s l o n of trade rnarkets. T h t s appreclatlon o f r e s e a r c h by lndustry ln canada ls falrly recent, but the Natlonal R e s e a r c h C o u n c l l h a s b e e n c o n c e r n e d a b o u t l n d u s t r l a l r e e e a r c h e l n c e

1 9 1 7 , T h e C o u n c l l h a s w o r k e d w l t h , a n d r e n d e r e d s e r v l c e t o , Canadl.an lndustrles durlng all this tlrne. Slnce lts forrnatlon the C o u n c l l has worked wlth lndustry ln prornotlng lndustrlal research, h a e f l n a n c e d research at Canadlan unlversltles a n d l n t h e Counclils l a b o r a t o r i e s , a n d r n o r e recently has lntroduced a systern of dlrect a s e l s t a n c e f o r r e s e a r c h b y l n d u s t r y .

T h e D l v l s l o n of Bulldlng Research of the Natlonal Research c o u n c l l has for sorne years been conductlng a modest program of r o o f l n g research and welcornes the opportunlty of presentlng thl.s p a p e r to thls young and actlve assoclatlon, t h e o t h e r k n p o r t a n t p a r t

of the rooflng lndustry. Since many rnay not be famlllar wlth the work o f t h e National Research Councll, a short hlstorlcal s k e t c h and ,, d e s c r i p t l o n will be glven, as an lntroductlon to the work of the Dlvlglon o f B u i l d i n g Research.

THE NATIONAL RESEARCH COUNCIL

T h e Natlonal Research Councll ls the short tltle of the F l o n o r a r y Advlsory C o u n c l l f o r Sclentlfic and Industrlal Research of C a n a d a . T h e Advisory C o u n c l l ls cornposed of twenty-one rrrembers, w i t h the Presldent and three Vlce-Presldents a s p e r r n a n e n t offlcere, a n d seventeen others each appolnted for three-year terrns and drawn f r o r n the senlor sclentlflc staff of unlversltles a n d f r o r n lndustry and l a b o u r , s e r v l n g wlthout salary. T h e f u n c t l o n of the Council ls to act a g t h e natlonal clvlllan research agency, and advlsor to the Federal G o v e r n r n e n t on sclentlfic and lndustrlal research, e x c l u d l n g that c a r r l e d out for defence, agrlculture, m i n l n g , f l s h e r l e s a n d f o r e s t r y .

(6)

z

-T h e Councll reports to the Chalrrnan of the Frlvy Councll C o m r n l t t e e on Sclentlflc and Industrlal Research whlch conslsts of t h e M t n l e t e r s o f t e n D e p a r t m e n t s o f G o v e r n m e n t . T h e C o u n c l l l s t h u s a p u b l l c a g e n c y eupported by publlc funds, reportlng a n n u a l l y t o t h e P a r l l a r n e n t o f C a n a d a , b u t p e r r n l t t e d a greater rneasure of

f l e x t b l l t t y l n operatlon than would be posslble as a Federal Govern-rnent DepartGovern-rnent.

T h e Councll was formed ln 1916 and for sorne years acted ln an advlsory capaclty only. Laboratory work by the Councll began I n L 9 2 5 ; f a c l l l t l e s f o r undertaking large-scale l a b o r a t o r y r e s e a r c h b e c a m e a v a l l a b l e to the Councll when the central laboratory o n S u s e e x D r l v e ln Ottawa was opened ln 1932" The developrnent of the Montreal R o a d L a b o r a t o r { e s b e g a n l n 1 9 3 9 . T h e s l t e a t t h a t t l m e w a s 1 3 0 a c r e s l n e x t e n t , b u t t o d a y c o m p r l s e s 4 0 0 a c r e s . T h e r e a r e a t p r e s e n t

a b o u t 7 0 b u l l d l n g s on this site, lncludlng storage and other anclllary b u l l d l n g s . T o d a y t h e C o u n c i l has a total staff of about 2500,

L n c l u d l n g 730 scientific research staff, more than 900 technlcal p e r s o n n e l and over 800 general servlce and adrnlnistrative s t a f f . I t c a r r l e s o u t lts work through sclentlflc dlvlslons of Applled Blology, A p p l l e d a n d Pure Physlcs, A p p l l e d a n d P u r e C h e r n l s t r y , a n d

e n g l n e e r l n g dlvlsions of MechanlcaL, Aeronautlcal, R a d l o and

E l e c t r l c a L , a n d B u l l d l n g R e e e a r c h . I t s l a b o r a t o r l e s o u t s l d e O t t a w a lnclude the Pralrie Reglonal Laboratory ln Saskatoon and the Atlantlc Reglonal Laboratory ln Hallfax.

T h e Natlonal Research Councll of Canada ls thus unlque ln t h e way ln whlch it ls organlzed, flnanced, and allowed to carry on t t s w o r k . T h e s e f e a t u r e s ln large measure deterrnlne the favourable condltlons under whlch all the Dlvlstons wlthln the Councll can operate.

THE DIVISION OF BUILDI NG RESEARCH

T h e D l v l s l o n o f Bullding Research was established by the N a t { o n a l Researcli Councll tn 1947 to provlde a research servlce to t h e c o n s t r u c t l o n i n d u s t r y of Canada. A s s o c l a t e d wlth thls rnajor r e s p o n s l b l l i t y t o s t u d y p r o b l e r n s of constructlon f o r t h e tndustry g e n e r a l l y , t h e D l v t s l o n p r o v l d e s a speclal research servlce ln the h o u s i n g f { e l d to Central Mortgage and Houslng Corporatlon. T h e D i v i s l o n also furnishes secretarlal a n d t e c h n l c a l asslstance to the A s s o c l a t e Comrnlttee on the Natlonal Bullding Code.

