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Protected membrane roofs in Canada: results of a survey
PROTECTED
MEMBRANE ROOFS LN CANADA-
RESULTS OF
A S U R V E Y Ser M . G . Baker T H l B92 no.89
c. 2i
1
O c t o b e r 1973I
I37u
---
74
- 7 3 - I D I V I S I O N O F BUILDEHG R E S E A R C H HATIOFEAL R E S E A R E R C O U N C I L O T T A W A.
C A N A D A1
IPROTECTED MEMBRANE ROOFS
IN
CANADA-
RESULTS OF A S U R V E Y b-YM.C.
BakerSloped roofs have b e e n in use f o r thousands of years, since prirni-
tive man first learned to build windbreak and l e a n - t o forms of s h e l t e r .
They have generally given good service because the details of design
and application are w e l l known from practice. Modern flat roofs have
a much s h o r t e r history and sometimes give v e r y poor service. In
recent years, much r e s e a r c h and development has gone into producing new materials f o r u s e in r o o f system, but this has not always resulted in s u c c e s s f u l r o o f s . The Division of Building R e s e a r c h has investigated the basic principles and the elements involved in the design of a
s u c c e s s f u l roofing systems,and l a b o r a t o r y and t e s t building studies
have been c a r r i e d out at the Saskatoon Prairie Regional Station since
1466.
D B R has promoted the protected membrane roofing system s i n c e1965 and has had a tremendous response f r o m designers and o w n e r s f o r
information about this approach, Although this type of system has b e e n
given a variety of o t h e r n a m e s , such a s , upside d o w n , i n v e r t e d and
insulated membrane, it is simply a r e a r r a n g e m e n t of €he n o r m a l elements of a roofing system t o o v e r c o m e some of the disadvantages of conventional
a r r a n g e m e n t s . The air vapour b a r r i e r and the roofing m e m b r a n e are combined on the sLoped structural deck, with thc insulation located on the
outside of this membrane like the fur on the outside of the skin of a n
animal. If m o i s t u r e penetrates the m e m b r a n e f rorn inside the structure, it can e a s i l y evaporate to the outside. Precipitation that falls on the
exposed i n s u l a t i o n d r a i n s over or through it, a l s o evaporating when conditions a r e suitable. The principle theref o r e involves a structural deck sloped t o d r a i n a g e , a waterproof membrane a n d insulation placed
outward of the membrane. A protective layer, landscaping or t r a f f i c
s u r f a c i n g completes t h e total system.
T h i s survey w a s m a d e by a q u e s t i o n n a i r e t o two g r o u p s i n t h e c o n s t r u c t i o n i n d u s t r y , architects and r o o f e r s , Its purpose was to d e t c r -
u s e in Canada and t o obtain some informatian on details and materials.
The r e s p o n s e t o the questionnaire was v e r y good, with 3270 r e t u r n from architects and 40% r e t u r n f r o m r o o f e r s when the results were analysed, about two months after questionnaires were sent out. A
f e w r e t u r n s have come in since that time,
The questionnaire w a s in t w o parts. The first part was a general q u e s t i o n n a i r e to ascertain amount of roofing being done
and the general opinion of such roofing. The second p a r t asked for d e t a i l s about individual projects. The analysis of results from both
p a r t s a r e included i n Table I. A copy of the questionnaire i s included
a s Appendix A t o this N o t e .
Some who responded to Part I did not cmnplete Part
U,
ands o m e of t h o s e who completed Part TX did not cover all of the p r o j e c t s
that t h e y had indicated in Part I. This was p a r t l y the fault: of the questionnaire: it allowed f o r recording a detailed r e c o r d af only six p r o j e c t s , as this was thought to be the maxim- that any one f i r m
might have done. In fact, there w e r e several architects and many
r o o f e r s who indicated more than six projects; one r o o f e r indicated 25.
N o n e reported in detail on mare than six and s m e on only one or t w o .
Some did not answer all items of the questionnaire, and where t h e r e was a choice of t y p e s some indicated more than one f o r an individual project. The results of the survey in Part U. have been tabulated accordingly.
