Abstract:
A built-up roofing structure (10) is provided which is characterized by low dead weight, enhanced fire retardancy, and ease of construction. The structure (10) includes a lowermost deck (12) with integrated, insulative sections (24) applied thereover an adhered in place by a novel fire retardant mastic (27); the sections (24) each include a preformed expanded foam layer (14) covered by a roofing board (16). A modified bitumen membrane (18) is applied over and completes the roofing structure (10). The improved mastic includes asphalt, low volatility mineral spirits and a fire retardant additive such as an intumescent glass, and particularly a borosilicate glass. The mastic is advantageously applied using a spreader apparatus (30) having an elongated, tubular, apertured mastic delivery bar (32, 58) and a spreader means (46, 62) with a plurality of separate, spaced apart, lightweight trailing spreader chains (48).

Description:
This application is a continuation of application Ser. No. 07/989,648, filed Dec. 11, 1992, abandoned which is a divisional of application Ser. No. 07/825,982, filed Jan. 27, 1992, abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with an improved fire retardant mastic composition particularly adapted for application to roofing decks, and which includes an additive therein causing the mastic to char and form a barrier to inhibit passage of flowable material therethrough, when the solidified mastic is subjected to temperatures of at least about 150° C. In another aspect of the invention, complete roof constructions are provided including a metal deck, a layer of expanded synthetic resin foam atop the deck, with the fire retardant mastic of the invention applied to the deck and adhering the foam layer thereto. Also, a mastic material extruding apparatus for evenly spreading a flowable roof mastic is provided. Use of the invention permits fabrication of low cost replacement roofs which give a minimum of added dead load to an existing roof structure, while also imparting a high degree of thermal insulation and the ability to form a barrier resistant to passage of melted resin foam or other materials through the deck, in the event of a fire. 
     2. Description of the Prior Art 
     Many industrial-type buildings constructed during the last 30 to 40 years were roofed with metallic decking panels. Such panels were normally secured by screws, bolts, or rivets penetrating the metal decking, these penetrations being sealed. Metal roofs of this type suffer from a number of disadvantages, including a tendency to leak, and poor thermal insulation qualities. Over the years, as these metal roofs have begun to wear out, the building owners are faced with the task of providing a replacement roof. Generally speaking, it is a very expensive proposition to remove the original metal decking, and replace it with new decking. A replacement would typically cost approximately two times that of the modified insulated roof system concerned in this patent. Another alternative is to simply place a new metal deck atop the original deck. This is a problem inasmuch as the new metal roof imposes a significant dead load upon the structure of the building, which is particularly troublesome in the case of older buildings. 
     It has also been suggested in the past to provide a replacement built-up roof using the worn metal roof as a substrait. In such systems, preformed panels of expanded polystyrene, adapted to be placed over the contour of the original deck are employed. Such panels have rigid boards secured to the upper surfaces thereof, and are generally provided in 4&#39;×4&#39; or 4&#39;×8&#39; sections. With such built-up roofs, hot asphalt is initially applied to the decking, whereupon the preformed insulation panels are applied. At this point a roofing membrane may be secured to the upper surface of the foam panels sections, followed by conventional lap joint sealing and finishing. In some of these prior built-up constructions, hot asphalt or existing mastics have been employed which include asphalt, mineral spirits, fibers and fillers. A problem with these roofs is that, in the event of a fire, the polystyrene foam readily melts and becomes flowable, and then drips into the building below with the asphalt. This can cause severe damage to the building and its contents, and indeed the fire insurance rates for a building having a built-up roof of this character are increased because of this hazard if insurable at all. 
     There is accordingly a real and unsatisfied need in the art for a new roofing system which can be used to form a safe built-up roof on an existing metal deck, while overcoming the problem of leak-through in the event of fire. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above, and provides a modified roof construction including the original metal deck, together with a layer of expanded synthetic resin foam situated atop the deck and having a roof membrane affixed to the outer surface of the foam layer. A layer of fire retardant mastic is applied to the deck and as solidified adheres perlite layer thereto. The mastic comprises respective quantities of asphalt, mineral spirits and a fire retardant additive for causing the mastic to char and form a barrier to inhibit passage of flowable materials such as melted resin foam through the deck, when the mastic is subjected to a temperature of at least about 150° C. 
     In preferred forms, the foam layer is made up of expanded polystyrene foam, with a rigid insulative roofing board interposed between the outer surface of the foam and the roofing membrane. Furthermore, it is desirable to use the fire retardant mastic in three locations, i.e., between the deck and foam layer, between the outer surface of the foam layer and the 1/2&#34; perlite board (U.S. Pat. No. 4,766,024), and between the roofing board and final modified roofing membrane. 
