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Built-up roofing practice in Canada
DIVISION OF BUILDING RESEARCH
NATIONAL RESEARCH COUNCIL OF CANADA
'f
E
C
1HI!if II COAlL
flUtI FOR PUBLICATION
NOTJE
No.
254
FOR ｉｎｔｅｒｎａｾ USE
""BIPARED BY
E, V, Gibbons
CHECKED BY APPROVED BYRFL
!i:IlEPAR'ED FOR
The CIB Committee on Flat Roof Construction,
DATEJune
1958
SUBJECT ｂｵｩｬｴｾｵｰ
Roofing Practice in Canada.
This note has been written to accompany copies of "A Special
Report on Built-up Roofings" which are being sent out for the
information of CIB members studying Flat Roof Construction.
While
this special report. prepared by the Northern California Chapter
of the Construction Specifications Institute, was intended for
building in California it is, in general, representative of current
practice in Canada in constructing built-up roofs.
There are,
however, instances which for various reasons require further
inter-pretation in view of Canadian conditions.
Roof Deck Insulation
In Canada more roof insulation is required than in California
where it is warmer.
The usual practice in this country is to place
the insulation on the roof deck and under the roofing membrane.
It has been established that unless a ceiling is already suspended
in place that it is more economical to place the insulation on the
deck.
Correspondingly, with many buildings there is no other
alternative than to follow this procedure.
Vents for Roof Insulation
The use of "breathing" vents for roof insulation is
receiving increased attention in Canada.
Two methods may be
used to overcome the tendency for built-up pressure within the
porous insulation to form blisters or pin holes in either the
vapour barrier or roofing membrane.
One method is to install a
number of ventilators from the insulation to the outside air.
The other method provides side venting through perforated edge
blocks beneath the flashing and through open vertical joints in
the masonry.
For more detailed information reference may be made
to the U. S.A. publication "Desfgn of Insulated Buildings for
Various Climates" by Tyler Stewart Rogers,
(" BUILDING RESEARCH
ｾ
LIBRARY·
JUL 7 1958
ｾ
2
-The insulation of roof decks with wood fibre insulation
boards 'cas been lJsed extensively
LlCanada for a :lumber of years.
[:oards
01' ｾｨｩＲt:"pe, now commercially available, ['lave been provided
with grooved edges to permit venting to parapet vent holes or to
roof deck ventilators.
Felts
Gravel surfaced, rag felt built-up roofing is by far the
most common in this country.
Glass fibre mat or felt materials
have become available recently but to date their use has been of
an experimental nature and
ｴｨ･ｲｾｯｲ･limited.
They have not been
entirely free of difficulty and are more expensive than the
con-ventional materials.
Some cracking has been encountered over
joints of roof boards as well as application problems in the field
in controlling the amount of asphalt coming through the mat.
A SPECIAL REPORT
ON
BUILT-UP ROOFINGS
BU1LDINr, RESEARCHUSt(,\RY
-i,lAY 8
1958
NATIONAL RESEARCH COUNCIL
-- \ !'-. . . .- - y• . . - ' .ｾｾＮＭＭＧ ,
-PREPARED BY NORTHERN CALIFORNIA CHAPTER,
Sacramento, California
Construction Specifications Institute
Completed
JULY 1, 1957
VI
A REPRINT FROM THE FALL ISSUE OF THE "CON-STRUCTION SPECIFIER," QUARTERLY TECHNICAL JOURNAL OF THE CONSTRUCTION SPECIFICATIONS INSTITUTE, INC., 1520 18TH ST., N.W., WASHINGTON 6,
D. C. COPYRIGHT 1957. PERMISSION TO REPRODUCE
THIS REPORT IN WHOLE OR IN PART MUST BE OB-TAINED IN WRITING FROM THE CONSTRUCTION SPECIFICATIONS INSTITUTE.
C.S.I. 12·8 57 CALIFORNIA
At right is ROLF T. RETZ, chairman of
the Calijornia Committee responsible for this report. Retz was recently named Chairman of CSI's National Programs Committee. He was appointed to the Institute's Board oj Di-rectors on September21, replacingJ.R. Liske oj Sacramento. Retz's comments on this re-port jollow:
INTRODUCTION
This report covers Built-up Roofings. Other types, such as Asphalt, Asbestos, and Wood Shingle and Tile Roofings will follow.
COMMITTEE MEMBERS
Rolf T. Retz, Chairman, Calif. State Division of Architecture
Arthur M. Balsam, Executive Committee, Free-Lance Spec. Writer
T. W. LeMieux, Executive Com mit tee, Sacramento Roofing &
Insulation Co.
John R. Skidmore, Koppers Co., Inc.
Donald M. Blackman, Owens-Corning Fiberglass Corporation J. R. Liske, Cox and Liske, Architectural Firm
George F. Winslow, California State Division of Highways A. D. Park, Johns Manville Corporation
Robert C. Gill, Lloyd A. Fry Roofing Co., Summit,Ill.
MAIN CONTRIBUTORS to whom the Chapter is primarily indebted: Ralph L. Hilton, Staff Engineer, Pabco Building Materials Div., S.F. John R. Skidmore, Koppers Co., Inc., Los Angeles
Donald M. Blackman, Sacramento S a I e s Representative, Owens-Corning Fiberglas Corporation
C. J. Van Til, Executive Manager, Western Asphalt Roofing
Manu-facturers Association
OTHER COMMENTS, which also have been of great assistance were those of:
G. W. Clarvoe, Research Dir., Johns Manville Corp, Manville, N. J. B. A. Vallerga, Managing Engineer, The Asphalt Institute, S. F. John J. Stanko, Ph.D., Vice President, Do u g 1a s Oil Co. of Calif.,
Paramount, Calif.
Richard T. Award, President, Pioneer Roof Co., Los Angeles
Frank Lander, U. S. Gypsum Co., Los Angeles
W. C. Thieleman, Pioneer Division, The Flintkote Co., S. F.
G. L. Oliensis, D ire c tor of Research, Lloyd A. Fry Roofing Co.,
Summit, Ill.
REFERENCE is especially made to paragraph I-B, "Controversial Issues," in the report. Unanimous agreement of contributors and others who commented is not to be inferred. The Committee itself must be held responsible for the report. However, without the contributions and comments from the roofing industry, this report would not have been
made possible. On behalf of CSI, we, therefore extend
to
thesecon-tributors our deepest appreciation.
ROLF T. RETZ, President
History of the Roofing Report
This "Roofing" report is the first of its kind prepared and issued by the Northern
California Chapter.
Itwas possible primarily because of the lively interest and
gen-erous assistance of the built-up roofing industry.
First proposed at the Bakersfield meeting in January, 1956, by the four CSI
chapters of California, our Chapter discussed the basic principles to govern prospective
reports at its March, 1956, meeting when a Committee on "Roofing" was appointed,
consisting of four specification writers, four manufacturer's representatives, and one
roofing contractor. In April a call for drafts of the report was sent out, resulting in
three separate comprehensive drafts by three roofing materials manufacturers, in
gen-eral following the proposed outline. When the Chapter met in May, the first
prelimi-nary report was presented and reviewed in detail. This draft was then distributed to
all interested parties in June, and reviewed again in July by the entire Committee in
session.
In August an Executive Committee of three members, two professional and
one roofing contractor, reviewed the comments which had been received. A second
draft was then retyped and issued in September to the entire Committee, 15
manu-facturers, and various experts. After comments had been received and a third
com-plete redraft issued by the three-man Committee in October, the manuscript was
sent out for "final" comments. When these were received, the "Final" fourth draft
was issued in December and published in the January, 1957, issue of the
"Specifi-cation Digest," comprising Parts I and II.