T h e m a l n task of the Dlvlslon ls essentlaLly that of pro-w l d i n g lnforrnatlon to those pro-who need lt, tn deslgn pro-work, ln relatlon t o c o n s t r u c t l o n problems on the job, in connectlon wlth materlals

(7)

3

-a n d t h e l r propertles, o r e v e n ln asslsttng wlth analysls of

d l f f i c u l t l e s , p o o r p e r f o r m a n c e o r f a l l u r e s . T h e Divl.slon Llbrary h a s a n e x t e n s l v e coverage through books, perlodlcals a n d p a m p h l e t s l n the flelds of constructlon, a r c h l t e c t u r e , b u l l d i n g materlals, s o l l r n e c h a n l c s , heatlng and ventllatlng, f l r e , standards, codes and

s p e c l f l c a t l o n s . P u b l l a h e d papers and prlvate records of other b u l l d l n g research work are avallable to the Dlvlslon from research

organlzatlons all over the world. When lnforrnatlon ls not avallable f r o r n these 6ources, or from results of the work of the Dlvlslon, t h e n the procurement o f t h e lnforrnatlon s o r n e t l r n e s results ln e x p e r i m e n t a l r e g e a r c h work in the laboratory o r ln the fleld. Naturally guch work cannot be carrled out for Indlvlduals, but c o n s l d e r a t l o n w111 always be glven to problerns of natlonal lnterest a n d c o n c e r n .

T h e D l v l s l o n does not engage ln any consultlng

a r c h l t e c t u r a l o r englneerlng work, and lnforrnatlon ln answer to l n q u l r l e e ls based on the bastc butldlng sclence lnvolved. I n t e r e e t l n f a l l u r e s ls not ln determlnlng responslbtltty b u t rather lg related o n l y to the nature and cause of the fallure, s o t h a t ways rnay be d e t e r r n l n e d to prevent fallure, a n d s o l m p r o v e building rnethodg.

I n s o f a r ae posslble the Dlvisl.on concentrates on problerns t h a t are peculiar to Canada, whlch therefore must be studied |n thtg c o u n t r y . B e c a u s e of close llnks wlth bulldlng research organlzatlons i n o t h e r countrles, t h e D i v l s l o n can draw on thelr experlence with m o r e general problems. T w o of the factors that make bulldlng ln C a n a d a dlfferent from that ln other countries are geoLogy and cllmate. G e o l o g y determlnes foundatlon condltlons and the avallabllltyof

n a t u r a l bulldlng rnaterlals. C l l m a t e deterrnlnes the condltlons to w h l c h bulldlngs are subjected, and the condltlons that must be over-c o m e lf the bulldlngs are to be over-comfortable for uge. The Dlvislon d o e s not dupllcate work being carried out elsewhere in canada by F e d e r a l Government Departments, u n l v e r s l t i e s , a n d o t h e r research o r g a n l z a t l o n s "

A l l the workof the Divislon ts ultlrnately dlrected to the b e t t e r m e n t o f b u l l d l n g in the whole of Canada. To ensure natlon-wlde

s e r v l c e , the Divtsi.on has, in addltlon to the Bulldlng Regearch Centre ln ottawa, a Reglonal statlon ln Hallfax to serve the four Atlantic P r o w l n c e s , t h e P r a l r l e R e g i o n a l statlon in saskatoon to handle

p r o b l e m s pertalnlng to Pralrie c o n d l t l o n s , a n d t h e B r l t l s h C o l u r n b l a Statlon ln Vancouver to deal wlth lnqulrleg ernanatlng from that p r o v i n c e .

(8)

4

-B U I L D I N G SCIENCE AND -BUILDING PRACTICE

T h e w o r k of the Dlvision can be dtvlded lnto two areas of w o r k : B u l l d i n g S c l e n c e and Bulldlng Practlce.

B u t l d t n g Sclence 1s the terrn used to descrlbe the work of t h e e l g h t s e c t l o n s w h o s e m a l n c o n c e r n l s l a b o r a t o r y r e s e a r c h .

T h e r e a r e s e c t l o n s r e s p o n s l b l e f o r S n o w a n d I c e R e s e a r c h , F l r e R e e e a r c h ; a n d S o i l s and Foundatlons. F o u n d a t l o n work ls closely r e l a t e d to the work of the Bulldlng Structures Sectlon whlch ls r e s p o n s l b l e f o r work relatlng to structural p e r f o r m a n c e u n d e r C a n a d l a n conditions. O t h e r sect{ons are Bulldlng Physlcs, c o n -c e r n e d with a-couetl-cs and ground vlbratlon; B u l l d l n g Servlces, c o n c e r n e d wlth the effects of alr, heat, and molsture flow through b u t l d i n g materlals; a n d f l n a l l y t h e B u l l d l n g M a t e r i a l s S e c t l o n s , O r g a n l c and Inorganlc.

B u l l d l n g Practlce rnay be descrlbed as the asslstlng ln the a p p l l c a t l o n of research results ln the practlce of bulldlng, and

d e a l l n g wlth bulldlng problems as they relate to the whoLe structure, T h l s f u n c t l o n ls sornetlmes described as |tbridglng the gaptt between r e s e a r c h a n d p r a c t l c e . T h e g r o u p s c o n c e r n e d w l t h t h l s p h a e e o f t h e D l v l s l o n r s o p e r a t l o n s are the Sectlons of Congtructlon, H o u s l n g , B u l l d l n g Standards, Publlcatlone and the Llbrary. A T a r g e p a r t of t h e w o r k o f t h e Reglonal Statlons also falls ln thls category.

T h e two phases, Bulldlng Sctence and Bulldlng Practlce, t o g e t h e r constttute butldlng research ln lts full sense. For not u n t l l the technlcal informatlon g a l n e d ln the laboratory r e a c h e e the r n e n ln lndustry can the project be consldered completed.

T h e work descrlbed above ls carrled on by a total staff a t p r e s e n t nurnberlng 2I0, of which approxlmately 8 0 a r e p r o -f e s s l o n a l s , p t l n c l p a l l y e n g l n e e r s . T h e r e a r e a t p r e s e n t 5

a r c h l t e c t s o n t h e staff, three lnvolved wlth buildlng standards and t w o studylng the performance o f b u l l d l n g s and bulldlng rnaterlals. D B R ' g I N T E R E S T I N R O O F I N G

T h e t w o s e c t i o n s c o n c e r n e d d l r e c t l y w l t h r o o f l n g a r e t h e O r g a n l c Butldlng Materlals a n d C o n s t r u c t l o n , a l t h o u g h several o t h e r sectlons also have an tnterest, ln particular t h e Bulldtng S e r v l c e s Sectlon ln connection with roof lneulatlons.