     Advantageously, the roofing mastic of the invention includes from about 30-60% by weight asphalt and from about 8-30% by weight mineral spirits, with from about 3-50% by weight of fire retardant additive. Other minor ingredients includes fibers (0.5-5% by weight), surfactant (0.1-1.5% by weight), filler (10-35% by weight) and clay (1-7% by weight). The fire retardant additive is preferably selected from the class of intumescent glasses, most especially amorphous sodium/calcium borosilicate glass. 
     The invention also comprehends a new device which greatly facilitates application of roof mastic to a metal deck Such apparatus comprises an elongated, hollow mastic delivery bar adapted to be transversely pulled across a roofing surface and having structure defining a plurality of mastic delivery openings therethrough along the length of the bar. Means is also provided for evenly spreading mastic delivered from the openings of the bar, including a plurality of chains operatively disposed relative to the delivery bar and oriented to contact and spread mastic delivered therefrom as the bar is pulled across a roof surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a partially schematic, side elevational view of the preferred mastic spreading apparatus of the invention, shown operatively coupled to a reservoir of flowable mastic; 
     FIG. 2 is an enlarged, fragmentary, vertical sectional view depicting the construction of the spreading apparatus; 
     FIG. 3 is a sectional view taken along line 3--3 of FIG. 2, and further illustrating the structure of the mastic delivery bar; 
     FIG. 4 is a fragmentary top view illustrating the spreading operation of the apparatus of the invention; 
     FIG. 5 is a rear elevational view of the delivery bar of the apparatus shown in FIGS. 1-3 illustrating the mastic delivery apertures; 
     FIG. 6 is a plan view of another type of delivery apparatus in accordance with the invention, wherein the mastic deliver bar has a generally U-shaped header secured thereto; 
     FIG. 7 is a rear elevational view of the apparatus shown in FIG. 6, and illustrating the header construction and the mastic delivery apertures; 
     FIG. 8 is an enlarged fragmentary sectional view illustrating a modified form of the invention wherein certain of the mastic delivery apertures are oriented obliquely relative to the longitudinal axis of the delivery bar, in order to properly coat an upstanding decking rib; 
     FIG. 9 is an exploded view illustrating an underlying metal deck together with a preformed polystyrene foam/roofing board panel designed to overlie the deck; and 
     FIG. 10 is a fragmentary vertical sectional view illustrating the construction of a built-up roof in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fire retardant roofing mastic of the invention is made up of a combination of asphalt and mineral spirits, together with a fire retardant additive for causing the mastic to char and form a barrier to inhibit passage of flowable material therethrough, when the mastic is solidified and subjected to temperatures of at least about 150° C. As indicated previously, the mastic may contain other conventional ingredients, such as fibers, surfactant, filler, clay and the like. 
     The following table sets forth the ingredients of the preferred fire retardant mastic, as well as approximate broad and preferred ranges of use thereof. 
     
                       TABLE______________________________________    Broad Range               Preferred Range                            Most PreferredIngredient    (% by wt.) (% by wt.)   (% by wt.)______________________________________Asphalt  30-60      35-55        48.60Mineral   8-30      12-20        16.20SpiritsFibers   0.5-5      1-2           1.33Surfactant    0.1-1.5    0.3-0.8       0.63Filler   10-35      15-25        19.92Clay     1-7        2-5           3.32Fire Retard-     3-50       5-15        10.00ant Additive______________________________________ 
    
     In preferred practice, the asphalt and mineral spirits fractions of the mastic are provided as a 75%/25% mixture of asphalt and mineral spirits. Such a mixture is referred to as a &#34;cut-back&#34; asphalt. The specific product found useful in the context of the invention is AC 20 cut-back asphalt having a softening point of about 115° F. This product is commercialized by Koch Industries of Wichita, Kans. It is somewhat important in this respect that the spirits fraction of the cut-back asphalt not be highly aromatic and therefore flammable. Generally, the mineral spirits fractions should therefor have a flash point of at least about 100° F., and most preferably about 104° F. 
     The preferred fibers are non-asbestos cellulose fibers (CAS No. 65996-61-4), which are insoluble but dispersable in water, and have a specific gravity of 1.58. Other physical properties include oil absorption of 500-600% and moisture content of about 13.2% and a pH in water of about 6.9. Fibers of this character are commercialized by Custom Fibers Central of Wellsville, Kans. While such cellulose fibers are preferred, other possibilities exist, such as rockwool fibers. 