At the California Regional Meeting of CSI Chapters at Fresno in January of
1957, a resolution was passed, further clarifying the scope of CSI "Reports." This
resulted in further work by the Committee, essentially carried out by three
mem-bers of the Committee, with the very valuable assistance of a manufacturer's
asso-ciation. This work, resulting in Parts III, IV and V, went through stages similar to
Parts I and II; that is, three separate drafts and redrafts with comments between,
primarily from roofing manufacturers, and final issue by July 1, 1957.
In conclusion, it may be stated that any such Committee assignment, to insure
adequate progress, requires considerable conscientious, hard work. This usually falls
upon one person, who should be a professional specification writer. In addition, much
assistance from the industry is imperative. Luckily, we had that from the beginning,
al-though some manufacturers rather belatedly realized that they should have been
in on the project from the beginning.
Finally, due to one particular controversy between advocates of the two basic
bitumens used for built-up roofings (which may be the case in other reports as well),
it becomes somewhat of a delicate problem at times to sift the claims of the various
commercial interests so that only recognized facts can be incorporated. That is a
chal-lenging problem to CSI and should be very carefully watched in every report issued.
We must not deviate from the straight and direct path, which means exercising
pro-fessional integrity and presentation of facts only, not "sales talk." Luckily, we had
a good start in the three, exceptionally unbiased first drafts, prepared by Associate
Members representing three different types of manufacturers. We are extremely
for-tunate in having such Associate Members in CSI ranks.
Built-up Roofings
PART I-GENERAL COMMENTS
A. PURPOSE OF REPORT-This report has been pre-pared for the purpose of supplying specification writers with basic technical information on materials for and construction of built-up roofings for buildings in California. Such information is meant to assist California specification writers in the selection of the proper type of built-up roofing and in the prepara-tion of better specificaprepara-tions.
B. CONTROVERSIAL ISSUES-Admittedly, many of the statements made herein are controversial, and unanimous agreement throughout is impossible. How-ever, everyone of the statements made are recom-mended by some segments of the roofing industry, and most of them are acceptable to most of the industry. Attempts have been made to present both sides of the controversial issues in a fair and impartial man-ner, but at the same time to indicate what is believed to be good practice. Further revisions will follow when new developments indicate different solutions. C. CALIFORNIA CONDITIONS-There is an appar-ent need for dissemination of this kind of informa-tion in California. In the past, many manufacturers' literature on roofing has been prepared for Eastern roofing conditions. To a large extent, Eastern cli-matic conditions do not apply to California. The colder climates are almost non-existent here in the populated areaSj and nowhere in the U.S.A. (except in parts of the South-West) are summer conditions equal to those here; that is, prolonged periods (six months or more) of hot and dry weatherwtlwutrain.
Such a climate means different problems and dif-ferent solutions.
D. FORM OF REPORT-The form and arrangement ofthis report has been set up in a manner that will facilitate revisions which become necessary from time to time, as new techniques and new methods are de-veloped and as new products appear on the market. Thus, it will be seen that this report is only the be-ginning of a continuing, long program of expansion, modifications, improvements, and developments of contemporary thinking on roofings.
E. BREAKDOWN OF REPORT - The subject of "BUILT-UP ROOFINGS" is broken down into sev-eral separate parts, as follows:
Part I-General Comments Part II-Detailed Discussion Part III-Scope of Work Part IV-Roofing Terms Part V-Bibliography
3
C. S.I.
12-B 57 CALIFORNIAF. BASIC CONSIDERATIONS-Each job and each roof must be considered separately and on its own merits. The danger of using "canned" specifications without proper consideration of their applicability to the job at hand, cannot be over-emphasized. In each case the correct answers must be found to the fol-
,
lowing basic questions:a. SLOPE-What is the slope of the roof deck? b. DECK-Of what material is the roof deck
con-structed?
c. CLIMATE-What are the climatic conditions? d. CODES-What are the building code
require-ments?
e. LIFE-What life expectancy is desired?
f. COST-Is initial cost a prime factor? g. COLOR-Is a colored roof surface desirable? h. MAINTENANCE-Will periodic maintenance be
available?
i. BUILDING INTERIOR CONDITIONS - Has building excessively high humidity?
Under each of the various types of roofings, lightwill be thrown on these basic considerations, so that the specification writer will be able to analyze each in-dividual job.
G. COORDINATION WITH DRAWINGS-The de-tailed drawings must in all cases be prepared to agree with the roofing industry's conception of proper con-struction, including such details as height of lip of metal edge stops, pitch pockets, cants, roof openings, flashings including plastic flashings, and many other details. These, in turn, must agree with the specifica-tions, and all work must be properly coordinated.
Many errors may be eliminated by having sheet metal shop drawings cleared through the Roofer
be-fore release.
PART II-DETAILED DISCUSSION
A. GENERAL DESCRIPTION
a. GENERAL: Built-up composition roofing is ex-actly what the name implies. It is "built-up" on the roof deck like a sandwich in alternate layers of comparatively lightweight felts and bitumen. Bitumens alone, without the reinforcing that the felts impart, would crack and alligator. The mem-brane of felts and bitumen together form a flexible waterproof roof cover that has sufficient strength to withstand the normal expansion and contrac-tion of structures. The bitumen is the weather-proofing material, and the felts hold the bitumens
The bitumens are either coal tar pitch or asphalt. Both of these are generally applied hot, although some asphalt roofings are also applied cold.
The felts are either "rag felts" (organic fibers), asbestos felts, or glass fiber felts.
Usually, built-up composition roofings have a surfacing over the last ply or felt layer in the assembly. According to this, the various types are divided into the following classifications:
1. GRAVEL SURFACED ROOFINGS: A flood coat of asphalt or coal tar pitch, followed by application of gravel, slag, or crushed rock. 2. GLAZE COATED ROOFINGS: A glaze coat
of asphalt.
3. CAP SHEET ROOFINGS: A cap sheet that may be a smooth, or mineral surfaced sheet. 4. COLD PROCESS ROOFINGS: A cold applied
asphalt emulsion or cut-back asphalt over the top felts.
Reflective coatings may be sprayed or brushed over the glazed surfaces or over the cap sheets. b. BONDs-Dne of the most important factors in
a built-up roofing is proper application and work-manship. In order to insure this eastern coal tar manufacturers started about 50 years ago to have roofings bonded by surety companies. These bonds assured owners that the roofing is applied by capable roofing contractors under the supervision and inspection of the roofing materials manufac-turer, and that, should water leaks occur, roofing will be repaired by the manufacturer (or surety company) during the period of the bond.
Prior to 1922, bonds were not offered in Cali-fornia. In 1922 West Coast (asphalt) roofing manufacturers began to offer 10, 15, and 20 year "Maintenance Agreements." These were not sup-ported by surety companies. Many thousands of such agreements were made in the next ten years. The practice was abandoned in 1933 and not re-sumed until a few years ago. In 1950, coal tar pitch was introduced for the first time in California, and a bond was offered, similar to the Eastern "bonded roofs." Such pitch was first shipped from the East, until Koppers' Fontana plant started production in 1952. Shortly thereafter the asphalt industry started bonding of roofings. However, all manufacturers maintain that the primary thought should be given to produce "a good roof rather than a bonded roo£''' This means proper specifi-cations and its necessary corollary, adequate in-spection and control, which in tum brings about proper application techniques. It should be re-membered that:
4
1. THE BOND covers only leaks due to normal wear and tear.
2. INSULATION is not covered by the bond. 3. THE VALUE of the repair work is limited, generally, to work not exceeding a cost of from $5.00 to $10.00 per square, although this figure is not the upper limit of the value of the work which some manufacturers will perform in repair-ing a roof.
4. THE BOND does not pay for any damage done to the building or its contents, nor for any damage caused by faulty roof deck.
5. BUILT-UP FLASHING requires a separate "Flashing Agreement."
6. METAL COUNTERFLASHING, which causes most of the roofing leaks, is not included (this work should not be covered under "Roofing" anyway, but under "Sheet Metal" and is usually guaranteed for two years).
