National Roofing Contractors Association8600 Bryn Mawr AvenueChicago, Illinois 60631312/693-0700January 1983

Revised Januaty 1985

FOREWORDThis Handbook of Accepted Roofing Knowledge is de-signed to provide designers, specifiers, owners, consul-tants, and roofing contractors with information pertinentto the design and installation of quality roof systems.

The practices herein contained represent a consensus ofopinion of roofing contractors throughout the country.Application techniques may vary according to climaticconditions, and each geographical area may employ"area practices" that are sound and time proven. We donot mean to imply by any exclusion that proven areapractices are unsatisfactory.

Roofing technology is currently experiencing revolution-ary changes. Recent pro~s have stimulated technicalresearch and investigations that are expanding ourknowledge of roof systems. In the interest of brevity.some minor technical points have been excluded fromthis text. If questions arise, designers are encouraged tocontact the National Roofing Contractors Association(NRCA) members in their geographical area for specificadvice.

The Built-Up Roofing Committee of the Asphalt Roofing Manu-facturers Association congratulates NRCA for the preparationand publication of this Handbook of Accepted Roofing Know-ledge. an important contribution to the built-up roofing industry.

TABLE OF CONTENTSTABLE OF CONTENTS

PagePage

XXVI. INSPECTION & MAINTENANCE.XXVII. FACTORY MUTUAL (FM) &

UNDERWRITERSLABORATORIES (UL) . . . . . . . . . .

XXVIII. TO THE OWNER AND DESIGNER

.51.1

.3

.4

,.6

,.8

,.9

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I.II.

III.

IV.

V.

VI.

VII.

VIII.

,53,54

GLOSSARY .55

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...86

...87

...88

APPENDIX. . . . .NRCA Detail C-1NRCA Detail D-1NRCA Detail H . .NRCA Detail M . .NRCA Detail N-1NRCA Detail N-2NRCA Detail N-3NRCA Detail 0 . .NRCA Detail P . .NRCA Detail R . .NRCA Detail V . .NRCA Detail W-2

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.19

.22

IX.X.XI.

.24

.26

.27XII.

XIII.

XIV..28

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.31

.33

.34

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xv.XVI.XVII.

XVIII.

XIX.

XX.

XXI.

PRE-ROOFING CONFERENCE .~.:

STORAGE & HANDLING. . . . . . . . . . . TEMPORARY ROOFS WEATHER CONSIDERATIONS DECK & STRUCTURAL DESIGN. . . . . . . .

SLOPE&DRAINAGE EXPANSION JOINTS & AREA DIVIDERS

MECHANICAL CURBS &

&PENETRATIONS (with the NRCA ROOF CURB CRITERIA)

PREFORMED ROOF INSULATION. . . . . .

VAPOR RETARDERS LIGHTWEIGHT INSULATING

CONCRETE DECKS ,.

POURED GYPSUM CONCRETE DECKS

PRECAST PLANK DECKS. . . . . . . . . . . .

PRECAST/PRESTRESSED

CONCRETE DECKS ..'.'.'...

REINFORCED CONCRETE DECKS. . . .

STEEL DECKS .

THERMO-SETTING INSULATING FILLS

WOOD PLANK OR PLYWOOD DECKS.

ROOF MEMBRANES BITUMENS. . ., WATER CUTOFFS &

WEATHER PROTECTION. . . . . . . . . ... . ..FLASHING & CANTS SURFACING&AGGREGATE ,

QUALITYASSURANCE&

TEST CUTS REROOFING ._,...

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.43

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XXII.XXIII.XXIV.

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.50xxv.

I. PRE-ROOFING CONFERENCE

A pre-roofing conference attended by the owner, archi-tect. general contractor. deck contractor, mechanicalcontractor and the roofing contractor should be sched-uled well in advance of ordering materials and beginningwork. If a roof bond is required, a representative from theroofing materials manufacturer should be present. A writ-ten record should be made of the proceedings and shouldbecome a part of the job record. If the roofing contractordiscovers roof probJems in his inspection of the roof. asecond pre-work inspection should be held.

The architect's specifications, roof plans and all roof andflashing details should be reviewed at the pre-roofingconference. Any discrepancies between the architect'sand the manufacturer's specifications should be re-viewed and resolved. In the event that certain discrep-ancies arise. the manufacturer's representative shouldbe consulted to resolve the issue. If FM or UL require-ments are included in the specifications, these require-ments should be carefully reviewed. Building code orarchitectural directives that are in conflict with these in-surance requirements should be resolved.

The directives listed below should be followed to assure asuccessful pre-roofing conference:

. Establish trade related job schedules, includingthe installation of mechanical equipment.

. Establish roof schedules and wort< methods thatwill prevent roof damage.

. Require that all penetrations and walls be in placeprior to installing the roof.

. Establish those areas on the job site that will bedesignated as work and storage areas.

. Establish weather and working temperature condi-tions to which all parties must agree.

. Establish the conditions for which a temporary roofwould be used and who will pay for its cost.

. Establish provisions for on-site monitoring afterthe completion of wort<.

1

II. STORAGE & HANDLINGIf changes in these conditions are desired, the partyrequesting the change should:

. Give written notice regarding the desired changesto all parties.

. Secure written agreement to the changes from allparties.

1. All roof system materials should be propertystored in a dry location prior to application.

2. When materials are stored outside, they shouldbe placed on platforms that are raised off theground or roof deck, and they should be coveredwith waterproof coverings (some which may beshrink wrapped coverings) that have been prop-erty secured. Coverings that are "breathable"(such as canvas) are preferred.

3. All roll materials should be stored on end to pre-vent their becoming deformed or damaged.

4. It is recommended that roofing materials be de-livered to the job site just prior to roof installationwhen possible or stored in closed vans.

5. Roofing bitumens may be stored unprotected onthe ground. However, moisture, dirt, snow or iceshould be removed from roofing bitumens beforethey are heated.

6. Lids should be re-placed on cans of materialstored on the job site.

7. Water based materials should be protected fromfreezing.

8. Insulation materials shoukt be handled with care.9. Some insulation materials are extremely light and

must be weighted in storage to prevent winddamage.

2 3

It should be noted that a temporary roof can increase thevalue received from the permanent roof because it allowsthe permanent roof to be constructed during suitableweather conditions. A temporary roof can also accelerateoverall building construction by providing a shelter be-neath which other trades may complete their work onschedule.

III. TEMPORARY ROOFSFrequently, construction pressures lead to the installa-tion of roofing materials during unsuitable weather condi-tions or ahead of construction schedule. In addition,these pressures sometimes cause roofing materials to beinstalled prior to the installation of wood blocking, curbsand penetrations, and prior to the erection of walls, all ofwhich may cause roof problems. As an effective means ofdealing with the problems caused by construction pres-sures, the use of a temporary roof is recommended toallow the application of the specified roof membrane insuitable weather and/or to allow other trades to completetheir work prior to the installation of the permanent roof.

The temporary roof specification (the type and number ofplies) will depend on the watertight integrity required forthe building and the length of time involved before thepermanent roof will be installed. (After suitable repairsare made, a temporary roof may be used, if desired, as avapor retarder in the permanent installation.) Generally, ifroof insulation is used in the temporary roof, it should beremoved prior to the installation of the permanent systemsince any moisture sustained from damage could beretained in this insulation, and damage to the permanentroof system could result.

If a temporary roof is to be used. the specifications shouldpositively state the following:

. That a temporary roof will be required

. The type and specification of temporary roof to beused.

In addition, consideration should be given to having thecost of the temporary roof itemized in the quoted price.

If doubt exists as to the necessity for a temporary roof, itcan be bid as an additional alternate on a per square footbasis. The decision to use a temporary roof, and overwhat areas it is to be used, can then be made during theconstruction period as weather and construction sched-ules dictate. The additional cost of a temporary roof is farpreferable to shortened roof life or roof failure!

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IV. WEA THEA CONSIDEAA TIONS 2. The handling of roll materials may become diffi-cult.

3. "Wind chill" may affect the proper applicationtemperatures of materials.

4. Sprays of cold mastics and coatings can be-come airborne and cause damage to surround-ing property.

4. PrecipitationRoofing materials should not be installed if pre-cipitation of any kind is occurring.

5. MoistureRoofing materials should not be installed if mois-ture, snow or ice is present on the roof.

No other trade is more directly involved in work relatedweather considerations than roofing. Many impressionsexist throughout the construction industry regarding suit-able roofing weather. Some restrictions prohibit roofingunder all but the most ideal conditions. The roofing con-tractor is vitally concerned with the limitations imposed onconstruction activity by the weather, but he must respondto "real world" conditions and construction demands. Tosatisfy construction demands and cope with the limita-tions imposed by weather, the roofing contractor shouldconsider the following guidelines for the application ofroofing materials during various weather conditions.

1. Cold TemperaturesRoofing materials should not be applied unlesscorrect bitumen application temperatures can bemaintained. The heating of asphalt bitumensshould conform to the Equiviscous Temperaturerange concept (EVT). (See Section XX,Bitumens.) The roofing contractor may use in-sulated heating equipment, insulated pumpinglines, insulated hot carriers, etc., to maintainproper bitumen application temperatures. If prop-er application temperatures cannot be main-tained, however, roof application should cease. Incold temperatures, roofing materials must be em-bedded directly with haste. "Brooming" directlybehind the felt embedment is advised to assist thebonding of the felt. Hot bitumen must not be al-lowed to cool substantially prior to placing feltsand insulation in the bitumen.

2. Warm TemperaturesWarm temperatures also present problems inmaintaining the proper application temperaturesfor bitumens. In hot weather the applied bitumenwill cool more slowly, which can lead to sticking,making the membrane susceptible to physicaldamage from mechanical equipment and foottraffic.

3. WindWind can affect the application of roofing ma-terials in the following ways:1. Hot materials may be blown about.

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V. DECK & STRUCTURAL DESIGN VI. SLOPE & DRAINAGEAll roofs should be designed and built to ensure positive.thorough drainage. (See Positive Drainage in the Glos-sary.) Ponding water can be detrimental to roof mem-branes and can result in:

. Deterioration of the surface and membrane

. Debris accumulation and vegetation growth

. Deck deflections (sometimes resulting in structuralproblems). Tensile splitting of water weakened felts

. Difficulties in repair should leaks occur

. Ice formation and resultant membrane damage

Good roof systems depend upon the structural integrity ofthe roof deck. To ensure the construction of a quality roofdeck, provisions for the following items should be in-cluded in the deck design:

. Live loads, such as moving installation equipment.wind, snow, ice, rain, etc.

. Dead loads, such as topside mechanical equip-ment and the deck itself. Strength of the deck. Deflections

. Drainage. Placement of expansion joints and area dividers. Curb details. Attachment provisions for the deck. Rolling construction loads of 300 Ibs.Since every roof has its own specific set of drainagerequirements, either the architect or the structural en-gineer is responsible for including proper drainage provi-sions in the roof design. The designer should not simplyspecify a standard Va inch or V4 inch of slope per foot butshould make provisions in his design for positive drain-age. In order to achieve the necessary slope in his de-sign, he must consider the structural framing of the roof,the deck type, the roof membrane specification, roof de-flections, and the building layout. The necessity for brev-ity herein prevents a complete explanation of each ofthese considerations. The following brief examples, how-ever, are typical slope and drainage computations.

The following chart shows the typical allowable deckdeflections for various spans under a concentrated loadof 300 pounds. Deflections greater than those listed in thetable may lead to roof problems.

Span Deck Deflection4 ft. 0.20 inches5 ft. 0.25 inches6 ft. 0.30 inches

Prior to the application of roofing materials, the roofingcontractor should make a visual inspection of the decksurface to see that it is ready for the application of roofingmaterials. The deck must be clean, smooth, free of voidsor depressions, must be rigid and must not deflect exces-sively under live loads.

Deflection SlopesRoof deflections are of critical importance in providingroof drainage. They should be limited to no more than1/240 of the roof span in order to accommodate thestresses of either concentrated or uniform loading.Drains should be located at points of maximum deflectionin the deck (i.e., midspan), if possible, and not at points ofminimum deflection (i.e., columns or bearing walls). Forexample, in Figure 1 a deck span of 50 feet should deflectnot more than 21/2 inches (1/240 of 50 feet) and shouldhave drains located at midspan in order to provide drain-age under maximum loading conditions.

If the roofing contractor discovers defects in the surfareof the deck during his inspection. a second inspectionshould be made prior to roofing by the roofing contractor.the general contractor. the deck contractor and the own-er's representative. All defects in the deck at the time ofthis inspection should be noted. and corrections shouldbe made prior to the commencement of work. The tradecontractor who is responsible for any defects or damageto the deck should be responsible for making repairs. Jobspecifications should clearly define this responsibility.