A s p h a l t research by the Butldtng Materlals S e c t i o n dates b a c k t o 1954, when studles of the weatherlng of roof coating

(9)

5

-a s p h -a l t s r v e r e s t -a r t e d u s l n g -a c c e T e r -a t e d m e -a n s l n t h e l -a b o r -a t o r y , a n d b y n a t u r a l w e a t h e r l n g a t s e v e r a l o u t d o o r e r q ) o s u r e s l t e s . T h e o b j e c t of thls study was to cofirpare the behaviour of asphalts pro-d u c e pro-d f r o m C a n a pro-d i a n c r u pro-d e s wlth those of known performance

r e c o r d s "

A mernber or members of the ataf.f. of the Bullding M a t e r l a l e S e c t l o n have served for rnany years on technlcal c o m r n l t t e e s o f such bodies as the Canadlan Government

S p e c l f l c a t l o n s B o a r d , t h e C a n a d i a n S t a n d a r d s A s s o c l a t l o n a n d t h e A r n e r i c a n S o c i e t y f o r T e s t l n g and Materl.als, w l t h a n t n t e r e s t l n b l t u r n l n o u s r n a t e r l a l e . A s s l s t a n c e h a s b e e n r e n d e r e d w h e r e p o s s i b l e l n t h e p r e p a r a t l o n o f s t a n d a r d s a n d s p e c l f l c a t i o n s , t h e

s e t t l n g u p o f t e s t p r o c e d u r e s , a n d l n s o m e c a s r e 6 t h e . t e s t l n g o f r n a t e r l a l s to deterrnlne the adequacy and practlcablllty o f standards a n d t e s t p r o c e d u r e s .

M o s t of the wrltten and telephone lnquirles whlch corne t o t h e D l v l s l o n o f B u l l d l n g R e s e a r c h a r e a n s w e r e d t h r o u g h t h e C o n s t r u c t l o n S e c t l o n . I n q u i r l e e f r o r n a r c h l t e c t s , e n g l n e e r s ,

b u l l d e r e a n d o w n e r s c o v e r l n g a b r o a d r a n g e o f p r o b l e m s c o n c e r n i n g r o o f s h a v e b e e n r e c e l v e d f o r a n u r n b e r o f y e a r s . T h e y h a v e b e e n c o n c e r n e d with such problems as lce-darnrnlng at eaves, pavlng of r o o f t e r r a c e s , r o o f d e c k c o n s t r u c t l o n , i n s u l a t l o n , v a p o u r c o n t r o l , a n d r e q u e s t s f o r l n f o r r n a t l o n o n n e w l y d e v e l o p e d r o o f c o a t i n g s . T h e S e c t l o n h a s e n d e a v o u r e d t o k e e p t h e c o n s t r u c t l o n i n d u s t r y l n f o r m e d o n s u c h r n a t t e r s b y a n s w e r i n g t h e l n q u l r i e s a n d l n s o r n e c a a e a p u b -I l s h i n g a r t i c l e s o n s u b j e c t s t h a t a p p e a r e d t o b e o f n a t i o n a L l n t e r e s t . I n r n o r e : r e c e n t years, the nurnber of inqulrles concernlng built'up r o o f l n g f a l l u r e s ln rnany parts of Canada has been lncreaslng s t e a d i l y . R e p o r t s o f r o o f f a l l u r e s w l t h l n a y e a r o r t w o o f c o n

-s t r u c t i o n l e d t o f l e l d l n v e -s t l g a t l o n e o f a f e w o f t h e -s e r o o f -s , a n d e a r l y i n l 9 6 l i t w a s p o s s l b l e t o s t a r t a d e t a l l e d s t u d y t o d e t e r r n i n e t h e n a t u r e a n d e x t e n t of the problerns leading to rooflng failures. T h e

s t u d y h a s b e e n c a r r i e d o n b y r e f e r e n c e t o r o o f l n g r e s e a r c h l n o t h e r c o u n t r i e s , e x a r n l n a t l o n of Canadlan roofing practlces, a n d f l e l d lnvestlgatlon o f rooflng fallures. I t was hoped that this study c o u l d p r o v i d e valuable inforrnatlon that could be passed on to the r o o f i n g i n d u s t r y for appllcation to rooflng practlce, a n d a l s o t o l n d l c a t e t h e type of additlonal rnaterlatrs research that ls necessary, s o r n e o f whlch the Materlals S e c t l o n o f t h e D l v l e l o n m l g h t u n d e r t a k e .

S o m e of the earlier work of the Materlale S e c t l o n h a s b e e n c o n t i n u e d and new studles have been started ln an atternpt to relate

(10)

6

-t h e p e r f o r m a n c e o f b u i l t - u p r o o f l n g t o t h e p r o p e r t i e s o f the r n a t e r i a l s , a n d t h e i r r n e t h o d o f c o m b i n a t i o n lnto a roofing rnern-b r a n e .

CURRENT RESEARCH ON BUILT -UP ROOF'ING

A very general descrlption has been glven of the Natlonal R e s e a r c h C o u n c i l , and ln particular o f the Dlvlslon of Buildlng R e e e a r c h a n d l t s i n t e r e s t i n r o o f l n g . M o r e s p e c l f l c a l l y t n r e l a t l o n t o b u i l t - u p roofing, c u r r e n t laforatory a c t i v i t y l s principally c o n -f i n e d to -five studies:

D u r a b l l i t y o f asphalte R . o o f ternperatures

L o w temperature p r o p e r t i e s o f blturnens

E n g i n e e r i n g p r o p e r t i e s o f b u l l t - u p r o o f l n g m e m b r a n e s C o r n b l n e d heat and molsture flow Ln rooflng eystems. Durabilltv of Asphalts

T h e program o f evaluatlng the durablllty o f asphalte was e x t e n d e d tn 1960; additional samples were put out on the outdoor e l c p o s u r e sites at Ottawa, Hallfax and Saskatoon, and the arnount of a c c e l e r a t e d t e s t i n g w a s i n c r e a s e d . N e w w o r k h a s l n c l u d e d r e d e s l g n o f the testlng equipment and an irnprovernent ln the method of pre-p a r i n g aspre-phalt test pre-panels. S t u d i e s h a v e generally been confined to h o t - a p p l l e d asphalts, and staternents in reference to durability and w e a t h e r i n g c o n c e r n t h a t s y s t e m .