The best argument for a bond is the rigid inspection of roofing materials and application provided by a representative of the roofing manu-facturer. Most manufacturers now provide such in-spection service or require that the roofer, licensed by the manufacturer, meet with his agent before work is started to clarify procedure and applica-tion technique. However, many roofers feel that the bond should be eliminated and that the selec-tion of a reputable Roofer by the Architectis the best guarantee against roofing failure. Public agencies cannot make such a selection; however, when a bonded manufacturer licenses roofers, this may actually result in the same thing.
The cost of the bond varies from $1.50 to $1.75 per square for 20 year bonds with a lower limit of from $50.00 to $150.00 (by some a minimum of 100 squares). Bonding should not be called for on roofs of less than 100 squares and should be confined to 20 year bonds.Itshould not be neces-sary to pay for a bond when only a ten year roof is desired.
Trouble-free roofings may actually beexpected far in excess of 20 years, and information is avail-able from manufacturers on built-up roofings that some roofs have lasted as long as 30, 40, and even 50 years in the East without need for repairs. This means an economical roofing over the years. c. GUARANTEE-Itisalways customary to require
a guarantee from any contractor on his work. Built-up roofings are usually guaranteed by the Roofing subcontractor for two years. This is re-quired by some Architects whether or not a bond is called for; the reason for this is that the guar-antee covers all work done by the Roofer, includ-ing the insulation, flashinclud-ings, and other items not covered by the bond.
d. BUILDING CODES require fire retardant roof coverings according to "Type" of building involved and the fire zone of the building. Most gravel sur-faced roofings and many glaze coated asbestos felt roofings rate Class "A" or "B" Underwriters' classi-fications, which the Uniform Building Code char-acterizes as "fire-retardant" roofs. Fire retardant roofs are required in Fire Zones 1 and 2 and on Type IV, one-hour buildings regardless of loca-tion. In Fire Zone 3, most types of built-up roofs are permitted, regardless of surfacing.
:By definition, Class "A" roofings include cov-erings which are effective against severe fire expo-sures. Under such exposures, roof coverings of this class are not readily flammable and do not carry or communicate fire; afford a fairly high degree of fire protection to the deck; do not slip from position; possess no flying brand hazard, and do not require frequent repairs in order to maintain their fire resistive properties. Class "B" roofings are effective against moderate fire exposure, while Class "C" affords a slight degree of fire protection. e. LIFE OF ROOFINGS IN GENERAL-The num-ber of plies (felt and bitumen) used in the mem-brane under the surfacing within each of the var-ious types of felts and bitumen used, determines the life of the roofing; these may vary from a single ply up to five ply roofings or more. The surfacing also affects the life, the gravel surfacing being recognized, generally, as having the longest life, followed by glaze coated asbestos roofings, cap sheet roofings, and cold process roofings.
B. BITUMENS-ASPHALT & COAL TAR PITCH a. GENERAL-Hot bitumens are used with three
of the four types of built-up roofings under dis-cussion here, that is, the gravel surfaced, glaze coated, and cap sheet roofings; cold bitumens are used with the fourth type, cold process roofings. b. ASPHALT-The asphalts with which we are fa-miliar in the West are manufactured from western petroleum crudes from which the lighter fractions have been removed. Most roofing asphalts are processed by the air blown method. Within the last few years, however, "new" or "dead level" asphalts have been placed on the market and of-fered for use on dead level decks. These asphalts are derived from the same sources as the older types, but with certain modifications in their pro-duction. Some are produced largely by steam dis-tillation with only a minimum of air blowing; others have been modified by the addition of asphaltic resins.
Roofing asphalts are currently available in a number of different grades, which II1akes it
pos-5
sible virtually to tailor-make them for the slope and climatic conditions at each separate location. These climatic conditions vary much more abruptly • in the West than in the East, and in particular in California. Here we start with 55° to 60° F coastal temperatures and go to 800 to 90° F
"Back-Bay" temperatures in 20 to 30 miles, then to 100° to 110° F hot valley temperatures in 75 miles. Asphalt for roofings are graded to take care of this, and the wise roofer will select the proper grade.
This grading of asphalt takes the fOrln of dif-ferent "Melting Points," (Softening Points) which for asphalts range from as low as 130° F to as high as 200° F. Such "Melting Points" are deter-mined according to more or less arbitrary test method (ASTM-D36). This "point" is NOT the temperature at which the asphalt starts to "flow"; actually, the asphalts "flow" at a somewhat lower temperature depending upon slope and mass weight and bulk of asphalt and surfacing.
In general, it can be said that the lower the melting point, the better the self-healing proper-ties, and the less the tendency to crack, and the longer the life expectancy. Therefore, the melting point should always be the lowest possible, con-sistent with slope and climatic conditions. The maximum possible weatherproofing qualities are required on dead level decks where water may be standing. As the slope of the roof increases, the need for waterproofing is lessened. Accordingly, low meh asphalts are used on dead level decks, and higher melt asphalts on the steeper decks, with 190°/200° F asphalt on slopes exceeding 2 inches per foot in the warm or hot climates and steeper in cool coastal areas.
In the past, ithas been the tendency of many roofers to use high melt asphalts regardless of the fact that job conditions would warrant low melt asphalt; this has been due to the fact that the handling of soft, low melt asphalt takes con-siderably more care in planning. Now, thanks to bonding, the manufacturer enters into the picture and can insist on the proper bitumen for bonded roofings.
c. COAL TAR PITCH is a by-product of the coking process in steel manufacture. In California, coal tar pitch is produced in Southern California; the crude tar is obtained from steel producers. The melting point in general varies between 1400 and
155° F; California tar is between 1500
and 155° F. Coal tar pitch is, therefore, a low melt type bitumen; as such it has been used for many years in the East on most dead level or nearly dead level surfaces and has given excellent service in such locations. Its main reputation rests on its "cold
TABU OF VAlUOVS MANVPACTUJU!ll'S 20.YEAR BONDED GRAVEL SURFACED ROOFINGS
CAllEY CERTAIN- J-M PIONEER
ASPHALT
..
CELOTEX TEED FIBERGLAS FRY ASPHALT KOPPERS PABCO FLINTKT.ASPHALT ASPHALT ASPHALT ASPHALT
....
COAL TAR ASPHALT ASPHALTWOOD DECKS
Sbeacbing P.per
--
N... I @ 7# NOlle I @ 5# NODe 1 @ 5# 1 @ 7# I @ 7# 1 @ 7#B... Sheou 2 @
u"
No.... 1 @ 30# 1 @ 14# 1 @ 30# 2 @ 15# 2 @ U# NODe NolleFinish I'<lu·
----
3 @ 15# 5 @ lSI 3 @lSI 3 @ 6# 3 @ 15# 3 @ lSI 3 @ 15# 5 @ lSI 5 @ lSIMopping. , @ 2'# 4 @ 2'# 3 @ 30# 3 @ 35# 3 @ 25# 3 @ 30# 3 @ 25# 4 @ 25# 4 @ 25#
Flood Coat 50# 60# 60# 60# 50# 70# 75# 60# 60#
Gravel 400# 400# 400# 400# 400# 400# 400# 400# 400#
CONCRETE DECKS
Primer 1Gal. 1Gal. I Gal 1Gal. 1\4 Gal. 1Gal. NOlle
Iv..
