RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/487,343, filed Jul. 15, 2003, the entire contents of which are herein incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention generally relates to building materials and more particularly relates to window sill flashing for a window frame to prevent the ingress of water.  
       BACKGROUND OF THE INVENTION  
       [0003]     Typical wall construction techniques include forming a rough opening from framing members such that a window opening is formed. The bottom portion of the window opening (called the sill) is susceptible to rotting if water is not prevented from penetrating from around the window perimeter. Additionally, adjacent ceilings, plastered walls, and the like are susceptible to damage if rain-water infiltrates under the window sill.  
         [0004]     Many systems are used to solve the problem of water intrusion. One method includes providing a means to collect and control the water that does infiltrate the window perimeter. Alternatively, surface sealing agents, such as caulk, expanding foam, and the like are used as filling agents to fill openings between the periphery of the window and the adjacent, wall surfaces. However, over time, the filling agents have a tendency to dry, crack and shrink, thereby exposing gaps which provide a passageway for water to infiltrate the window perimeter.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is directed towards a window sill flashing comprising a base having a substantially rectangular shape. A front flange projects perpendicularly downward from a front edge of the base and at least one side flange extends vertically from a side edge of the base. The side flange includes a front surface. The window sill flashing is made from a vacuum formed, rigid homopolymer vinyl film. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is an isometric view of a wall having a window opening and a flashing according to an embodiment of the present invention.  
         [0007]      FIG. 2  is an isometric view of a flashing and window assembly according to an embodiment of the present invention.  
         [0008]      FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 2 .  
         [0009]      FIG. 4  is an isometric view of the flashing and window assembly according to an alternate embodiment of the present invention.  
         [0010]      FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 4 .  
         [0011]      FIG. 6  is a isometric view of the flashing according to yet another alternate embodiment of the present invention.  
         [0012]      FIG. 7  is a cross-sectional view taken along line  7 - 7  of  FIG. 6 .  
         [0013]      FIG. 8  is an isometric view of the flashing according to still yet another alternate embodiment of the present invention.  
         [0014]      FIG. 9  is a cross-sectional view taken along line  9 - 9  of  FIG. 8 .  
         [0015]      FIG. 10  is a perspective view of a wall having a window opening covered with housewrap.  
         [0016]      FIG. 11  is a perspective view of a wall having a window opening with the housewrap folded to the proper positions for window installation.  
         [0017]      FIG. 12  is a perspective view of a wall having a window opening with a first portion of the flashing of the present invention installed.  
         [0018]      FIG. 13  is a perspective view of a wall having a window opening with a second portion of the flashing installed.  
         [0019]      FIG. 14  is a perspective view of a wall having a window opening with two flashing portions taped according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]     Referring to  FIG. 1 , a window sill flashing (hereinafter referred to as “flashing”)  10  is generally shown according to an embodiment of the present invention. The flashing  10  is formed to fit within and snugly conform to a bottom portion  12  of a window opening  14  of a wall  15 . Window opening  14  has a width W and is adapted to accept a window assembly  13 . As illustrated, the face portion (or flange)  22  of flashing  10  is generally U-shaped and constructed as one piece. The flashing  10  comprises a base  16 , a first side flange  18  integrally formed with base  16  at one end, a second side flange  20  integrally formed with base  16  at an opposite end, and a front flange  22  integrally formed with base  16 . Preferably base  16 , side flanges  18 ,  20  and front flange  22  are all vacuum formed from a common sheet. Front (U-shaped) flange  22  extends perpendicularly downward from an edge of base  16 . First side flange  18  includes a front surface  18   a  and second side flange  20  includes a front surface  20   a.  The flashing  10  is glued, calked, taped, or otherwise permanently secured within window opening  14 . It is contemplated that flashing  10  of  FIG. 1  is formed in various standard size lengths and widths to accommodate various standard window openings  14  and wall thicknesses.  
         [0021]      FIGS. 2 and 3  illustrate a first alternative embodiment of the flashing of  FIG. 1 , wherein like features are indicated by the same reference number. Flashing  10   a  is fabricated as two separate portions  10   a ′ and  10   a ″. Portions  10   a ′ and  10   a ″ form the left and right side of flashing  10 . Alternatively, flashing  10   a  is fabricated as a one piece member with a length (prior to cutting) that spans beyond the width W of window opening  14 . Prior to installation of flashing  10   a  into window opening  14 , flashing  10   a  is cut, resulting in portions of flashings  10   a ′ and  10   a ″. It can be appreciated that flashing  10   a  may be cut at any point along its length, so long as flashings  10   a ′ and  10   a ″ fit within window opening  14 . Thereafter, portions  10   a ′ and  10   a ″ are placed so that they partially overlap one another in a region  24  producing flashing  10   a  having length L that is generally equal to the width W of window opening  14 .  FIG. 3  is a cross-sectional view of the overlap region  24  of portions  10   a ′ and  10   a ″. One advantage of flashing  10   a  is that flashing  10   a  may be cut to size in the field to accommodate any width W of window opening  14 .  
         [0022]      FIGS. 4 and 5  illustrate a further alternate embodiment of the flashing of the present invention. Flashing  10   b  is similar to flashing  10  and flashing  10   a,  except portions of flashing  10   b ′ and  10   b ″ do not overlap at region  24 . Instead, portions  10   b ′ and  10   b ″ are separated by a gap  26 . As illustrated, gap  26  is narrow relative to the width W of window opening  14 . However, it can be appreciated that gap  26  may be any desired length. For instance, gap  26  may expose a substantial portion of width W of window opening  14 . Further, gap  26  may be optionally covered with a sill flashing cap  28 .  