SUMLMARY
O F
RESULTSArchitects
1 0 4 9 questionnaires w e r e sent out to architectural f i r m s a c r o s s
Canada. Of these, 29 did not reach their destination hacause of i n c o r r e c t
a d d r e s s e s , firm defunct o r o t h e r such r e a s o n s ; 1020 w e r e assumed t o
have reached t h e i r destination. At the time of the a n a l y s i s , 329 c n m p l c t e d
r e t u r n s had been r e c e i v e d , r e p r e s e n t i n g 32% or appraximateIy a o n v - t h i r d response.
U s e of PMR by architects
150 ( 4 5 . 6 % ) of 329 architects who replied reported they had done
protected membrane roofs {PMR) ranging in s i z e f r o m 500 sq f t t o
7 0 0 , 0 0 0 sq f t and totalling approximately 8 , 0 0 0 , 0 0 0 sq f t . 1 7 9 (54.4%) of 3 2 9 a r c h i t e c t s who replied had not done P M R ,
1 2 1 (68%) of the 1 7 9 architects who had not done P M R anticipate doing t h e m in the future.
2 5 (14Y~'o)of the 1 7 9 architects who had not done P M R d o not anticipate doing them in the future.
3 3 (18%) of the 1 7 9 who have not done PMR did not answer t h e gue stion.
Cost of P M R system
93 ( 6 2 % ) of the 1 5 0 architects who have done P M R said it c a s t s m o r e .
1 6 (11%) of the 150 architects who have done PMR said i t c o s t s l e s s .
21 (14%) of the 150 architects who have done P M R said c o s t s were about the s a m e , or more or less depending on the type of deck. 2 0 ( 1
370)
of the 150 a r c h i t e c t s who have done P M R did n o t k n o w ordid not answer.
2 0 (1 1
DJo)
of the 1 7 4 architects who had not doneW
R
said it c o s tm o r e , and none said it c o s t less.
159 ( 8 9 % ) of the 1 7 9 architects who had net done
M
R
did
not know or did not a n s w e r.
26
s a i d it c o s t 5% more (including 5 who had not done any).33 said it c o s t 107~3 more (including 5 who had not done any).
19
said it c o s t 15% m o r e (including 5 who had not done any). 7 said it c o s t 20% m o r e (including 4 who had not done any).1 said it cost 25% more. 1 said it c o s t 3 0 % m o r e .
7 said it cost 5% l e s s .
4 said it c o s t 207~1 less. 1 said it cost 15% less. 1 said it c o s t 20% l e s s .
Some did not answer, or said more or less depending on t y p e of deck,
membrane, etc.
P e r f o r m a n c e r e c o r d
1 6 ( 1 1 % ) of the 1 5 0 architects who have done P h d R said t h e y have had
caIlbacks.
107 (71%) of the 150 architects who have done P M R said they have n o t had call backs,
27 (18al,) of the 1 5 0 architects who have done PM.R did not a n s w e r ,
or said too soor, a f t e r completion, or jc?b not completed, e t c .
1 5 1 (46%) of 329 who replied said they recornmended t h i s type of roof
2 5 (8%) of 329 who replied m i d they did n o t recommend t h i s type af r o o f .
5 (3%) of the 1511 who had done t h i s t y p e of roof s a i d t h e y d i C n o t r e commend them.
2 0 (1 1%) of the 179 architects who had not done P M R said they r e c o m m e n d e d them.
20 ( 1 1%) of the 179 architects who had not done P M R said they did n u t recommend them.
127 (85%) of the 150 who had done P M R would recommend them. 18 (12%) of thc 1 5 0 who had done PMR did not answer or wanted ti,
wait and see.
9 9 (30%) of the 329 who replied have designed 1 8 3 roof garderts
a n d plazas of this type.
3 0 (30%) of the 99 a r c h i t e c t s who have done roof g a r d e n s and p l ~ z a ~ of t h i s type c o n s i d e r them as s u c c e s s f u l as c o n v e n t i o n a l plazas.
48 (48%) of the 99 architects who have done roof gardens and plazas
of this type consider them to be m o r e s u c c e s s f u l than c o n v e n t i o n a l
plazas.
21 ( 2 1 % ) of the 9 9 architects who have done roof g a r d e n s a n d plazas of this type did n o t h o w or did n o t a n s w e r ,
R o o f e r s
212 q u e s t i o n n a i r e s w e r e sent out t o r o o f i n g c o n t r a c t o r firins a c r o s s Canada. None w a s r e t u r n e d because of i n c o r r e c t address, e t c . ; 2 1 2 w e r c
a s s u m e d t o have r e a c h e d t h e i r d e s t i n a t i o n . At the time of thc analysis of r e s u l t s , 8 5 completed r e t u r n s had been r e c e i v e d , r e p r e s e n t i n g a 4C70
response.