Gal. 1Gal.Pint Mopping
- - -
<40# Solid 10#Spot 10#Spot 15#Spot 25#Solid 10#Spot 35# Solie! 10#Spot 10#SpotFinDII F.I.. • 4 @ 15# 4 @ 15# 4 @ 15# 1 @ 14# 4 @ 15# 4 @lSI <4 @ 15# 4 @ 15 4 @ 15#
2 @ 6# Moppings 3 @ 25# 3 @ 25# 3 @ 30# 2 @ 35# 3 @ 2$# 3 @ 30# '@ 30# 3@ 25# 3 @ 25# Flood Coat 50# 60# 60# 60# 50# 70# 75# 60# 60# Granl 400# 400# <400# 400# 400# <400# 400# 400# 400# INSULATED DECKS OVER INSULATION Flnt Mopping 46# 30' 30# 35# 25# 40# 35# 30# 30#
Fmial> Fetu· 4 @ 15# 4 @ 15# 4 @ 15# 1 @ 1<4# 4@ 15# 4@ 15# 4 @lSI 4@lSI 4 @ 15# 2 @ 6#
Mopping. 3 @ 25# 3 @ 25# 3 @ 30# 2 @ 35# 3 @ 25# 3 @ 30# 3 @ 30'# 3 @ 25# 3 @ 25#
Plood eo.t 50# 60# 60# 60# 50# 70# 75# 60# 60#
Gravel 400# 400# 400# 400# 400# 400# 400# 400# 400#
...
-
-
-
-
-
--
-
-.. Allfeleo.bove .... orglUlic (r.g) feltl.
•• Abo IIoDdaCoalTarRoofia,.,'imilar to Koppen.
••• TIUa roaf is beadedonlyfor deaellevel eleclu .ptoｾ iDc!l '. .ThitIiUJlafAmuuaboboodaglazecoated aabeoca. felt roou for alo.... from
°
to6intllpor f - ..... For cODltruetiml _der intul.tioIl, _ catalogs of ...ufacmuen.
NOTE: All manufacturers haY.UUntareOIldwUroofing
,.001_.
Some of these .reftiypodanel """cain ...alualli. mformatloB.SUMMAIlY OF BUILT.UP COMPOSmON ItOOl'!NGS
GRAVEL SURFACED GLAZE COATIi:ASBEST. FLTS. CAP SHEET COVERED COLD PROCESS
Slo.... TllI:rl 0to1" or 1" 1"to(,H 1"to6" 1"to ,"
Aspllalt:
°
to,N
(Onc Wg.°
to6") (One Mfg. 2"to6")P.rmiuable Wood, OOIIcrece. 8YPInm, Same asgra...el Same .. gravel Oil nailable
Deck Type. inlalated.teeI,moot lurEace. onl,
intal••ion.
Clima... Anywlsere, Utept for Goodin hot clima.... Best in moderate Warm CIinsa....
sloping roof. ia ... also in mod... climates;inhot
coantry clima... under
certain conditions
Code. ClaSlifiecl accordingto Same ..V ...L P-lrt retardant when Onlycertain
..umber ofJarv' - asedwitlland.rlay. ....mblies recognized
Fire retardate. mtJIt of proper type as 'lrt retardan••
and amoant.
life Longcrc Nearly .. long .. gravel Ulng for Iteep do<:1u Shortest, generally.
whc.D carefally innalled. (as gravel). Not10lona ｓｾｩ｡ｬ types llave
for flatterdec:ko lona life
InitialCoot Asph.Ii:Asb. (orgIau)felts: Higherdian.sphalt rag felt Almost .ame .. LowCost.
Highes. of aU roof.. and granl. About equal ...phalt rag fel.., SpecialtypeIare
TarJtezt. eo tatand graYe!- "nel graveL high incost.
A.pllalt &: Rag Fel...Neu
color T.r: Gra"ol or .Jag only. Maybecoated in a1nmin... Red, green, gray, Black or alnmin_
AopllajtlSomecolOftd or colan. black, or a1nminnm coated
.ggregate OK bathigher CO". coatin!_
Mail>...ce Nomal!>t. for 20 yr, botocled Periodic ..glazing, or Periodic reeoating P.riodic resurfacing
Lo", ..aiDe. (lIl n_·beaded. recoating. wllere colORCl. may prolong lif.. may proloRg lif..
6
---flow" or self-healing properties. It will flow to-gether and close up cracks that may have formed. The manufacturers state that this is due to the fact that the molecular structure of pitch is such that the individual molecules have a physical at-traction for each other, not depending on heat for self healing. Coal tar roofs, according to its manu-facturers, are entirely unaffected by water, when adequately covered with mineral aggregate, and are stated to be actually preserved by water, the life prolonging oils being protected by dampness. These qualities explain coal tar's extended accept-ance for low slope roofs.
d. COAL TAR VS. ASPHALT is an old controversy still raging. Actually, in the past they have found their respective separate uses, and that has been, by and large, coal tar for dead level or nearly dead level decks and asphalts for the steeper decks. Both are claimed to have low water absorption and low moisture permeability, and are both virtually waterproof. The so-called "new" or "dead level" asphalts are also claimed to be little affected by water standing on the roof. In the past, however, asphalt, when used on dead level surfaces, was generally used with a double-graveled surfacing. The new dead level asphalts do not require this, although in their present composition they have not had an extended service record behind them. Some of the older asphalts, which were of high melting point, were poor in self-healing prop-erties. Weathering left the asphalts impoverished due to the drying out of the oils, and with each passing year cracks developed which were incapable of self-healing. On the steeper roofs this is of lesser consequence, but on dead level roofs this can be disastrous.
The "new dead level" low softening point as-phalts are advertised as having overcome this defect and as having "self-healing" properties; some of these asphalts are stated not to crack in cold weather and to be not nearly as brittle as the older asphalts. The dead level asphalts are also claimed to be less subject to deterioration resulting fmm direct exposure to the weather than are coal tar pitches; however, the latter are never used with-out gravel surfacing, while asphalt, it is stated, may be exposed more readily or covered with other surfacing treatments than gravel or slag. One manufacturer is willing to bond a dead level as-phalt and asbestos roofing with a glaze coated surface; that is, membrane surfaced with a light mopping of so called "filled" asphalt instead of flood coated asphalt and gravel.
In summary, it may be stated that both of these two materials will provide serviceable roofs; a conscientious Architect would do well to
investi-7
gate other roofs in the area in which the new building is to be located.
e. SLOPE OF ROOFS-As has been pointed out above, coal tiu pitch is primarily suitable for low slope roofs. Coal tar pitch manufacturers state that pitch may be used (with gravel surfacing in all cases) up to one inch slope per foot on non-nail-able decks and two inch slope on nailnon-nail-able decks. Asphalt manufacturers recommend gravel surfaced asphalt roofs up to three inch slope. Some Archi-tects limit asphalt roofs to 20 inch slope in the hot California Valleys and coal tar pitch to
0
inch slope.The maximum limit for gravel surfaced roofs is determined by two criteria: One, the ability to place the hot and heavy (60-75 lb.) flood coat for the gravel over the felts and make it stay in place until it has cooled off, and, two: The ability to keep gravel in the heavy flood coat from slipping or sliding in the hot summer months. The limit for gravel surfaced dead level asphalts ranges from zero to
0
inch slope; that is, steeper slopes would call for higher melt asphalts.Where insulation is used, the bitumen over the insulation becomes hotter than on roofs with-out insulation. This fact should, therefore also be considered when choosing bitumens, melt point, and surfacing.
Non-graveled roofings may be used on slopes up to 6 inch per foot, with a lower limit of varying recommendations from
0
inch, and even as high as two inches. (Exception: One manufacturer will bond a dead level roof without gravel; that is, with glaze coat surfacing (See II-D-h and II-B-f.)Many roofers are of the opinion that every roof should have some slope, notwithstanding the claims of manufacturers that their bitumens will be OK for dead level roofs. However, the problem is pri-marily one of keeping the roof dry during and immediately after installation. Unless adequate provisions are made for rapid and complete drain-age during this period, wet insulation and inade-quate adhesion of the roofing will result.
f. GLAZE COAT ROOFS have a 20 to 25 pound asphalt "glaze" coat applied to the top surface of the last felt ply in the roofing membrane. Actu-ally, this glaze coat is not expected to have. a very long life, perhaps five to six years. Its mam pur-pose is to protect the underlying smooth ｳｵｲｦ｡ｾ･
felts from curling at the edges. However, even If this glaze coat should disintegrate, the roofing itself will last for many years after that. In apply-ing the felts for this roofapply-ing, special care must be exercised in laying the felts to insure full adhesion between felts along all exposed felt edges.