         [0023]      FIGS. 6 and 7  illustrate a further embodiment of the flashing of the present invention. Flashing  10   c  is substantially similar to flashing  10   a ; however, flashing  10   c  includes a rear, vertical rising wall  30  to further impede the ingress of water. Rear, vertical rising wall  30  is located along an edge of base  16 , opposite of front flange  22  and extends perpendicularly upward from base  16 .  
         [0024]      FIGS. 8 and 9  illustrate yet another embodiment of the flashing of the present invention. Flashing  10   d  is substantially similar to flashing  10   b ; however, flashing  10   b  includes rear, vertical rising wall  30 .  
         [0025]      FIGS. 10-14  illustrate the steps for installing flashing  10  within window opening  14 . Initially, the window opening  14  is covered with housewrap  32 . Housewrap  32  is then cut along perforated lines  34 . Perforated lines  34  divide housewrap  32  into upper section  32   a,  lower section  32   b,  left side  32   c  and right side  32   d.  The lower section  32   b  and left and right sides  32   c,    32   d  of housewrap  32  are folded inwardly, towards the interior surface of wall  15 . Upper section  32   a  is rolled up towards the exterior of wall  15 , in the direction of arrows A (see  FIG. 11 ). Thereafter, flashing  10  or portions of flashing  10   a″ ,  10   b ″,  10   c ″ or  10   d ″ are placed on top of bottom portion  12  of window opening  14  (see  FIG. 12 ).  FIG. 13  illustrate flashing portions  10   a ′,  10   b ′,  10   c ′, or  10   d ′ being placed along bottom portion  12 . Finally, flashing  10  is secured to bottom portion  12 .  FIG. 14  illustrates flashing  10  being secured to bottom portion  12  with adhesive tape  36 . Adhesive tape  36  is also used to seal the seam created by the overlap  24  between right and left portions of the flashing  10 . Where there is no overlap  24 , adhesive tape  36  may be used to cover the bottom portion  12  of window opening  14 . Thereafter, a window  13  is installed within window opening  14 .  
         [0026]     The flashing  10  of the present invention is preferably manufactured from sheets of thermoforming film, such as a rigid homopolymer vinyl film, or polyvinyl chloride (PVC), or the like. The preferable material properties for flashing  10  are listed in the table below:  
                                           Property   Units   Value       Gauge Range   Mils   7.5-35       Gauge Tolerance   %   ±5       Specific Gravity   —   1.33       Material Yield (Nominal)   in. 2 /lb.   2770 (7.5 mil)               2080 (10.0 mil)               1390 (15.0 mil)               1040 (20.0 mil)       Tensile Strength (Yield)   lb./in. 2     6600       Elongation (Break)   %   180       Tensile Impact Strength   ft-lb./in. 2     275       Cold Break Temperature   ° C.   −30       Heat Deflection Temperature at 264 psi   ° F.   162       Gloss   %   115                  
 
 It can be appreciated that the flashing  10  may be covered with a silicone coating for ease of manufacturing and separation of the flashing  10  and for ease in installation of window assembly  13 . 
 
         [0028]     Flashing  10  is preferably fabricated using vacuum forming techniques. Vacuum forming flashing  10  from thin gage material allows the first and second side flanges  18 ,  20  to be substantially perpendicular to base  16 . The material properties, including the material thickness, provides flexibility to flashing  10 , thus allowing the vacuum forming dies to separate from the flashing  10  once the vacuum forming process is completed. Additionally, vacuum forming flashing  10  allows the material to have a minimum thickness (as thin as 7.5 mm). Therefore, when portions of flashing  10  overlap, the resultant gap under the flashing  10  is minimal and does not allow water intrusions.  
         [0029]     Due to the geometry and thinness of flashing  10 , flashing  10  cannot be manufactured using an injection molding process. If flashing  10  were to be manufactured by injection molding, the minimum thickness feasible for flashing  10  is 40 mm, significantly higher than the practical thickness of flashing  10  formed by the vacuum forming process. Moreover, to maintain the perpendicularity of surfaces  16 ,  18 ,  20  and  22  over the depth of base  16 , flashing  10  would require ribs, or support struts, to be molded into base  16 . These ribs would detract from the functionality of flashing  10 . Furthermore, it would be necessary to include ports along base  16  to ensure that sufficient material flows across and covers the entire base  16 . These ports would give rise to dimples, or other imperfections in the surface of base  16 . The imperfections could create gaps or openings along the window sill, thereby comprising the water impermeability of flashing  10 . Even with the use of ports along base  16 , obtaining complete flow coverage of injected material is problematic because the preferred depth of base  16  is in the range of 1 inches to 3¼ inches.  
         [0030]     The embodiments disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the invention. Although preferred embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of the invention as described in the following claims.
The present invention is directed towards a window sill flashing comprising a base having a substantially rectangular shape. A front flange projects perpendicularly downward from a front edge of the base and at least one side flange extends vertically from a side edge of the base. The side flange includes a front surface. The window sill flashing is made from a rigid homopolymer vinyl film.