Abstract:
A method for forming a sill pan is provided that includes the measurement of a width and length of an opening sill to be sealed. A piece of flexible sill pan material is cut based on the measured opening sill. Fold lines and cuts are created in the piece to form the sill pan. The resulting sill pan is readily formed to have at least one attribute of self-adherence, draining without shims, nail hole self-sealing, and provision of dams without resort to frame cutting.

Description:
RELATED APPLICATIONS 
     This application claims priority benefit of U.S. Provisional application Ser. No. 61/878,442 filed Sep. 16, 2013; the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention in general relates to building products for weatherproofing window and door installations and in particular, to a sill pan adapted to waterproof a sill surface and a method for forming the sill pan. 
     BACKGROUND OF THE INVENTION 
     The incursion of unwanted air and/or moisture into buildings and homes around door and window joints is a major concern for builders, property owners, and occupants. The penetration of air and/or moisture is a serious concern, and may result in exterior and interior damage if not prevented or corrected in a timely manner. In addition, heat losses caused by air leakage around building openings have taken on new significance due to today&#39;s high energy costs. Sealing such openings has typically been accomplished by caulking or using putty-like compound around openings between door and window frames to seal the gaps and prevent inward seepage of air and/or water into a building. 
     An existing approach to sealing window joints is the use of a sill pan to flash windows into a window opening. The sill pan is typically made of metal and is formed in an off-site fabrication shop based on measurements made of the opening at the building site. Typically there are variations in the size for each window so each pan is somewhat unique. Furthermore, if the measurement is not precise, the pan will not fit correctly, and must be remade or swapped around to make sure the sill pans fit each opening. An additional problem with metal sill pans is that sill pans create a thermal short from outside to inside of the window to be sealed due to the pans large mass, and creates condensation on the inside of the window at the sill. 
     A recent more common practice is the use of polyvinyl chloride (PVC) for sealing panels for windows. The PVC is made in two pieces that slide so they can be used in residential applications, which have become more common. The PVC based sill pans slide to fit the opening and are then sealed with glue or sealant to make a watertight assembly. The PVC based products can have built-in shims and other elements to create a slope for directing water drainage. The PVC material is usually thicker than metal. However, plasticized PVC can also have compatibility problems with bitumen based membranes. Furthermore, the PVC based sill product has openings at the point of connection of the two pieces that can be prone to leakage. Both the aluminum and plastic sill pans need to be bonded to the underlying surface so no water can pass underneath, which is typically achieved with non-skinning butyl beads or tapes. 
     A further trend has been the increased use of vinyl windows in recent years. However, it has been generally been recognized that vinyl windows take in water and can leak at the sills notwithstanding the weep holes built into the frame at the sill. Therefore, the use of vinyl windows has significantly increased the use of sill pans, not just flashing membranes. Many manufacturers now encourage the use of sill pans. An available option is to create a pan from a self-adhered membrane cutting it to fit. A self-adhered membrane that is cut to fit has the advantage of sealing to the underside of the window and forming the product in the field that it is not rigid. The self-adhered membrane will not allow drainage since the window will create a seal unless shims are put under the window to create sufficient space to create drainage. Many manufacturers of vinyl windows want the window to be fully supported which means shims do not work with their vinyl window designs. Furthermore, the membrane is not very durable and the cutting of the membrane can create joints and pinholes that must be filled with sealant to make sure a seal is created. 
     While many materials and approaches for sealing window and door joints have been tried, there still exists a need for a material and method of application that can be used for a sill pan that has the advantages of a self-adhered membrane, but can drain without shims, and has sufficient sealing materials to seal around nail holes, while being thin enough to properly function and provide end and back dams without cutting the material. 
     SUMMARY OF THE INVENTION 
     A method for forming a sill pan is provided that includes the measurement of a width and length of an opening sill to be sealed. A piece of flexible sill pan material is cut based on the measured opening sill. Fold lines and cuts are created in the piece to form the sill pan. The resulting sill pan is readily formed to have at least one attribute of self-adherence, draining without shims, nail hole self-sealing, and provision of dams without resort to frame cutting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1D  illustrate a method for forming a sill pan from a sheet material according to embodiments of the invention; and 
         FIG. 2  is a side perspective cut away view of an installed sill pan according to embodiments of the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     The present invention has utility for sealing window and door joints and provides a material and method of forming and application of the seal that can be used for a sill pan that has the advantages of a self-adhered membrane, but can drain without shims, and has sufficient sealing materials to seal around nail holes, while being thin enough to properly function and provide end and back dams without cutting the material. 