One manufacturer uses a "filled" asphalt for the glaze coat. This adds protection against actinic sunrays, same as gravel surfacing, and therefore affords longer life than unfilled asphalts.
The surface of glaze coat is black, but may be coated, provided the surface is properly prepared, with aluminum or white coating with or without the addition of asbestos fibers. These coatings will offer some protection for the glaze coat but must be renewed every five to six years. They will also provide some insulating value by reflecting the sun's rays.
Glaze coated roofings are used with asbestos or glass fibre felts and asphalt bitumens only. They may be used, where gravel cannot be prop-erly applied, such as on very steep roofs, barrel roofs, and the like, or where the Architect wishes another surface. This type of roofing has been used in coastal climates and also in the hot val-leys in connection with reflective coatings as above explained. Cost is higher than rag felt and gravel roofings because of higher felt cost.
g. COST OF BITUMENS-Coal tar costs more than standard asphalts, while some of the "dead level" asphalts cost about the same as coal tar.
h. APPLICATION OF BITUMENS-It is very im-portant that bitumens not be overheated in the kettles before application. Where this is done, the bitumen is seriously damaged and its life consid-erably shortened. Asphalt should never be heated over 4500 F and should not be applied under 3500
F at the mop. Coal tar should be 3750
and 2750
F, respectively. Dead level asphalt, 3750
and 2750
F. To insure this, specifications should call for suitable thermometers and should require kettle-men to be in constant attendance at all times. The manufacturers' precautions as to rapid heating, overheating and maintaining maximum tempera-tures too long, must be strictly followed.
i. SPREADING RATES vary between coal tar and asphalt. As the pitch weighs about ＱＰｾ pounds per gallon, and asphalt about Ｘｾ pounds per gallon, more pitch by weight is applied between felts than asphalt, 30 and 2S pounds respectively per square with a little more over insulation. Glass fiber felts require 3S pounds of asphalt between felts. Over concrete, an asphalt primer is applied before applying hot asphalt. A primeris generally not applied where coal tar is used. The first hot coat of asphalt over the primer on concrete is a "spot mop" coat, about 15-20 pounds per square, except that insulation is laid in a "full coat" of as-phalt, about 30 pounds per square and covered with 30 pounds of asphalt. (Some companies specify a solid mop coat in all cases on concrete).
8
j. COLD PROCESS ROOFING is rather limited in use in California and generally used here for reroofing rather than in new construction. It is
particularly useful over areas where a dangerous fire hazard exists; for rural areas where there is a scarcity of skilled mechanics and equipment; and over confined decks inaccessible to kettles and hoists.As the name implies, cold bitumen (emulsi-fied or cut-back asphalt) is used instead of hot bitumen. Emulsified asphalt can be used as a top coat over felts or as a cementing asphalt between plies of felt sufficiently porous (such as glass fibre felts) to allow the water in the emulsion to evap-orate. Cutback asphalt may be used for both cementing and coating with all types of asphalt felts. Asphaltic emulsions must not be applied during freezing weather.
Only certain process assemblies are recognized as fire retardant. Resurfacingis necessary for long life. Do not use this roofing for the flatter decks. Apply over a nailable surface. For the professional applicator, this process may be more costly; just the opposite would be true for the inexperienced applicator.
A "special type" of cold process roofing is being bonded by one manufacturer for 20 years, con-sisting of three heavy cold process sheets (@ 50
#
each) laminated with cold applied cutbackas-phalt and surfaced with a cold emulsified asas-phalt. C.
FELTS-a. RAG FELTS (Asphalt saturated) are maIiufac-tured from a combination of felted papers, shredded wood fibers and, contrary to its name, very little rag content, except in the case of one manufacturer. They are available in weights of 7, 15, and 30 pound per square and are usually 36 inches wide. The IS-pound felt is the felt most commonly used for the layers or plies in gravel surfaced assemblies; the 30-pound felt requires fewer layers as under-lays for heavier cap sheets or tile, mostly on steeper slopes. The seven pound felt is used as a dry sheet to protect wood sheathing against dripping asphalt. The IS-pound felt is supplied both perforated and non-perforated. Perforations permit escape of en-trapped moisture or vapor during the application of the roofing. This minimizes voids in the bitu-men under the felts and hence the later formation of blisters. Perforations also increase bond be-tween felts.
Asphalt saturated rag felts are the least expen-sive of all the felts on the market.
b. ASBESTOS FELTS (asphalt saturated) are man-ufactured from asbestos mineral fibers and are available in weights of 15, 45, and 55 pounds per
square. Widths are either 32 or 36 inches. The 15 pound asbestos felt is perforated. In price they are, as a rule, the most expensive of all felts on the market. However, due to their inorganic make-up, they are much less affected by weather and humidity than most other felts, and often result in maintenance-free service for many years, espe-cially under difficult climatic conditions such as in the hot, dry parts of California, the South-West, and where interior humidity conditions are high. c. TARRED FELTS are coal tar saturated rag felts; coal tar saturated asbestos felts are also available, but not much in use in California. Coal tar rag felts are available in IS and 30 pounds per square weights and in 36 inch widths. They are supplied both with and without perforations; cost is higher than for asphalt rag felts.
Coal tar felts, like all other types of felts, are saturated with the same type of bitumen as is
used between the felts. Opposite bitumens, i.e. coal tar and asphalt, are not compatible.
d. GLASS FIBER FELTS are a recent development; they consist of glass fibers formed into monolithic asphalt-glass fibre mats for use with asphalt in built-up assemblies. They are available in weights of 6 to 7 and 14 to 15 po'Unds and in 36 inch widths. The glass fibers have high tensile strength. When lightly saturated with asphalt, the resultant "felt" gains in strength, yet retains a high degree of porosity, thus assuring maximum escape of en-trapped moisture or vapor during application, and maximum bond between felts. Cost is about the same as that for asbestos felts.
e. APPLICATION-Felts should be laid on the roof
inshingle fashion for all plies and should be rolled into the hot asphalt, not flopped in. This should be done by rolling the felts closely behind the mop, followed by brooming-in of the felts while the bitumen is still hot. One manufacturer recom-mends, where slope of concrete deck is under 2 inches but over 1 inch per foot, that nailing strips be installed in deck at ridges and edges only, and that felts in such cases be laid up and down the slope and nailed securely at upper ends to prevent slippage.It is important that felts not touch felts, but be separated by the bitumen, except, of course, when applied directly over dry sheets.
Application of felts by laying machines is satisfactory, provided machines are operated ex-pertly and at the proper speed. A complete, solid coating of bitumen at the specified weight must be obtained between layers. Again, brooming of felts directly behind the felt laying machine while the bitumen is still hot, is strongly recommended. Drum-type felt layers are not recommended.
9
All felts, as well as insulation, should be coated over with hot bitumen at the close of each day's work to prevent wrinkling, buckling, and curling of seams due to moisture action. This coating is not required over glass fiber felts. No "waterglaz-ing" should be permitted, that is, sprinkling water on the surface of the felts before coating with hot bitumen.
f. NAILING of felts is absolutely necessary on steep slopes, and may be desirable on slopes as low as one inch in some cases. As no nailing can be said to affect the roofing adversely, nailing should rather be too much than too little. All felts must be nailed to wood nailers along gable ends and at lower side of roof openings. All felts should always be nailed to wood decks, regardless of slope. On poured gyp-sum decks, the first felt should be nailed thereto, not mopped, using large-head, square-cut bright roofing nails or square-cut galvanized nails. On concrete decks, when slope exceeds two inches per foot and asphalt is used, felts should be mopped-on as well as nailed to nailers set in deck; the same where coal tar is used when slope exceeds one inch; the same limits for nailing apply also to nailing of felts for insulated roofs.
