CA2264800A1 - Metal roof sealing system and method - Google Patents

Abstract

A sealing system and method for a metal roof (1) having a plurality of sheet metal panels (4) attached to a roof deck (2) covered by a layer of insulation (17), such as polystyrene. The joints and seams (10) formed at junctions of adjacent panels are sealed with a non-flammable or low combustible, char forming, non-absorbent layer of material (20, 23) which is applied over the seams in a liquid or slurry form, which subsequently hardens to form a liquid proof seal to reduce the flow of molten polystyrene from melting of the adjacent layer of insulation, into the fire below.

Description

WO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141METAL ROOF SEALING SYSTEM AND METHODCROSS REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application SerialNo. 60/052,004, filed July 9, 1997.BACKGROUND OF THE INVENTIONTechnical FieldThe invention relates to roofing structures for buildings and moreparticularly to metal deck roof structures having an overlay of a meltableinsulation material. Even more particularly the invention relates to such a roofingstructure which seals openings formed at the junctions of the overlapping metalsheets and provides both a thermal and physical barrier preventing the insulationmaterial upon becoming liquid during a fire, from leaking into the building below.Background InformationRoofing systems for commercial and industrial buildings utilize varioustypes of sheet metal panels which are laid in an overlapping relationship andsecured to a lower structured frame of a roof deck. An insulation layer is laid ontop of the metal sheets which is then covered by a waterproof material, onecommon type of which is EPDM, together with a ballast or other hold downsystem. One type of insulation material is a polystyrene foam which is expandedor extruded, usually in sheets, which provide the desired insulating qualities aswell as being lightweight thereby contributing very little to the overall weight loadof the roof.However, one problem with the use of such foam insulation in roofingstructures is that the foam can melt and burn when the building experiences afire, and more importantly becomes liquid with the resulting molten liquid flowingthrough the joints of the roof deck into the building interior below increasing the1WO 99/027941015202530CA 02264800 1999-03-03PCT/US98/1414]hazard to occupants as well as to the safety forces during a fire. These metalroof deck sheets are usually fluted with peaks and valleys, with the overlying jointformed between adjacent panels, which usually occurs in a valley, which makesthe joint opening very susceptible to the molten liquid flowing through the jointopening and other openings in the steel deck and into the building below.Various systems have been devised to provide an effective seal to metal roofdecks, either to prevent the flow of water or other liquid through the joints andpanel openings and into the building interior.U.S. Patent Nos. 2,106,390 and 2,616,283 disclose roof structures inwhich the flutes of the metal decks are filled with a granular material. However,this filling material hardens and is used to provide the attachment means forreceiving nails or other fasteners for securing the insulation on the top of themetal sheets and not for sealing the overlap joint of adjacent roof deck sheeting.U.S. Patent No. 4,936,071 discloses a metal roof wherein the joints aresealed with a tape laminate formed of an unvulcanized EPDM and butyl rubberto provide for a waterproof seal at the overlapping joints.U.S. Patent No. 5,392,583 discloses another metal roof installation usingflexible elongated elastic strips for sealing the overlapping joints.U.S. Patent No. 5,479,753 discloses a metal roof in which an elongatedstrip of flexible hot melt thermoplastic bituminous composite material is placedover the overlapping joints or seams and heated to bond the strip to the metalroof to provide a weather proof seal therebetvveen.U.S. Patent Nos. 3,763,614 and 4,449,336 disclose other metal roofingstructures using various types of barriers between the insulation and the roofdeck for reducing the harmful affect should the building experience a fire.U.S. Patent No. 4,747,247 discloses a roof system in which the troughsor valleys of the metal sheets are filled with various nonflammable loose packedgranular inorganic material which is intended to absorb the molten liquid resultingfrom the insulation sheets during a fire. However, a major draw back of thistype of system is that it adds considerable weight to the building since nearlyevery trough or valley must be filled with this loose packed granular material.Even if a light weight granular material is used, the weight required to besupported by the underlying roof deck is increased considerably due to the vastWO 99/027941015202530CA 02264800 1999-03-03PCT/US98/I414]amount of material that is required to fill the valleys and troughs in order toabsorb the heated liquid material.U.S. Patent No. 3,511,007 discloses still another metal roofing structurein which a closed cell non-absorbent foam material is sprayed on the edge of themetal roof sheet, individually or in combination with a breaker strip, for bondingto the undersurface of the adjacent metal sheet edge when it is placed thereonto provide a waterproof seal at the joint formed by the overlapping metal paneledges.Although these various roof systems achieve certain desired results, inmany instances they either materially increase the weight that must besupported by the