8 9

drain the roof. Thus, to drain the 50 foot span in Figure 1where the drain is placed at the point of maximum deflec-tion. the designer should provide at least 3.125 inches ofdifferential slope for positive drainage under all loadingconditions. For Figure 2, where the drain is located at apoint of minimum deflection, the positive slope required is6.25 inches, which, when added to the 5 inches of deflec-tion slope, yields a total required slope of 11.25 inchesunder all loading conditions.

AGURE1

If drains are required to be placed at columns or bearingwalls, the slope of the roof must be increased in order tocompensate for the minimum deflections that exist atthese locations. The allowable deflection will still be 2V2inches, but the designer must provide for 5 inches ofadditional slope at the column or bearing wall location inorder to keep this deck level at midspan under maximumloading conditions. (See Figure 2.)

Certain decks, such as precast concrete decks or longspan prestressed concrete decks, incorporate camber inanticipation of future loading conditions. The cambermust be considered in the design of the drainage slopesystem. Depending upon the structural design of the roofand the placement of drains, the camber may assist orrestrict drainage. (See Figure 3.)

FIGURE 3FIGURE 2

These examples illustrate that the computations for roofslope should be determined by the deflections expectedin each particular roof deck and that the commonlyspecified Y8 inch or Y4 inch of slope per foot is inadequateas an absolute specification to attain proper drainage on

all roofs.

Maintaining a roughly level line between one support anda 2Y2 inch midspan deflection requires raising the othersupport 5 inches.

Positive SlopesAfter the drain locations have been selected and thedeflection slopes have been computed. the designermust provide additional slope to ensure positive drain-age. Since drainage must occur under both minimum andmaximum loading conditions. an additional minimumslope of Ve inch per foot should be added to the deflectioncomputation in order to attain a slope that will positively

In providing for drainage, the designer must carefullyconsider all areas of the roof. Good practice dictatesthat there be no ponding water. For information perti-nent to deck design for ponding water conditions, de-signers may consult the American Institute of TimberConstruction [AITC], the Steel Joist Institute [SJI], or theAmerican Institute of Steel Construction [AISC]. Drain-age crickets should be provided between drains and onthe high side of mechanical curbs to drain these areas.(See NRCA Detail "P" in the Appendix.)

11

*NOTE: Figures 1, 2, and 3 have been exaggerated to helpillustrate the respective drainage conditions more clearly.

10

VII. EXPANSION JOINTS & AREA DIVIDERSExpansion JointsRoof expansion joints are used to minimize the effect ofthe stresses and movements of a building's componentsand to prevent these stresses from splitting or ridging theroof membrane. Joints in the roof assembly (the termroof assembly includes the roof deck) must be placed inthe same location as the building's structural expansionjoints (although they may also be required in other loca-tions as discussed in this section). Each of a building'scomponents has varying coefficients of expansion andcontraction, and each of them is subjected to varyingtemperature changes. Therefore, in the design andplacement of expansion joints, the designer should con-sider:

To ensure the proper draining of water in the heaviestrains, the design of drain sizes and drain placementshould be based on either:

. The requirements of the American National Stan-dards Institute (ANSI)-Standard A 112.21.2, or

. Building code requirements, or

. Maximum rainfall information of the geographicalarea.

Drains should be recessed (sumped) below the roofsurface. and sufficient insulation must remain around thedrains to prevent condensation from occurring. This isaccomplished by setting the drain head below the level ofthe insulation and tapering the insulation down to thedrain. (See NRCA Detail"W-2" in the Appendix.) Regularmaintenance should be performed to prevent clogging ofdrains. To avoid the dangers of water buildup from clog-ged drains. the use of auxiliary drains or throughwallscuppers is recommended and, in many cases, is a partof building code requirements.

. The thennal movement characteristics of thebuilding. The structural roof deck

. The roof membrane selected. The climatic conditions to be encountered.

Expansion joints must extend across the entire width ofthe roof; they must never terminate short of the roof edgeor perimeter. They should be designed to accommodatecontraction as well as expansion. The expansion jointshould be detailed and constructed to a raised (nominal)height of 8 inches above the roof line. (See NRCA Detail"C-1" in the Appendix.) Water drainage should NEVERbe attempted through or over an expansion joint.

Expansion joints are required and should always beprovided at the following locations:

. Wherever expansion or contraction joints are pro-vided in the structural system

. Where steel framing, structural steel, or deckingchange direction. Where separate wings of "L," "U," "T," or similarconfigurations exist

. Where the type of decking changes; for example,where a precast concrete deck and a steel deckabut

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VIII. MECHANICAL CURBS &PENETRATIONS

To avoid deflections that are damaging to the roof, thestructural design of the roof should always allow for theconcentrated loading of mechanical equipment. Vibra-tions from roof-mounted or joist-mounted mechanicalequipment should be isolated from the membrane andflashing. Some equipment may allow moisture to enterthe building either from the exterior or from condensationwithin. Therefore. it is imperative that mechanical equip-ment housings be watertight. Water discharge frommechanical equipment should not be allowed upon theroof surface.

. Whenever additions are connected to existingbuildings

. At junctions where interior heating conditionschange. such as a heated office abutting an un-heated warehouse. canopies. etc.

. Where movement between vertical walls and theroof deck may occur.

Area DividersWhere expansion joints are not provided, area dividershelp control the thermal stresses in a roof system (theterm roof system does NOT include the roof deck). Theyminimize the transmission of stress from one area of theroof to another by dividing the entire roof area into smallerroof sections. These sections should be of rectangularshape and uniform spacing where possible. The designershould determine the respective location and the type ofarea divider to be used.

When large mechanical units are used, drainage cricketsshould be provided around the units to allow adequatedrainage of these areas. Mechanical units should notrestrict the flow of water. Adequate space should beprovided between mechanical units, penetrations andwalls so that roofing materials can be installed correctly.(See NRCA Detail"V" in the Appendix.)

An area divider is designed simply as a raised, double-wood member attached to a properly flashed wood baseplate that is anchored to the roof deck. (See NRCA Detail"0-1" in the Appendix.) Depending upon climatic condi-tions and area practices, area dividers for attached mem-brane systems are generally required at 150-200 footintervals. They should be located between structural roofexpansion joints. They should not restrict the flow of

water.

Units using curbs that have built in metal base flashingflanges are difficult to seal and, therefore. are not recom-mended for use. Composition base flashing should ex-tend a minimum of (a nominal) 8 inches above the roofline. Wood or fiber cants must be provided at any gooangle created by rectangular curbs or projections. Woodnailers should be provided on all prefabricated curbs. Thecomposition flashing (base flashing) should be fastenedeither with 1 inch, solid caP-head nails or with nails driventhrough tin discs. The nails should be spaced approxi-mately 8 inches apart. (See NRCA Detail "R" in theAppendix.)

The use of elastic, preformed "control" joints that aredesigned to be installed in the flat plane of the roof is notrecommended because roof system movement may re-sult when these units are used. The use of raised curbarea dividers is consistent with good roofing practice.

On mechanical units, two piece metal counterflashingshoukj be installed over the base flashing. On units thatwill be frequently serviced. the counterflashing shouldextend down over the cant to the roof line so that no baseflashing is exposed.

Penetrations around short pipe projections may beflashed into the membrane by using soft metal or leadflashing with integral flashing flanges stripped into the

1514

membrane. (See NRCA Detail "M" in the Appendix formajor pipe penetrations.) Good practice dictates thatcurbs be placed around all penetrations; the use ofso-called "pitch boxes" or "pitch pockets" aroundpenetrations should be avoided because they pose aconstant maintenance problem. Projections shouldnot be located in valleys or drain areas. Adequate spaceshould be provided between pipes. curbs and walls toallow for the installation of roofing materials. (See NRCADetail "V" in the Appendix.)

All curbs, penetrations, roof drains and plumbing pipesmust be in place before installing the roof. Openings forcurbs cut through the roof membrane after the roof hasbeen completed can present a serious bitumen drippageproblem when the membrane is constructed of low soft-ening point bitumen. All curbs should be firmly fastenedto the building structure or to the roof deck prior to theapplication of roofing materials. Roof drains, vent pipes,etc., should all be in place prior to roofing and restrainedto prevent damage to the flashings or membrane thatmay occur if mechanical devices are installed over thecompleted membrane.

Mechanical units mounted on pipe standards beneathwhich roofing materials will extend must be mounted to aheight sufficiently above the roof to allow room to installthe roof system and to make repairs beneath the unit.(See NRCA Detail "N-1" in the Appendix.) Heavy loads.such as large mechanical units, should not be rolled overthe completed membrane as they may cause damage tothe roof. A failure in horizontal shear between the mem-brane. insulation or deck from these loads may result infuture splitting of the roof. NRCA recommends that me-chanical equipment be installed on fully enclosed curbs(not on support stands) to eliminate the need for reroofingunder these units when reroofing becomes necessary inthe future.

As a final consideration, it should be noted that helicopterplacement of mechanical equipment can cause damageto the roof system if the helicopter is operated too close to

the roof surface.

NRCA, in cooperation with certain mani,lfacturers, hasdeveloped the following criteria for pre-manufacturedroof curbs.The NRCA Roof Curb Criteria

1. The curb should be furnished with adequate sup-ports on all sides.

2. The curb and mechanical equipment should bestructurally capable of supporting intended loadsand should be so designed that no penetration fordrains, power lines, etc., will occur through thecurb flashing. The curb should extend around theentire perimeter of the mechanical unit.

3. The curb should be furnished by the manufacturerwith insulation and a wood nailer, which provides2 inches of nailing surface, mounted at the top ofthe curb to permit mechanical attachment of theflashing material.

4. The metal frame should be of heavy construction;either 16 gauge minimum, 18 gauge with struc-tural bracing to reinforce the metal frame, orequivalent construction.

5. Pre-manufactured curbs should be (a nominal) 14inches in height (effective as of January 1, 1981)and should provide a minimum clearance of ap-proximately 8 inches between the top of the fin-ished roof surface and the top of the wood nailer.This height is needed to accommodate thevarying insulation thicknesses commonlyused in tapering "slope to drain" insulation.(See NRCA Detail "A" in the Appendix.)

6. The design of the curb should be such that it willaccommodate the installation of a metal counter-flashing receiver (supplied by the curb manu-facturer) and the counterftashing (supplied by thesheet metal contractor). On units requiring a greatdeal of servicing, this metal counterftashingshould extend down over the base flashing so thatno composition material is exposed, thereby elim-inating the danger of foot abuse. (See NACA De-tail "A" in the Appendix.)

7. Installation instructions should require the instal-ler of the rooftop mechanical unit to provide aweather-tight seal between the mechanical unitand the top of the curb.

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IX. PREFORMED ROOF INSULATIONRoof insulation provides both the insulation for the build-ing and a substrate to which the built-up roofing materialsare applied. Therefore. it must be compatible with, andshould provide support for, the roof membrane.

8. A detailed illustration of the curb in the NRCAConstruction Details clearly indicates who is re-sponsible for furnishing each element of the curband flashing system. (See NRCA Detail "R" in the

Appendix.)9. Detail "R" requires a 450 cant strip at the base ofthe curb to permit the proper application of com-position flashing. The use of uninsulated, integral,metal cant strips is not acceptable to NRCA.

10. Where drawings call for support of part or all of amechanical unit on legs or piers instead of on acurb, which requires that part of the roof mem-brane extend beneath the mechanical unit, theheight of the unit above the finished roof shouldmeet the requirements of NRCA Detail "N-1". Theflashing of the unit supports should meet the re-quirements of NRCA Details "N-2" and "N-3".

11. Installation instructions for flashing pipes andelectrical conduits extending through the roofshould conform to NRCA Detail "M". All pipingand plumbing should be flashed with a sleeve androof flange and should extend a minimum of 8inches above the roof surface. It is suggested thatelectrical and gas lines for rooftoP units be ser-

viced externally.12. The installation instructions for mechanical equip-

ment should call attention to the desirability ofinstalling roof walkways where they are needed

for servicing rooftop equipment.

An ideal roof insulation would have the following theoreti-cal properties:

. It would be able to withstand the bitumen applica-tion temperatures required for installation of theroof membrane.. It would have good physical strength, rigidity, andimpact resistance.

. It would be incombustible and would be accept-

able for insurance and building code require-

ments.. It would be constructed of materials that will resistdeterioration.. It would be moisture resistant.

. It would have a low "k" value (thermal conductivity)so that the highest possible "R" values (thermalresistance) can be obtained in the thinnest possi-ble piece of a particular insulation.

. The "k" value would remain constant and wouldnot "drift" higher with age.

. Its surfaces would accommodate secure attach-ment.. It would have dimensional stability under varyingtemperature and moisture conditions.