U s e of P M R by roofers
6 0 (71%) of the 8 5 roofers who replied r e p o r t e d t h e y had don^ m o r c
than 238 P M R ranging in s i z c f r o m 400 sq f t t o 5 3 0 , 0 0 0 s q f t a n d totalling approximately 6,000, 0 0 0 s q f t .
2 5 (29%) of the 8 5 r o o f e r s who replied reported they had not done any
PMR.
6 (24%) of the 2 5 r o o f e r s who had not done PrvlR said t h e y anticipated doing t h e m in t h e future.
8 (327'3) of the 2 5 r o o f e r s who had not done FMR said. they did
n o t anticipate doing them in the f u t u ~ e ; 2 or 3 said they would n e v e r d o them.
C o s t of PMR system
42 (49%) of the 8 5 r o o f e r s who replied said PMR c o s t moye than
c o n v e n t i o ~ a l roofing systems. jKncludes 5 who had nct done
any FTdR),
12 (PSYo) of the 85 r o o f e r s who replied said PMR c c s t less.
6 s a i d F M R . c o s t 5% more 1
' said m t l R c o s t 13% msre (includes i w h o had not done any).
6
s a i dP M R
c o s t 1 % more (includes 2 who had not done any).14 said
P M R
c o s t 2070 more (includes 2 who had n o t done any). 4 saidP M R
c c s t 570 l e s s .77 s a i d P M R cost 10% less.
9
(11%) of the 3 5 rcufers v k o replied szid PMX cost: t h e s a m e , ormere or l e s s d e p - d i n g on deck and membranes; the ryst did
not a.nswer.
P e r f orrnance record
8 ( 1 376) of the 60 r o o f e r s who had done P M R had had callbacks.
4 5 (5370) of t h e 8 5 who replied rerolnrnended PPAX.
14 (16%) of the 8 5 v:ho replied dc not rzcornrrlen.;! PMR.
6 (1070) of the 6 0 who have done PMR do no$ recommend them.
2
(870)
of the 25 who have not done PMR d o recommend tllem.Roof g a r d e n s and t e r r a c e s
26 (31%) of the 8 5 who replied had d o n e roof g a r d e n s ar terraces of this type.
4 5 ( 5 3 % ) of thc 8 5 w h o replied had not done roof g a r d e n s or t e r r a c e s of t h i s type.
7
(1670)
of the 45 who had done roof g a r d e n s or t e r r a c e s considered them to be as s u c c e s s f u l as conventional r o o f s .1 2 (2770) of the 4 5 who had done r o o f gardens and t e r r a c e s considered them. to be m a r e succc ssful than conventional,
TABLE
I
-
STUDY
OF
PROTECTED MEMBRANE ROOFS (PMR)-
Architects
General Questionnaire
-
PartI
R o o f e r sNumber Percent Number Percent
1. Firms that
have
donePMR
Firms t h a t have not done PMR
2. N u m b e r of P M R reported 3 5 5 2 3 8
3 . PMR c o s t more than co-nveational 1 1 3 3 4 42 49
PMR c o s t lees than conventional
16
5 12 14C o s t the same; did not know; did not answer 2130 61 3 1 37
4. PMR c o s t more b y
PMR c o s t less by
5 . H a v e had callbacks on PME; H a v e not had callbacks on
PMR
Did not answer
6 . R e c o m m e n d PMR
D o not r e c o m m e n d PMR
Did not a n s w e r
7 . Firms having done FM roof gardens and
plazas 9 9 3 0 2 4 3 1
€3- PAM roof gardens and plazas reported 1 8 3 $4
9. PM roof gardens and plazas as successful
as conventional s y s terns 3 0 3 0 14 54
P M roof gardens and plazas m o r e s u c c e s s
-
f ul than c onventional s ys terns 4 8 49 9 3 5
Did not answer 21 2 1 3 11
10, H a v e not done PMR, anticipate doing them
in f utur e 12 1 68
6
24Have not done PMR, d o not anticipate doing
them in future 25 14 8 32
STUDY O F PROTECTED MEMBRANE ROOFS (PMR) ( C o n t . )
Detailed Questionnaire - Part I1 Architects R o o f e r s
N u m b e r Percent N u m b e r P e r c e n t
- --
NO.