roof, or are expensive and time consuming to install due to theamount of material required and the labor cost to install the same.Therefore the need exists for an improved method and roof sealingsystem which does not materially increase the weight of the roof and which isinexpensive and easy to install, yet provides for the desired fire resistant liquidseal between overlapping joints of adjacent metal panels to prevent the moltenliquid formed by the overlying insulation during a fire from flowing into thebuilding below.SUMMARY OF THE INVENTIONObjectives of the invention include providing a metal roof sealing systemand method having a plurality of overlapping fluted metal sheets covered with ameltable insulation layer for supporting an overlying waterproof membrane andhold down means, wherein the openings formed at the overlapping joints of themetal sheets are sealed with a sealing compound such as polyurethane foamand/or a type of cementitious material which forms both a thermal and physicalbarrier to the passage of molten material.A further objective of the invention is to provide such a roofing system inwhich the overlapping metal sheets or metal plates are sealed both along theoverlapping side edge joint and also along the end edge joints by the sealingmaterial.WO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141A still further objective of the invention is to provide such a roof sealingsystem in which the cementitious material may be a common mortar, gypsumplaster, Portland cement and sand, etc. which when applied is in a paste orslurry form and then hardens to form the sealing bead or strip which extendsalong the overlapping joint, usually in the bottom of a trough or valley of thefluted metal sheets.Another objective of the invention is to provide such roof sealing systemin which a polyurethane sealing foam is applied in a liquid or slurry state andquickly turns into a solid to form an effective thermal liquid proof barrier for thesteel deck joints.Still another objective of the invention to provide such a roof sealingsystem in which the sealing material needs to be applied only at the joints orother openings in the metal deck, such as around vent ducts or the like,eliminating its use in the other troughs or valleys of the fluted metal sheets,thereby reducing the weight required to be supported by the underlying roofstructure and reducing the amount of materials and associated costs of applyingthe same.A further objective of the invention is to provide such a roof sealingsystem in which the sealing of the joints materially reduces the amount of meltedinsulation material which drops into the space below thereby removing materialwhich heretofore is ignited by the existing fire.These objectives and advantages are obtained by the improved metalroofing system of the invention the general nature of which may be stated asincluding a plurality of sheet metal panels attached to a structure of a buildingand forming seams at the junctions with adjacent panels; and in which anonflammable or low combustible, char—forming, nonabsorbent layer of anapplied-in-place sealing material is applied in a liquid or slurry form along theseams and upon hardening forms a thermal liquid proof barrier for the seam.These objectives and advantages are further obtained by the improvedmethod of fabricating a roof system, the general nature of which may be statedas including the steps of providing a supporting roof deck; securing a plurality ofoverlapping sheet metal panels to the roof deck thereby forming seams atjunctions with adjacent overlapped panels, said panels having alternatingWO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141grooves and ridges; placing a nonflammable or low combustible, char—forming,nonabsorbent layer of sealing material in a slurry form along certain of theseams; permitting said slurry to harden to form a thermal and liquid barrier oversaid certain seams; placing a plurality of thermoplastic insulation panels on theridges of said metal panels; placing a waterproof membrane over the insulationpanels; and securing said membrane to said roof deck.BRIEF DESCRIPTION OF THE DRAWINGSA preferred embodiment of the invention illustrative of the best mode inwhich applicants have contemplated applying the principles is set forth in thefollowing description and is shown in the drawings and is particularly anddistinctly pointed out and set forth in the appendant claims.FIG. 1 is a diagrammatic perspective view with portions broken away andin section, of a metal roof incorporating the improved sealing system therein;FIG. 2 is an enlarged fragmentary sectional view showing the seamopening formed at the junction of a pair of adjacent roof panels prior toplacement of the sealing strip thereon;FIG. 3 is an enlarged fragmentary sectional view similar to FIG. 2,showing the sealing seam being formed of a cementitious material;FIG. 4 is an enlarged fragmentary sectional view similar to FIGS. 2 and3, showing the seam formed of a polyurethane foam;FIG. 5 is a chart showing the rate of heat release in a test fire when themetal roof joints are not sealed in accordance with the present invention; andFIG. 