. It would be manufactured so as to be compatiblewith the roof membrane.Note: Check with roof curb manufacturers to see that

their materials meet the standards set forth in the NRCARoof Curb Criteria. The qualifications listed above would be present in an

ideal insulation. In practice, however, NO single com-mercial product contains all of the ideal properties. Thus,the designer should choose materials whose propertiesare best suited to the specific project.

Roof insulations, when used for the control of heat flow,should be installed in two layers when thickness permitswith all joints offset between the upper and lower layers.The joints of the insulation should be installed in such away as to provide moderate contact at the joints. The

1918

upper layer should be installed with the long dimension ofthe insulation boards placed in a continuous line and theend joints staggered.

Performance-type specifications should be avoidedwhen specifying any insulation since manufacturers' datamay vary considerably. Instead of listing performance-type specifications, the designer should list the ASTMSpecification. the thickness requirement and the "C"value for any insulation board to be used in the roofconstruction.

Over steel decks. mechanical fasteners should be usedto attach the first layer of insulation. Where possible thefirst layer of insulation should have an insulation valueequal to or lower than that of the second layer. Thesecond layer of insulation should be laid in moppings ofhot asphalt and, normally, should have the greater insula-tion value.

All roof insulation should be protected from the elementsbefore, during and after installation. During and afterinstallation, this protection is provided by the immediateinstallation of the roof membrane. On low-sloped roofs,proper merflbrane application dictates that roofing feltsbe laid perpendicular to the flow of water, beginning atlow points (or drain points) in the deck. All roof membraneplies should be installed in an unbroken time period;phased construction is NOT recommended. The longdimension of the insulation boards should be laid perpen-dicular to the flow of water.

Roof membranes should NOT be installed directly to thetop side of any felt-skinned, foam-type insulation, includ-ing poly~tyrene and polyurethane because of the poten-tial for blister formations.

When composite board roof insulation, polyisocyanuratefoam board roof insulation or polyurethane foam boardroof insulation is used as the insulation substrate, one ofthe two procedures listed below should be followed:

. Over the top surface of the insulation, a thin layerof wood fiberboard insulation, perlitic board insula-tion, or glass fiber board insulation should be in-stalled. The roof membrane should then be ap-plied as specified by the designer

. Over the top surface of the insulation, a ventingtype base ply should be installed in such a way asto allow for venting. The balance of the roof mem-brane should then be applied as specified by the

designer.

20 21

x. VAPOR RETARDERS-Roof system vapor retarders generally fall into two class-ifications:

1. Bituminous membranes, in which a continuousfilm of bitumen serves as the vapor resistant eIe-ment. A typical two-ply installation using threemoppings of steep asphalt can provide a vaporretarder which is rated less than .005 perms.

2. Non-bituminous sheet systems, in which thesheet serves as the vapor retarder, and adhesiveis used to seal the laps. These include PVC films,kraft paper and aluminum foil combinations,which may provide vapor retarders having per-meability ratings ranging from 0.10 to 0.50perms. PVC films and associated cold-appliedadhesives are not recommended by NRCAbecause of their susceptibility to damage fromother components in the system, such as themelting of vinyls by hot asphalt.

The term "vapor retarder" refers to a broad range ofroofing materials which are used to control the flow ofwater vapor from the interior of the building into the roofsystem. Moisture in the form of water vapor generallycomes from the following sources:

. Construction processes, which include interiorconcrete and masonry. cementitious roof fills.plaster finishes. and fuel burning heaters

. Occupancy-generated sources. which includesuch areas as swimming pools. textile. food andpaper plants. and other wet-process industrial

plants.

In the generally temperate climate of the United States.during the winter months. water vapor flows upwardthrough the roof system from a heated. more humid in-terior toward a colder. drier exterior. Vapor retarders aremore commonly required in northern climates than insouthern regions. where downward vapor pressure maybe expected. and the roof membrane itself becomes thevapor retarder.

Wherever vapor retarders are used, they should be con-structed of materials which are compatible with other roofsystem components. It is recommended that the de-signer pay particular attention to flashing details at edgeseals and at all penetrations through the vapor retarder inorder to ensure the moisture-tight integrity of the vaporretarder. Vapor retarders can be easily punctured anddamagoo by foot traffic and mechanical equipment.These punctures must be carefully repaired prior to theinstallation of insulation, using a patch that is at least 12inches larger in each direction than the puncture. In orderto properly install and help prevent damage to a vaporretarder system, the laps must be made on solid bearing.For more specific information on vapor retarders, seeVAPOR RETARDERS in the DECK section of the NRCARoofing Manual.

As a general guide, vapor retarders should be consideredfor use when both of two conditions are anticipated:

1. The outside, mean, average January temperatureis below 40°F.

2. The expected winter, interior, relative humidity is45% or greater.

Vapor retarders should be installed at a location wherethey will be warmer than the winter design dew-pointtemperature. The dew-point should fall within the insula-tion. It is recommended that moisture relief vents, prefer-ably one-way vents, be incorporated into the roof systemat the minimum quantity of one vent per one thousandsquare feet of roof area (10 roof squares) or less.

2322

Additional roof insulation should NOT be installed directlyover lightweight insulating concrete decks as it will inhibitthe drying of the concrete. However. when above-deckinsulation is specified. the insulation should be protectedfrom moisture by a low perm-rated vapor retarder placedbetween the lightweight insulating concrete and the insu-lation. (See Section X. Vapor Retarders.) The insulationmust be vented. Smooth surfaced roof membranesystems are generally not recommended for use overlightweight insulating concrete decks.

XI. LIGHTWEIGHT INSULATINGCONCRETE DECKS

Lightweight insulating concrete is used for the construc-tion of composite structural decks and as a fill materialover some structural decks. (It is not recommended foruse, however, directly over poured-in-place or precastconcrete decks.) The installation of lightweight insulat-ing concrete requires the use of large quantities of water.and some moisture will remain in the concrete even afterthe surface is dry. Thus, venting must be provided toallow additional drying of the concrete and to prevent thebuildup of water vapor pressure. Either topside venting orunderside venting is advised on all lightweight insulatingconcrete decks. (Topside. one-way venting in the fiekj is

preferable.)

N RCA recommends that specifiers consult with the mem-brane manufacturer for specific recommendations re-garding their requirements for roofing over lightweightinsulating concrete decks.

Ughtweight insulating concrete decks must have the fol-

lowing physical properties:. A minimum thickness of 2 inches of lightweight

concrete. A minimum dry density of 22 Ibs. per cubic foot

(pcf), or a dry density capable of providing a fas-tener withdrawal resistance of 40 Ibs. per fastener

. A minimum compressive strength of 125 Ibs. persquare inch (psi).

Ughtweight insulating concrete decks should be installedaccording to the lightweight insulating concrete manufac-turer's specifications.

The roof membrane should be attached to the lightweightinsulating concrete deck in accordance with the deckmaterial manufacturer's recommendations. If no recom-mendations are provided, a coated base ply or a ventedbase ply should be used as the first ply of the membraneand should be attached to the lightweight insulating con-crete deck with approved mechanical fasteners. In nocase should the base ply of the membrane be attach-ed to these decks in moppings of hot asphalt or bythe use of adhesives.

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XII. POURED GYPSUM CONCRETE DECKS- XIII. PRECAST PLANK DECKS

Poured gypsum concrete is used in various combinationswith other building products as a structural deck. The roofmembrane should be attached to the poured gypsumconcrete deck in accordance with the deck material man-ufacturer's recommendations. If no recommendationsare provided, a coated base ply or a vented base plyshould be used as the first ply of the membrane andshould be attached to the poured gypsum concrete deckwith approved mechanical fasteners. Venting to the in-terior should be provided and is generally accomplishedthrough the use of a vapor permeable formboard. If thistype of formboard is not employed, topside ventingshould be designed and installed.

Precast plank decks are constructed of metal boundgypsum, structural lightweight insulating concrete orcementitious wood fiber and are used either as structuraldecking or in combination with sub-purlins. Voids andjoints over sub-purl ins must be grouted with materialssupplied or recommended by the deck manufacturer andshould provide approximately VB inch of slope per foot.Particular attention must be given to the storage andhandling instructions for these materials. The designermust carefully consider the concentrated live loads ofroof application equipment in the selection of thesedecks. All slabs should be securely fastened to resistuplift and horizontal movements.

The gypsum fill should be reinforced with wire mesh. Itshould have a minimum thickness of 2 inches. not includ-ing the formboard. and should cover the top of bulb tees aminimum of 1/4 inch. A coated base ply or a vented baseply is generally used as the first ply of the membrane andis attached to the gypsum concrete deck with mechanicalfasteners. The membrane should NEVER be installedto gypsum concrete decks in mappings of hot as-phalt or by the use of adhesives.

Precast plank decks should be roofed promptly afterinstallation. The planks may be fragile and should betreated with care. Planks should be installed duringweather conditions that are suitable for the installation ofroofing materials. or temporary protection should be pro-vided.

Membrane application to these decks should follow thedeck manufacturer's recommendations. Generally,attachment of the base ply with approved mechanicalfasteners is recommended. If insulation is used, a nail-able base ply is required as the attachment layer. Insula-tion should then be solidly adhered to the base ply withhot asphalt only. Adequate ventilation of the underside ofthe deck during the construction process is mandatory.In no case should the first ply of the roof membranebe mopped directly to precast planks.

Roof insulation should NOT be installed directly overnewly poured gypsum concrete decks as it will inhibit thedrying of the concrete. However. when above-deck insu-lation is specified. the insulation should be protected frommoisture by a low perm-rated vapor retarder placed be-tween the poured gypsum concrete and the insulation.(See Section X. Vapor Retarders.) The insulation mustbe vented.

Smooth surfaced roof membrane systems are not recom-mended for use over poured gypsum concrete decks.Roofing materials may be installed as soon as the deck isset and is surface dry (approximately 1 hour). After theroof is installed. the general contractor should providesufficient ventilation on the underside of the deck andwithin the building to allow continued drying of the deck.

2726

this reason the use of cast-in reglets is not recom-mended. A flashing detail similar to Detail "H" should beincorporated to properly secure the roof to the precastwall units. (See Detail "H" in the Appendix.) In all suchflashing situations. consideration should be given tocamber and creep.

XIV. PRECAST IPRESTRESSEDCONCRETE DECKS

Precast concrete units are used as structural roof decks.The manufacturing process of precast concrete unitsmay produce units which vary in joint elevation when setin place. If variations in the elevations of adjacent unitsexceed V4 inch, the deck should be levelled with a fibrous,cementitious grout that has been feathered to a slope ofVB inch per foot prior to roofing. Venting for this fill shouldbe provided. A vapor retarder may be required, depend-ing upon the fill material used. (See Section X, VaporRetarders.) The joints between adjacent units should befilled with a compressible material to prevent drippage ofthe cementitious fill that is used to level the units.

When precast walls are used. it is recommended thatprovisions be made for low parapet walls. The base flash-ing should be fastened to a vertical wood upright whosehorizontal base is attached to the deck only. After thebase flashing has been attached to the wood upright. themetal wall cap flashing may be installed. Then thecounterflashing may be attached fo the wall cap. extend-ing down over the top of the base f~ing. This methodallows lateral movement of the wall without damage tothe base flashing.

Recommendations of the Precast Concrete Institute fordeck installation should be followed. Weld plates shouldbe provided between other structural components andthe deck units and between the deck units themselves.The top surface is sometimes neglected in the casting ofprecast units. A smooth surface, free of voids and depres-sions, should be provided for proper adhesion of the roofsystem. In order to provide adequate drainage, the de-signer must consider the "bowing" (or vertical camber) ofprecast units that occurs in the manufacturing process ofthe units. Depending on structural design and drainplacement, the camber may assist or restrict drainage.(See Figures 1, 2, & 3, pages 10 and 11.)

The designer should carefully detail all wood blockingprovisions at roof edges and penetrations to ensure prop-er attachment of the membrane and sheet metal. If nocase should the roof membrane be attached directly toprecast/prestressed concrete decks. Prefonned roof in-sulation (preferably in 2 layers) should be installed on topof the deck prior to the application of roof membranematerials.

When precast walls are used, the designer should care-fully consider the flashing provisions required to properlysecure the roof to the precast wall units. Cast-in reglets,which are frequently used for this purpose, are difficult toalign properly. When they are not properly aligned, theycan hinder the proper installation of counterflashing. For

28 29

XVI. STEEL DECKSxv. REINFORCED CONCRETE DECKSReinforced concrete is used as a structural deck. Thepouring process requires large quantities of water. andsome moisture will remain in concrete decks even afterthe surface is dry. Prior to the application of roofing mate-rials, the concrete surface must be smooth. level and freeof moisture. The deck contractor is responsible for re-moving sharp ridges or other irregularities in the decksurface. Wood blocking nailers should be designed andprovided at all roof perimeters and penetrations for fast-ening the flashings and sheet metal. Concrete curingcompounds which are used to finish the deck surfacemust be compatible with the bitumen being used (eitherasphalt or coal tar bitumen).

