Abstract:
A pre-manufactured self-flashed curb assembly for rooftop daylighting systems is provided. The curb assembly includes a curb defining a clear opening therein of predetermined dimensions for use in attachment to roof trusses having common and standard inter-spacing. The curb includes beams having at least two apertures therethrough for receipt of roof attachment fasteners. Also included is a flashing skirt carried by the outside perimeter of the rectangular curb, for a complete, water-tight assembly.

Description:
BACKGROUND 
   Rooftop daylighting systems, such as skylights and windows, enjoy popularity with both commercial and residential buildings. Such systems illuminate rooms with natural light and thus reduce the consumption of electricity associated with artificial lighting. They increase the perceived spaciousness of a room and may also be configured to enhance air circulation. Such daylighting systems may be used on many types of roofs, including an inclined shingled roof and a high profile tile application. 
   Rooftop daylighting systems involve an opening cut through the entire thickness of the roofing structure, including interior ceiling sheetrock, roof sheathing, and the like, between adjacent roof trusses. Typically, to maximize the amount of daylight transmitted, the opening is cut to the inside edges of adjacent roof trusses. In residential construction, for example, such trusses typically are positioned twenty-four inches on center, with twenty-two and a half inches of clear opening between them; to maximize the amount of illumination provided through the skylight, the skylight opening usually would be such twenty-two and a half inches in width. 
   At an opening so configured, a mounting structure known as a curb is typically constructed for receipt of a skylight or rooftop window itself. In a typical application, such a curb would be constructed of 2×4 or 2×6 stock lumber, with the shorter side edge of the lumber disposed against roof sheathing carried by the roof trusses, and with the longer side edge disposed perpendicular to the plane of the roof. At finishing, the exposed trusses, as well as the interior-facing curb members, are covered with sheetrock (also known as drywall) so as to present an attractive completed light shaft suitable for painting, wallpaper, or other treatments. 
   Conventionally, the members constituting the curb, such as 2×4 or 2×6 stock lumber, would be constructed in situ by “toenailing” into the roof structure, including the roof sheathing and roof trusses. “Toenailing” involves driving a nail obliquely through the side of the curb lumber into the roof sheathing and/or roof truss. However, toenailing causes difficulties. If the curb frame members are toenailed from the light shaft side of the curb frame member, the nailing and construction must be performed before any finishing sheetrock is installed to the interior of the daylighting system opening. On the other hand, if the toenailing is performed from the exterior side of the curb frame members, care must be taken that the nails are not driven so far through the structure as to protrude through the wooden members into the area to be occupied, or perhaps already occupied, by finishing sheetrock thereby breaking, spaulling, or otherwise damaging the finished surface of the light shaft. Furthermore, it has been found that toenailing from either the interior side or the exterior side requires a large number of nails to produce a resulting rooftop daylighting system that will satisfy wind uplift requirements of governmental entities or recommendations of trade associations such as the American Architectural Manufacturers Association. Considerable labor is also involved in making and installing a curb in a roof opening in situ, and often leads to final products of less than optimal quality. 
   Flashing is installed around the exterior perimeter of the curb at the roof to provide weatherproofing to the entire system. While adequate water-tight techniques and products have been developed and employed for suitably flashing a skylight opening, the systems are typically more labor intensive and time-consuming at the site. Particularly, such flashing must be installed by a tradesman piece-by-piece while upon the roof. The flashing is typically “mopped in” to the roof sheathing—roofing cement is spread upon the roof sheathing and the flashing pieces are pressed into the cement and nailed to the curb member piece-by-piece. 