6 is a chart showing the heat release rate in a similar test firerepresented in FIG. 5 utilizing the sealing system of the present invention.Similar numerals refer to similar parts throughout the drawings.DESCRIPTION OF THE PREFER ED EMBODIM NTThe improved metal roof system of the present invention is indicatedgenerally at 1, and is shown in a generally diagrammatic fragmentary sectionalbreakaway view in FIG. 1. Roof system 1 includes a structural frame of the roofWO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141deck, which as shown in the drawing consists of a plurality of spaced l—beams2, which could be other types of roof deck supports, such as bar joists, woodenor metal pylons or the like.A plurality of generally similar sheet metal panels, each of which isindicated generally at 4, are mounted on and secured to beams 2 by plurality offasteners 5 such as nails, screws, by welding or other attachment means. Eachpanel 4 is formed by a plurality of alternating flutes or grooves 6 and interveningridges 7. Adjacent panels 4 have their terminal longitudinally extending ends 8overlapped by the inmost ridge of adjacent panels as shown particularly in FIG.2. The adjacent panels are secured to each other usually in the flutes or valleys6 by spot welds or by a plurality of sheet metal screws or other fasteners. Thisoverlapping relationship forms a longitudinally extending seam 10, which due tomanufacturing tolerances and irregularities in the roof deck, will usually result inan opening 12 formed at seam 10. Also the transverse ends 13 of adjacentpanels are overlapped, as shown in FIG. 1 forming a seam 14 which extendstransversely to the longitudinal direction of the flutes and ridges of each panel.This seam will also result in an elongated transverse opening 16 through whichwater and molten liquid insulation can flow through and into the building below.Roof system 1 further includes a plurality of sheets or panels of insulation17 such as polystyrene, which are loose—|aid or secured to ridges 7 of panels 4by usual attachment means and extend generally throughout the entire area ofthe roof. Next, a layer of a waterproof membrane 18, such as EPDM, extendsacross and can be secured to insulation panels 17 by well known fasteningmeans, or a layer of a ballast 19, such as gravel, is then applied to keepmembrane 18 in position. Other types of membrane retaining means other thanballast 19 can be used without affecting the concept of the invention.In accordance with the invention, a bead or strip of a flame retardantwaterproof barrier 20 is applied along both the longitudinal and transverseseams 10 and 14, respectively, as shown generally in FlG.1 and in detail inFIGS. 3 and 4, to seal openings 12 and 16, and at other openings such asaround vents, ducts, skylights, etc.In a first embodiment as shown in FIG. 3, sealant strip 20 is acementitious material such as gypsum plaster with or without a vermiculite, aWO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141common mortar, such as Portland cement and sand. The advantage of this typeof material is that upon setting there is very little (a slight contraction)dimensional change, which is important in this application. Different types ofplasters are made which vary in the time taken to set, the amount of water tomake a pourable material and the hardness. These characteristics arecontrolled by the calcination conditions and by addition of other materials(organic and inorganic) to the plaster. Mortar is mixture of solids and water usedto generally bond masonry units together. The principal solids in mortar aresand and cementitious materials, such as hydrated lime, (or slaked quicklime)and Portland cement. The definition of portland cement is given in ASTM C 150as a hydraulic cement produced by pulverizing clinkers consisting essentially ofhydraulic calcium silicates, usually containing one or more of the forms ofcalcium sulfate as an interground addition. The definition of hydraulic cementsis that they harden by reacting with water to form a water-resistant product.Gypsum will dissolve in water after it is hardened and is therefore not as usefula portland cement in many application. There are many other cementitiousmaterials, but none is more important than portland cement. The latter is absentin pure lime mortar. Portland cement reacts rapidly with water, which gives themortar its initial set. Lime react more slowly, both with carbon dioxide from theatmosphere to form calcium carbonate and with sand to form calcium silicates.Thus, mortar hardens with age and has good workability. Again, variations incomposition can effect how flowable the mortar is and how fast it hardens.Organic and inorganic materials including organic plastics can be added to themortar to improve performance.FIG. 4 shows a modified form of sealant strip 23 which is a polyurethanefoam having a flame retardant of approximately 100 parts per hundred partspolyol, and with an index up to 250. Other examples of flame retardants can beantimony oxide, calcium carbonate, and pentabromodiphenyl oxide. The use ofsucrose and/or aromatic polyols (Hoechst Celanese’s Terate 2541 (aromaticpolyester polyol) and Dow's Voranol 490 (sucrose based)) which forms aprotective char layer during a fire is highly resistant to further combustion. Thecorresponding polyurethane foam has a density of approximately 1 to 6 poundsper cubic feet.WO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141Sealant strips 20 and 23 provide a physical barrier to the flow of moltenthermoplastic material which results when insulation panels 17 are subjected tovery high temperatures, such as in a fire. This molten thermoplastic material isprevented by strips 20 and 23 from flowing through openings 12 and 16 and intothe building below through the space normally present between the overlappedroof deck panels. Various sealant strips 20 and 23 will be fire resistant and/orchar forming and are able adhere to the sheet metal panels 4, and turn into asolid from a liquid or slurry state relatively quickly when applied thereto.The method of the present invention is best understood by reference toFIG. 