Flexible Flashing Material And Method of Manufacture

Abstract

A flashing material for a building structure is provided. The flashing material includes a flexible water-resistive membrane having an upper textured surface with a series of separate, laterally paced-apart, elongate spacers bonded thereto. The elongate spacers can be polymeric filaments that define an air space and drainage paths across the upper surface of the membrane. Preferably, the filaments have a series of depressions formed therein that provide transverse drainage paths across the filaments. Sill, decking and other building structure assemblies and methods of making the flashing material are provided.

Description

BACKGROUND OF THE INVENTION

The present invention relates to waterproofing a building structure, such as a building opening, a deck ledger or joist, a corner of an exterior wall, a roof-to-wall interface, a through-wall passage, or the like, and more particularly, the present invention relates to a flexible drainage-promoting flashing material and its method of manufacture.

By way of example, water leakage or seepage can occur through the joints of a window and/or window frame, and moisture infiltration within and around a window opening in a wall can be caused by blowing rain, melting snow or ice, and/or condensation of moisture vapor. Similar leakage and/or seepage can also occur via through-wall passages and other building openings, behind deck ledger boards, within a corner of an exterior wall or wall-to-roof interface, or at other areas of a building structure. Moisture that infiltrates these areas will likely become trapped within the building structure and over time will cause structural damage such as rotting of windowsills, framing elements, ledgers and joists, adjacent wall or roof sheathing and studs, and exterior sidewall and trim building materials. In addition, trapped moisture will also cause the undesired growth of mold within the wall or adjacent structure.

For purposes of preventing such damage with respect to window openings, it is conventional practice to install a sill pan or like flashing material to a window opening before a window is installed within the opening. The sill pan or like flashing material provides a water impermeable layer of material that prevents any moisture, which may infiltrate the opening, from contacting the generally wooden framework members of the sill and like surfaces within the wall. Preferably, the sill pan or flashing material should also permit and/or promote removal of moisture from the sill area to an area on an exterior side of the building envelope. Thus, the sill pan and flashing is used to prevent structural damage of the building structure about the window opening, drain moisture to an exterior of the building, and lessen the likelihood of mold forming within the walls of the structure.

By way of example, the following U.S. patents and U.S. published applications disclose various known sill pans, sill drainage systems, flashing, and like building materials: U.S. Application Publication Nos. 2008/0105363 A1 of Ford, 2008/0010917 A1 of Hopkins et al., 2006/0101726 A1 of Collins, 2005/0217189 A1 of Moffit, 2008/0178557 A1 of Parsons et al., 2006/0010788 A1 of Nettleton, 2007/0289226 A1 of Lokkart, 2006/0236618 A1 of Williams, 2006/0137263 A1 of Casey, 2003/0056444 A1 of Ackerman, Jr., 2003/0177727 A1 of Gatherum, 2006/0143994 A1 of Allen, 2007/0157528 A1 of Gawoski and 2005/0144856 A1 of Conlin and U.S. Pat. No. 6,676,779 B2 issued to Hopkins et al., U.S. Pat. No. 7,201,820 B2 issued to Wiercinski, U.S. Pat. No. 6,964,136 B2 issued to Collins et al., U.S. Pat. No. 1,677,130 issued to Cherry, U.S. Pat. No. 4,555,882 issued to Moffit et al., U.S. Pat. No. 7,222,462 B2 issued to Ellingson, U.S. Pat. No. 6,385,925 B1 issued to Wark, U.S. Pat. Nos. 5,822,933 and 5,921,038 issued to Burroughs et al., U.S. Pat. No. 7,367,164 B2 issued to Burton et al., U.S. Pat. No. 7,134,245 B2 issued to Burton, U.S. Pat. Nos. 6,401,402 and 6,401,401 issued to Williams, U.S. Pat. No. 6,725,610 B2 issued to Murphy et al, U.S. Pat. No. 6,305,130 B1 issued to Ackerman, Jr., and U.S. Pat. Nos. 7,059,087 B2 and 7,290,379 B2 issued to Allen.