   The problems and difficulties described above generally pertain both to original construction of a daylighting system and to re-construction on an older structure. The problems are exacerbated in a re-roofing application, in which old shingles are removed from a building and new shingles are installed. Typically in such re-roofing efforts, new skylights are installed, either for customer preference to update the skylighting system or to insure water tightness, as older skylights may be damaged from the re-roofing work and thereafter leak. However, replacement of the skylight during re-roofing is difficult. As stated above, typically the flashing is mopped into the roof sheathing and nailed to the curb on original construction. Removal of the old flashing and replacement with new flashing is often necessary to insure weatherproofing, but removal of the old flashing that has been mopped in to the roof sheathing and nailed to the curb tends to damage or destroy the curb. However, in a re-roofing application, the interior to the building has already been finished and used for years. Removing the old curb leaves interior sheetrock that has already been installed into the skylight opening, also referred to as the light shaft—as noted above, such sheetrock usually is used to cover the roof trusses and the curb used at the skylight opening to create the light shaft. To construct a new curb using the materials and techniques heretofore known requires either removal of the sheetrock so that toenailing may be accomplished on the interior side of the new curb frame members, or toenailing from the exterior side with the resultant risk of damaging the sheetrock/drywall from nailing overpenetration. Furthermore, the roofing tradesmen tend to prefer to avoid “inside” work, which is not within their specialty, and therefore prefer to avoid tampering with or repairing the sheetrock/drywall. Moreover, as with an initial application, numerous (for example, eighteen) nails must be used in order to satisfy uplift requirements and recommendations when toenailing is used. 
   The present invention relates to an improvement upon the known systems and methods for providing a flash curb assembly for rooftop daylighting systems and provides distinct advantages over the conventional systems and methods. 
   SUMMARY 
   In response to the discussed difficulties and problems encountered before, a new pre-manufactured self-flashed curb assembly for rooftop daylighting systems has been discovered. 
   The present invention provides for a pre-manufactured self-flashed curb assembly, to be installed as a single unit upon a new construction, or in re-roofing of an existing construction, or in retrofitting a newer skylight or roof window to an existing structure. 
   According to the present invention, a curb is provided. Defined within the curb is an opening of predetermined dimensions in accordance with conventional dimensions for roofing truss member spacing, such as twenty-four inches on center. So dimensioned, the curb provides for the maximum amount of clear opening for maximum light transmission and also is adapted for receipt of commercial skylighting systems of standard dimensions. The curb may be of any shape, including regular or irregular polygonal shapes. In one embodiment, a rectangular curb is provided with first and second pairs of standards or beams, each pair parallel and the respective pairs perpendicular, to form a rectangular curb configuration. 
   The beams of the rectangular curb each have at least two apertures, such as center-bored holes, therethrough, disposed parallel to the inside and outside faces of the beams, for receipt of roof attachment fasteners such as nails or screws. So configured, a roof attachment fastener, such as a nail, may be driven through an aperture directly into an underlying roof truss of the building. For ease of manufacture, it is preferred that the apertures are also disposed generally perpendicular to the cub and thereby also perpendicular to the plane of the roof upon which the curb is installed, but such perpendicularity is not required. So configured, the roof attachment fastener would not disturb sheetrock preexisting within the opening. Furthermore, it has been discovered that attachment of a roofing curb in such a fashion with ring shank nails allows for a minimum number of nails while still satisfying wind uplift requirements and industry recommendations. 
   Carried about the outside perimeter of the rectangular curb is a flashing skirt. The flashing skirt may include a plurality of individual flashing units, each having an L-shaped cross-section defining two legs, one leg of which resides in a plane parallel to the plane of the roof and the other leg attached to one of the corresponding rectangular frame standards or beams. The individual flashing units, disposed about the outside perimeter of the rectangular frame, are in waterproof attachment one to another, such that the finished flashing skirt provides a pre-manufactured waterproof assembly. 
   Additional objects and advantages of the invention will be set forth in part in the following description or may be obvious from the description and the included drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a pre-manufactured self-flashed curb assembly in accordance with one exemplary embodiment of the present invention; 
       FIG. 2  is a cross-sectional view taken along line A-A in  FIG. 1 ; 
       FIG. 3  is a cross-sectional view taken along line B-B in  FIG. 1 ; 
       FIG. 4  is a diagrammatic sectional view showing one aspect of a pre-manufactured self-flashed curb assembly as installed in exemplary building with roof sheathing, roof truss, drywall, and skylight included for illustration. 