All felts should cross, not be parallel to, the nailers. All nailing should be through flat tin discs, and must be covered by succeeding felts; this means nailing along the back edges, generally at 12 inches, except "dry sheets" which should be scatter nailed.
g. CAP SHEETS represent another solution where gravel surfacing cannot be used. Cap sheet roofs are similar to gravel s,!rfaced roofs, except that a single or double ply smooth or mineral surface cap sheet replaces the flood coat arid gravel. Cap sheets are heavy roofings, either black or colored, either rag, asbestos or glass felts, saturated and coated on both sides with asphalt and surfaced on the exposed side with mineral granules, mica, as-bestos fiber, or similar materials. These sheets may be lapped 2 inches, or if two-ply const.IUction of cap sheet is used, the lap is 19 inches, called "split sheet." Cap sheets may be used on slopes between 1 and 6 inches. They are best in moder-ate climmoder-ates. Periodic aluminum or white coatings, applied the first time after a minimurn of a 60 day weathering period, may lengthen the life of the roofing in the hotter climates and provide a re-flective finish. Life expectancy in cool climate and steep slopes is high. Cost is approximately the same as comparable gravel roofs.
D. ROOFING
AGGREGATES-a. GENERAL CONSIDERATIONS--Since the pri-mary function of roofing aggregates is to protect
the bitumen from the sun and to provide a fire resistive surface, it is important that they be firmly embedded, cover the surface, and resist abrasion from rain, wind, and occasional foot traffic. In or-der to be firmly embedded, the aggregates must be clean, dry, opaque, and of sufficient size and weight to sink into the bitumen flood coat. They must be so graded as to nest properly, filling voids between individual particles, and there must be enough to completely hide the bitumen. So that it may resist abrasion properly, the aggregate must be hard, but not brittle, and not subject to excessive crushing under foot.
b. GRAVEL-With these qualifications in mind, the clean, dry, natural river washed gravel or crushed gravel so screened and graded as to vary between
ｾ and
%
inch in size, generally produces the best results. This gravel will be of sufficient weight to embed itself firmly in the hot asphalt flood coat when "graveled-in." Also, it is heavy enough to resist movement on the surface of the roof occa-sioned by high winds and rain. The cost of gravel is in most locations less than any other aggregates. c. SLAG is also acceptable and available at a low price in Southern California. Slagisthe fused refuse substance separated in the reduction of iron ores. Where available, it is a good aggregate for roofing,if clean, dry, and properly graded. It is quite porous and adheres readily to the hot bitumen. d. DOLOMITE and marble chips make an attractive
white aggregate for roofs, but some of these aggre-gates are often very dusty; this prevents 100 per cent adhesion to the bitumen. Also, if individual pieces are small, they are quite translucent, per-mitting the light to pass through to the underlying bitumen and thereby causing premature weather-ing. When the bitumen thus becomes prematurely, brittle, the aggregate loosens and washes and blows away. Therefore, white aggregate must be carefully screened, cleaned, and graded (between
ｾ and
%
inch) and it must be made certain that it does not further pulverize in handling. For best results, a double graveling job should be ap-plied, first a regular gravel surfacing and second the white aggregate surfacing over the first. This becomes quite costly.e. OTHER COLORED ROCK or crushed tile or brick has also been used. All of these cost more than gravel surfacing; they are harder to control, and may have other objectionable features. Bitu-men manufacturers and roofers who are familiar with these aggregates should be consulted before deciding on this type of surfacing.
f. QUANTITIES-In general, the flood coat into which the gravel is laid should be about 60 pounds
10
of hot asphalt or 75 pounds coal tar. The gravel should amount to about 400 pounds per square and slag about 300 pounds. Since Dolomite weighs less than gravel, about 350 pounds Dolomite com-pares in volume with 400 pounds gravel. Special white aggregates differ from these figures.
g. CLEAN AND DRY AGGREGATES-That ag-gregate be clean and dry when placed, cannot be over emphasized. Gravel is now available in some locations in California kiln dried and packed in bags. Aggregate should be dried before delivery and promptly upon delivery adequately protected so that it will be dry when placed upon the roof. When aggregate is stockpiled upon the roof, the areas over which aggregates are piled should be glaze coated with bitumen.
h. IN SUMMARY, for slopes 3 inches per foot and less, experience has shown that roofings with the proper number of plies of felt (from four to five, generally for rag, and from three to four, generally for inorganic felts) and bitumen covered with a flood coat and gravel, have given the best and the longest service. All coal tar roofs MUST be so covered.
Itshould be noted that one manufacturer with a "new" asphalt is willing to bond a dead level roof-ing consistroof-ing of asbestos felts and asphalt in the membrane, this to be covered with a 20 pound glaze coat of "filled asphalt," without any gravel.
Ifthis dead level roof will last just as long as the gravel surfaced roofings, an important step will have been made in reducing the dead weight of the roofing, and possibly also the cost of the roof-ing.
E. INCIDENTAL AND RELATED WORK-a. INSULATION on top of the roof should, in
gen-eral, be avoided and should preferably be placed in the ceiling. This practice is more effective from an insulation standpoint and the cost is consid-erably less (one inch on the roof costs almost as much as four (nominal) inches in the ceiling). Furthermore, roof insulation is often a source of trouble on composition roofs; and it is not included in the manufacturers' bonds. However, roof insula-tion is required over all types of steel decks regard-less of whether smooth or ribbed type; and also where the underside of the roof deck is exposed; and where the attic space is used as a plenum. Roof insulation material should be sufficiently rigid to avoid punching of felts when roof is being walked upon. If made of wood fiber or vegetable fiber, it should be impregnated to repel moisture, fungi, and rot.
Roof insulation should always be nailed when installed on sloping wood decks. On concrete and
steel decks, when slope is one inch or less, insula-tion need not be nailed to decks, because it is held in place at the lower edge with a wood nailer or stop. On steeper ｾｯｮ｣ｲ･ｴ･ and steel decks, wood nailers should, preferably, be used, between which insulation is placed. On steel decks over one inch slope, insulation may be secured to steel by special fasteners that do not puncture the deck; however, the additional nailers above mentioned are pref-erables. Under no circumstances should more in-sulation be applied in one day than can be com-pletely roofed over by the end of the day's work. b. WATER CUT-OFFS should be provided on all insulated decks. First, apply at eaves, rakes, and vertical walls a 12 inch wide felt edge strip, ce-menting 6 inches to the roof deck, then folding the remainder of the strip up and over the insulation edge and mopping it solidly to top of insulation. Second, in order to isolate any leaks that might develop, path stripping cut-offs, somewhat similar to edge strips, should be installed over insulated concrete decks for each 300 square feet of roof
insulation.
c. VAPOR SEAL under roof insulation is rarely necessary in California, because average January temperatures, except for elevations above 4,000 feet, do not go below 45° F. Vapor seals, therefore, are only necessary in mountain areas (or when temperatures will last for several days below 30° F) and where high inside humidities exist, such as in laundries and the like, or where other special conditions exist that may justify a vapor seal. This should, preferably, consist of two plies of felts and two moppings of bitumen under insula-tion. Nails should preferably not puncture the vapor seal.
Some opinion is held that vapor seals should be called for, generally, even in California, par-ticularly over a concrete deck that contains mois-ture evaporating therefrom for a long time after construction. This applies especially to lightweight concrete decks. However, it should be remembered that the solid mopping of bitumen over the con-crete deck, into which the insulation is laid, also is somewhat of a vapor barrier.