Steel decks should be designed according to the steeldeck manufacturer's specifications and installed accord-ing to the application procedures recommended by theSteel Deck Institute in order to obtain optimum perform-ance of the steel deck. Decks should be 22 gauge orheavier. Maximum span recommendations for typical 1 Y2inch steel decks with 6 inch rib spacing are published byFactory Mutual (FM) in Bulletin 1-28. FM field offices andsteel system deck manufacturers should be consulted foradvice on the maximum span recommendations for steeldecks.

Insulation commonly applied to steel decks prior to theapplication of the roof membrane should be applied intwo separate layers where insulation thicknesses permit.The first layer should be capable of spanning the flutewidth of the metal deck in accordance with the insulationmanufacturer's specifications. The first layer of insulationshould be attached with mechanical fasteners in accord-ance with Factory Mutual Data Sheet 1-28. Th~ secondlayer should be laid with joints offset from the first layerand in moppings of hot asphalt.

Reinforced concrete should be primed. and the primermust be allowed to dry prior to the application of roofingmaterials. If roof insulation is to be installed over rein-forced concrete. the insulation and membrane must beprotected from the effects of latent moisture in the con-crete. In northern climates. this is generally accom-plished by using a vapor retarder or a venting sheet. (SeeSection X. Vapor Retarders.) In southern climates. how-ever. vapor retarders are often omitted. and venting of theinsulation alone has proved to be adequate. In coldweather poured concrete is usually protected by insula-tive batts or blankets. When these batts or blankets areremoved. the concrete may be cured at the surface. butsome moisture will remain inside the concrete deck. Inthese situations. if subsequent insulation is to be in-stalled. the use of a vapor retarder is recommended toprevent moisture damage to the insulation.

When specifications call for only one layer of insulation,the insulation should be attached with mechanical fasten-ers in accordance with Factory Mutual Data Sheet 1-28.

Certain FM or UL requirements for the deck surface andfor the attachment of the ins:ulation may be applicable.The most current FM and UL publications should beconsulted for specific deck surface and insulation attach-ment requirements. Generally, these requirements placelimitations on the concavity ("cupping") of contactflanges and stiffening ribs. They also require that side lapfasteners be used to secure steel deck panels to adjacentpanels. Provisions should be made to have the topflanges of the steel deck units installed perpendicular tothe roof slope. This will allow for the long dimension of theinsulation boards to be laid parallel to the steel deck asFM requires and wi[ help to avoid phased construction ofthe roof membrane.

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XVII. THERMO-SETTINGINSULATING FILLS

Adequate side lap bearing is necessary to support rigidinsulation boards. To help achieve the proper bearing,the steel deck units should be installed with a maximumhorizontal-alignment tolerance of V4 inch for every 100feet of deck length (i.e., after installation, the deck unitsshould vary in horizontal alignment by no more than '/4

inch).

Thermo-setting insulating materials are used as insula-tive fills over structural decks. They should be installedaccording to the manufacturer's specifications. Thesematerials require compaction by weighted rollers, and thestructural designer must consider the concentrated liveloads of these rollers in the design. When thermo-settinginsulating fill is placed over a metal deck, the deck mustbe rigid enough to prevent flexing during the compactionprocess. The compacted density of the fill should rangebetween 18 and 22 Ibs. per cubic foot. This density isgenerally attained by compacting the thermo-settinginsulating fill in one layer or, if the total thickness isgreater than 6 inches, in two layers. A spray of water isusually used to cover the surface prior to compaction.The quantity of water in this spray should be kept to aminimum.

Mechanical fastening of steel deck units to the structuralsteel provides the most positive means of attachment.When steel deck units are spot welded. the weld materialwill frequently "pop" loose due to improper welding tech-niques or minor flaws in welding. When it is desired thatsteel decks be welded. it is recommended that "puddlewelds" of 1/2 inch or larger. welded into washers andspaced a maximum of 12 inches on center at every

support. be used.

Thermo-setting insulative fills should be protected frommoisture. Roofing materials should be applied eachday. or temporary protection should be provided. Thebase ply over these fills should be applied in a solidmopping of steep asphalt, and provisions for roof ventingshould be incorporated into the fill by the designer torelease moisture vapor. If roof insulation is installed overthese fills, a protective. base ply vapor retarder should bemopped to the fill to protect the insulation from substratemoisture and to allow time to install the insulation and roofmembrane. Wood nailers must be provided at all perim-eters and projections through the roof. It is preferred thataggregate surfaced roofs be applied over these fills.

3332

P-Igrad8

~XVIII. WOOD PLANK OR PLYWOOD DECKS

~1at\8v RATED SHEATHING32/16 1/2 INCH

SIZED FOR SPACINGMW--- -- EXPOSURE 1 //

~~ ~ 000:-~~ PS 1-74 CoD INTiEXT GLUE-

~.".I."'-

Wood Plank DecksPlanks for wood plank decks should be (a nominal) 1 inchor thicker and of tongue and groove construction. Cracksor knot holes larger than 1h inch in diameter must becovered with sheet metal if roof insulation is not used.End joints of the wood deck units should be staggered.Since wood can be adversely affected by moisture. wooddecks should be constructed of air dried or kiln driedlumber and should be protected from moisture.

~ dlllablUty_I_loa

Bitumens or adhesives are not generally used to attachthe membrane to a wood deck. The use of mechanicalfasteners is recommended for the attachment of themembrane directly to a wood deck.

A separator sheet of rosin-sized sheathing paper is re-commended for use over wood plank decks.

Note: Caution should be exercised when wood decks areconstructed of wood that has been treated with an oilborne preservative. When such treated wood is used inthe deck, a barrier of rosin paper or similar materialshould be placed between the roof membrane and thedeck.

A label smilar to this one and oontaining the same categ~ of infor-mation should be fooM on each panel of plywood. The Span Rating(32/16 in this label) is of partiwar significance. The left-hand nuna, ofthe Span Rating (32 in this label) indicates the maximum recommendedcenter-tO-(:enter spacing of SUA>Qrts in inches when the panel is usedfor roof decking with the k>ng dimension of the panel running across thesupports. The right-hand number of the Span Rating (16 in this label)indicates the maximum reconvnended spacing of supports in ~when the panel is used for SlbfIooring in doubIe-layer construction withthe k>ng dimension of the panel running across the supports. Thereforethe Span Rating of 32/16 in this sample label means that this particularplywood panel may be used either for roof ded<ing over supports thatare spaced 32 inches on center or for subflooring over supports that arespaced 16 inches on center. In all cases panels are assumed continu-ous over two or more spans.

Note: Though the industry terminology refers to plywood sheathing withexterior glue as C-DX. the "X" (which refers to Exterior Glue) is not usedin the label. The words EXTERIOR GLUE or EXT GLUE appear on thebottom of the label to denote this requirement

End joints of the plywood panels should be staggeredand supported by framing members, and deck supportclips should be installed on the unsupported sides ofplywood sheets. Temporary protection should be pro-vided by the installer to prevent the delamination of ply-wood boards. (See Section III, Temporary Roofs.)

Plywood DecksMost building codes require a label on plywood panels,assuring that the plywood complies with the standardsset forth in Department of Commerce Standard PS 1-74.This is a voluntary standard, and producers do not haveto meet these standards in order to sell their product.NRCA recommends that plywood decks be designed andapplied in accordance with the recommendations of theAmerican Plywood Association. Plywood should be in-terior type (with exterior glue), bear the APA, PTl, orTECO trademark, be graded C-D or better, and be sec-ured to structural joists either by annular threaded nails,ring-shank nails or by staples. (See the sample on the

following page.)

A slip sheet of dry sheathing paper is recommended foruse over wood plank decks but is not needed over ply-wood decks. It is good practice. however. to nail a mini-mum layer of insulation over plywood decks. On plywooddecks not covered with insulation. a base ply should bemechanically fastened over the plywood deck (preferablywith annular threaded nails) to serve as the base ply ofthe roof membrane.

3534

XIX. ROOF MEMBRANESEach built-up roof system is designed to satisfy a specificset of conditions for substrate, life span, roof slope, andclimate. The designer should relate these conditions tofield conditions in order to determine the proper specifica-tions. The geographical location and climatic conditionsto be encountered frequently determine the type of mem-brane to be installed. A roof membrane in Arizona, withlittle rainfall and extreme sunlight, may require a differentroof system than one in Montana with its extreme tem-

perature changes.

. Uplift Resistance

. Fire Resistance

. Fungus Attack Resistance

While some disagreement exists as to the priority andacceptability of these attributes. the designer is urged tostudy the above mentioned National Bureau of Stan-dards documents to better understand their relationshipto the membrane selection process.

In the past designers have lacked sufficient engineeringdata for existing and proposed membranes. Studies,however, have provided much needed technical informa-tion for use in selecting roof membranes. In 1967, theNational Bureau of Standards issued Building ScienceSeries #9, "Thermal Shock Resistance for Built-UpMembranes." This study proposed the development of a"strength" factor for membranes, rating their resistanceto thermally induced loads. In 1974, Building ScienceSeries #55. Preliminary Performance Criteria for Bitu-minous Membrane Roofing, proposed performance cri-teria for built-up membranes and selected the followingperformance attributes desirable in a good roof mem-brane:

Roofing felts should be laid in bitumen whose tempera-ture falls within the correct application EVT temperaturerange. (See Section XX. Bitumens.) The rates of interplybitumen application will vary according to:

. A particular mopping asphalt's EVT temperaturerange (and its corresponding viscosity range). The weights of the rolls

. The ambient temperature and wind chill factors

. The type of felt material to be used

. The rate of speed at which the bitumen is applied(when mechanical application procedures areused).

The application of interply bitumens at excessive rates isdiscouraged. (See Section XXIV. Sampling & TestCuts.) Bitumen is used as an adhesive as well as awaterproofing layer. and a thin. complete layer of bitumenis required for the installation of felts. All plies should beimmediately broomed after application to aid the fusionprocess. When possible. all plies should be installed inshingle fashion. Any irregularities. such as fish mouths orblisters. should be repaired prior to the application ofsurfacing. Membranes should be laid as continuously aspossible; therefore. it is important that edge nailers. curbsand penetrations be in place prior to roofing. On low-sloped roofs. the roof membrane should be applied per-pendicular to the flow of water. beginning at low points inthe deck. On slopes over 2 inches per foot. considerationmay be given to laying the felts parallel to the slope.

. Tensile Strength

. Thermal Expansion. Flexural Strength. Tensile Fatigue Strength. Flexural Fatigue Strength. Shear Strength (punching). Impact Resistance. Notch Tensile Strength. Moisture Effects on Strength. Creep. Ply Adhesion. Abrasion Resistance. Tear Resistance. Pliability. Permeability. Moisture Expansion. Weather Resistance

36

For asphalt roofs. treated wood nailers are required oninclines exceeding 2 inches per foot to help secure insu-lation and roof membranes to non-nailable decks or to

37

decks with insulation. These nailers should be the samethickness as the insulation and should be installed per-pendicular to the slope (on 20 foot centers for slopes up to3 inches per foot and on 4 foot centers for slopes greaterthan 3 inches per foot). This method dictates that roofingfelts be installed parallel to the slope and backnailed intothe wood nailers. (See Backnailing in the Glossary.)Spacing of the wood nailers should not exceed the rec-ommendations of the roof insulation manufacturer or theroof membrane manufacturer.

xx. BITUMENSAsphalt and coal tar are the bitumens used for roofingpurposes. They are versatile waterproofing materialswhose properties are desirable for use in built-up roofingpractice. They are thermoplastic. becoming more fluidwith heat and reverting to a more solid material as theycool.

An erroneous impression exists that roofing bitumens arethe "glue"with which roofing felts are cemented together.Actually, the process is more of a "welding" or "fusion"process than a glueing process. The heated moppingbitumen melts and fuses with the saturant bitumen in theroofing felts, creating a "welding" together of the plies.Correct application temperatures are thus vital to thecreation of a quality roof membrane system, and a highbitumen temperature must be maintained to create thewelding process.

After the built-up roof membrane has been applied. theroofing contractor should advise the general contractoror owner to provide surveillance and protection of theroof during the remainder of the construction period.Damage to the roof membrane by other trades during thisperiod is a major cause of roof problems. On gravelsurfaced roofs. damage is most difficult to discover andcan remain undetected for years.