   

   DETAILED DESCRIPTION 
   Reference will now be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not by way of limitation. For example, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. It is intended that the present application include such modifications and variations as come within the scope and spirit of the invention. Repeat use of reference characters throughout the present specification and appended drawings is intended to present the same or analogous features, elements, or steps of the invention. 
     FIG. 1  shows an exemplary embodiment of a curb assembly generally  10  that may be used in accordance with the present invention. The curb assembly  10  is adapted for installation about an opening through a roof. Upon an inclined roof, the curb assembly  10  is oriented such that the top gutter  40  is uppermost in the assembly, with the incline of the roof being upwards in the direction of arrow  11 . The curb assembly  10  may be used with new construction or may be used in re-roofing applications upon existing, older structures, or may be used to retrofit newer daylighting systems to existing structures. 
   The curb assembly  10  includes four standards or beams in its rectangular frame, such as sill curb beam  70 , right curb beam  72 , left curb beam  74 , and gutter curb beam  76 . The beams  70 ,  72 ,  74 , and  76  may be high quality clear stain grade smooth surface wooden beams of standard commercial dimensions, such as 2×4 or 2×6. The beams may be suitably joined as by screws and glue or the like at their junctures, with optional nailing. Alternatively, the beams  70 ,  72 ,  74 , and  76  may be of other materials, such as polycarbonate, resins, plastics, and the like, and may be formed by attaching separate beams together or may be formed as a single integrated molded unit. While curb assembly  10  is depicted in  FIG. 1  as a rectangular configuration, such is for illustration purposed only, and it should be understood that the curb assembly may be of any regular or irregular geometric configuration. 
   Within each of the beams  70 ,  72 ,  74 , and  76  are disposed at least two fastening member receiving openings, apertures, or holes  88 . The holes  88  are pre-drilled and center-bored into the beams. As depicted in for example  FIG. 2 , the holes  88 , such as hole  881 , may be bored straight through the beams  70 ,  72 ,  74 , and  76  so as to be adapted for receipt of a roof fastening member, such as a nail or screw, generally perpendicular to the plane of the roof. Alternatively, the holes  88  may be oriented through the beams  70 ,  72 ,  74 , and  76  at an acute angle to the plane of the roof, such as depicted with holes  882  and  883  in  FIG. 2 . Nevertheless, as shown in  FIG. 3 , holes  88 , whether perpendicular holes  881  or angled holes  882 / 883 , are disposed generally parallel to the inside surface  721  and the outside surface  722  of a beam such as right curb beam  72 . So configured, the holes  88  allow for attachment directly into underlying roof truss members. 
   In a preferred embodiment, nails  80  are used through the holes  88  to attach the curb assembly  10  to the structure. Specifically, when the beams  70 - 76  are composed of 2×4 conventional lumber, 6″ ring shank nails are preferred. When the beams  70 ,  72 ,  74 , and  76  are constructed of conventional 2×6 lumber, 8″ ring shank nails are preferred. 
   Disposed about the outside perimeter of the rectangular frame constructed of beams  70 ,  72 ,  74 , and  76  is a flashing skirt, generally  15 . Flashing skirt  15  may be understood to have an annular aspect, generally  16 , carried by the curb beams, and a planar aspect, generally  17 , adapted to reside upon the plane of a building roof upon installation. Flashing skirt  15  may be constructed of aluminum, tin, copper, elastomerics, plastics, or other suitable materials, or combinations thereof. The flashing skirt may be constructed of a plurality of individual flashing units,  20 ,  22 ,  24 ,  26 ,  30 ,  32 ,  40 ,  42 ,  44 , and  46 , and preferably have an L-shaped cross section and smooth surfaces both topside and underside to facilitate easy installation on shingled roofs and hot-mopped roofs. Specifically, one such a flashing unit is a sill flashing unit  20 . The sill flashing unit  20  includes one leg of its L-shaped cross section to be carried by the sill curb beam  70  and the other leg to be carried upon the roof of the structure. 