A c c e l e r a t e d w e a t h e r i n g i s a c c o m p l l s h e d i n a s t a n d a r d w a y l n t h e l a b o r a t o r y b y e x p o s i n g thin filrns (0. 025 in. ) of asphalt

s u p p o r t e d on alumlniurn panels to an ultravlolet a r c , a n d l n t e r -r n i t t e n t l y sp-raying wlth wate-r. T h e radlatlon frorn the arc is such t h a t the panels rlse to a maxlrnurn temperature o f I40"F and fall to

4 5 " F when the water spray is in operation. T h e o p e r a t i o n o f t h e w e a t h e r o r n e t e r i s carefully c o n t r o l l e d i n accordance with an ASTM

s t a n d a r d . T h e panels are exarnlned datly for fallures ln the asphalt. T h i s exarnlnation is rnade by a high voltage probe, whtch detects p i n h o l e s and cracks by producing a spark to the alurniniurn base. T h i s s p a r k c a n b e r e c o r d e d o n a p i e c e o f p h o t o g r a p h i c p a p e r , a n d t h e a r e a h a v i n g p i n h o l e s a n d c r a c k s c a n b e a s s e s s e d . A n a r b i t r a r y 1 "

z "

3 . 4. 5 .

(11)

7

-l i r n i t f o r the extent of fai-lure is set and when the pane-ls re4ch th-ls I i m i t they are considered to have failed. T h e v a r i a t i o n l n t l m e f o r t h e a s p h a l t s s t u d i e d i s c o n s i d e r a b l e . T h e m o s t d u r a b l e a s p h a l t b y t h i s r n e t h o d r e q u i r e d 7 5 d a i l y c y c l e s t o r e a c h f a i l u r e , c o m p a r e d t o 2 l f . o r t h e least durable.

C h e r n i c a l analysis of the asphalts under study was rnade t o t r y to relate dur:ability to physical properties a n d c h e m i c a l

c o r n p o s l t i o n . I t w a s f o u n d that degradatlon was accompanied by a d e c r e a s e ln oil content of the asphalt, and also that the asphalts h a v i n g l o w oll content had poor durability. T h e nature of the eulphur c o n t e n t of the asphalt also appeared to influence the subsequent

durabillty.

T h e n a t u r a l weathering studles appear to be show{ng the s a m e relative differences In durablllty, b u t there also appears to b e a relation between durabillty and the surface pattern that the a s p h a l t develops durlng degradation. T h e pattern appears to be a p r o p e r t y o f t h e a s p h a l t , a s i t i s p r e s e n t o n a s p h a l t s e x p o s e d to a c c e l e r a t e d a s w e l l a s t o n a t u r a l w e a t h e r l n g .

R o o f T e m p e r a t u r e s

A t O b t a w a in 1960 an outdoor exposure study was started t o m e a s u r e r o o f t e r n p e r a t u r e s , a n d o b s e r v e t h e w e a t h e r i n g o f r o o f i n g asphalts on a variety of built-up roofing eysterns, but p r i n c i p a l l y a s b e t w e e n insulated and non-insulated c o n s t r u c t i o n . T e s t speclrnens l8-ln. s q u a r e include insulated and non-insulated r o o f s with rag and glass fibre roofing felts, and a variety of hot-a p p l i e d hot-asphhot-alts hot-and surfhot-ace finishes. A continuous record of t e m p e r a t u r e s h a s b e e n m a d e f o r f o u r o f t h e s p e c k n e n s , w h i c h w e r e i n s t r u r n e n t e d w i t h t h e r m o c o u p l e s , t o m e a s u r e t e m p e r a t u r e s a t t h e u n d e r surface of the rnembrane. v l s u a l exarninations of the sur -f a c e s o -f t h e s p e c i m e n s a r e r n a d e a t r e g u l a r i n t e r v a l s . T h e

r e s u l t s frorn this investigatlon have not yet been cornpletely studied a n d a n a l y s e d , a n d n o r e p o r t h a s b e e n w r i t t e n , b e c a u s e o f l a c k o f t i r n e a n d p e r s o n n e l . T h e r e s u l t s , h o w e v e r , r n l g h t b e s u m r n a r i z e d a s f o l l o w s :

A built-up roofing mernbrane lnsulated from the roof deck wlll a t t a i n appreciably htgher temperatures a s t h e r e s u l t o f s o l a r h e a t i n g than its non-insulated counterpart.

E m l s s i v e c o o l i n g o r n i g h t r a d i a t i o n o f r o o f i n g e x p o s e d t o a c l e a r nlght sky, can reduce the ternperature of the roofing l "

(12)

3 .

B

-c o n s i d e r a b l y below the air ternperature; w i t h a n i n s u l a t e d d e c k t h i s r e d u c t i o n i s a s m u c h a s l 5 ' F .

C o n s i d e r e d o f g r e a t i m p o r t a n c e a r e t h e l a r g e a n d r a p i d f l u c t u a t i o n s in temperature o f b u i l t - u p roofing mernbranes o v e r i n s u l a t e d roof decks under varying weather conditions. E v e n during a normal sunny day in surnmer when ternperatures m a y e a s i l y r e a c h 1 5 0 ' F o n a b l a c k r o o f , a h e a v y r a i n s t o r m c a n r e d u c e t h e r o o f t e r n p e r a t u r e t o 8 0 " F o r l o w e r i n l e s s t h a n an hour.

4 . L i g h t - c o l o u r e d g r a v e l and liquid surfaclng rnaterlals tend to r e d u c e the ternperature build-up frorn solar heatlng.

5 . O n s m o o t h s u r f a c e d s p e c i m e n s , t h e r e a p p e a r s t o b e g r e a t e r d e t e r i o r a t i o n f o r roofing over insulation.

I t r n i g h t seern that these comrnents are sufficlent r e a s o n s t o s u g g e s t t h a t i n s u l a t i o n s h o u l d n o t b e u s e d b e t w e e n t h e r o o f d e c k a n d t h e b u i l t - u p r o o f i n g . F o r o t h e r p r a c t i c a l r e a s o n s t h i s ls not a logical conclusion, but it is obvious frorn this work t h a t r o o f i n g i s r e q u i r e d t o u n d e r g o a l a r g e r a n g e o f t e m p e r a t u r e c h a n g e s , and allowance rnust be made for this ln the design and a p p l i c a t i o n of roofing systern.

L o w T e m p e r a t u r e P r o p e r t i e s o f B i t u r n e n

D u r i n g the durability s t u d i e s o n asphalt lt was notlced t h a t t h e l o w t e m p e r a t u r e s o f w i n t e r c a u s e d c r a c k i n g o f t h e

r n a t e r i a l s , w i t h o u t any accompanying chemlcal change. A l s o about t h i s time many cases of splltting of built-up rooflng were brought t o t h e attention of the Division. I t w a s d e c i d e d therefore to begin a

s t u d y o f the low ternperature c h a r a c t e r i s t l c s o f t h e c o m p o n e n t s o f b u i l t - u p roofing. O n e study is principally c o n c e r n e d w i t h b r i t t l e -n e s s o f b i t u r -n e -n a t l o w t e m p e r a t u r e s , a n d t h i s o f c o u r s e g l v e s s o m e indication of the ductility and the ability of the material to w i t h s t a n d deforrnation.