     Embodiments of the inventive sill pan may be formed from a waffled aluminum membrane that has a thick butyl backed adhesive on the back, or other materials that inhibit moisture and can be used in the inventive method of forming sill pans. The waffled aluminum membrane is sold as a roll good that can be cut with scissors. The roll goods can be taken to an application or construction site and cut to size as required. In the inventive method for forming a sill pan, instead of cutting and sealing to form the pan, the material is folded to form the end and back dams so there is no hole or bonded surface. In the inventive method, the end dams and back dams of a sill pan may be formed to any required height. In forming the sill pan, the waffled aluminum membrane material is rigid enough to stand up by itself, so that the majority of a backing may be removed leaving the last one-inch, so the material can be turned up when the sill trim at the back of the window interior is installed. Alternatively in an embodiment, the back dam may be formed with a metal angle to which the back dam can be immediately bonded creating a free standing back dam. The waffle pattern on the face of the aluminum membrane creates a drainage course. If water were to travel through the window the pan will pick it up. The waffle pattern in the membrane material allows the water to drain to the exterior without putting the window to be sealed on shims. The pan can be sloped by gently sloping the sill framing or adding a continuous wood ‘chair’ with very gentle sloping. The thick butyl backing of the membrane material acts to seal around penetrations. The aluminum surface is compatible with all materials currently in use as a flashing material. Packaged as a rolled good, the aluminum membrane allows for the expansion of the sill to the exterior to any amount the installer requires. 
     In installations where metal sills are usually exposed, embodiments of the inventive sill pan are more appropriate for a ‘nail-on’ window that used to be sealed with a nailing flange on all four sides. The concept used by builders today is to leave the sill open to allow and water that enters to drain out instead of entering the building, but to avoid air from entering the building to create an exterior air barrier. The waffled aluminum membrane material achieves the desired sealing performance by allowing drainage at the bottom, and sealing the window to the back dam with a butyl or polyurethane seal. Self-adhered membranes typically have a polyethylene face that serves as a water impervious barrier, and is not a good surface for sealant bonding. However, while the aluminum face of the waffled aluminum membrane material, used in embodiments of the inventive sill pan, also has a zero perm it still also provides a good sealing surface. The aluminum membrane is thick enough to provide rigidity, but thin enough to cut with scissors and to create a thin profile. 
     Referring now to the figures,  FIGS. 1A-1D  illustrate an inventive method for forming a sill pan  32 . It is noted that a waffled or dimpled aluminum membrane is the material used in the example embodiment shown; however additional sheet materials may be used to carry out the inventive method. In  FIG. 1A , a rectangular sheet of flexible sill pan material  10  with the dimple or waffle side  12  showing is laid out and cut to a required size for a window sealing application. In general the inner  11  and outer  13  edges are along the long dimension of the cut sheet  10 . In  FIG. 1B , the smooth surface  14  of the flexible sill pan material  10  is shown, and the surface is measured and marked as follows with a first fold line  16  that defines the height of a back dam  20  at a first distance measured from the inner edge, and a second fold line  18  that defines a rectangular area  17  on opposing sides of the flexible sill pan made up of folded segments  26  and  28  (see  FIG. 1C ) that define side flaps and the end dams, respectively. The first fold line  16  is parallel to the long side of the rectangular sheet  10 . The pair of second fold lines  18  are perpendicular to the first fold line  16  and are parallel to short side dimension of the sheet  10  at a second distance (D 2 ) measured from the side edges  19 . In  FIG. 1C , a third fold line  22  is added that is parallel to the first fold line  16  at a third distance (D 3 ) as measured from the outer edge, and bisects the sheet  10 . Fold line  22  defines the width of the seat  30  of sill pan  10  for seating the window frame, and the downward flap  24  that extends down the wall  34  (see  FIG. 2 ) below the window sill. The fold along third fold line  22  also creates a drip edge. Additionally in  FIG. 1C , the back dam  20  is folded upward along fold line  16  relative to the seat  30 . In  FIG. 1D , a cut is made along second fold lines  18  that extend from the outer edge  13  until the third fold line  22 , and the segments  26  and  28  that form the side flaps and the end dams, respectively are bent upward and perpendicular to the seat  30 . The side flaps  26  are subsequently bent away from the seat  30  and made perpendicular to the end dams  28 . The opposing ends  15  of back dam  20  that are defined by the area between the inner edge  11 , first fold line  16 , and second fold lines  18  are folded upward after a small cut is made to first fold line  16  that extends from the side edges  19  to the second fold line  18 . The upward opposing ends  15  seal against the end dams  28 . The entire sill pan  32  formed above is now ready to be placed in the opening for the window sealing application. 
       FIG. 2  is a side perspective cut away view of an installed sill pan  32  in a building wall opening  34  prior to placement of a window frame (not shown) according to embodiments of the invention. As shown the downward flap  24  extends down the wall  34 . Metal angle  36  provides vertical support to back dam  20 , and seat section  30  of the flexible sill pan  32  fits onto the sill  38  of the window opening. A toe bead of sealant  40  is placed at the right angle bend between the seat  30  and back dam  20 . When placing the window frame the bottom rear edge of the window frame is set into the toe bead of sealant  40 .