     A number of fillers can also be used in the mastics of the invention. The most preferred filler is limestone. In actual practice, Hubercarb limestone commercialized by J. N. Huber Corporation of Quincy, Ill. has been used to good effect. This product is principally made up of calcium carbonate, with minor amounts of magnesium, carbonate and silica therein 
     The clay and surfactant materials present in the compositions of the invention to provide a homogeneous gel-like consistency, and to maintain the filler in suspension. The preferred surfactant is isodecyloxypropyl amine acetate (CAS No. 28701-67-9), sold by Exxon Chemical company of Milton, Wis. This surfactant is known for use in roof coating formulations, and has a total amine value of 185-205, an acid value of 185-205, a neutralization of 95-105%, and a water content of about 0.75%. Of course, other types of alkyl amine salt surfactants can also be employed in the invention. 
     The clay fraction of the mastic is preferably selected from the atapulgite clays, which can be obtained from a number of commercial sources, e.g. Oil-Dri Corporation of Chicago, Ill. The most preferred atapulgite is commercialized as the &#34;Select 520&#34; clay of Oil-Dri Corporation. This product includes a number of inorganic oxides such as SiO 2 , Al 2  O 3 , CaO, MgO, Na 2  O, K 2  O, Fe 2  O 3 , MnO, TiO 2  and P 2  O 5 . The product has a free moisture content of from about 10-15% and a pH from about 8.5-10.0. Again, other types of clays and clay/surfactant combinations can be used. 
     In preparing the mastic, the cut-back adhesive is first warmed (e.g., 140° F.), and the clay and surfactant added thereto, with sufficient moisture to assure homogeneity. At this point, the remaining ingredients are added in any desired order, with further mixing. 
     Attention is next directed to FIG. 10 which shows a final built-up roof 10 in accordance with the invention. Broadly speaking, the roof structure 10 includes an underlying metal deck 12, a layer 14 of synthetic resin foam situated atop the deck 12, rigid roofing board 16 applied over the layer 14, and finally, a final roofing membrane 18 (preferably formed of modified bitumen) presenting the weather surface for the roof construction. 
     In more detail, the metal deck 12 is completely conventional and is in the form of a series of co-planar main panels 20 with elongated, upstanding ribs 22 between adjacent main panels. 
     The foam layer 14 and roofing board 16 are preformed as integrated sections 24 (see FIG. 9). That is to say, each of the sections 24 a layer of expanded polystyrene foam whose underside is configured to closely conform with the configuration of deck 12. To this end, the depicted foam layer underside has a plurality of main planar surfaces 25 with elongated, concave, rib-receiving recesses 26 between the surfaces 24. Generally speaking, the sections 24 are provided in 4&#39;×4&#39; or 4&#39;×8&#39; sizes. A variety of polystyrene foams can be used, e.g., the Fostafoam styrenes commercialized by American Hoechst Company of Leominster, Mass. 
     The roofing board 16 may be of any conventional material, and is preferably formed of the well known &#34;Perlite&#34;. This board is rigid and weather resistant, and can be readily bonded to the foam layer 14. In the later regard, although not specifically shown in the drawings, it is preferred that the fire retardant adhesive of the invention be used to secure the roofing board 16 to the underlying foam layer 14. 
     The modified bitumen membrane 18 is itself entirely conventional, and can be UL Class A, and is laid as elongated strips, using any desired roofing mastic, but preferably the fire retardant mastic of the invention. 
     In constructing the modified roof 10, the fire retardant mastic of the invention is first applied over the upper surface of deck 12 of a thickness to form, once the mastic has solidified, a layer 27 of perhaps 25 mm in thickness. After the mastic is applied, an is still in the heated, flowable condition, the preformed roofing sections 24 are applied, simply by laying the panels in place and applying moderate downward pressure thereto in order to ensure that the mastic properly adheres the sections to the deck 12. 
     In the next step, an additional layer 28 of the fire retardant mastic is applied over the upper surfaces of the roofing boards 16. Here again, the thickness of the mastic layer 28 is not critical, but would generally give a solidified thickness of perhaps 25 mm. At this point, the membrane 18 is applied in the entirely conventional fashion over the flowable mastic, and the necessary lap joints 29 (see FIG. 10) are created and sealed using a 25 pound lap roller. This completes the roofing structure 10. 
     The complete roof structure 10 exhibits a number of very desirable advantages. First, a considerable degree of thermal insulation is provided, usually on the order of R-12. This is of course is a decided improvement over a conventional raised rib metal deck roof, which provides little if any thermal insulation. Furthermore, the modified roof concerned in this invention adds very little dead load. The new modified roof can also be installed at a price approximagely 50% of a conventional metal re-roof, owing to the use of relatively low cost materials, but also because of the fact that the system of the invention can be installed with a minimum of labor. Specifically, the modified roof hereof can be applied at a rate of 1-11/2 roofing squares per man hour, whereas typical roofs using hot asphalt or metal fasteners and BUR require something on the order of 21/2 man hours per roofing square. In this same vein, it has been found that perfectly acceptable applications can be produced using from 11/2-2 gallons of the fire retardant mastic per roofing square. This compares with applications of perhaps three gallons per roofing square using conventional asphalts. 