A b r i t t l e p o i n t t e s t a p p a r a t u s d e v l s e d b y F r a a s s , a n d l n u s e in Europe for a number of years, has been rnuch knproved and m o d i f i e d for easier operation and for obtaining reproducible r e s u l t s . In this test, a uniform thin sarnple of bitumen applied to a rnylar p o l y e s t e r filrn plaque is flexed once every rnlnute, while its t e m p e r a t u r e l s r e d u c e d a t t h e r a t e o f I ' I ' p e r r n i n u t e . T h e

t e m p e r a t u r e a t w h l c h a crack occurs acrosa the asphalt sarnple ls t a k e n as the brlttle point of the material.

(13)

9

-U s l n g t h i s a p p a r a t u s , b r i t t l e p o i n t t e m p e r a t u r e s h a v e b e e n o b t a i n e d f o r a v a r i e t y o f r o o f i n g a s p h a l t s , s o r n e p a v i n g a s p h a l t s , a n d a l s o f o r c o a l t a r p i t c h e s .

A p r e l i r n i n a r y s t u d y h a s a l s o b e e n r n a d e o f t h e e f f e c t s o f o v e r h e a t i n g on softening point and brlttle point as indicated by t h e b r i t t l e point apparatus. I t appears also that the test rnight be u s e d t o e v a l u a t e t h e s e l f - h e a l i n g p r o p e r t i e s o f b i t u m e n s .

A n i n i t i a l r e p o r t o n t h i s w o r k w a s p r e s e n t e d t o t h e C a n a d i a n T e c h n i c a l A s p h a l t A s s o c i a t i o n i n N o v e r n b e r L 9 6 2 .

A p p a r a t u s that can test 5 sarnples at one tirne is being buitt by the D i v i s i o n in order to continue this work.

E n g i n e e r i n g P r o p e r t i e s o f B u i l t - u p R o o f l n g M e r n b r a n e s

D u r i n g 1 9 6 2 , i n v i e w o f t h e r e p o r t e d h l g h i n c l d e n c e o f r o o f m e r n b r a n e s p l i t t i n g , a s t u d y w a s b e g u n t o a s s e s s t e m p e r a t u r e e f f e c t s on strength and deforrnation in relatlon to shrinkage and e r n b r i t t l e r r i e n t . S i n c e roofing rnernbranes are norrnally classed as n o n - l o a d - b e a r i n g , t h e r e i s v e r y l i t t l e i n f o r m a t i o n a v a i l a b l e r e g a r d i n g t h e s t r e s s - s t r a i n p r o p e r t i e s . T h e r e i s n o d o u b t t h a t t h e y a r e s u b -j e c t e d t o s t r a i n s , h o w e v e r , d u e t o b u i l d i n g o r r o o f deck rnovernents, a n d t o t e n i p e r a t u r e a n d r r , o i s t u r e changes. M o s t of the splitting of r o o f i n g membranes h a s been attributed to therrnal shock due to a r a p i d drop of ternperature d u r i n g c o l d w e a t h e r conditions, w h e n t h e r e is little or no snow on the roof. I t h a s n o t b e e n p r o v e d that t h i s i s t h e c a s e , a n d t h i s s t u d y l s b e i n g r n a d e t o o b t a i n r n o r e

i n f o r m a t i o n r e g a r d i n g s h r i n k a g e and extensibtlity o f rooflng rnaterials a t l o w ternperatures i n an atternpt to deterrnine potential perforrnance. I n i t i a l work is being confined to controlled conditions in the

l a b o r a t o r y . T e c h n i q u e s for preparing a n d l o a d t n g o f the rooflng s a m p l e s h a v e b e e n w o r k e d o u t , a n d t h e f i r s t p h a s e o f t h e t e s t l n g p r o g r a m w i l l b e r e p o r t e d a t a n A S T M S y m p o s i u r n l n J u n e L 9 6 3 .

T h e t e n s i l e s t u d i e s w e r e p e r f o r r n e d a t 7 5 ' F a n d - 2 0 o F , u s i n g t w o r a t e s o f s t r a i n i n g , o n b a r e f e l t s a n d o n r n e m b r a n e s p r e -p a r e d with bitumen. T h e results indicate that the felt plays a rnajor r o l e ln the strength of the mernbrane. A t both ternperatures t h e f e l t s contributed B0 to 90 per cent of the strength of the rnembrane, a l t h o u g h the actual strength in the case of rag felts was generaltry t r i p l e d w h e n t h e t e m p e r a t u r e d r o p p e d f r o r n 7 0 ' F t o - 2 0 ' F . A t - 2 0 ' t r ' t h e s a m p l e s h a d a l m o s t t h e s a r n e t e n s i l e p r o p e r t i e s r e g a r d l e s s o f t h e rate of strainlng, i n d i c a t i n g that little creep of the biturnen o c c u r s a t t h i s t e m p e r a t u r e . A t 7 5 " F c r e e p d i d h a v e a n a p p r e c t a b l e e f f e c t .

(14)

1 0

-A s y e t i t i s d i f f i c u l t t o r e l a t e t h e s e r e s u l t s t o t h e s p l i t t i n g o f r e a l r o o f r n e r n b r a n e s . T h e y d o g i v e a n i n d i c a t l o n o f w h a t f u r t h e r w o r k i s n e c e s s a r y t o b e g i n t o a s s e s s t h e s t r a i n s t h a t r n a y be occurring o n actual roofs. S h r i n k a g e d u e t o l o w e r i n g t h e t e m p e r a t u r e w i l l h a v e to be determined for comparison with the

s t r a i n s w h i c h t h e m e m b r a n e s e x h i b i t a t b r e a k i n g . T h e

t e r n p e r a t u r e e f f e c t s t h e r n s e l v e s a r e c o m p l i c a t e d b y t h e n a t u r e o f t h e m e r n b r a n e , w h i c h r n a y b e r e g a r d e d a s t h r e e c o r n p o n e n t s -f l b r e , s a t u r a n t a n d c o a t i n g . T h e p r e s e n c e o f m o i s t u r e i n t h e f e l t s c a n also be a cornplication affqcting the dlrnensional changes on c o o l i n g . P r e l l r n l n a r y t e s t s a t t h e D i v i s i o n a n d r e s u l t s f r o m o t h e r t e s t agencies show that the shrinkage effects are not linear wlth t e r n p e r a t u r e , b u t can lncrease at a rnuch greater rate below the f r e e z i n g point.