The properties of bitumen are such that heating it atextreme temperatures for extremely long periods oftime may reduce the softening point of asphalt and raisethe softening point of coal tar pitch. This property ofbitumen has produced the erroneous impression that thetemperatures ordinarily employed in bituminous heatingare damaging to the material. In the past this impressionhas led to restrictive heating criteria. These restrictionshave substantially contributed to poor roof installations.

The roofing contractor should make a final inspection ofthe roof, and, if he finds evidence of so-called "work-bench" abuse, he should prepare a written report to thegeneral contractor and/or owner of any visible damagefound in the roof system. Where damage can be ex-pected, the use of a temporary roof should be con-sidered. (See Section III, Temporary Roofs.)

The key words above are "extreme temperatures" and"extremely long periods of time." Bitumens can beheated at high temperatures for short periods of timewithout damage. In fact. they must be heated to hightemperatures in order to achieve complete fusion andstrong bonding of the plies.

Temperature affects the viscosity. or flow, of the bitumenand. thus. the mopping weight. Temperatures that aretoo high (bitumen that has low viscosity and high flow)can lead to light mappings. incomplete film coverage,voids and a potential lack of waterproofing qualities.Temperatures that are too low (bitumen that has highviscosity and insufficient flow) can lead to heavy map-pings. which result in poor adhesion, potential slippage

3938

problems. high expansion properties and low tensilestrengths. which can contribute to roof splits. Obviously.an optimum viscosity range and, therefore, an optimumtemperature range at the point of application, exists forachieving complete fusion, optimum wetting and mop-ping properties, and which results in the desirable interplybitumen weight.

. The Softening Point (SP) Range. The tempera-ture ranges of the asphalt determined in accor-dance with ASTM 0-312 and 0-36.

. The Flash Point (FP). The flash point of the as-phalt as determined by ASTM Method 0-92.

. The Eqiviscous Temperature (EVT) Range. Thetemperature range at which a viscosity of 125centistokes is attained. plus or minus 25°F.

. The Finished Blowing Temperature (FBT). Thetemperature at which the blowing of the asphalthas been completed.

In 1975, this optimum application condition was defin~das the "Equiviscous Temperature" (EVT). The EVT isthe temperature at which asphalt will attain a targetviscosity of 125 centistokes. This is the practical andoptimum temperature for wetting and fusion at the pointof application. A tolerance range is added for practicalapplication in the field to accommodate the effects ofwind chill, sunshine, or ambient temperature. This rangeis expressed as a temperature, plus or minus 25°F. Goodpractice indicates the use of this EVT range as the tem-perature range at which hot bitumen should be applied.Asphalt bitumen should be sufficiertly heated in thekettle/tanker to achieve this optimum viscosity /temperature range (EVT) at the point of application.

In the event EVT information is not furnished by themanufacturer, the following maximum heating tempera-tures should be used as guidelines. The same two re-straints for bitumen heating previously listed (i.e., FlashPoint and Finished Blowing Temperature) pertain tothese temperatures.

Bitumen heating is subject to two restraints:

1. It should NOT be heated to or above the actualCOC Flash Point. (ANSI/ ASTM Method D 92.Test for Flash & Fire Points by Cleveland Open

Cup.)2. It should NOT be heated and held above the

Finished Blowing Temperature (FBT) for morethan 4 hours.

Coal tar roofing bitumens are produced by a limited num-ber of manufacturers and have fewer material variationsthan asphalt. Although EVT has not been applied to coaltar bitumens for this reason, the same concept is applic-able. Heating and application temperatures for coal tarare slightly lower than asphalt bitumens. Most manufac-turers recommend a kettle temperature of 425°F, with ap-plication temperatures ranging from 325°F to 4000F. Aswith asphalt, higher heating temperatures may benecessary to attain the proper application temperature,but higher heating temperatures should be maintainedonly for short periods of time.

This concept emphasizes that the temperature of bitu-men at the point of application is the main considera-tion and that kettle/tanker heating should. therefore, bebased on reaching the desired application temperature.

The Roofing Systems Technical Committee. a joint com-mittee of the Asphalt Roofing Manufacturers Associationand the National Roofing Contractors Association. en-dorses and recommends the following identificationsystem for mopping grade asphalts. This informationshould be printed on all asphalt packages or bills of ladingcovering bulk asphalt:

4140

XXI. WATER CUTOFFS &WEATHER PROTECTION

XXII. FLASHING & CANTSThe most vulnerable part of any roof system is that pointat which the horizontal roof deck and a vertical surfacejoin. Most roof leaks occur at these flashing locations.The designer should carefully consider the design offlas.hing details at these locations. (See NRCA Construc-tion details for FLASHING in the NRCA Roofing andWaterproofing Manual.)

Water cutoffs are temporary felt courses that are installedto prevent moisture from entering the insulation andmembrane during construction. They should be appliedat the end of each day's work and whenever wort< ishalted for an indefinite period to protect the membranefrom precipitation. They must be removed prior to instal-ling additional insulation.

The term "flashing" can be divided into two groups:Temporary flashings should be installed as weather pro-tection if permanent flashings are not in place. All open-ings in the membrane should be sealed to prevent anymoisture from entering the roof system prior to the com-pletion of membrane application.

Composition Flashing (Base Flashing)The bending radius of present composition roof-ing materials is generally limited to 45°. To allowfor this bending radius, all vertical surfaces musthave cant strips installed between the roof and thevertical surface. The height of the base flashingshould be not less than (a nominal) 8 inches andnot higher than (a nominal) 14 inches above thefinished roof surface. Walls requiring flashingshigher than 14 inches should receive specialmoisture-proofing. A wood nailer strip or suitabledetail allowing mechanical fastening of the baseflashing at the top must be provided. Masonrysurfaces should be primed with asphalt concrete

primer.

Specifications requiring gravel installation each day areunrealistic and sometimes detrimental to the quality ofthe completed roof. Where working conditions permit.roofing felts should be "glazed" and sealed at the end ofeach day's work if final surfacing is not installed.

An expansion joint type flashing (one allowingexpansion and contraction) should be con-structed as detailed in NRCA Construction Detail"H" (in the Appendix). It should be attached to thewood curbing. The wood curbing should beplaced against the wall and secured only to thedeck. The designer is cautioned to consider thatbuilding components are subjected to thermalmovements at different rates and in different di-rections from the roof membrane. If the roof is tobe "tied into" these components. special consid-eration should be given to the design of that junc-ture.

4342

XXIII. SURFACING & AGGREGATEMost roof membranes, if not presurfaced, require sometype of wearing surface. This surfacing should be appliedas soon as is practical after the membrane is installed.Gravel, slag, marble chips, etc., are the aggregates usedfor aggregate surfaced roofs. Asphalt and liquid surfacecoatings are used on some smooth surfaced roofs.

Gravel or aggregate surfacing should be set in hot bitu-men, either by a bitumen dispenser or by hand pouring.Gravel placed by machine will result in somewhat lightersurface bitumen poundages in some locations since thegravel, as it flows from the gravelling machine. tends tocreate a "wave" effect in the hot bitumen as it is placed.Hand pouring produces heavier poundages but less uni-form coverage, and neither method is preferable to theother. Gravel or other aggregate should be fairly roundedin shape and should contain a minimum of flat. sharp orelongated particles. At the time of application, the aggre-gate should be hard, durable, opaque, surface dry andfree of clay, loam, sand or other foreign substances.Storage piles of aggregate should be placed on coated orgravelled portions of the membrane and not on bare felt.Occasionally, on well applied roofs, small black globulesknown as "raspberries" or "blueberries" will form in theroof surface. These are not detrimental to the roof andsimply indicate that large quantities of bitumen flood coatwere applied and have bubbled up around the aggregate.To avoid excessive aggregate loss, aggregate surfacingshould not be applied to roofs whose slope is greater than3 inches per foot.

2. Metal Flashing (Counterflashlngand Cap Flashing)Since metals have a high coefficient of expansion.metal flashing must be isolated from the roofmembrane wherever possible to prevent metalmovements from splitting the membrane. Flash-ing details that require metal flanges to be sand-wiched into the roof membrane should be avoidedif possible.

For all walls and projections that receive composi-tion base flashing, metal counterflashing shouldbe installed in the wall above the base flashing.The design of this detail should be two piece.allowing installation of the counterflashing afterthe base flashing. Single piece installations can-not be flashed properly nor can reroofing androofing maintenance be performed without de-forming the metal. Sheet metal should NEVER beused as a base flashing.

Metal wall cap flashing is often used to cover thetop of a wall in lieu of masonry copings. In mostcases the metal counterflashing is attached to theinside face of the metal wall cap flashing withsheet metal screws~

Gravel stops should be raised above the waterlineby using tapered cants and wood blocking. Whenthis is not possible. the metal flanges for low pro-file gravel stops should be set in mastic on top ofthe completed roof membrane and nailed at closeintervals to the wood nailer. (See NRCA Detail"C" in the Appendix.) The metal flange shouldthen be primed with asphalt primer and felt flash-ing strips applied. Interior drainage is recom-mended. and edges should be raised wheneverpossible. A metal edging should NEVER be usedas a water dam or waterstop. The practice ofconnecting sheet metal to the roof membraneshould be avoided whenever possible. Pipeprojections through the membrane require metalflashing or the insertion of roof jacks into the mem-brane. Metal flanges should be set in mastic overthe completed membrane, primed and stripped inwith flashing strips.

Generally. smooth surfaced coatings should be appliedas soon as possible after the membrane is installed.Some coatings, however. must be applied over a previ-ously applied thin coating of hot asphalt. The manufactur-er's instructions should be consulted to determine if thisthin coating is required. If it is, that asphalt should beallowed to "age" (or oxidize) for a period of two to fourweeks, depending upon the amount of sunlight, beforefinal surfacing is applied. Emulsions must be protectedfrom freezing and must not be applied in freezing tem-peratures or when precipitation is occurring or expected.Frozen materials must be discarded.

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XXIV. QUALITY ASSURANCE & TEST CUTSFoot traffic can be highly detrimental in extremely cokj orwarm temperatures and should be controlled. Walkways,if required, should be constructed of 2 inch x 4 inchredwood materials, and fasteners for these walkwaysshould not extend through the roof membrane. All sharpedges should be eliminated from these walkways.

Some pad-type composition walkways have exhibitedextreme degradation in a short period of time. Whenthese walkpads are used. a flood coat and aggregatesurfacing should be appfied first, and the walkpad areathen swept clear of loose aggregate. Good practice dic-tates that one piece of the walkpad be spaced no closerthan 6 inches from an adjacent piece. The walkpad canthen be set in hot bitumen on top of the surfacing aggre-gate and. thereby, raised above the plane of the roof.

NRCA believes the most effective method of verifyingcorrect roof application is visual inspection during theapplication process by persons experienced and knowl-edgeable in roofing. To help obtain a quality roof applica-tion, the following items should be verified.

1. Deck SurfaceThe surface of the deck shoukt be clean, fim1,smooth, visibly dry and properly secured againstmovement.

2. MaterialsRoofing materials used on the job should complywith material specifications for the job. All materialsshould be clean, visibly dry and free from damage.

3. Storage of MaterialsRoofing materials should be stored and protected.

4. AttachmentThe roof membrane and/or insulation should be sec-ured with the specified number and types of fasten-ers, nails or bitumen.

5. BitumenThe type of bitumen should be checked to insure thatit is the proper type for the specification. roof slopeand climatic conditions. Proper heating tempera-tures should be maintained in the kettle or tanker toinsure that the bitumen will be the E. V. T. at the pointof application on the roof.

6. Bitumen ApplicationBitumen applicators should be well versed in thespecified bitumen application rates. In addition. ap-plicators should be thoroughly knowledgeable of thevolume capacity of the equipment being used andthe length of runs required to achieve the specifiedbitumen application rates.

7. Ply' of FeltThe specified number of plys of felt should be appliedin accordance with specification procedures. The

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lapping sequence of the felt plyS should satisfyspecification requirements to achieve completecoverage.

solely to determine membrane weight after thegravel or final surfacing has been applied. When testcuts are required. the NRCA recommends proce-dures as called for in ASTM 03617. This procedureis an acceptable quality control method. If gravelsurfacing has been applied, a test cut should betaken only where significant evidence of roof defici-encies exists.

8. Phased ApplicationThe installation of all plys should be completed in thesame day. and the plys should be surfaced eitherwith a glaze coat or complete surfacing on all organicroof membranes. The final surfacing can be delayedon glass fiber roof membranes. It should be noted that the layer of bitumen between

plys of the membrane reinforcement should not beexcessive. Maximum bond strength is achieved withthe thinnest practical continuous application of bitu-men between the plys. There should be sufficientbitumen to penetrate the membrane reinforcing, inaddition to that required to provide waterproofingproperties.