In case of doubt, it is suggested that a mechan-ical engineer analyze the situation to ascertain whether vapors will have a chance to condense in-side the insulation and reduce the insulation value. d. COMPOSITION BASE FLASHING at the inter-sections of the flat and vertical surfaces is a most important item. In general, this should consist of several plies of felt and bitumen extending up on
11
the wall to and over a nailing strip to which it should be nailed and down and over the cant strip out onto the roof where it should be feathered off. It should be covered with an asphalt saturated asbestos sheet. The cant strip should preferably NOT consist of wood or concrete or mortar, but of premoulded impregnated material same as insula-tion board. It should be mopped-in solid in bitumen on horizontal and vertical surfaces. Cant should be 4 inches by 45 degree strips. Counter-flashing over base flashing may be metal or plastic type; the latter is gaining favor among many roofers; some manufacturers will bond a 5-course plastic counter-flashing system.
e. GRAVEL STOPS of sheet metal should be fur-nished under "Sheet Metal" and installed in col-laboration with both roofing and sheet metal trades. It should be installed at eaves, edges, and rakes on top of the roofing felts and in roofer's putty, with all laps coated with roofer's putty. It should extend a minimum of 4 inches on the deck and should be covered with two plies mopped-in or with one ply mopped-in and nailed along the middle and folded back over the nails and cemented to the nailed half. Gravel stops should have an upstanding lip about one inch above the roofing surface on dead level bitumen gravel surfaced decks; on glaze coated decksｾ inch. They should be nailed to roof (or nailer) at 3 inches on centers. Use six nails for laps.
f. VENT PIPES passing through dead level roofs should be flashed with two sheet metal collars, one set directly on deck in roofer's putty and another one set on top of felts in roofer's putty outside the first collar. These should be furnished by Plumber, who is the only one who knows where the vents are to be located and set by Roofer.
g. STORAGE of roofing materials must be in the dry. Felts should not be laid directly over new concrete floors, but on pallets over kraft paper covered concrete floors, and on edge. No moisture should be tolerated on any materials when roof is laid.
h. VENTING OF LIGHTWEIGHT CONCRETE DECKS is a new procedure devised to eliminate the damaging effects of moisture within the slow-curing lightweight concrete. Such lightweight con-crete fill should be avoided on roof decks, where possible. Where roofing is placed over such decks, metal roof vents, one per ten squares, are placed directly on the deck, 2 inch diameter, 4 inches high; roofing is then placed over and sealed around vent flanges.
BUILT-UP ROOFINGS
PART m-SCOPE OF WORK
In the writing of a Specification for Built-Up Roofing, tbis Section should include the following:
A. ITEMS TO BE INCLUDED
a. A statement that it is the Roofer's responsibility to ascertain whether or not the roof deck. is in a satisfactory condition to receive the roofing, and to notify the General Contractor of any defects which may be present. Preparation of the deck is not the Roofer's responsibility.
b. A statement that the Roofer shall furnish and ap-ply the following (when applicable):
1. All materials constituting the built-up roofing membrane and surfacing, i.e., all bitumens for priming, mopping, flood coats, and glaze coats, including any temporary glaze coats which may be necessary at the end of a day's work; all felts, dry sheets, base sheets, and cap sheets; and all mineral aggregates for surfacing.
2. All roof insulation, when applied above the roof deck..
3. All vapor seals, including bitumens for mopping and priming, and all felts, and dry sheets. 4. All fasteners, including all roofing nails and
tin caps, and all fasteners required for applying roofing or insulation (except special patented fasteners for use with certain steel decks, which are furnished by the roof deck. supplier and applied by Roofer).
5. All materials for built-up base flashings, plastic counter or cap flashing, including fibrous cant strips and the treatment of concrete or masonry parapet walls to receive these tlasbings.
6. All bituminous primers and bituminous plastic cement and other bitumen for setting metal vent sleeves and metal mastic (pitch) pockets.
7. All edge stripping, including felts and bitumens required.
8. All color coatings.
c. A statement that the Roofer shall install, when applicable, the following items furnished by others: 1. Metal vent sleeves and metal mastic (pitch)
pockets.
2. Special patented fasteners for applying insula-tion on certain steel decks.
d. A statement regarding the guarantee required to be given by the Roofer and the bond to be fur-nished by the manufacturer, where applicable. e. References to special details and to other sections
of the specifications, when advisable for clarifica-tion, particularly to the section on sheet metal work.
B. ADDITIONAL ITEMS BY ROOFER
Certain additional materials, such as that required for Membrane Waterproofing or for Dampproofing, are usually furnished and applied by the Roofer, but are often included in a section other than "Built-Up Roofings."
12
C. ITEMS NOT TO BE INCLUDED
The following materials are normally not furnished nor applied by the Roofer:
a. Sheet Metal Work, in general, including metal edge strips (gravel stops)
b. By Sheet Metal Worker:
1. Priming both sides of flange of metal edge strips and all laps, including upstanding lip.
2. Setting of metal edge strips in bituminous plastic cement and sealing all laps, including lip, with plastic cement.
c. Gutters and downspouts d. Metal countertlashings.
e. Roof drains and their connections to leaders. f. Nailing strips on decks of non-nailable materials.
PART IV-ROOFING TERMS
1. ASPHALT TERMS
a. Asphalt-a dark colored, more or less viscous-to-solid residue obtained from the distillation of cer-tain petroleum crudes.
b. Roofing Asphalt (Hot Applied)--asphalt which
has been modified by steam refining and/or air or catalytic blowing to produce the characteristics desirable for use in hot-applied built-up roofing. At the time of application, roofing asphalt (hot) should be heated only sufficiently to give it the proper consistency for application.
c. Roofing Asphalt (Cold Applied)-asphalt which, either by "cutting back" with suitable low-viscos-ity petroleum products or by emulsification with water, has been given the necessary flow charac-teristics which enable it to be applied usually without heating.
d. Asphalt Primer-asphalt which has been thinned to have relatively liquid properties, for use, where necessary, for preparing surfaces to receive hot asphalt. May usually be applied without heating. e. Asphalt Emulsion---asphalt which has been ren-dered liquid by emulsification with water, usually with the aid of a small quantity of an emulsifying agent. After application, the emulsion "breau," allowing the water to evaporate and leaving the desired grade of asphalt behind. (See "Roofing Asphalt (Cold Applied)").
f. Cutback Asphalt-asphalt which has been ren-dered liquid by blending (or "cutting back") with low viscosity volatile petroleum products such as
naphtha or kerosene. After application, the vola-tile materials evaporate, leaving the desired grade of asphalt behind. (See "Roofing Asphalt (Cold Applied)"). Kerosene is not a desirable solvent for cutback asphalts to be used for roofing, as it is not sufficiently volatile and will slow down the setting of the asphalt and possibly introduce slid-ing or other objectionable developments.
g. Air-Blownor"Blown"Asphalt-asphalt which has been modified by blowing air through it at an elevated temperature. Air blowing raises the soften-ing point and reduces the temperature suscepti-bility of the asphalt, but lowers its ductility. When a catalyst is used during the blowing process, the asphalt is usually referred to as "catalytically blown."
h. Steam-Refined Asphalt-asphalt which has been refined by agitating it with superheated steam. Asphalt which has been refined by steam only, i.e., not further modified by air blowing, has a rela-tively low softening point and is more susceptible to temperature changes than air-blown asphalt. i. Vacuum--Refined Asphalt-asphalt which has been
refined by subjecting it to vacuum during the dis-tillation process. The vacuum serves about the same purpose as steam agitation. Frequently both steam agitation and vacuum are used in combina-tion. Vacuum-refined asphalt or steam-and-vacuum refined asphalt both have the same characteristics as steam-refined asphalts.
j. Semi-Blown (or Partially Blown)
Asphalt-as-phalt that has been steam-refined or vacuum re-fined during the greater part of its refining process, but is in addition touched up by air-blowing (or by the additi.on of a percentage of fully air-blown asphalt), so that it will be less susceptible to tem-perature changes than ｳｴ･｡ｭｾｲ･ｦｩｮ･､ asphalt and yet retain a substantial amount of the ductility and
ｳ･ｬｦＭｨ･｡ｬｩｮｾ features of the steam-refined asphalt. k. Bituminous Plastic Cement-a trowelable, plastic cement, composed of bitumen, asbestos fibers (or other inorganic reinforcing fibers), and a solvent. A highly sag-resistant grade is required when it is to be used as a flashing compound. Sometimes called "Roofer's Putty."