C o m b i n e d Heat and Molsture Flow

F o r a number of years a study has been under way at t h e D i v i s i o n b y t h e B r r i l d i n g S e r v i c e s S e c t l o n t o d e t e r m i n e t h e r a t e o f rnoisture galn, and the rnoisture content distrlbution o f v a r i o u s i n s u l a t i n g r n a t e r l a l s e x p o s e d t o a t e m p e r a t u r e g r a d i e n t , w i t h t h e c o l d s u r f a c e s e a l e d a n d t h e w a r m s u r f a c e o p e n t o c o n -t r o l l e d r n o i s -t a i r c o n d i -t i o n s . O b s e r v a t i o n s a r e b e l n g m a d e f o r a n u m b e r of controlled air conditlons and a nurnber of cold surface t e m p e r a t u r e s .

D . B. R. AND THE ROOFING INDUSTRY

F r o r n these descriptions i t m i g h t appear that the work o f the Division is somewhat rernote from the day-to-day p r o b L e r n s o f r o o f e r s . T h i s i s n o t t h e c a s e , h o w e v e r ; t h e C o n s t r u c t l o n

S e c t i o n rnaintains very close contact wlth the rooflng industry. O f g r e a t importance in connection with roofing studles has been the e s t a b l i s h r n e n t of a close liaison with manufacturers o f r o o f i n g m a t e r i a l s a n d r o o f i n g contractors. B o t h the Asphalt Roofing T e c h n i c a l Comrnittee of the manufacturers a n d the Canadian R o o f i n g C o n t r a c t o r s r A s s o c i a t i o n h a v e b e e n t h e r n o s t c o - c . ) e r a t i v e i n t h i s r e g a r d . W i t h t h e h e l p o f t h e s e g r o u p s , a n d t h e c o - o p e r a t i o n o f a r c h i t e c t s , e n g i n e e r s , c o n t r a c t o r s a n d r o o f i n g c o n s u l t a n t s , t h e C o n s t r u c t i o n S e c t i o n h a s b e e n p r l v i l e g e d t o e x a m i n e a l a r g e n u r n b e r o f roof.ing jobs exhibiting failures, a n d a l s o a considerable number o f j o b s u n d e r c o n s t r u c t l o n a c r o s s t h e c o u n t r y .

I t b e c a m e e v i d e n t e a r l y i n t h e s e f l e l d s t u d l e s t h a t a c c u r a t e inforrnation o n c o n d i t i o n s existing durlng construction a n d f r o m c o n s t r u c t i o n t o t i r n e - o f - r o o f - f a i l u r e w a s v e r y d i f f i c u l t

(15)

- I 1 ,

t o o b t a i n . E v e n with the co-operation o f r n a n u f a c t u r e r s h o l d i n g

g u a r a n t e e b o n d f i l e s o n c e r t a i n j o b s , it is alrnost always difflcult

t o p i n p o i n t t h e f a c t o r s t h a t m a y h a v e c a u s e d p r e m a t u r e f a i l u r e . F r o m t h e r o o f s i n v e s t l g a t e d l t w a s o b v l o u s t h a t t h e r e l s n o o n e g e n e r a l s o l u t i o n , n o r a n y o n e s p e c i f i c f a c t o r w h l c h c a u a e g a r o o f t o f a l l t o p e r f o r m a s e x p e c t e d . F i e l d i n v e s t i g a t i o n o f f a i l u r e s a n d o b s e r v a t i o n o f r o o f i n g t e c h n i q u e s w i l l b e c o n t i n u e d a s a n e c e s s a r y c o m p l e m e n t t o t h e l a b o r a t o r y r e s e a r c h . I t l s h e r e t h a t t h e C a n a d l a n R o o f i n g C o n t r a c t o r s r A s s o c i a t l o n c a n b e o f g r e a t a s s i s t a n c e , p a r t l c u l a r l y

in rnaking known to the Division the nature and extent of rooflng

p r o b l e r n s encounter ed.

CAUSES OF ROOFING F'AILURES

I t i s n o t d l f f i c u l t t o p r e p a r e a l i s t o f s o m e o f t h e c a u s e s

o f roofing failures. M o s t u s u a l l y q u o t e d a r e t h e f o l l o w l n g :

l . F a u l t y deslgn of the bullding

z .

L a c k o f , or improper l o c a t i o n o f , s t r u c t u r a l e x p a n s i o n j o l n t s

3 . M o v e r n e n t s o f the roof deck, due to expanslon and contractlon

o r shrinkage and creep deflectlon, or from sorne other cause

4 . l m p r o p e r o r i n a d e q u a t e roofing speciflcatlons f o r t h e specific

j o b

5 . L a c k o f a p p r o v e d v a p o u r b a r r i e r w h e r e s u c h p r o t e c t i o n l s

r e q u i r e d b e c a u s e o f h t g h r e l a t i v e h u m l d i t l e s w i t h l n a b u i l d i n g

I n s u f f i c i e n t insulatlon to prevent interlor s u r f a c e c o n d e n s a t l o n

b e l o w t h e r o o f

T r a f f i c o v e r the roof by other trades durlng cornpletlon of the

b u i l d i n g or after the building is in use

R o o f i n g n o t applied according to speclflcations w l t h q u a n t i t l e s

o f pitch o r asphalt below the requlrements

A p p l l c a t i o n o f r o o f i n g d u r i n g inclernent weather and improper

s t o r a g e o f f e l t s and insulation 6 .

7 .

B .

(16)

r z

-1 0 . O v e r h e a t i n g of pitch or asphalt, thus changing and

d e t e r i o r a t i n g t h e p h y s i c a l p r o p e r t i e s

I l . F a u l t y f l a s h i n g s .