Although the sill pans, flashing materials, assemblies, and methods disclosed in the above referenced patents and published applications may be satisfactory for their intended purpose, there is a need for an improved building material and method for waterproofing internal components of a through-wall opening or the like of a structure, wall corners, wall-to-roof interface areas, deck ledgers and joists and like structures and for removing moisture that penetrates into such openings or structures. The building material should be inexpensive to manufacture and require only a minimum of skill and labor to apply within an opening or on a structure.

SUMMARY OF THE INVENTION

A flashing material for a building structure is provided. The flashing material includes a water-resistive membrane sufficiently flexible to conform to underlying surfaces and a series of separate, laterally spaced-apart, elongate spacers bonded to an upper surface of the membrane. The elongate spacers are polymeric filaments and define an air space and drainage paths across the upper surface of the membrane.

The filaments are of a thickness that projects to a predetermined height above the upper surface of the membrane and that defines a thickness of the air space above the upper face of the membrane. The filaments have a series of depressions formed therein that do not extend to the predetermined height and that provide drainage paths in a direction transversely across the filaments, According to one contemplated embodiment of the present invention, the series of depressions are located at spaced intervals along a length of each filament and are formed by flattened sections of the filaments, and each filament is continuous and consists of an alternating array of the flattened sections and non-flattened full-size sections of the filament.

The membrane can be of multi-layer construction including an upper layer of polymeric material to which the filaments are bonded and a lower integral layer of adhesive providing an underside of the membrane. A release sheet can be used to cover the adhesive whereby the layer of adhesive can be exposed when the release sheet is removed from the membrane. Alternatively, the membrane can be provided without an adhesive layer and release sheet. In addition, an elongate flexible wedge can be secured to a rear edge portion of the underside of the membrane to provide the membrane with a forward slope from its rear edge toward its front edge. Alternatively, the membrane can be provided without the integral wedge component.

According to another aspect of the present invention, an assembly of a window, door, or like opening of a building is provided. The assembly includes framework defining an opening in an exterior wall of a building. The framework includes a sill member extending between opposite upright framing members. The assembly also includes an outer sheathing member applied to the wall below the opening. A flexible water-resistive membrane is applied over the sill member and is folded over a front edge of the opening and extends on the outer sheathing member. The membrane has a series of separate, laterally spaced-apart, elongate spacers bonded to an upper surface of the membrane, and the elongate spacers are polymeric filaments that define an air space and drainage paths across the upper surface of the membrane. Each of the filaments extends generally in a direction from one of the upright framing members to the opposite one of the upright framing members along the length of the sill member of the opening.

As discussed above, the filaments are of a thickness that projects to a predetermined height above the upper surface of the membrane and that defines a thickness of the air space above the upper face of the membrane, and the filaments have a series of depressions formed therein that do not extend to the predetermined height. The depressions provide the drainage paths which extend transversely across the filaments. Preferably, the series of depressions are located at spaced intervals along a length of each filament and are formed by flattened sections of the filaments, and each filament is continuous and consists of an alternating array of the flattened sections and non-flattened full-size sections of the filament.

The assembly can include a pre-applied layer of adhesive on the underside of the membrane to adhesively secure the membrane to the sill member and outer sheathing, and/or the assembly can include an elongate wedge or backdam secured to the sill member underneath a rear edge portion of the membrane to provide the membrane with a forward slope from its rear edge toward its front edge. In addition, the assembly can include a window or the like installed within the opening over the sill member and membrane. In this case, the air space and drainage paths are provided between the upper face of the membrane and lowermost framing elements of the window, including a lower window flange of a flanged window. In addition, the same membrane with filament spacers used on the sill can also be applied adjacent the jambs and header of the opening behind exterior window trim to promote drainage behind the trim.

A further aspect of the present invention is directed to a method of making a flashing material for an opening in an exterior wall of a building. A series of separate, laterally spaced-apart, elongate polymeric filaments are bonded on an upper surface of a flexible water-resistive membrane. The filaments are flattened at spaced intervals along their length to create drainage paths extending transversely across the filaments. The method can also include the steps of applying a layer of adhesive on an underside of the membrane and thereafter applying a release sheet to the underside of the membrane to cover the layer of adhesive. Further, the method can include the step of securing a wedge of flexible material to an underside of the membrane along a rear edge portion of the membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a an exterior wall of a building having a window;

FIG. 2 is a partially cut-away perspective view of a flexible window sill flashing material according to the present invention;