   Proceeding counterclockwise around the curb assembly  10 , attached to the sill flashing  20  is the right sill hip flashing unit  22 . As shown in  FIG. 1 , right sill hip  22  includes leg  26 , adapted to be attached to the right curb beam  72 . The right sill hip  22  is preferably attached to the sill flashing  20  by means of a roll formed hem  50 , providing a water-tight seal. Attached to the other side of the right sill hip  22  is a right side flashing unit  30 . The lower end  53  of the right side flashing unit  30  is disposed atop the upper end  55  of the right sill hip  22  at the juncture  54 , such that water flowing down the roof of the structure upon the right side flashing  30  will flow down the top of the right sill hip  22  rather than beneath it. 
   Above the right side flashing  30  is a right gutter shoulder unit  42 . The lower edge  56  of the right gutter shoulder  42  is disposed atop the right side flashing unit  30  to allow the flow of water from the right gutter shoulder  42  to the top of the right side flashing  30 . As shown in  FIG. 1 , the right gutter shoulder  42  includes an arm  46 , adapted to be attached to the right curb beam  72 . 
   Across the top of the curb assembly  10  is the top gutter unit  40 . One leg  57  of the L-shaped cross section of the top gutter  40  extends upward on the roof deck, preferably about nine inches. The other leg  58  of the L-shaped cross section of the top gutter  40  is attached to gutter beam  76 . As shown in  FIG. 2 , leg  58  may be further formed to create a gutter lip  48 . The gutter lip  48  acts as a built-in water diverter, preventing water flowing down the roof to the curb assembly  10  from reaching the gutter curb beam  76 . 
   The left gutter shoulder  44  is configured similar to the right gutter shoulder  42 , and attached to the top gutter  40  with a roll formed hem  50 . The left side flashing (not shown) is configured and attached like the right side flashing  30 . Finally, the left sill hip  24  is configured and attached in like fashion to the right sill hip  22 , with the connection between the left sill hip  24  and the sill flashing  20  being a roll formed hem  50 . 
   The flashing skirt so configured is attached to the curb beams  70 - 76  by staples, screws, nails, and the like. In the preferred embodiment, no adhesives are used between the flashing skirt components and the frame beams, as such adhesives would interfere with and make more difficult the removal of the flashing skirt components should the roof including the curb assembly  10  be re-roofed in the future. It is likewise preferred that roofing shingles be nailed over all aspects of the flashing units residing in the plane of the roof, with the exception of the sill flashing  20 , which should be disposed atop shingles adjacent to the lowermost aspects of the curb assembly  10 . 
     FIG. 4  is a diagrammatic cross-sectional view of a portion of the curb assembly  10  installed upon an exemplary roof. As illustrated therein, the right curb beam  72  is affixed and attached to the roof decking  97  by means of the nail  80 , penetrating through the cross section of the right curb beam  72 , through the thickness of the roof decking  97 , and into the roof truss  98 . As shown, installation of the curb assembly  10  in such an environment does not interfere with the integrity or appearance of the sheetrock  96 . For illustration, a portion of a typical skylight assembly  90  is shown in  FIG. 4 , including the glass or glazing  91 , the skylight frame  92 , and a sealing gasket  93 . As illustrated, the skylight frame  92  extends over and beyond the right side flashing  30 , to provide a weatherproof, watertight system. 
   Various modifications and variations can be made in the embodiments of the present invention without departing from the scope and spirit of the invention. It is intended that the present invention include such modifications and variations as come within the scope of the appended claims and their equivalents.