T h i s i s by no rneans an exhaustive list, and rnany of the

I t e r n s shown could befurther a r n p l i f i e d . I t l s o b v i o u s , h o w e v e r , t h a t

t h e r e a r e o n l y a few of these iterns over which a roofer has control. W h i l e t h e r e m a y b e c a s e s w h e r e p o o r a p p l i c a t l o n h a s r e s u l t e d f r o r n a

d e f i n i t e i n t e n t t o skimp on materlals, r n o r e o f t e n poor workmanship

r e s u l t s f r o m c a r e l e s s n e s s a n d l a c k o f k n o w l e d g e o f m a t e r l a l l l m l t a -t i o n s a n d g o o d r o o f i n g p r a c -t i c e . P r l n c i p a l s o f f i r m s u s u a l l y a r e w e l l a w a r e o f g o o d r o o f i n g p r a c t i c e , b u t m a n y f o r e m e n a n d m o s t r o o f l n g l a b o u r e r s a r e o f t e n n o t s u f f i c l e n t l y l n f o r m e d .

P o o r R o o f i n g P r a c t i c e s

D u r i n g fteld inspectlons rnany poor roofing practlces h a v e been noticed, any one of which could have an effect on the q u a l i t y o f the finished roof and a cornbinatlon of whlch would most

c e r t a i n l y c a u s e early failure. I t ls considered worthwhlle t o n o t e

j u s t a f e w o f t h e s e p r a c t i c e s .

S t o r a g e of rnaterlals is often a very difflcuLt rnatter on

c o n s t r u c t i o n j o b s , brit it is irnperative that roofing rnaterials be kept

d t y . W a t e r in building rnaterials and in the elernents of bullding

e n c l o s u r e s p r e s e n t s a c o n s t a n t p r o b l e r n , a n d i t s h o u l d b e r e c o g n i z e d b y t h e r o o f e r a s h i s w o r s t e n e m y . S a t u r a t e d f e l t s a r e n o t w a t e r p r o o f , a n d c a n t a k e u p m o i s t u r e r e a d i l y u n l e s s p r o t e c t e d . F e l t s i n r o l l s w i l l swell unevenly and cause difficulty ln rolling the felts out flat. A n y m o i s t u r e trapped in the roof construction wlll try to escape when t h e t e m p e r a t u r e o f t h e r o o f i s r a i s e d , a n d m a y c a u s e b l i s t e r i n g .

M a n y types of insulation are capable of absorbing very large

q u a n t i t i e s of water, and when built into a rooflng systern can cauae r o t t i n g , s e v e r e b l i s t e r i n g , a n d v e r y r a p i d d e t e r l o r a t i o n o f t h e c o r n

-p l e t e r o o f i n g . P r o b l e r n s f r o r n t h e s e s o u r c e s a r e g r e a t l y c o r n p o u n d e d

w h e n rnaterials a r e a p p l i e d durlng lnclernent weather.

T h e condition of the roof deck ln the early mornlng when

r n o s t r o o f e r s s t a r t w o r k l s o f v e r y g r e a t l m p o r t a n c e . M o i s t u r e f r o m

o v e r n i g h t rains, frost or dew, snow or lce can cause a gteat deal of

t r o u b l e . I t r n a y penetrate lnto saturated felts, causing swelllng, a n d

i t c a n prevent adheslon between the bitumen and the deck. A1so, of c o u r s e , i t c a n p e n e t r a t e i n t o t h e r o o f s y s t e m t o c a u s e p r o b l e r n s l a t e r .

(17)

1 3

-H e a t i n g o f t h e a s p h a l t o r p l t c h i s n e c e s s a r y o n l y s o t h a t i t will be of. t}:^e right consistency to flow onto the roof or f e l t s to obtain a thin uniform filrn whlch will adhere to the dry

s u r f a c e . C o r r e c t heating will produce a physlcal change but no c h e r n i c a l change. P r o p e r flow and adheslon can be achleved at t e m p e r a t u r e s a p p r o x i m a t e l y 2 0 0 " F a b o v e the melt point

t e r n p e r a t u r e . T h i s s t i l l a l l o w s a c o n s i d e r a b l e m a r g l n o f t e r n p e r a t u r e before the properties o f t h e m a t e r i a l a r e affected b y h e a t . T h e t e r n p e r a t u r e l e v e l at which severe degradatlon wlll o c c u r appears to depend on the source and nature of the blturnen, a n d f o r some rrraterials may be qulte hlgh, but aleo qulte crltical. T h e r e rnay be only sllght loss of flexibillty w l t h r n o d e r a t e o v e r -h e a t i n g , but it is t-houg-ht t-hat biturnen -has a cornplete lose of f l e x i b i l i t y w h e n h e a t e d f o r even short periods at the crltlcal t e m p e r a t u r e .

I n a roofing mernbrane the felts provlde the strength a n d t h e bitumen the w.aterproofing; t h e o b j e c t l v e ig to produce a b a l a n c e d combination. E v e n a very thln layer of biturn en t/64 of. a n i n c h or less in a contlnuous filrn provides an excellent water b a r r i e r , b u t i n practice this cannot be achleved and malntained. T h i c k e r f i k n s are used to assure contlnuous filrns over surfaces n o t entirely srnooth, and felts are used to build up and malntaln t h e s e contlnuous filrns. I t s h o u l d be obvlous that felt rnust be l a l d as srnoothly as possible without wrinkles and the bitumen s p r e a d uniformly t o a c h l e v e thls. M o p p l n g more than a few feet l n f r o n t of the roll and scuffing down felts without proper broornlng w i l l c e r t a l n l y n o t p r o d u c e t h e r e q u l r e d m e m b r a n e .

T h e top pour of biturnen ls the final weather coatlng, t h e f i r s t barrier a g a i n s t water penetratlon lnto the mernbrane. I t i s e s s e n t i a l that this be a continuous fllm wtth no weak spots t h r o u g h which water can penetrate into the fibre felts of the mern-b r a n e . L a p s improperly s t u c k and broorned down, penetrating t h r o u g h this top pour, provide wicks for drawing water lnto the f e l t s . T h e normal shingle -twe laying may allow penetration of t h i s moisture r ight down to the insulation or deck.