FIG. 3 is a cross-sectional of the flexible flashing material along line 3-3 of FIG. 2;

FIG. 4 is a perspective view of the flexible window sill flashing material of FIG. 2 applied to a window opening;

FIG. 5 is a cross-sectional view of a window opening and the flexible sill flashing material installed within the window opening;

FIG. 6 is a perspective view of a wall on which the window and the flexible sill flashing material are installed before exterior trim and sidewall building materials are installed;

FIG. 7 is an elevational view of a wall on which the window flanges at the header and jambs have been covered with the flashing material according to the present invention; and

FIG. 8 is a perspective view of a deck ledger and joists on which a flexible flashing material according to the present invention is applied.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a flexible membrane that can be used, for instance, to waterproof a sill surface of framework of a window opening of a building structure. However, the flexible membrane is not limited to use in window openings and can also be used to promote drainage at other locations within or adjacent an exterior wall and/or roof assembly of a building. Examples include use of the flexible membranes about building openings such as doors or the like, other through-wall openings such as for conduits, pipes, wires and the like, wall corner and wall-to-roof interfaces, and deck ledger boards and joists.

By way of example, the flexible membrane is applied to the window opening at the sill before the window is installed. After installation of the window and adjacent outer sidewall and trim building materials, the membrane is embedded within the structure and hidden from sight. The flexible membrane can also be utilized to promote drainage behind trim elements of an opening adjacent header and jamb surfaces and to protect the sill surfaces of doors. Of course, the flexible membrane can also be used to promote drainage within a wall corner or wall-to-roof interface and about deck ledger boards and joists as discussed above.

According to one example, FIG. 1 illustrates a finished exterior wall 10 of a building having a window 12, exterior window trim 70, and exterior siding material 74. Over the course of the life of the wall 10 and window 12, moisture may infiltrate through the joints of the window or its frame as well as through small cracks or the like between the wall 10 and window 12 due to blowing rain, melting snow and ice, condensation of moisture vapor, and the like. Moisture often collects within the sill area 14 of the wall beneath the window 12. Accordingly, it is important to provide protection against moisture infiltration in the sill area 14 and to provide a drainage path for any moisture accumulating in the sill area 14 such that the moisture is properly directed to ambient atmosphere on an exterior side of the building envelope.

FIGS. 2 and 3 illustrate one contemplated embodiment of a membrane 20. The membrane 20 has waterproofing qualities and provides a substantially impermeable barrier to moisture. As an example, the membrane 20 can be made of a single sheet or multiple layered sheets of plastic, polymeric material, elastomeric material, rubber, synthetic rubber, bitumen-containing material, or any other water-resistive barrier material that is flexible and is of a size to cover the sill area of a window opening as discussed below in greater detail.

The membrane 20 can be at least slightly elastic so that it can be tightly fitted within and/or around corners of the window opening and can accommodate various-shaped underlying surfaces, edges, overhangs, uneven surfaces, and the like. Alternatively, the membrane 20 need only be flexible and not elastic. Preferably, the membrane 20 is sufficiently tear-resistant such that it does not tear during installation of the window or over the expected life of the window installation. If desired, additional tear-resistance can be provided by using a multilayer membrane that includes one or more reinforcing layers, such as a mesh reinforcing layer.

When the membrane 20 is applied to a window opening, it will typically be applied over a sloped sill area with a backdam or the like that prevents undesired flow of moisture on the sill toward the inside of the building. In some contemplated embodiments of the present invention, a wedge 22 of material is pre-applied, adhered, bonded, or otherwise secured to a rear portion 24 of the underside 26 of the membrane 20. See FIG. 2. Alternatively, the wedge 22 or some other type of backdam can be applied separately to the window opening, and the membrane 20 can thereafter be applied over the wedge or backdam at the building site.

The embodiment of FIG. 2 integrates the wedge 22, or backdam, directly on the membrane 20 and, as illustrated, the wedge 22 provides a forward-directed slope between its front and rear edges to provide a forward-sloped surface along the width of the wedge material 22. Thus, the wedge 22 elevates the rear portion 24 of the membrane 20 when the membrane 20 is applied to a substantially horizontally-disposed sill surface. Accordingly, any moisture collected on an upper surface 28 of the membrane 20 will be directed by the force of gravity toward and off the front edge of the sill and onto a water-resistive barrier (not shown) applied on and covering the wall sheathing adjacent the window opening.