9. FlashingsComposition base flashings should be completed ona daily basis. Any metal or masonry surfaces wherebitumen materials are to be attached must be primedand allowed to dry. Composition and metal materialsmust be properly secured with appropriate mechani-cal fasteners using the spacing required (sheetmetal 3" on center; masonry 6" on center; wood 9"on center). Walls, projections. wood nailers andother termination points should be completed beforeroof membrane and flashings are commenced. Allsheet metal flashings. such as pipe collars, drains,gravel stops. etc.. should be on site before roofing isrequired to be commenced. No condition should beallowed that would permit moisture entering behind.around. or under roof or flashing membrane. Flash-ing installations should be monitored for lap open-ings and voids.

The important criterion is to apply a sufficient quan-tity of bitumen to provide a full and continuouscourse of bitumen for the embedment of each subse-quent ply of roofing reinforcement. The bitumenshould be applied in a manner that will not allowcontact between layers of reinforcements. Thequantities to achieve this may vary from as low as 15Ibs. per 100 square feet to possibly 35 Ibs. per 100square feet for application of bitumen between mem-brane plys. For open type fiber-glass reinforcementplys, the variances are narrower.

Difference in application rates may result from at-mospheric conditions, methods of application, temp-erature at actual time of placement, and the type ofequipment locally available to the applicators. Bitu-men flows less readily at lower application tempera-tures and the interply layer of bitumen tends to beheavier in weight. The quantity may also vary be-tween the machine application and mop application.These quantity variations are recognized as normaland acceptable, as many factors affect the applica-tion of hot bitumen. Bitumen is used as an adhesiveas well as a waterproofing layer, and a thin, continu-ous layer of bitumen is required for the installation offelts.

10. Gravel AdhesionThe gravel which makes initial contact with the hotbitumen flood coat should become embedded in thebitumen, leaving the balance of the gravel to serveas ballast and protection for the roof membranesystem.

11. Roof CutsRoof cuts are sometimes used to determine the av-erage weight of the interply bitumen quantities.When the job documents call for test cuts, a reliablescale should be maintained on the job site and cutsshould be taken during application, evaluated. andreplaced before the application of the surfacing. Inno instance does the NRCA recommend a test cut

48 49

XXVI. INSPECTION & MAINTENANCEXXV. REROOFINGAll roofs require periodic maintenance to achievemaximum roof life. While complex repairs and somemaintenance should be performed by qualified roofers,the owner can help maintain the roof by seeing thatregular clean up procedures are performed. The de-signer and roofing contractor should make the owneraware of these procedures after the roof is completed.

Each reroof or recover project has its own specific prob-lems that require individual assessment. The designercan obtain much of the information needed to prepare forreroofing by a thorough study of the existing roof systemand the reasons for its deterioration.

The existing roof deck must be sound and undamaged. Asample of the existing membrane should always be re-moved down to the deck. The insulation should be care-fully examined, and wet or damaged insulation, in mostevery case, should be replaced. It may be possible tosalvage existing roof insulation if it is undamaged or if it isdry. Some insulation products cannot be salvaged sinceremoving the membrane causes delamination of the in-sulation boards. If doubt exists as to the adequacy of theattachment of the first layer of insulation, this layer shouldbe mechanically attached prior to the attachment of thesecond layer. Where removing the membrane maycause minor surface damage to the existing insulation, asingle minimum layer, or recover board, should be con-sidered for installation over the existing insulation to pro-vide a suitable surface for the new membrane. In addi-tion, the designer should carefully calculate the dew-point location and make provisions for it in his reroofingplans. The practice of installing a new roof membranedirectly to the existing roof is discouraged.

Building owners may wish to consider the use of addi-tional insulation in order to anticipate future energy re-quirements. In selecting a new membrane specification,the designer should consider the performance of the oldroof specifications. Changes in the wood blockingheights and additional expansion provisions may be re-quired at the time of reroofing. The existing drainageprovisions should be examined and revised as needed.

Owner Inspection andMaintenance Recommendations

1. Inspect the roof at least twice yearly, in the springand fall, and inspect all roofs after any severestorm. Make frequent inspections on buildingsthat house manufacturing facilities that evacuateexhaust debris onto the roof. Clean roof drains ofdebris. Remove leaves, twigs, cans, balls. etc.,which could plug roof drains. Bag and remove alldebris from the roof since debris on the roofsurface will be quickly swept into drains by heavyrains, and drainage problems may occur.

2. Notify the roofing contractor immediately after aroof leak occurs. If possible. note conditions re-sulting in leakage. Heavy or light rain, wind direc-tion, temperature and the time of year that the leakoccurs are all important clues to tracing roof leaks.Note whether the leaks stop shortly after each rainor continue to drip until the roof is dry. If the owneris prepared with facts, the diagnosis and repair ofroof problems can proceed more rapidly.

3. File all job records, plans and specifications forfuture reference. Set up a maintenance schedule.Record maintenance procedures as they occur.Log all access times and parties working on theroof in case damage should occur.

4. Do not allow foot traffic on the roof in very cold orvery hot temperatures as damage can result. Donot allow the installation of television and radioantennas or mechanical equipment without notify-ing the roofing contractor and consulting with himabout the methods and details for these installa-tions. One of the keys to avoiding roof damage isthe key to the padlock on the roof hatch! Allow only

51

Sample evaluation cuts are used to investigate existingroofs. In the hands of skilled investigators. they may helpto identify the nature of the existing roof system. It mustbe stressed that their usefulness in this area is in directproportion to the experience and expertise of the investi-

gator.

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XXVII. FACTORY MUTUAL (FM) &UNDERWRITERSLABORATORIES (UL)

authorized personnel on the roof.5. In emergency situations. patch leaks to minimize

property loss.6. Except for emergency situations. do not attempt

owner-performed roof repairs. The puncturing of ablister or the spreading of a coating or mastic onlycovers up evidence the roofing contractor needsto ascertain the problem. Do not consider usingmaintenance coatings, "resaturants... sprays or"miracle" products without consulting a qualifiedroofing contractor.

Insurance bureaus rely on FM and UL requirements forinsurance rating purposes. These requirements havehad a strong impact on the construction of quality roofsystems. They were established to reduce physical dam-age to roofing materials and the ensuing financial losses.The requirements, however, are aimed at preventingmaterial waste and financial loss and do not necessarilyguarantee the construction of quality roof systems. Roofcomponents are tested for loss prevention but are NOTtested for the overall performance of the roof system thatis desired. In summary. the use of FM & UL classifiedmaterials or methods will not necessarily result in qualityroof systems.

Roofing Contractor Maintenance Recommendations

After completion, each roof is subjected to various weath-ering conditions. Roofs do not wear uniformly since cer-tain areas may be affected more severely than others.Equalizing wear by upgrading worn areas is the secret toprolonged roof life. To equalize wear the maintenanceand repair of these areas should be done by a qualifiedroofing contractor. Maintenance may be as simple asregravelling a windswept corner. or more complex. suchas correcting a water ponding problem, but maintenanceis a necessary part of good roofing practice.

Since some FM and UL requirements change every year,it is good practice to consult current issues of FM & ULbulletins for the latest information on installation methodsand approved materials that pertain to a specific buildingproject. This document will exclude specific FM & ULinformation. For further information see the FM & ULsection of the NRCA Roofing and WaterproofingManual.

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XXVIII. TO THE OWNER AND DESIGNER GLOSSARY

Aggregate:(1) crushed stone, crushed slag, or water-worn gravelused for surfacing a built-up roof; (2) any granular mineralmaterial.

Ailigatoring:the cracking of the surfacing bitumen on a built-up roof,producing a pattern of cracks similar to an alligator's hide;the cracks mayor may not extend through the surfacingbitumen.

Application Rate:the quantity (mass. volume or thickness) of material ap-plied per unit area.

Area Divider:a raised, double wood member attached to a propertyflashed wood base plate that is anchored to the roof deck.It is used to relieve thermal stresses in a roof systemwhere no expansion joints have been provided. (SeeNRCA Construction Detail "0-1".)

Asbestos:a group of natural fibrous impure silicate materials

Asphalt:a dark brown to black cementitious material in which thepredominating constituents are bitumens which occur innature or are obtained in petroleum processing.

Asphalt, Air Blown:an asphalt produced by blowing air through molten as-phalt at an elevated temperature to raise its softeningpoint and modify other properties.

The successful performance of a built-up roof requires:

1. Proper DesignCompatible materials and systems that will with-stand the environmental conditions of the areawhere the building is constructed should be care-fully selected. The roof system components. asthey relate to each other. should be carefully de-tailed. While primary responsibility for proper de-sign is placed with the designer. the roofing con-tractor and the material manufacturer may be con-sulted for input helpful to the design.

2. Quality MaterialsThe selection of materials should be based on thequality of the roof system rather than on economicconsiderations.

3. Quality WorkmanshipOnly skilled. trained workmen familiar with theproducts to be used should perform the work.Interference from other parties involved in theconstruction process should be avoided.

4. Weather ConsiderationsThe permanent roof system should be con-structed under reasonable weather conditions.

5. Timely MaintenanceDamage to the roof by other trades or by ownerpersonnel should be prevented. The roof shouldbe maintained in top condition by equalizing wearand by reducing degradation factors with periodicinspections and repairs. A good maintenance pro-gram is the owner's greatest assurance of value.

6. Qualified Roofing ContractorsWork with qualified roofing contractors! Consultthem before issuing plans and specifications. Besure that all contractors are bidding on exactly thesame application procedures and materials.

Asphalt Felt:an asphalt-saturated felt or an asphalt-coated felt.

Asphalt Mastic:a mixture of asphaltic material and graded mineral aggre-gate that can be poured when heated but requires mech-anical manipulation to apply when cool.

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Blister:a spongy raised portion of a roof membrane. ranging inarea from 1 inch in diameter and of barely detectableheight upwards. Blisters result from the pressure buildupof gases entrapped in the membrane system. Thesegases most commonly are air and/or water vapor. Blis-ters usually involve delamination of the underlying mem-brane plies.

Asphalt, Steam Blown:an asphalt produced by blowing steam through moltenasphalt to modify its properties, normally used for high-way bitumen.

Backnailing:the practice of blind nailing (in addition to hot-mopping) allthe plies of a substrate to prevent slippage. (See BLIND

NAILING.)Bond:the adhesive and cohesive forces holding two roofingcomponents in intimate contact.

Base Flashing:see FLASHING.

Brooming:embedding a ply by using a broom to smooth out the plyand ensure contact with the adhesive under the ply.

Base Ply:the base ply is the first ply when it is a separate ply and notpart of a shingled system.

BTU:(British Thermal Unit)-the heat energy required to raisethe temperature of 1 lb. of water 1 degree Farenheit.

Base Sheet:a saturated or coated felt placed as the first ply in somemulti-ply, built-up roof membranes.

Built-Up Roof Membrane:a continuous, semi-flexible membrane assembly consist-ing of plies of saturated felts. coated felts, fabrics or matswith alternate layers of bitumen, generally surfaced withmineral aggregate, bituminous materials, or a granulesurfaced sheet. (Abbreviation: BUR.)

Bitumen:the generic term for an amorphous, semi-solid mixture ofcomplex hydrocarbons derived from any organic source.Asphalt and coal tar are the two bitumens used in the

roofing industry.

Bituminous:containing or treated with bitumen. Examples: bitumin-ous concrete. bituminous felts and fabrics. bituminouspavement.

Cant Strip:a bevelled shaped strip of wood or wood fiber that fits intothe angle formed by the intersection of a horizontal sur-face and a vertical surface. The 45 degree slope of theexposed surface of the cant strip provides gradual angu-lar transition from the horizontal surface to the verticalsurface.

Cap Flashing:see FLASHING.

Bituminous Emulsion:(1) a suspension of minute globules of bituminous mate-rial in water or in an aqueous solution; (2) a suspension ofminute globules of water or of an aqueous solution in aliquid bituminous material (invert emulsion).

Bituminous Grout:a mixture of bituminous material and fine sand that willflow into place without mechanical manipulation whenheated.

Capillarity:d'le action by which the surface of a liquid (where it is incontact with a solid) is elevated or depressed. dependingupon the relative attraction of the molecules of the liquidfor each other and for those of the solid.Blind Nailing:

the practice of nailing the back portion of a roofing ply.

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Cap Sheet:a granule-surfaced coated sheet used as the top ply of abuilt-up roof membrane or flashing.

Coping:the covering piece placed on top of a wall that is exposedto the weather. It is usually sloped to shed water.

Caulking:a composition of vehicle and pigment, used at ambienttemperatures for filling joints, that remains plastic for anextended time after application.