1 which shows the attachment of panels 4 to the supporting roof deck whichis then followed by the application of the cementitious material or polyurethanefoam sealing strips 20 and 23. Since only the seams are covered by the sealingstrips, it results in very little additional weight to the roof and requires only arelatively small amount of material in order to provide the thermal and/or physicalbarrier in contrast to those systems in which the grooves or troughs arecompletely filled with a particulate material. Next, installation panels 17 areloose—laid or secured to ridges 7 of panels 4 aften/vhich waterproof membrane18 is laid thereon and secured by fasteners or by ballast 19.Two full scale compartment fire tests were conducted on prototype roofsystems to quantify the effects of the subject roof sealing system. One test hadno roof sealing material which is referred to as the “control”, and the other testhad the openings in the roof deck sealed with gypsum plaster which is one of thecementitious materials discussed above. Each fire test involved placing an“ignition source” below the roof deck and producing a steady flame on theunderside of the roof deck. Both roof deck assemblies contained 10 inch thickExpanded Polystyrene (ESP) foam directly applied to the steel deck. Thecompartment was 12 feet long and 8 feet wide, and there was a full widthopening in one of the 8 foot wide walls. The ignition source consisted of astandardized propane-fire burner one foot square which was programmed toproduce a steady flame source on the underside to the roof deck. This ignitionsource represented a serious fire, but a fire that was localized to the rear half ofthe 12 foot long compartment. There were flames out the front of thecompartment within 2 minutes 21 seconds in the control test with out the sealingWO 99/027941015202530CA 02264800 1999-03-03PCT/US98/14141material. These flames were clearly caused by flammable vapors from the EPSbeing forced through the two seams in the test deck, and they continued to exitthe compartment for over 5 minutes. At times these flames were extending morethan 8 feet beyond the front of the compartment. In the fire test with the sealeddeck seams there was some light flaming on one of the seams for approximately3 minutes, but there were only a few flame “packets” that came out of the frontof the compartment. There was also some localized flaming at the back of thecompartment at intersection of the side and rear wall. This flaming at the backof the compartment was an artifact of a defect in the test set-up where themolten EPS could leak into the compartment.A video recording was made of the test, and careful observations showthat the sealing of the seams prevented the EPS from contributing significantlyto the spread of the fire in the test compartment.Another important measurement in fire testing is the "heat release rate"(HRR). The HRR can be calculated by measuring the oxygen “depletion" in thecombustion products leaving the test compartment. The HRR for the control testis shown in FIG. 5, and that for the sealed deck is shown in FIG. 6. The HRR isa good measure of the way in which a material might spread a fire inside abuilding. The ignition source in these fire tests is between 260 kW and 290 kW,and the most meaningful measure of the fire contribution of a material or systemis to subtract the HRR associated with the ignition source and consider the “net"HRR. The net HRR for the control test is approximately 467 kW while that forthe sealed deck test is 154, and thus the “control" experiment without the firestop material gives three times higher HRR than the sealed deck. Thus, aconsiderable reduction in HRR is achieved by the sealing system of the presentinvention which materially reduces the amount of molten melted insulation whichheretofore dripped into the fire area below the roof.Thus, the roof system of the present invention provides an extremelysimple and inexpensive solution to a problem that has long existed in the art, thatis the providing of a thermal and/or physical liquid barrier preventing the moltenliquid resulting from the melting of the installation panels from flowing throughopenings in the roof and dropping into the building space below the roof deck.WO 99/027941015CA 02264800 1999-03-03PCT/US98/14141Accordingly, the improved metal roof sealing system and method issimplified, provides an effective, safe, inexpensive, and efficient device whichachieves all the enumerated objectives, provides for eliminating difficultiesencountered with prior devices, and solves problems and obtains new results inthe art.In the foregoing description, certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to be impliedtherefrom beyond the requirement of the prior art, because such terms are usedfor descriptive purpose and are intended to be broadly construed.Moreover, the description and illustration of the invention is by way ofexample, and the scope of the invention is not limited to the exact details shownor described.Having now described the features, discoveries and principles of theinvention, the manner in which the improved metal roof sealing system andmethod is constructed and used, the characteristics of the construction, and theadvantageous, new and useful results obtained, the new and useful structures,devices, elements, arrangements, parts and combinations, are set forth in theappended claims.10