The wedge 22 can be made of any material having sufficient structural rigidity to maintain the rear portion 24 of the membrane 20 elevated when a structure (e.g., door or window) is installed on top of the membrane 20. Such material may include, without limitation, plastics, closed cell foams, and open celled foams. Another contemplated material is an openwork mat of polymeric filaments. It is desirable that the wedge 22 be formed of a flexible material such that the resulting membrane 20 is flexible for purposes of ease of installation.

In some contemplated embodiments of the present invention, the membrane can be formed of multiple layers. The upper surface 28 can be formed by a waterproof non-woven sheet layer such as known for use with respect to housewrap materials. The underside 26 of the membrane 20 can be provided by a separate waterproof adhesive layer that bonds to the upper layer and that is used to bond the membrane 20 directly to the surface of the underlying sill to which the membrane is applied. The adhesive layer eliminates the need for nails, staples or like fasteners to pierce the membrane 20 or the use of a separately applied layer of adhesive or sealant. As an alternative, the membrane can be provided without an adhesive layer and can be secured to the sill with fasteners, tape, adhesives, or the like.

The membrane 20 illustrated in FIGS. 2 and 3 includes an adhesive layer, and therefore, also includes a release sheet 30 that is removably bonded to the adhesive underside 26 of the membrane 20. Thus, the membrane 20 can be a peel-and-stick type of product. Removal of the release sheet 30 exposes the adhesive nature of the underside 26 of the membrane 20 and permits the membrane 20 to be adhered to a desired surface enabling ready installation. As examples, the flexible release sheet 30 can be made of foils, metals, plastics, or papers treated with silicon or other substances to provide a low level of adhesion to the underlying adhesive layer 26 of the membrane 20. In addition, the single or multi-layer membrane 20, optional wedge material 22, and release sheet 30 all should be capable of being readily cut thereby enabling the membrane to be cut to size to fit window openings of any dimension. Alternatively, the membrane 20 can be provided in various standard sizes of window openings to avoid a cutting step.

The upper surface 28 of the flexible membrane 20 according to the present invention carries a series of spacing elements 32 that ensure the presence of a small air space between the upper surface 28 of the membrane 20 and any other materials, such as the window frame or the like, applied over the membrane 20. The spacing elements 32 also provide drainage paths on the upper surface 28 enabling moisture to drain forward on the membrane 20 and over the front edge of the sill area thereby preventing moisture from accumulating long term in the sill area.

As best illustrated in FIGS. 2 and 3, the spacer elements 32 on the upper surface 28 of the membrane 20 are provided as a series of separate, laterally spaced-apart, elongate spacer elements that arc bonded, adhered, or otherwise integrally secured to the upper surface 28. Preferably, the elongate spacer elements 32 are thermally bonded to the membrane 20 at spaced intervals; alternatively, the elements 32 can be thermally bonded to the membrane 20 continuously along their full length.

According to one contemplated embodiment of the present invention, the spacer elements 32 are filaments 34, such as continuous extruded polymeric filaments. Each filament 34 is bonded to the upper surface 28 of the membrane 12 where it contacts the membrane 20 and extends in a generally longitudinal direction generally following the direction of the front and rear edges, 36 and 38, of the membrane. Thus, when the membrane 20 is installed within a window opening, the filaments 34 extend generally along the longitudinal axis and front and rear edges of the windowsill and the longitudinal axis of the backdam or wedge 22. As an example, see FIG. 4.

In the illustrated embodiment, the filaments 34 are laterally and uniformly spaced-apart, do not intersect, and generally extend in a wavy, undulating, serpentine or sinuous pattern. However, they can also extend substantially parallel to each other following a straighter path. Alternatively, the filaments 34 of the present invention can extend in non-linear, saw tooth, and/or random paths or the like and can intersect and/or cross at random locations or at uniform spaced intervals.

As best illustrated in FIG. 5, each filament 34 can have a substantially circular cross-section of a predetermined diameter “D”. Of course, other cross-sectional shapes can be utilized, such as square, rectangular, oval and triangular filament cross-sections. Accordingly, each filament 34 projects a distance “D” from the upper surface 28 of the membrane 20 to provide a desired spacing between an overlying building material and the upper face 28 of the membrane 20.

