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The National Research Council and Roofing Research
Ser TH1 NzLT2 no" t51 e . 2 BLDG
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
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 .
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
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 .
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
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
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 .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 "
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.
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 .
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
- 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 s3 . 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 .
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 .
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-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
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-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
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-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