of buildings reported in detail 292 152Roof Type 334 259 Roof Roof garden Plaza roof Type of Building 292 Offic e s Schools Hospitals Factories W a r e h o u s e s Houses Apartments Recreational Other Roof S i z e 2 5 0 0 s q f t (25 squares) 5 0 0 0 s q ft (50 squares) 1 0 0 0 0 s q f t ( 1 0 0 squares) 15000 a q f t (150 squares) 2 0 0 0 0 sq f t (200 squares) 25000 sq f t ( 2 5 0 squares) 5 0 0 0 0 sq ft ( 5 0 0 squares) O v e r 5 0 0 0 0 s q f t (over 500 squares) Deck Type - Wood
Steel with plywood S t e e l w i t h gypsum C o n c r e t e c a s t in place Concrete precast O t h e r
S T U D Y O F P R O T E C T E D MEMBRANE ROOFS (PMR) ( C o n t . )
Detailed Questionnaire
-
PartII
Architects Roofers-
N p b e r Percent N u m b e r P e r c e n t~Mernbrane Type 3 06
# 15 f e l t and asphalt # 1 5 f e l t and tar
Asbestos felt and asphalt Glass f e l t and asphalt Coated felt Rubberized asphalt Other felt O t h e r l i q u i d O t h e r Insulation Type 29 1 Polystyrene Extruded P o l y s tyxene Bead U r e t h a n e
Perlite and Asphalt
Other Surfacing 353 Paint Cast c o n c r e t e Precast c o n c r e t e slabs Gravel Earth Felt Other Deck Slope Slope No slope Membrane Adherence 2 7 6 Full Partial Insulation Adherence F u l l N o n e
S T U D Y
O F
P R O T E C T E D MEMBRANE ROOFS (PMR} A r c h i t e c t s Detailed Q u e s t i o n n a i r e-
PartII
R o o f e r s Number Percent N u m b e r P e r c e n t location^ R e p o r t i n g British Columbia Alberta Saskatchewan Manitoba O n t a r i o Quebec New B r u n s w i c l c N o v a Scotia P r i n c e Edward Island Newfoundland N o r t h W e s t T e r r i t o r i e s United States of A m e r i c aN A T I O N A L R E S E A R C H C O U N C I L O F CAI!AI)A n i v i s i o n o f B u i l d i n g R e s e a r c h S T U D Y O F P R O T E C T E D ~ I E M S K A F ? --- R O O F S I N C A N A D A T h e p u r p o s e o f t h i s s t u d y i s t o e x a m i n e t h e u s a g e o f ~ r c t e c t e d m e m b r a n e r o o f i n g s y s t e m s i n C a n a d a , a n d t o d e t e r r r t j . a e t h e p e r f o r m a n c e to d a t e o f s u c h s y s t e m s . T h e D i v i s i o n o f B u i l d i n g S e s e a r c h h a s b e e n p r o m o t i n g s u c h s y s t e m s s i n c e 1 9 6 5 , a n d h a s b e e n c a r r y i n g o u t l a b a r a t o r y a n d t e s t b u i l d i n g s t u d i e s a t S a s k a t o o n , b u r do n o z k n o w t . h e e x t e n t t o w h i c h p r o t e c t e d m e m b r a n e s y s t e m s a r e in u s e . T h e S a s j c s y s t e ~ a n d s o m e v a r i a t i o n s a r e i n d i c a t e d b e l o w .
