Abstract:
Disclosed is a roof assembly for a modular building unit that comprises a roofing sheet that is welded to the frame of the modular building unit to form a unitary, continuous sealed weld between the roofing sheet and the generally horizontal structural frame of the modular building unit, and that is pitched to downwardly direct water toward one end of the modular building unit. The welded roof assembly prevents water infiltration into the modular building unit, and such watertight structure may then receive any gutter configuration the user wishes to implement without risking water infiltration into the building unit. The welded roofing sheet avoids the use of screws or other fasteners, and the associated possibility of water leakage around the screws and into the building unit. The welded roof also is able to employ a single slope all of the way through the full span of the roof, thus avoiding the need for a centrally pitched roof assembly, and its unitary construction avoids the tiling effect that results from the use of multiple, overlapping roofing sheets. The welded roof also avoids the need for silicon or other filler agents between the unitary roofing sheet and the frame of the modular building unit.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims benefit of U.S. Provisional Patent Application Ser. No. 62/026,249 entitled “WELDED ROOF FOR MODULAR BUILDING UNITS,” filed with the U.S. Patent and Trademark Office on Jul. 18, 2014 by the inventor herein, the specification of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to modular building construction, and more particularly to a welded roof assembly for a modular building unit configured to receive various gutter system configurations. 
     BACKGROUND OF THE INVENTION 
     Roofing members for modular buildings are typically attached by way of screws or other fasteners, and are supplied in sheets arranged in a tile configuration with a portion of one roofing sheet overlapping a portion of an adjacent roofing sheet. In order to channel rainwater and water from snow and ice melt away from the modular building, gutters may be provided along the edges of the modular building unit. However, the type of gutter assembly, and in fact whether a gutter system is required at all, can vary from location to location based upon annual weather patterns, and particularly rain, snow, and ice amounts received in a given area. Different weather patterns may call for different gutter configurations, and at times even no gutter. Moreover, even with water diversion and drainage, conditions may result in water collecting on the roof and leaking into the modular building unit, such as through gaps between adjacent roofing sheets, gaps between the roofing sheets and the frame of the modular building unit, openings around fasteners, and the like. While silicone or other fillers may be provided, they are temporary and subject to failure and leakage over time. While differing gutter configurations may be provided to address different rain, snow, and ice conditions, they will require varied adaptations of the roof structure as well in order to accommodate the varied environmental conditions. 
     Thus, there remains a need in the art for a roofing configuration for a modular building unit that is able to accept gutters of varied configurations without requiring adaptation or modification of the building unit structure, and that protects against water leakage through the roof in all such gutter configurations, and in the case of no gutter. 
     SUMMARY OF THE INVENTION 
     Disclosed is a roof assembly for a modular building unit that comprises a roofing sheet that is welded to the frame of the modular building unit so as to form a unitary, continuous sealed weld between the roofing sheet and the structural frame of the modular building unit, and that is pitched to downwardly direct water on the roofing sheet toward one end of the modular building unit. The welded roof assembly prevents water infiltration into the modular building unit, and such watertight structure may then receive any gutter configuration the user wishes to implement without risking water infiltration into the building unit. Further, the welded roof assembly allows the modular building unit to carry a heavy snow load, as the welds attaching the roofing sheet can easily carry heavy loads. The welded roofing sheet avoids the use of screws, and the associated possibility of water leakage around the screws and into the building unit. The welded roof also permits attachment, e.g. via welding, of safety rings or other accessories directly on the roof sheet without need for specialized holes or other configurations or specific location requirements. The welded roof also is able to employ a single slope all of the way through the full span of the roof, thus avoiding the need for a centrally pitched roof assembly, and its unitary construction avoids the tiling effect that results from the use of multiple, overlapping roofing sheets. The welded roof also avoids the need for silicon or other filler agents between the unitary roofing sheet and the frame of the modular building unit. Still further, the recessed roofing panel within the exterior frame formed by the upper rails of the building unit, along with the horizontal top surfaces of such rails, provided for easy vertical stacking of modular building units atop one another. 