Drainage paths “P” are provided transversely across the series of filaments 34. Preferably, this is provided by a series of depressions 40 that are formed in the filaments 34. The depressions 40 can be created by flattening the filaments 34 at spaced-apart intervals along the length of the filaments 34. This is best illustrated in FIG. 3. Thus, each filament 34 includes an alternating array of depressions 40 and full size filament sections 42. The flattened sections of the filaments 34 forming the depressions 40 project a distance from the upper surface 28 of the membrane 20 less than that of the diameter “D” of the full size filament sections 42. This permits the drainage of moisture and/or the flow of air transversely across the filaments 34. Preferably, the depressions 40 in adjacent filaments 34 are aligned to provide substantially straight drainage/ventilation paths “P” that extend transversely, or perpendicularly, across the filaments 34 and upper surface 28 of the membrane 20. See path “P” shown in FIGS. 2 and 4.

The filaments 34 are preferably made of polymeric materials capable of being extruded directly onto the upper surface 28 of the membrane 20 or a surface of a conveyer, drum, or like transfer mechanism. As examples, the filaments 34 can be made of nylon, polypropylene, polyester, polyolefin, polyethylene, or like material. By way of example, and not by way of limitation, each filament 34 can be extruded such that it has a diameter “D” between about 1/64 to ¼ inch, can be flattened in intervals “I” of about 0.5 to 6 inches, and can be spaced a distance “S” of about ⅛ to 1 inch from adjacent filaments. Of course, other dimensions, shapes, patterns, etc. can also be utilized.

Preferably, the filaments 34 are thermally bonded to the membrane 20. The polymeric material of the filaments 34 and membrane 20 engage, melt and then solidify together to fuse the filaments 34 to the membrane 20 via the application of heat and/or pressure, particularly at the depressions 40. Thus, a separately applied adhesive is not required, and a strong bond can be formed. The depressed sections 40 of the filaments 34 that are flattened are particularly strongly fused to the membrane 20 since the pressure exerted on the filaments 34 to create the depressions 40 results in the formation of a strong bond between the filaments 34 and membrane 20. Alternatively, adhesive bonding, sonic bonding, mechanical bonding, or other techniques can be utilized depending on the materials of the filaments and membrane. Further, the upper surface 28 of the membrane 20 can be textured to strengthen the bond, for example, see the grid like textured areas “T” randomly shown in FIGS. 2 and 4.

FIGS. 4 and 5 illustrate assemblies within which the flexible membrane 20 is utilized to waterproof a sill surface 50 of the framework of a window opening 52 while providing an elevated backdam 22. FIG. 4 shows the membrane 20 applied to the sill surface 50 of the framework prior to the installation of the window 54. Opposite ends, 56 and 58, of the membrane 20 extend partially up the upright studs 60 and 62 of the framework on opposite sides of the window opening 52 and tightly conform to the corners of the window opening 52. As an alternative, the opposite ends, 56 and 58, of the membrane 20 can be applied only over the windowsill itself and not onto the upright studs 60 and 62. In this case, other waterproofing materials would first he installed in the corners of the window opening, and thereafter, the membrane 20 would be installed on the windowsill.

If required, the wedge 22 can be cut away and removed from the opposite end sections, 56 and 58, of the membrane 20 that are adhered and/or secured to the studs 60 and 62. The remainder of the membrane 20 and wedge 22 extends on the horizontally-disposed sill member 64 and can be bonded thereto after the release sheet 30 is removed from the underside of the membrane 20 in a peel-and-stick manner. The wedge 22 extends under the rear portion 24 of the membrane 20 and can also be bonded or otherwise secured to the sill member 64 such that the wedge 22 forms a backdam along a rearward edge of the windowsill. The forward portion 66 of the membrane 20 is folded over the front edge of the windowsill 64 and adhered or secured to the outside surface of the vertically-disposed sheathing 68.