I
I
F%UTECTI~!.,E LAYE'R
2
2
INSULATING
LAYER
3
3
ROOF
MEMBRAbIE
4
4 ROOF DECK
5
DRAINAGE LAYER
QOTSHWNI
BASIC
SYSTEM
N A T I O N A L R E S E A R C H C O U N C I L O F CANADA D i v i s i o n of B u i l d i n g R e s e a r c h Q U E S T I O N N A I R E O N
-
PROTECTED MEMBRANE R O O F S-
-- P A R TI
C i r c l e o r c h e c k mark( 4 )
o n e answer l t Has y o u r f i r m d o n e a n y u p s i d e down'' ( p r o t e c t e d m e m b r a n e ) r o o f s ? If y e s t o q u e s t i o n I, how many? D o e s t h i s t y p e o f r o o f c o s t m o r e o r l e s s t h a n a n e q u i v a l e n t c o n v e n t i o n a l r o o f ? H o w much m o r e o r l e s s ? Have y o u h a d c a l l b a c k s o n ' ' u p s i d e down" r o o f s ? D o y o u r e c o m m e n d t h i s t y p e of r o o f ? H a s y o u r f i r m d o n e r o o f g a r d e n o r p l a z a roofs o f t h i s t y p e ? I f y e s t o q u e s t i o n 7 , how m a n y ? H a v e r o o f g a r d e n s o r p l a z a s o f t h i s t y p e b e e n ( 1 ) a s s u c c e s s f u l , o r ( 2 ) m o r e s u c c e s s f u l t h a n c o n v e n t i o n a l d e s i g n s ? T f v o u h a v e o a t d o n e any p r o t e c t e d m e m b r a n e t y p e r o o f s , d o y o u a n t i c i p a t e d o i n g a n y in t h e f u t u r e ? Y E S N O 1, 2, 3 , 4 , 5 , 6 PiORE L E S S Y E S N O Y E S N O Y E S C O M M E N T S : - -- - L. - --_
- - - --- - - -_
- - ._ _
R E T U R N T O : M a x w e l l C, B a k e r , H e a d , D e s i g n S e c t i o n , D i v i s i o n o f B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C n r l n r i 1 n f r a n a d aN A T I O N A L R E S E A R C H C O U N C I L OF CANADA C i v i s i o n o f B u i l d i n g R e s e a r c h Q U E S T I O N N A I R E O N .- P R O T E . C T E D MEMBRANE R O O F S
--
P A R T I1 P a g e 4 s h o w s a c o d e of l e t t e r s t h a t m a y b e u s e d t o c o m p l e t e s o m e i t e m s o f P a r t 1 1 if a p p l i c a b l e a n d c o n v e n i e n t . If w o r d d e s c r i p t i o n s a r e p r e f e r r e d , p l e a s e u s e t h e m . I f s p a c e is i n a d e q u a t e , p l e a s e p r o v i d e a d d i t i o n a l i n f o r m a t i o n o v e r l e a f . R E T U R N TO: M a x w e l l C . B a k e r , H e a d , D e s i g n S e c t i o n , I l i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a , O t t a w a , C a n a d a . K I A O R 6---
T y p e o f B u i l d i n g P l a c e o r P r o v i n c e --- -- S F z e o f R o o f1
'v -I
D e c k T y p e ?ternbrane T y p e L n s u l a t i o n T y p e S u r f a c i n g T y p e I D e c k S l o p e S l o p e 110 S l o p eI
: I e m b r a n e : . d h e r e n c e F u l l P a r t i a l . I- Y - f ~ n s u ~ a t i o n A d h e r e n c e F u l l N o n eN A T I O N A L R E S E A R C H C O U N C I L OF C A N A D A D i v i s i o n o f B u i l d i n g R e s e a r c h
B U E S T I O N N A l R E O N P R O T E C T E D M E M B R A N E ROOFS _.
E x a m p l e s a n d l e t t e r c o d e t h a t may b e used t o c o m p l e t e some o f t h e i t e m s
o f P a r t 11. I f p r e f e r r e d , w o r d d e s c r i p t i o n s may b e used. B ~ ~ i l r i i n y EIenhr fine I n s u l a t L n n S u r f a c i n g T y p e
I
- J P o l y s t y r e n e E x t r u d e d P a i n r -:::~,~;sIl5
F C I ~ L i ~ c p i \ a ~ c1
-1
ti::
iwnod
S t e e l .5 P t v w n o d # 1 5 F e l t & T a r P v l y s t y r c n c Bcad1
C o n c r e t e C a s t1
- - - -. - - -. - - -
l l o s p i t a l lD000 S t e e l 6 G!psum A s b e s t a n F e l t & Asphslt U r e c h o n ~ C s n c r c l e P r e c a s t
I I I I 1 F a c t o r y 15000 P e r l i t e L A s p h a l t - G r a v e l I 1 W s r e l ~ o u s e Rubberized A s p h a l t A p a r t m e n t s 30000 O t h e r F e l t S y s t e m R c c r e a t i n n o v e r 5 0 0 0 0 --- O t h e r L i q u i d S y s t e m