Claims (21)

WE CLAIM

1. A metal roofing system including:
a plurality of sheet metal panels attached to a structure of a building and forming seams at junctions with adjacent panels; and a nonflammable or low combustible, char forming, non-absorbent layer of an applied-in-place sealing material positioned over the seams of adjacent panels in a liquid or slurry which hardens to form a liquid proof seal there between.

2. The roofing system defined in Claim 1 in which the sealing material is a flame retarded polyurethane foam.

3. The roofing system defined in Claim 2 in which the polyurethane foam has a density of approximately 1 to 6 pounds per cubic feet.

4. The roofing system defined in Claim 1 in which the sealing material is a cementitious material.

5. The roofing system defined in Claim 4 in which cementitious material is Portland cement and sand.

6. The roofing system defined in Claim 1 including a plurality of insulation panels overlaying and supported by the metal panels.

7. The roofing system defined in Claim 6 in which the insulation panels are formed of a thermoplastic.

8. The roofing system defined in Claim 7 in which the thermoplastic is polystyrene.

9. The roofing system defined in Claim 6 including a waterproof membrane overlaying the insulation panels.

10. The roofing system defined in Claim 9 including a layer of ballast overlaying the waterproof membrane.

11. The roofing system defined in Claim 10 in which the ballast is gravel.

12. The method of fabricating a roof system including the steps of providing a supporting roof deck; securing a plurality of overlapping sheet metal panels to the roof deck thereby forming seams at junctions with adjacent overlapped panels, said panels having alternating grooves and ridges; placing a nonflammable low combustible, char-forming, nonabsorbent layer of sealing material in a slurry form along certain of the seams; permitting said slurry to harden to form a thermal and liquid barrier over said certain seams; placing a plurality of thermoplastic insulation panels on the ridges of said metal panels;placing a waterproof membrane over the insulation panels; and securing said membrane to said roof deck.

13. The method defined in Claim 12 including the step of forming the sealing material of a flame retarded polyurethane foam.

14. The method defined in Claim 13 including the step of forming the polyurethane foam with a density of approximately 1 to 6 pounds per cubic feet.

15. The method defined in Claim 12 including the step of forming the sealing material of a cementous material.

16. The method defined in Claim 12 including the step of forming the cementous material of portland cement and sand.

17. The method defined in Claim 12 including the step of forming the insulation panels of a thermoplastic.

18. The method defined in Claim 12 including the step of forming the insulation panels of polystyrene.

19. The method defined in Claim 12 including the step of applying a layer of ballast on top of the waterproof membrane.

20. The method defined in Claim 19 including the step of forming the ballast of gravel.

21. The method defined in Claim 12 including the step of putting cover boards over the insulation panels of polystyrene and mechanically attaching the cover board to the polystyrene and the waterproof membrane to the steel deck.