Counterttashing;formed metal or elastomeric sheeting secured on or into awall, curb, pipe, rooftop unit or other surface to cover andprotect the upper edge of a base flashing and its as-sociated fasteners.

Coal Tar Bitumen:a dark brown to black, semi-solid hydrocarbon formed asa residue from the partial evaporation or distillation ofcoal tar. It is used as the waterproofing agent in dead-level or k>w-slope built-up roofs. It differs from COAL TARPITCH in having a lower front-end volatility. (For specifi-cation properties, see ASTM Standard 0450, Type III.)

Course:( 1) the term used for each application of material thatforms the waterproofing system or the flashing; (2) onelayer of a series of materials applied to a surface (i.e., afive course wall flashing is composed of three applica-tions of mastic with one ply of felt sandwiched betweeneach layer of mastic).

Coal Tar Felt:See TARRED FELT

Coal Tar Pitch:a dark brown to black, semi-solid hydrocarbon formed asa residue from the partial evaporation or distillation ofcoal tar. It is used as the waterproofing agent in dead-level or low-slope built-up roofs. (For specification prop-erties, see ASTM 0450. Types I and II.)

Coverage:the surface area (in square feet) to be continuously coat-ed by a specific roofing material, with allowance made fora specific lap.

Crack:a separation or fracture occurring in a roof membrane orin a roof deck, generally caused by thermally inducedstress or substrate movement.

Coated Base Sheet (or Felt):a felt that has been impregnated and saturated with as-phalt and then coated on both sides with harder. moreviscous asphalt to increase its im~m\eability to mois-ture; a parting agent is incorporated to prevent the mate-rial from sticking in the roll.

Creep:the permanent deformation of a roofing material or roofsystem caused by the movement of the roof membranethat results from continuous thermal stress or loading.

Cricket:a superimposed construction placed in a roof area toassist drainage. (See NRCA Construction Detail "P".)

Cold-Process Roofing:a continuous. semi-flexible membrane consisting of pliesof felts. mats. or fabrics that are laminated on a roof withalternate layers of cold-applied roof cement and surfacedwith a cold-applied coating.

Cutback:any roofing bituminous material that has been solventthinned. Cutbacks are used in cold-process roofing adhe-sives, flashing cements, and roof coatings.Condensation:

the conversion of water vapor or other gas to liquid as thetemperature drops or the atmospheric pressure rises.(See DEW-POINT.)

Cutoff:a material seal that is designed to prevent lateral watermovement into the edge of a roof system where the

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membrane terminates at the end of a day's work or usedto isolate sections of the roof system. Cutoffs are usuallyremoved before the continuation of work.

Edge Sheets:felt strips that are cut to widths narrower than the stan-dard full felt roll width. They are used to start the felt-shingling pattern at a roof edge.

Dampproofing:treatment of a surface or structure to resist the passage ofwater in the absence of hydrostatic pressure. Edge Stripping:

application of felt strips cut to narrower widths than thenormal felt-roll width to cover a joint.

Dead Level:the term used to describe an absolutely horizontal roof.Zero slope. (See SLOPE.)

Edge Venting:the practice of providing regularly spaced protectedopenings along a roof perimeter to relieve moisture vapor

pressure.Dead Level Asphalt:a roofing asphalt that has a softening point of 140°F(60°C) and that conforms to the requirements of ASTMSpecification D 312. Type I.

Elastomer:a macromolecular material that returns rapidly to its ap-proximate initial dimensions and shape after substantialdeformation by a weak stress and the subsequent re-lease of that stress.

Dead Loads:non-moving rooftop loads, such as mechanical equip-ment, air conditioning units, and the roof deck itself.

Elastomeric:the term used to describe the elastic. rubber-like proper-ties of a material.

Deck:the structural surface to which the roofing or waterproof-ing system (including insulation) is applied.

Embedment:(1) the process of pressing a felt, aggregate. fabric, mat,or panel uniformly and completely into hot bitumen oradhesive; (2) the process of placing a material into an-other material so that it becomes an integral part of thewhole material.

Delamination:separation of the plies in a membrane system or separa-tion of laminated insulation layers.

Dew-Point:the temperature at which water vapor starts to condensein cooling air at the existing atmospheric pressure andvapor content.

Emulsion:the intimate dispersion of an organic material and waterachieved by using a chemical or clay emulsifying agent.

Drain:a device that allows for the flow of water from a roof area.(See NRCA Construction Detai"'W-2".)

Envelope:a continuous felt fold formed by wrapping and securing aportion of a base felt back up and over the felt plies aboveit. Envelopes help prevent the seepage of bitumen.Dropback:

a reduction in the softening point of bitumen that occurswhen bitumen is heated in the absence of air. (SeeSOFTENING POINT DRIFT.)

Equilibrium Moisture Content:(1) the moisture content of a material stabilized at a giventemperature and relative humidity. expressed as percentmoisture by weight; (2) the typical moisture content of amaterial in any given geographical area.

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Equiviscous Temperature (EVT) Range:the optimum application temperature of asphalt. It is thetemperature range at which a viscosity of 125 centistokesis attained, plus or minus 25°F.

Fine Mineral Surfacing:a water-insoluble, inorganic material. more than 50% ofwhich passes through the No. 35 sieve. that may be usedon the surface of roofing material.

Expansion Joint:a structural separation between two building elementsdesigned to minimize the effect of the stresses and move-ments of a building's components and to prevent thesestresses from splitting or ridging the roof membrane.(See NRCA Construction Detai"'C-1".)

Fishmouth:(1) a half-cylindrical or half-conical opening formed by anedge wrinkle; (2) in shingles. a half-conical opening form-ed at a cut edge.

Flashing:the system used to seal the edges of a membrane atwalls, expansion joints. drains, gravel stops. and otherareas where the membrane is interrupted or terminated.Base flashing covers the edges of the membrane. Capflashing or counterflashing shield the upper edges ofthe base flashing.

Exposure:(1) the transverse dimension of a roofing element notoverlapped by an adjacent element in any roof system.The exposure of any ply in a membrane may be comput-ed by dividing the felt width minus 2 inches by the numberof shingled plies; thus. the exposure of a 36 inch wide feltin a shingled. four-ply membrane should be 8V2 inches;(2) the time during which a portion of a roofing element isexposed to the weather.

Flashing Cement:a trowel able mixture of cutback bitumen and mineralstabilizers. including asbestos or other inorganic fibers.

Fabric:a woven cloth of organic or inorganic filaments. threads.or yams.

Flat Asphalt:a roofing asphalt that has a softening point of approxi-mately 170°F <"C) and that conforms to the require-ments of ASTM Specification 0312, Type II.

Factory Mutual (FM):an organization which classifies roof assemblies for theirfire characteristics and wind-uplift resistance for insur-ance companies in the United States.

Flood Coat:the top layer of bitumen into which the aggregate isembedded on an aggregate-surfaced, built-up roof.

Factory Square:108 square feet (10 square meters) of roofing material.

Fluid Applied Elastomer:an elastomeric material, which is fluid at ambient tem-perature, that dries or cures after application to form acontinuous membrane.Felt:

a fabric manufactured from vegetable fibers (organicfelts), asbestos fibers (asbestos felts), or glass fibers(glass-fiber felts). The manufacturing process involvesmechanically interlocking the fibers of the particular feltmaterial in the presence of moisture and heat.

Glass Felt:a felt sheet in which glass fibers are bonded into the feltsheet with resin. They are suitable for impregnation andcoating. They are used in the manufacture and coating ofbituminous waterproofing materials. roof membranes.and shingles.Felt Mill Ream:

the mass in pounds of 480 square feet of dry. unsaturatedfelt; also termed "point weight." Glass Mat:

a thin mat of glass fibers with or without a binder.

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Insulation:a material applied to reduce the flow of heat.

Glaze Coat:(1) the top layer of asphalt in a smooth-surfaced built-uproof assembly; (2) a thin protective coating of bitumenapplied to the lower plies or top ply of a built-up mem-brane when application of additional felts or the flood coatand aggregate surfacing are delayed.

Knot:an imperfection or non-homogeneity in materials used infabric construction, the presence of which causes sur-face irregularities.

Grain:the weight unit equal to 1/7000 lb.; used in measuringatmospheric moisture content.

Live Loads:moving roof installation equipment. wind. snow. ice orrain.

Gravel:coarse. granular aggregate. containing pieces approxi-mately % inch to V2 inch in size and suitable for use inaggregate surfacing on built-up roofs.

Manufacturer's Bond:a security company's guarantee that it will stand behind amanufacturer's liability to finance membrane repairs oc-casioned by ordinary wear within a period generally limit-ed to 5.10.15. or 20 years.Gravel Stop:

a flanged device, frequently metallic. designed to providea continuous finished edge for roofing materials and toprevent loose aggregate from washing off of the roof.

Mastic:see FLASHING CEMENT or ASPHALT MASTIC.

Membrane:a flexible or semi-flexible roof covering or waterproofing.whose primary function is the exclusion of water.

Headlap:the minimum distance. measured at go'degrees to theeave along the face of a shingle or felt as applied to a roof.from the upper edge of the shingle or felt. to the nearestexposed surface. Mesh:

the square or circular opening of a sieve.

Holiday:an area where a liquid-applied material is missing. Metal Flashing:

see FLASHING; frequently used as through-wall flash.ing, cap flashing, counterflashing or gravel stops."Hot Stuff" or "Hot":

the roofer's term for hot bitumenMineral Fiber Felt:a felt with mineral wool as its principle component.Hygroscopic:

the term used to describe a material which attracts, ab-sorbs and retains atmospheric moisture. Mineral Granules:

opaque, natural, or synthetically colored aggregate com-monly used to surface cap sheets. granule-surfacedsheets. and roofing shingles.

Incline:the slope of a roof expressed either in percent or in thenumber of vertical units of rise per horizontal unit of run.

Mineral Stabilizer:a fine. water-insoluble, inorganic material used in a mix-ture with solid or semi-solid bituminous materials.

Inorganic:being or composed of matter other than hydrocarbonsand their derivatives. or matter that is not of plant oranimal origin.

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Mineral-Surfaced Roofing:built-up roofing materials whose top ply consists of agranule-surfaced sheet.

Nailing:(1) in the exposed-nailing method, nail heads are ex-posed to the weather; (2) in the concealed-nailingmethod, nail heads are concealed from the weather.(See also BLIND NAILING.)Mineral-Surfaced Sheet:

a felt that is coated on one or both sides with asphalt andsurfaced with mineral granules. Neoprene:

a synthetic rubber (polychloroprene) used in liquid-applied and sheet-applied elastomeric roof membranesor flashing.

Mole Run:a meandering ridge in a membrane not associated withinsulation or deck joints.

Nineteen-Inch Selvage:a prepared roofing sheet with a 17 inch granule-surfacedexposure and a nongranule-surfaced 19 inch selvageedge. This material is sometimes referred to as SIS or asWide-Selvage Asphalt Roll Roofing Surfaced with Min-erai Granules.

Mop-And-Flop:an application procedure in which roofing elements (insu-lation boards. felt plies. cap sheets. etc.) are initiallyplaced upside down adjacent to their ultimate locations.are coated with adhesive. and are then turned over andapplied to the substrate.

Organic:being or composed of hydrocarbons or their derivatives,or matter of plant or animal origin.

Mopping:an application of hot bitumen applied to the substrate orto the felts of a built-up roof membrane with a mop ormechanical applicator. Perlite:

an aggregate used in lightweight insulating concrete andin preformed perlitic insulating boards, formed by heatingand expanding siliceous volcanic glass.

Solid Mopping:a continuous mopping of a surface, leaving no un-mopped areas.

Perm:a unit of watervapor transmission defined as 1 grain ofwater vapor per square foot per hour per inch of mercurypressure difference (1 inch of mercury = 0.491 psi). Theformula for perm is: P = GRAINS OF WATER VAPOR!SQUARE FOOT-HOUR-INCH MERCURY.

Spot Mopping:a mopping pattern in which hot bitumen is applied inroughly circular areas, leaving a grid of unmapped,perpendicular bands on the roof.

Sprinkle Mopping:a random mopping pattern wherein heated bitumenbeads are strewn onto the substrate with a brush ormop.

Permeance:an index of a material's resistance to water-vapor trans.mission. (See PERM.)

Phased Application:the installation of a roof system or waterproofing systemduring two or more separate time intervals.

Strip Mopping:a mopping pattern in which hot bitumen is applied inparallel bands.

Picture Framing:a rectangular pattern of ridges in a membrane over insu-lation or deck joints.

6766

Reinforced Membrane:a roofing or waterproofing membrane reinforced withfelts. mats, fabrics. or chopped fibers.