     In accordance with certain aspects of an embodiment of the invention, a roof assembly is provided for a modular building unit, comprising: a first long rail having a top wall, an exterior wall, and an interior wall; a second long rail parallel to the first long rail and having a top wall, an exterior wall, and an interior wall; a first short rail extending between the first and second long rails and having a top wall, an exterior wall, and an interior wall; a second short rail extending between the first and second long rails and having a top wall and an exterior wall, wherein the first and second long rails and the first and second short rails are joined to form a rectangular exterior roof frame of a modular building unit; and a roofing sheet, wherein the roofing sheet is joined to the first short rail at a first elevation below the top wall of the first short rail, the roofing sheet is joined to each of the first and second long rails at a point below the top wall of each of the first and second long rails and extending in a downward slope from the first elevation, and the roofing sheet is joined to the top surface of the second short rail at a lowest elevation of the roofing sheet; and wherein the roofing sheet is joined to the first short rail, each of the first and second long rails, and the top surface of the second short rail by a continuous weld. 
     In accordance with further aspects of an embodiment of the invention, a method of forming a roof assembly for a modular building unit is provided, comprising the steps of: providing a roof frame comprising a first long rail having a top wall, an exterior wall, and an interior wall; a second long rail parallel to the first long rail and having a top wall, an exterior wall, and an interior wall; a first short rail extending between the first and second long rails and having a top wall, an exterior wall, and an interior wall; and a second short rail extending between the first and second long rails and having a top wall and an exterior wall, wherein the first and second long rails and the first and second short rails are joined to form a rectangular exterior roof frame of a modular building unit; joining a roofing sheet to the first short rail at a first elevation below the top wall of the first short rail; joining the roofing sheet to each of the first and second long rails at a point below the top wall of each of the first and second long rails and extending in a downward slope from the first elevation; and joining the roofing sheet to the top surface of the second short rail at a lowest elevation of the roofing sheet; wherein the steps of joining the roofing sheet to the first short rail, each of the first and second long rails, and the top surface of the second short rail is performed by making a continuous weld. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a modular building unit in accordance with certain aspects of an embodiment of the invention. 
         FIG. 2  is a perspective view of a skeletal frame of the modular building unit of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the skeletal frame of  FIG. 2 . 
         FIGS. 4 a  through 4 d    are close-up, cross-sectional views of the lower roof edge of the frame of  FIG. 3  with varying gutter configurations. 
         FIG. 5  is a top view of a roof portion of the modular building unit of  FIG. 1 . 
         FIG. 6  is a perspective view of the roof portion of  FIG. 5 . 
         FIG. 7  is a close-up, detail cross-sectional view of the frame of  FIG. 3 . 
         FIG. 8  is a cross-sectional view of a first, higher elevation top short rail of the frame of  FIG. 7 . 
         FIG. 9  is a perspective view showing connection of the first top short rail and one of the top long rails of the frame of  FIG. 7 . 
         FIG. 10  is a cross-sectional view of a roofing sheet short side mounting bracket of the frame of  FIG. 7 . 
         FIG. 11  is a perspective view of the roofing sheet short side mounting bracket of  FIG. 10 . 
         FIG. 12  is a close-up, detail cross-sectional view of the frame of  FIG. 3  along an axis parallel to the first top short rail (showing the long rails in cross-section). 
         FIG. 13  is a perspective view of a roofing sheet long side bracket  146  for a first long side of the frame of  FIG. 7 . 
         FIG. 14  is a rear view of the roofing sheet long side bracket of  FIG. 15 . 
         FIG. 15  is a cross-sectional view of the roofing sheet long side bracket of  FIG. 14  along section line A-A. 
         FIG. 16  is a cross-sectional view of the roofing sheet long side bracket of  FIG. 14  along section line B-B. 
         FIG. 17  is a cross-sectional view of a second, lower elevation top short rail of the frame of  FIG. 7 . 
         FIG. 18  is a perspective view showing connection of the second top short rail and one of the top long rails of the frame of  FIG. 17 . 
         FIG. 19  shows an external gutter and drain pipe for use with the roof portion of  FIG. 6 . 
         FIG. 20  is a cross-sectional view of the gutter and drain pipe of  FIG. 19  attached to second top short rail of the frame of  FIG. 7 . 
         FIG. 21  shows an external water deflector for use with the roof portion of  FIG. 6 . 
         FIG. 22  is a cross-sectional view of the water deflector of  FIG. 21 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is of a particular embodiment of the invention, set out to enable one to practice an implementation of the invention, and is not intended to limit the preferred embodiment, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
       FIG. 1  provides a perspective view of a modular building unit  100  in accordance with certain aspects of an embodiment of the invention. Modular building unit  100  includes a skeletal frame formed by corner support posts  112 , bottom rails  114 , top long rails  115 , a first top short rail  116  (shown in  FIG. 2 ), and a second top short rail  117 . This skeletal frame provides the key structural integrity for the modular building unit. Positioned between corner support posts  112 , bottom rails  114 , and top rails  115 ,  116  and  117  are wall panels  118  that form the wall structures spanning each side of the modular building unit. Other standard building features, such as doors  120  and windows  122 , may be provided and integrated with individual wall panels  118 . 