     The construction of built-up roofs in accordance with the invention is greatly facilitated by the mastic applicator devices illustrated in FIGS. 1-8. Turning first to FIGS. 1-5, it will be seen that the applicator apparatus 30 includes an elongated, hollow mastic delivery bar 32 adapted to be transversely pulled across a roofing surface and having structure defining a plurality of mastic delivery openings 34 along the length thereof. As shown, the bar 32 is coupled to a handle 36 which extends upwardly from the bar and includes manipulation end 38. The handle 36 is tubular in construction, and is adapted to be connected to a reservoir 40 of hot, flowable mastic, by means of line 42 and pump 44. In this way, hot mastic is delivered via line 42 and handle 36 to bar 32, whereupon it flows out of the openings 34 during the application process. 
     The overall apparatus 30 further includes means 46 for evenly spreading mastic from the openings 34. The spreading means 46 includes a plurality of elongated, lightweight chain sections 48 which are operatively disposed in trailing relationship to the bar 32 and are oriented to contact and spread mastic as the bar is pulled across the roofing surface. As best seen in FIGS. 2 and 4, an elongated chain draw bar 50 mounted generally parallel with and spaced from delivery bar 32 is provided, with the chains 48 being secured to the draw bar 50 in spaced relationship along the length thereof. Attachment between the delivery bar 32 and draw bar 50 is provided by means of a plurality of spaced apart eyes 52 welded to bar 32 with trailing swivels 54 serving to interconnect the draw bar 50 and eyes 52. It will thus be appreciated that as bar 32 is pulled across a roofing surface, the chain draw bar 50 and spreading chains 48 are likewise drawn across the surface of the roof. 
     Attention is specifically drawn to FIG. 4, which illustrates the spreading operation of the chains 48. That is to say, flowable mastic is delivered from the openings 32 in respective streams 56 which slightly spread of their own accord; however, the effect of the chains 48 is to evenly merge and spread the individual streams 48 in order to completely cover the roofing surface. 
     In those instances where a metal deck such as the previously described deck 12 is to be covered with mastic, it may be advantageous to specifically orient certain of the openings 34 of delivery bar 32 to ensure that the upstanding ribs of the deck are covered with mastic. Referring specifically to FIG. 8, it will be seen that delivery bar 32 includes a plurality of apertures 34 having their longitudinal axis transverse to the longitudinal axis of the delivery bar; however, in this embodiment, others of the openings 34a are obliquely oriented relative to the longitudinal axis of bar 32, so that the streams of mastic 56a therefrom converge towards each other and thereby more readily cover the sloping sidewalls of a rib 22. It will be observed in this respect that the rib-coating apertures 34a are separated by a central aperture 34 properly coats the planar top wall of the rib. 
     Another embodiment of the invention is illustrated in FIGS. 6-7. In this case, a somewhat longer mastic delivery bar 58 having spaced delivery aperture 60 is provided, along with a trailing, multiple-chain spreading device 62. In order to feed the elongated bar 58 and ensure that all the apertures 60 thereof receive an adequate supply of mastic, the bar 58 is provided with a generally U-shaped tubular header 64 having the ends thereof in communication with bar 58. A handle 66, again of tubular design, extends upwardly from header 64 and is adapted, as in the case of handle 36, to be coupled with a supply of mastic from a remote location. 
     It has been found that use of a chain-type spreader/applicator in accordance with the invention, gives complete coverage of a metal deck with a single pass. This is to be contrasted with traditional mopping operations, wherein adequate coverage is obtained only by multiple passes and is labor-intensive. Moreover, the applicator device hereof readily covers roofing surfaces of all normal configurations, including any upstanding bolt or rivet heads which may be present. 
     Although a variety of reservoirs may be used for preparing and storing mastic, a heated mobile, 500-1,000 gallon tank rig has proved completely workable. The lengths of the spreading chains described previously are also variable, and it has been found that chains should range from about 5-12 inches in length. This permits ready manipulation of the complete spreader assembly, and also gives the proper degree of mastic spreading and coverage. 
     It has been found that the roofing systems of the invention have a very decided advantage in the event of a fire. That is to say, the fire retardant material present in the adhesives of the invention begins to char at about 150° C. and form a solid barrier. This inhibits the passage of flowable material through the metal decking of the roof, as is common with the conventional built-up roofs including an insulative synthetic resin foam layer. As a consequence of this characteristic, building owners having the built-up roofs hereof are subject to lower fire insurance rates, than those having conventional built-up roofs.