O n exposure to sunlight biturnens are readlly oxidized b y u l t r a - v i o l e t r a d i a t i o n . T h i s p r o c e s s , s o r n e t l r n e s r e f e r r e d t o a s p h o t o - o x i d a t i o n , f o r m s water soluble and volatlle products. T h e l o s s o f t h e s e p r o d u c t s o f o x i d a t l o n r e s u l t s ln a materlal that 1 s harder and less flexible than it was originally, a n d shrlnkage c a u s e s cracklng called alligatoring. T h e useful rife of the

(18)

7 4

-a s p h -a l t c o -a t i n g c-an be gre-atly extended ln the -absence of he-at -and l i g h t . T h e rnain purpose of light coloured gravel on a roof ls to p r o v l d e protectlon to the bitumen frorn the sunrs rays, and by r e f l e c t i o n to reduce the ternperatures a t t h e r o o f surface. T h e e u r f a c l n g g r a v e l should therefore be graded as normally recom-m e n d e d , and spread evenly and ln sufficient quantity to obtaln a

c o m p l e t e coverage. I f t h e materlal l s t o o f i n e lt will be dis -l o d g e d eas-l-ly or b-lown off; tf -lt -ls too -large or poor-ly graded gaps w i l l result between gravel particles"

T h e practice of glaze-coatlng a roof, and flnishlng with t h e top Pour and gravel at a later more convenlent tlrne ls becornlng v e r y common. T h i s r n a y sirnpllfy the roofing operatlon but it ls t h e s o u r c e of rnuch roofing trouble. F e l t s become wet despite the

g L a z e - c o a t l n g and water gets under irnproperly adhered laps. J o b organlzation s h o u l d be such that durlng any worklng perlod an a m o u n t o f roofing can be entirely completed lncludlng gravelllng-ln. G L a z e - c o a t i n g should be used onry to protect felts against sudden s t o r m s d u r i n g t h e p r o g r e s s o f t h e w o r k , a n d n o t b e d e p e n d e d o n as a d e q u a t e waterprooflng o v e r n l g h t or over week-ends. w o r k should b e completed each night as lf the crews did not e>cpect to

r e t u r n to the job for weeks.

When gravel is wet frorn rain or snow, it w111 not a d h e r e in the biturnen, and will be easily dislodged at gome later tirne. Also, gravel lytrg over unfinlshed felt or even over gLaze -c o a t e d felt -colle-cts rnoisture whi-ch wlll penetrate into the felte to c a u s e later blistering o f the top coating.

C O N C L U S I O N

T h e very real concern of the Canadian Rooflng c o n t r a c t o r s t A s s o c i a t l o n f o r the problerns of rooflng has led to t h e production of a specifications M a n u a l . T h l s has been an a t t e m p t to assure that roofing ls speclfied adequately by archltects a n d engineers. w h l l e architects undoubtedly deserve rnuch of the c r i t l c i s m w h l c h they recelve in connection wlth inadequate rooflng d e s l g n and specificatlons, t h e architect should not be e>cpected to b e an ex^oert roofer. M e m b e r s o f t h e Rooflng contractorsl

A s s o c l a t l o n rnust be the competent, responsible and honeet sub-c o n t r a sub-c t o r s w h o can solve the job problerns, r e r n e d y undeslrable c o n d l t i o n s , a n d a s s u r e f i r s t - c l a s s w o r k m a n s h i p . T h e r e i s a g r e a t deal to do inthis regard. R o o f l n g c o n t r a c t o r e l n g e n e r a l , ernall and large, are lncurably-olitim{btic itr believing that problerns

(19)

1 5

-w i l l n o t o c c u r , no matter ho-w or under -what condltlons roofing i s applled. I t i s unfortunate that euch a large industry as the r o o f i n g industry has practlcally n o educatlonal prograrn on r o o f l n g and roof application. P e r h a p s thle ls an area where the D i v l s i o n of Bullding Research mlght co-operate wlth the

A s s o c i a t i o n i n t h e preparation o f a roofing appllcatron manual, a n d i n t h e o r g a n i z a t l o n o f c o u r s e s f o r r o o f e r s o n v a r l o u s aspects o f rooflng.

W e appear to be at the edge of a new era in rooflng. T h e p l a s t i c s l n d u s t r i . e s a r e p r o d u c l n g n e w p r o d u c t s for use in rooflng, and new systerns of appllcatlon wlth single-ply thin fllrns a r e b e l n g p r o p o e e d t o r e p l a c e t h e o l d r n u l t l p l e p l y systems. s o m e o f these are factory-produced f l l m s and others are liquld-applled s p r a y e d - o r r o l l e d - o n s y s t e m s . F o r t h e bulk of industrial

b u i l d l n g s , a n d many cornrnerctal buildlngs, it ls doubtful lf any o f these new materials wllI displace the conventlonal systems of r o o f l n g s for sorne years to come. s o r n e of the new systems have b e e n lntroduced to serve a particular f u n c t l o n whlch conventlonal r o o f l n g can accomplish only wlth difficulty, s u c h as the many e x o t i c - t y p e r o o f s , b u t s o m e o f t h e m are also belng offered as g u b s t i t u t e s for conventlonal rooflng. c e r t a l n l y a n lncreaelng p e r c e n t a g e , p e r h a p s z to 5 per cent, of rooflng over the next few y e a r s will be done using these new eystems. N e w words u'llt h a v e t o b e a d d e d t o r o o f e r r s v o c a b u l a r y , such as neoprene,

c h l o r osulfonate d polyethylene (hypalon), polyvinyl fluorlde (T edLar ), p o r y v i n y l c h l o r i d e , e p o x l e s , butyt rubber and butyl latex,

poly-i s o b u t y l e n e , a n d trade names such as Monoforrn, B l t u r n a g l c , L a s t , - o - R o o f , T / N A 2 0 0 , t o r n e n t i o n a few. s o m e rooferg have u n d o u b t e d l y already handled appllcatlons of neoprene-hyPalon and M o n o f o r r n . M a n y of these materials a r e still experlrnental and I a c k ' e x h a u s t i v e f i e l d testing. T h e C a n a d l a n Roofing Contractorsl A s s o c i a t i o n c o u l d do a great service to rnanufacturers, t o t h e p u b l i c , and for the roofing lndustry, if each mernber reported on h i s experience in appllcatlon and problems lnvolved with these new r n a t e r i a l s o n e a c h j o b that is applied.

F i n a l l y , t h e Divlsion of Building Research is a research s e r v i c e serving the construction industry. V i s i t s f r o m indlviduals o r g r o u p s o f r o o f e r s a n d d i s c u s s i o n s concerning the work of the D i v l s l o n and rooflng problems are welcomed. B e t t e r buildlng in c a n a d a can be achleved by co-operation of the canadlan Roofing G o n t r a c t o r s r A s s o c i a t l o n a n d t h e D i v l s i o n of Buildtng Researchl

Figure

Updating...

Références

Updating...