       FIG. 2  is a perspective view of the skeletal frame forming the modular building unit of  FIG. 1 . As shown in  FIG. 2 , the skeletal frame comprises four corner posts  112  extending upward from bottom rails  114  and supporting the roof portion of the modular building unit  100 . The roof portion includes top long rails  115  extending lengthwise between adjacent corner support posts  112 , a first top short rail  116  extending between adjacent corner supports posts  112  and generally perpendicular to top long rails  115 , and a second top short rail  117  extending between adjacent corner support posts  112  and generally perpendicular to top long rails  115 . A roofing sheet  140  forms the exterior roof of the modular building unit, and sits within the interior of the frame defined by top long rails  115 , first top short rail  116 , and second top short rail  117 . Roofing sheet  140  may have a thickness of preferably 1 to 3 mm, and more preferably 2 mm, and may either comprise a flat sheet or a corrugated sheet comprised of continuous or segmented ribs as shown in  FIG. 2 . If corrugated (which may be desirable depending upon typical roof rain and snow loads in the locale where the modular building unit is to be installed), ribs from the corrugated sheet may help with drainage of water. The roofing sheet  140  is welded around its entire perimeter to top long rails  115 , first top short rail  116 , and second top short rail  117 , all as discussed in greater detail below, to ensure complete water tightness, particularly in the case of snow and ice. Roofing sheet  140  is also welded, such as by spot welding, to purlins  124  spanning the width of the roof portion and extending between parallel top long rails  115 , again as discussed in greater detail below. 
     Moreover, and as better shown in the cross-sectional view of the skeletal frame of  FIG. 3 , roofing sheet  140  slopes downward from first top short rail  116  to second top short rail  117  so as to direct all water to the lowest elevation of the roof portion of the modular building unit. In order to provide such downward slope, purlins  124  are positioned at progressively lower elevations, with each end of each purlin being rigidly affixed (e.g., welded) to an interior face of each top long rail  115 . Such configuration results in roofing sheet  140  realizing a downward slope of preferably between 0.5% and 5% from one end of the module to the other. In certain configurations, roofing sheet  140  may have two, opposite sloping sections (not shown), each having a downward slope of 0.5% to 5% from the middle of the modular building unit to the end of the modular building unit. 
     Because the modular building unit is configured with a fully welded roof, the modular building unit may be configured with varied gutter options, including no gutter. Those varying gutter options are shown in the exemplary configurations reflected in  FIGS. 4 a  through 4 d   .  FIG. 4 a    shows the lowest roof edge of modular building unit  100 , including roofing sheet  140  welded directly to the top face of second top short rail  117 , which in turn is mounted above wall panel  118 . In this configuration, no gutter is provided, in which case water from the room will directly flow off of the roof, while the weld around the perimeter of roofing sheet  140  prevents infiltration of water into the modular building unit. Next,  FIG. 4 b    shows the same roof edge of modular building unit  100 , with a water deflector  200  attached to the exterior face of second top short rail  117 , which deflector  200  may aid in directing water flowing from the roof away from the side wall panels  118  of modular building unit  100 . Likewise,  FIG. 4 c    shows the same roof edge of modular building unit  100 , with gutter  190  attached to the exterior face of second top short rail  117 , which gutter  190  may receive water flowing from the roof and direct such water to a downspout (not shown) as discussed further below. Similarly,  FIG. 4 d    shows the same roof edge of modular building unit  100 , with an alternative gutter  119   a  attached to the exterior face of second top short rail  117 , which alternative gutter  119   a  is attached in the same manner as gutter  119  but embodies a decorative design to improve the overall aesthetic appearance of the modular building unit  100 . Those of ordinary skill in the art will recognize that gutter assemblies of other varying configurations may likewise be provided without departing from the spirit and scope of the invention. 