Pitch Pocket:a flanged. open bottomed metal container placed aroundcolumns or other roof penetrations that is filled with hotbitumen and/or flashing cement to seal the joint. The useof pitch pockets is not recommended by NAGA. Relative Humidity:

the ratio of the weight of moisture in a given volume ofair-vapor mixture to the saturated (maximum) weight ofwater vapor at the same temperature. expressed as apercentage. For example. if the weight of the moist air is 1lb. and if the air could hold 2 Ibs. of water vapor at a giventemperature. the relative humidity (RH) is SOO/o.

Plastic Cement:see FLASHING CEMENT.

Ply:a layer of felt in a built-up roof membrane system. Afour-ply membrane system has four plies of felt. Thedimension of the exposed surface (the "exposure") ofany ply may be computed by dividing the felt width (minus2 inches) by the number of plies; thus, the exposedsurface of a 36 inch wide felt in a four-ply membraneshould be 81/2 inches. (See EXPOSURE.)

Reroofing:the practice of applying new roofing materials over exist-ing roofing materials.

Ridging:an upward. "tenting" displacement of a membrane, fre-quently occurring over insulation joints, deck joints andbase sheet edges.

Point Weight:see FELT MILL REAM.

Roll Roofing:the term applied to smooth-surfaced or mineral-surfacedcoated felts.

Pond:a roof surface which is incompletely drained.

Positive Drainage:the drainage condition in which consideration has beenmade for all loading deflections of the deck. and addi-tional roof slope has been provided to ensure completedrainage of the roof area within 24 hours of rainfall precip-itation.

Roof Assembly:an assembly of interacting roof components (includingthe roof deck) designed to weatherproof and, normally, toinsulate a building's top surface.

Roofer:the trade name for the workman who applies roofingmaterials.

Primer:a thin, liquid bitumen applied to a surface to improve theadhesion of subsequent applications of bitumen.

Roof System:a system of interacting roof components (NOT includingthe roof deck) designed to weatherproof and, normally, toinsulate a building's top surface.

Rake:the sloped edge of a roof at the first or last rafter.

Re-entrant Corner:an inside comer of a surface, producing stress concen.trations in the roofing or waterproofing membrane.

Saturated Felt:a felt that has been partially saturated with low softening-point bitumen.

Reglet:a groove in a wall or other surface adjoining a roof surfacefor use in the attachment of counterflashing.

68 69

Slag:a hard. air cooled aggregate that is left as a residue fromblast furnaces. It is used as a surfacing aggregate andshould be surface dry and free of sand. clay, or otherforeign substances at the time of application.

Screen:an apparatus with apertures for separating sizes of ma.terial.

Seal:(1) a narrow closure strip made of bituminous materials;(2) to secure a roof from the entry of moisture. Slippage:

the relative lateral movement of adjacent components ofa built-up membrane. It occurs mainly in roof membraneson a slope. sometimes exposing the lower plies to theweather.

Sealant:a mixture of polymers. fillers, and pigments used to filland seal joints where moderate movement is expected; itcures to a resilient solid. Slope:

the tangent of the angle between the roof surface and thehorizontal. It is measured in inches per foot. The AsphaltRoofing Manufacturers Association (ARMA) ranks slope

as follows:

Selvage:an edge or edging which differs from the main part of (1) afabric, or (2) granule-surfaced roll roofing material.

uptOY2inchperfoot.Y2 inch per foot to 11/2 inches per foot.. . . . . . . . . . . .over 11/2 inches per foot.

Level SlopeLow Slope .Steep Slope

Selvage Joint:a lapped joint designed for mineral-surfaced cap sheets..The mineral surfacing is omitted over a small portion ofthe longitudinal edge of the sheet below in order to obtainbetter adhesion of the lapped cap sheet surface with thebituminous adhesive.

Smooth-Surfaced Roof:a built-up roof membrane surfaced with a layer of hot-mopped asphalt. cold-applied asphalt-clay emulsion.cold-applied asphalt cutback. or sometimes with an un-mopped inorganic felt.

Shark Fin:an upward-curled felt sidelap or endlap.

Shingle:(1) a small unit of prepared roofing material designed tobe installed with similar units in overlapping rows oninclines normally exceeding 25°; (2) to cover with shing-les; (3) to apply any sheet material in overlapping rows

like shingles.

Softening Point:the temperature at which bitumen becomes soft enoughto flow. Asphalt softening point is measured by the "ring-and-ball" test (ASTM 02398). Coal-tar pitch softeningpoint is measured by the "cube-in-water" test (ASTM

061).

Shingling:(1) the procedure of laying parallel felts so that one longi-tudinal edge of each felt overlaps, and the other longitud-inal edge underlaps, an adjacent felt. (See PLY.) Nor-mally, felts are shingled on a slope so that the water flowsover rather than against each lap; (2) the application of

shingles to a sloped roof.

Softening Point Drift:a change in the softening point of bitumen during storageor application. (See DROPBACK.)

Solid Mopping:see MOPPING.

Sieve:an apparatus with apertures for separating sizes of ma-terial. 71

70

Substrate:the surface upon which the roofing or waterproofingmembrane is placed (i.e., the structural deck or insu-lation).

Special Steep Asphah:a roofing asphalt that has a softening point of approxi-mately 220°F (104°C) and that conforms to the require-ments of ASTM Specification D 312. Type IV.

Superimposed Loads:loads that are added to existing loads. For example. alarge stack of insulation boards placed on top of a struc-tural steel deck.

Split:a separation in roofing material resulting from movementof the substrate. (See CRACK.)

Split Sheet:see NINETEEN-INCH SELVAGE. Tapered Edge Strip:

a tapered insulation strip used to (1) elevate the roof atthe perimeter and at curbs that extend through the roof;(2) provide a gradual transition from one layer of insula-tion to another.

Spot Mopping:see MOPPING.

Sprinkle Mopping:see MOPPING. Taping:

see STRIPPING

Square:the term used to describe 100 square feet of roof area. Tar:

a brown or black bituminous material. liquid or semi-solidin consistency. in which the predominating constituentsare bitumens obtained as condensates in the processingof coal. petroleum. oil-shale. wood. or other organic ma-terials.

Stack Vent:a vertical outlet in a built-up roof system designed torelieve any pressure exerted by moisture vapor betweenthe roof membrane and the vapor retarder or deck.

Steep Asphalt:a roofing asphalt that has a softening point of approxi-mately 190°F (88°C) and that conforms to the require-ments of ASTM Specification D 312, Type III.

Tarred Felt:a felt that has been saturated with refined coal tar.

Test Cut:a sample of the roof membrane. usually 4 inches x 40inches in size. that is cut from a roof membrane to:

1. Determine the weight of the average interply bitu-men poundages

Strawberry:a small bubble or blister in the flood coating of a gravel-surfaced membrane.

2. Diagnose the condition of the existing membrane(e.g., to detect leaks or blisters).

Strip Mopping:see MOPPING.

NRCA recommends that the test cut procedure NOT beused as a means of determining the quality of a roof

system.

Stripping:strip flashing: (1) the technique of sealing a joint betweenmetal and the built-up membrane with one or two plies offelt and hot-applied or cold-applied bitumen; (2) the tech-nique of taping joints between insulation boards on deck

panels.

7372

Vapor-Pressure Gradient:a graph, analogous to a temperature gradient. indicatingthe changes in water vapor pressure at various cross-sectional planes through a roof or wall system.

Vapor Retarder:a material designed to restrict the passage of water vaporthrough a wall or roof. In the roofing industry, a vaporretarder should have a perm rating of 0.5 or less.

Thermal Conductivity (k):the heat energy that will be transmitted by conductionthrough one square foot of one inch thick homogeneousmaterial in one hour when there is a difference of 1degree Farenheit perpendicularly across the two sur-faces of the material. The formula for thermal conductivityis: k = BTU/SQUARE FOOT/INCH/HOUR/DEGREEFARENHEIT.

Vent:an opening designed to convey water vapor or other gasfrom inside a building or a building component to theatmosphere. thereby relieving vapor pressure.

Vermiculite:an aggregate used in lightweight insulating concrete,formed by the heating and consequent expansion of amicaceous mineral.

Thermal Insulation:a material applied to reduce the flow of heat.

Water Cutoff:see CUTOFFS.

Waterproofing:treatment of a surface or structure to prevent the passageof water under hydrostatic pressure.

Thermal Shock:the stress-producing phenomenon resulting from suddentemperature changes in a roof membrane. (For example.when a rain shower follows brilliant sunshine.)

Through-Wall Flashing:a water-resistant membrane or material assembly ex-tending through a wall and its cavities, positioned to directany water entering the top of the wall to the exterior.

Underwriters Laboratories (UL):an organization which classifies roof assemblies for theirfire characteristics and wind-uplift resistance for insur-

ance companies in the United States.

Vapor Migration:the movement of water vapor from a region of high vaporpressure to a region of lower vapor pressure.

74 75

Thermal Resistance (R):an index of a material's resistance to heat flow; it is thereciprocal of thermal conductivity (k) or thermal conduc-tance (C). The formula for thermal resistance is:

EX~ANSION JOINTAPPENDIXThe illustrations contained herein pertain to the NRCADetails referred to in this document. The complete set ofNRCA Construction Details is included in the NRCARoofing and Waterproofing Manual.

NOTE:This detail allows for building movement in bothdirections. It has proven successful with manycontractors for many years.

7776

AREA DIVIDER BASE FLASHING FORNON-WALL SUPPORTED DECK

NOTES:This detail allows wall and deck to move indepe~Y.

This detail should be used where there is any possI)iIitythat differential movement will occur between the lied<and a vertical surface. sudl as at a penthouse wall. Thevertical wood member should be fastened to the deckonly. This is one satisfactory method of joiNng the twopiece flashing system. Other methods may be used.

79

NOTE:An area divider is designed simply as a raised double-wood member attached to a properly flashed wood baseplate that is anctK>red to the roof deck. Area dividersshould be located between the roof's expansion joints at100-200 foot intervals. depending upon dimatic cOndi-tions and area practk:es. They shoukj never restrd theflow of water.

78

PIPING THROUGH ROOF DECK MECHANICAL EQUIPMENT STAND

;~&TRUCTURAL

FRAMEDETAIlON N-2

,~f~.

!:",

HEIGHTSEE TABLE~

PIPE COlUMN ~ I,," ';->~"

... ",.,.(, "'~

MI'8HT OF LI..

14"

,."

14"

H";I

WIDTH 0' aOUIPMINT

UP TO a." TO ""

11" TO TO '0"

.," AND WIDEA

NOTE:This detail is preferable wt1en the concentrated k>ad canbe located directly over columns or heavy girders in thestructure of the building. Ths detail can be adapted forother uses such as sign ~.

NOTE:This detail illustrates another meth<Xj of eliminatingpitch pockets and a satisfactory method of ~ngpiping that must come up above the roof surface.

80 81

INSULATED DECK STEEL FRAME CONCRETE DECK AND FRAME-

8382

:-~. ;;:_"-;:"-,,-,,~,,-,,:-~-~--=.,,,:,,,-.

CRICKET DETAil- ~ -LIGHT METAL ROOF EDGE DETAIL

T

~

NOTE:Crlcket8 should be located in low valleys betweenroof drains and on the high side of all curbs.

NOTES:Envelope shown for ooaI tar pitch and k)w ~ asphalt.

Attach nailer to masonry wall. Refer to Factory MutualData Sheet 1-49.

This detail stM)U1d be used only where deQ( is ~by the outside wall.

This detaH shcMJld be used with light gauge met8s. suchas 16 oz. copper. 24 gauge galvanized metal. (M' 0.040"aIu~num. A tapered edge strip is used ~ r8ise !hegravel amp. Frequent nailing is necessary to ~thermal movement.

Wood blocking may be ~ed for verIting whererequired.

8584

::,~:':::-:-::}~Jj;~;::;;::~'; ::;::;:'~:"'.~.~~

CURB DETAil FOR ROOFTOPAIR HANDLING UNITS

CLEARANCES FOR MULTIPLE PIPESBETWEEN PIPES AND FROM

WALLS AND CURBS

~\~IBER CANT-\SET IN BITUMEN

~

n

~,...cz

i~o~z- I-/..

'2"~ ')w'

NOTE:The curb, wood naUer, insulation and seal strip areto be supplied by the curb manufacturer. Thenominal 14 inch curb height is effective as ofJanuary 1, 1981.

86 87

~

NOTESROOF DRAIN

I

II

f~OTES:Min. 30" square 2'h# to 4* lead or 16 oz. softcopper flashing set on finished roof felts inmastic-prime top surface before stripping.

Membrane plies, metal flashing, and flash-in pliesextend under clamping ring.

Stripping felts- extend 4" and 6" beyond edge offlashing sheet.

88