1. Flashing Compound-(see "Bituminous Plastic Cement").
m. Flux-(I) the asphaltused by the roofing industry as the starting point in the manufacture of roofing asphalts, including saturant and coating asphalts, (2) to reduce the viscosity of an asphalt by blend-ing with it a petroleum product of lower viscosity. n. Saturant-an asphalt of rather low softening point which is used in saturating felt to produce the "saturated felt" which is used in built-up roofing and as the base for the manufacture of asphalt-coated and of asphalt-asphalt-coated and mineral-surfaced roofing.
o. Coating-an asphalt, of higher softening point than saturant, which is used for coating saturated felt in the manufacture of asphalt-coated and of asphalt-coated and mineral-surfaced roofing. Coat-ing asphalts are usually "filled" asphalts, i.e.,
con-13
tain an appreciable percentage of finely divided mineral matter.
2. BITUMEN
That portion of petroleum asphalt or coal tar which is soluble in carbon disulphide. In roofing, the term is used more loosely to designate any asphalt or coal tar product used in the application, repair, or coat-ing of roofs.
3. BOND
A roofing bond is a guarantee furnished to the owner by a bonding company for the manufacturer of the roofing materials to maintain a specified roof in a weathertight condition for a specified period of time, usually 20 years, by repairing any leakage occa-sioned by ordinary wear and tear of the elements. Most bonds have a limited liability. See also para-graph II-A-b.
4. CANT STRIPS
These are placed in the right-angle juncture between the (flat) roofing surface and the vertical surface of adjacent parapet, wall, or roof curb in order to pro-videit gradual transition from horizontal to vertical application of roofing and base flashing felts. The slope of the cant strip is 45 degrees; It consists of impregnated insulation material, or wood, impreg-nated wood, or concrete (mortar); the first of these are most desirable. See also paragraph II-E-d.
5. COAL TAR
A bituminous substance derived as a by-product in the manufacture of coke from bituminous coal, usu-ally done in a steel mill that requires coke in the manufacture of steel.
6. CODES
In general, codes｡ｲｾ rules and regulations establish-ing standards.
a. Uniform Building Code (U.B.C.)
A code largely worked out by city and county building officials throughout the United States which establishes standards for buildmg construc-tion. It sets the fire resistive standards for built-up roofs in various fire zones and for varioustypes
of buildings and occupancies. b. Underwriters'
Underwriters' Laboratories, Inc.isthe most widely known and accepted testing agency for testing fire resistive properties of materials and construc-tions. It tests and classifies various built-up roof assemblies according to their ability: (1) to resist fire, (2) to prevent spread of fire, (3) to afford some degree of fire protection to the deck, (4) to remain in position (do not slip), and (5) to not require frequent repairs to maintain their fire resistive properties.
7. COWR COATINGS
ap-plied to bituminous roofs for decorative purposes or, in the case of the light color coatings, to partially reflect the heat of the sun.
8. DOLOMITE AGGREGATE
A white crushed rock consisting of calcium-carbonate and magnesium-carbonate in equal molecular pro-portions. Effective as a decorative topping instead of or in conjunction with gravel in the surfacing of built-up roofs. Should preferably be of the crystalline (not amorphous) type.
9. DRY SHEET
An uncemented lightweight sheet which is scatter-nailed to wood or other roof decks under the roofing membrane to prevent seepage of bitumen through cracks in the deck. Rosin sized paper, unsaturated and saturated felts are commonly used for this pur-pose.
10. EDGE STRIPPING
The application of felt strips which are narrower than the conventional roll roofing, at all eaves, rakes, and vertical walls on decks which are to be insulated. A part of the edge strip is cemented to the roof deck, then the remainder of the strip is folded up and over the insulation edge and mopped solidly to the top of the insulation. This is provided to insure against leakage of water into the roofing deck insulation.
11. FASTENERS
There are a number of different types of fasteners and nails used on built-up roofing work:
a. Roofing Nails, generally, are galvanized barbed large-head. Some nails are made with a flat disc (washer) attached. Square cut steel nails through tin discs are used for gypsum decks.
b. Concrete Nails, used for nailing into concrete or masonry, are hardened nails. Some of these are special alloy nails designed to be driven by means of a special tool which guides the nail as it is driven.
c. Staples is a new development in roofing work, pri-marily designed for nailing felts to plywood. Some manufacturers do not permit the use of staples. d. Steel Deck Fasteners are special fasteners for se-curing insulation to steel decks. There are several types, some that are placed directly in the narrow throat of the rib, some that pierce the deck, and some that are set in the bottom of the wider type ribs and held in place there, by friction teeth. e. Other Patented Types are also available.
12. FELTS
Light weight sheets used in multiple ply construc-tion of built-up roofs. Composed of rag and/or other organic components, asbestos, or glass fibers, sat-urated with asphalt or coal tar.
a. Organic (Rag)-15# and 30# saturated felts 14
composed of waste paper, wood flour and wood fiber, or rag fiber, and asphalt or coal tar. b. Asbestos-15# saturated roofing felt composed
primarily of asbestos fibers and asphalt or coal tar. c. Glass-Saturated light weight felt composed of
glass fibers and asphalt.
d. Base-Heavy asphalt saturated and coated felt, sometimes used over wood decks as the foundation layer for certain types of built-up roofings. e. Finishing-This is the term generally· used to
identify the 15 Ib felts laid in shingle fashion, so that each felt is partly exposed.
f. Cap Sheet-The sheet used as the top ply in a built-up roof assembly. It can be one of many types. Most cap sheets are saturated with as-phalts; some are plied sheets with top ply not saturated. See paragraph II-C-g.
g. Flashing Felts-Felts used in construction of base flashing.
h. Flopping Felts-Turning a length of roofing felt over into hot bitumen. Generally, should not be used for finishing felts.
i. Back Mopping-Mopping the underside of a length of roofing felt before "flopping" it into place on the roof. See above.
j. Pulling-In-Laying a length of roofing felt by having one roofer "unreel" it while a second roofer holds the "reel" (a roll of roofing felt with a metal bar run through its core). The roofing is then dropped into the hot bitumen. Generally, should be used only where "Rolling" is impracti-cable.
k. Rolling-Technique of applying roofing felt by quickly rolling it out along the deck into the bitumen. Preferable method.
I. Machine Application-The technique of applying roofing felt, utilizing a felt laying machine, or of spreading the gravel by means of a gravel spreader.
13. FLASHING
That portion of roof waterproofing system which connects the main body of the built-up roofing with the vertical surfaces that adjoin the roof.
a. Built-Up Base-Is applied at the angle of the roof and adjoining vertical surfaces. Usually not included in the bond, but in a separate "Flashing Endorsement."
b. Counter-flashing covers and protects the top edge of the Built-Up Base Flashing.
c. Plastic System-A flashing system which utilizes a cold plastic asphalt cement rather than hot bit-umen in application of the flashing felts; usually used as "Counter-Flashing."
d. Metal--Mostly used as "Counter-Flashing," is a sheet metal device used to protect the top edge of built-up base flashing. Is made from galvanized sheet metal, or copper, or copper-zinc alloy.