       FIG. 5  provides a top view, and  FIG. 6  provides a perspective view, of the roof portion of modular building unit  100 . Roofing sheets  140  are shown spanning the full length of the roof, and as mentioned above, may optionally include ribs  142  that may aid in directing water toward the lowest elevation point on the roof (i.e., toward second top short rail  117 ). Optionally, roofing sheets  140  may be provided in separate sections, in which each of the sections are preferably welded together to form the same waterproof, welded seam that is provided along the perimeter of roofing sheet  140 . Mounting brackets are provided at the interior faces of each of first top short rail  116  and the two top long rails  115 . More specifically, roofing sheet short side mounting bracket  144  is affixed to and runs parallel to first top short rail  116 , and roofing sheet long side brackets  146  are affixed to and run parallel to each top long rail  115 . Roofing sheet short side mounting bracket  144  provides a horizontal mounting and welding surface for the highest elevation portion of roofing sheet  140 , while roofing sheet long side brackets  146  provide a downwardly angled mounting and welding surface for the long edges of roofing sheet  140 , resulting in the roofing sheet  140  following a downward slope from first top short rail  116  to second top short rail  117 . The lowest elevation point of roofing sheet  140  is welded directly to the top surface of second top short rail  117 , again allowing water on roofing sheet  140  to flow directly onto and over second top short rail  117 . 
     Corner boxes  119  may be provided at each corner of the roof portion of modular building unit  100 , which corner boxes  119  principally serve as corner elements for joining each perpendicular pair of rails and one of corner support posts  112 . Corner boxes  119  may also be provided features, such as openings, in the top and side walls of each corner box  119  to receive a crane hook or other device to aid in lifting the entire modular building unit when necessary for transport or installation. 
       FIG. 7  provides a close-up, detailed cross-sectional view of the skeletal frame of modular building unit  100 . First top short rail  116  is shown at the left most portion of  FIG. 7 , with roofing sheet short side mounting bracket  144  extending from the interior face of first top short rail  116  and supporting roofing sheet  140 . The underside of roofing sheet  140  overlaps a portion of roofing sheet short side mounting bracket  144  and is welded to short side mounting bracket  144 . Likewise, as roofing sheet  140  extends toward second top short rail  117 , it rests on and is preferably welded to purlins  124 . At the opposite end from first top short rail  116  (i.e., the right edge as viewed in  FIG. 7 ), roofing sheet  140  overlaps a portion of second top short rail  117  and is welded to the top of second top short rail  117 . 
     Other features, including sealed joints attaching the overall roof portion to wall panels  112 , interior ceiling trays, and subfloor construction details, are shown in  FIG. 7  but are not critical to the roofing structure of the instant invention, and thus are not described further here. 
       FIG. 8  is a cross-sectional view of first top short rail  116 , and  FIG. 9  is a perspective view of first top short rail  116  connecting to one of top long rails  115  through a connecting corner box  119 . As shown in  FIGS. 8 and 9 , first top short rail  116  has a planar top face  150 , a planar outer face  152  that forms a portion of the exterior side wall of modular building unit  100 , interior bracket flange  154 , and bottom profile  156  to fit with a modular wall panel as shown in  FIG. 7 . Interior bracket flange  154  extends downward from the interior edge of planar top face  150 , and provides an attachment surface for roofing sheet short side mounting bracket  144 . 
       FIG. 10  provides a cross-sectional view of roofing sheet short side mounting bracket  144 , and  FIG. 11  provides a perspective view of such roofing sheet short side mounting bracket  144 . Bracket  144  comprises a back wall  170  configured for attachment, such as by welding, to interior bracket flange  154  of first top short rail  116 . Bracket  144  also has a short side roofing sheet support surface  172  which, when bracket  144  is mounted on first top short rail  116 , extends generally horizontally and parallel to planar top face  150  of first top short rail  116 . Support surface  172  supports the highest elevation end of roofing sheet  140 , with the underside of roofing sheet  140  resting on the top side of support surface  172  and the two being joined by a continuous weld. Bracket  144  may also include a top lip  174  extending generally parallel to short side roofing sheet support surface  172 , which top lip  174  limits the opportunity for wind to blow water onto top short rail  116 , so that water remains contained on roof sheet  140 . Further, corner notches  176  are provided at opposite ends of support surface  172  to allow contact with edges of roofing sheet long side brackets  146 , in order to provide a continuous surface to receive a continuous weld around the entire perimeter of roofing sheet  140 . 
     Next,  FIG. 12  provides a cross-sectional view of the skeletal frame of modular building unit  100  along an axis parallel to first top short rail  116  (showing the top long rails  115  in cross section). Top long rails  115  are of generally the same cross-sectional configuration as first top short rail  116  (although obviously with a longer overall length dimension). Roofing sheet long side mounting brackets  146  are affixed (e.g., welded) to interior bracket flange  154  of long rails  115  and support roofing sheet  140  along its long edge. The underside of the long edge of roofing sheet  140  overlaps a portion of roofing sheet long side mounting brackets  146  and is welded to long side mounting brackets  146 . Likewise and as mentioned above, roofing sheet  140  is supported by and is preferably welded to purlins  124  for additional support. 
       FIG. 13  is a perspective view of a roofing sheet long side bracket  146  for attachment to a first one of top long rails  115 . Those of ordinary skill in the art will appreciate that the opposite top long rail  115  will receive a similarly configured long side bracket  146  that is the mirror image of the bracket shown in  FIG. 13 . Likewise,  FIG. 14  is a rear view of roofing sheet long side bracket  146 . Further,  FIG. 15  provides a cross-sectional view of bracket  146  along section line A-A of  FIG. 14 , and  FIG. 16  provides a cross-sectional view of bracket  146  along section line B-B of  FIG. 14 . As shown in  FIGS. 13 through 16 , bracket  146  includes a back wall  180  providing an attachment surface for attaching (e.g., welding) bracket  146  to interior bracket flange  154  of top long rails  115 . Back wall  180  has a generally horizontal top edge and a downwardly sloping bottom edge. Likewise, bracket  146  has a long side roofing sheet support surface  182  which, when each bracket  146  is mounted on its respective top long rail  115 , extends outward from back wall  180  and provides a downwardly sloping support surface for the long edge of roofing sheet  140 , with the underside of such long edge of roofing sheet  140  resting on the top side of support surface  182  and the two being joined by a continuous weld. Such continuous weld seamlessly extends from the weld joining the highest elevation portion of roofing sheet  140  to short side roofing sheet support surface  172 . Bracket  146  may also include a top lip  184  extending generally parallel to top long rails  115 , again serving to keep water from being blown off of roofing sheet  140 . 
       FIG. 17  shows a cross-sectional view of second top short rail  117 , and  FIG. 18  is a perspective view of second top short rail  117  connecting to one of top long rails  115  through a connecting corner box  119 . As shown in  FIGS. 17 and 18 , second top short rail  117  has a planar top face  160  configured to directly receive an overlapping portion of the lowest elevation section of roofing sheet  140 . As noted above, roofing sheet  140  is welded directly to such planar top face  160  of second top short rail  117 , and such weld seamlessly continues from the weld attaching roofing sheet  140  to each of roofing sheet short side mounting bracket  144  and roofing sheet long side brackets  146 . Second top short rail  117  also has a planar outer face  162  which is configured to directly receive various gutter configurations as discussed in greater detail below, or alternatively to form a portion of the exterior side wall of modular building unit  100  (in cases where no gutter system is to be used). Second top short rail  117  further includes planar interior face  164  and a bottom profile  166  to fit with a modular wall panel as shown in  FIG. 7 . 
       FIG. 19  shows an external gutter  190  for use with the welded roof described above. External gutter  190  may include a plurality of overflow openings  192  provided on the outermost wall of gutter  190 , and a spigot  194  at one end of gutter  190 . Spigot  194  is shaped to fit within a drain pipe  196 , which drain pipe may be joined to modular building unit  100  with, by way of non-limiting example, an angle bracket  198 , such as to one of corner support posts  112  that is adjacent to second top short rail  117 . Likewise,  FIG. 20  shows a cross-sectional view along section line C-C of  FIG. 19  of the gutter  190  and drain pipe  196 , with external gutter  190  attached to second top short rail  117  with one or more fasteners  199 , such as a screw. 
     Similarly,  FIG. 21  shows an external water deflector  200  for use with the welded roof described above, and  FIG. 22  provides a cross-sectional view of such water deflector  200 . With reference to both  FIGS. 21 and 22 , water deflector  200  has a back wall  202  that is configured for facing attachment to planar outer face  162  of second top short rail  117 , a plurality of openings  204  for receiving connectors (e.g., screws) for such attachment, and an upper angle  206  configured to direct water outward and away from the edge of the roof of modular building unit  100  as it flows off of the roof. 
     The foregoing configuration results in a modular building unit having a roof structure that may readily receive a variety of gutter configurations, and that is simultaneously effective with no gutter, in an assembly that protects against water infiltration into the modular building unit regardless of the gutter configuration. Thus, a single modular building unit configuration may be provided in geographies having widely varied rain and snow conditions, with gutters being added (or not) depending upon the specific precipitation conditions of that particular environment, saving the user from having to maintain multiple configurations for differing environements. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.