As best illustrated in FIG. 4, each elongate filaments 34 is continuous and extends in a direction generally from upright stud 60 to upright stud 62 and in a relatively longitudinal direction on the sill member 64. The depressions 40 permit moisture to flow along drainage paths “P” transversely across the filaments 34 from the rear portion 24 of the membrane 20 toward and off the front edge of the windowsill 64. See FIG. 4.

A window 54, door, or the like may be placed on the membrane 20 and sill 64 and installed within the opening 52. The wedge 22 forms a backdam or elevated area along the rearward edge of the windowsill 64. The forward edge portion 66 of the membrane 20 extends over the outside surface of the sheathing 68 and will be at an elevation lower than that of the rear portion 24 of the membrane 20 disposed over the wedge 22. Accordingly, the downward slope provides a flow path “P” across the depressions 40 of the filaments 34 and away from the rear of the sill 64 such that moisture is directed forwardly off the windowsill 64 underneath the window 54. See FIG. 5.

The above described flexible membrane 20 having the filament spacers 34 can also be used at other locations within the assembly for drainage-promoting purposes, such as behind exterior window trim 70 (see FIG. 1). For example, after the window 54 is installed within the opening 52, the membrane 20 can be applied over the flanges 72 of the window 54 adjacent the jambs and header of the window 54. See FIGS. 6 and 7. If needed, the membrane 20 is cut to a desired size for this application. After the membrane 20 is installed over the flanges 72, the exterior window trim 70 or like exterior siding material is applied over the membrane 20.

The filaments 34 provide drainage paths on the upper surface 28 of the membrane 20 underneath the trim 70. This is true regardless of the orientation of the filaments 34 on the membrane 20. For instance, drainage paths are provided between adjacent, spaced-apart filaments 34 as well as transversely across the filaments 34 via the depressions 40.

As stated above, the flexible membrane flashing material can be applied to other building openings, such as doors, skylights, and the like, as well as to through-wall openings for wires, cables, pipes or other conduits. The membrane can also be applied within and along wall corners and within and along wall-to-roof interfaces which form corner structures or the like.

Further, as illustrated in FIG. 8, the membrane 20 according to the present invention can be applied over a deck ledger board 80 of a deck. The deck ledger board 80 is fastened to a wall structure 82 of a building, and the membrane 20 is positioned to prevent water and moisture from seeping behind the ledger board 80 to a location between the ledger board 80 and the adjacent wall 82. The filaments 34 on the exterior face 28 of the membrane 20 provide spacing elements and the flattened sections 40 of the filaments 34 provide drainage paths “P” transversely across the filaments 34. Thus, any moisture penetrating within this area will be directed down and over the ledger board 80 by the membrane 20. The membrane 20 can also be applied over the upper edges 84 of the deck joists 86 so that any moisture penetrating between the joist 84 and upper deck members (not shown) can drain or be removed by evaporation from the upper edges 84 of the joists 86 to prevent water damage to the joists 86 and/or the overlying deck members.

While preferred flexible membranes, assemblies, and methods have been described in detail, various modifications, alterations, and changes may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A flashing material for a building structure, comprising: a flexible water-resistive membrane; anda series of separate, laterally spaced-apart, elongate spacers bonded to an upper surface of said membrane, said elongate spacers being polymeric filaments and defining an air space and drainage paths across the upper surface of said membrane.

2. A flashing material according to claim 1, wherein said filaments are of a thickness that projects to a predetermined height above said upper surface of said membrane and that defines a thickness of said air space above said upper face of said membrane, and wherein said filaments have a series of depressions formed therein that do not extend to said predetermined height and that provide said drainage paths which extend transversely across said filaments.

3. A flashing material according to claim 2, wherein said series of depressions are located at spaced intervals along a length of each filament and are formed by flattened sections of said filaments, and wherein each filament is continuous and consists of an alternating array of said flattened sections and non-flattened full-size sections of said filament.

4. A flashing material according to claim 3, wherein said filaments are thermally bonded to said membrane and do not intersect.

5. A flashing material according to claim 4, wherein said membrane has a multi-layer construction and includes an upper layer made of a sheet of polymeric material having a textured upper surface to which said filaments are bonded and a lower adhesive layer providing said membrane with a self-stick property.

6. A flashing material according to claim 5, further comprising a release sheet covering said underside of said adhesive layer whereby said adhesive layer is exposed when said release sheet is removed from said membrane.

7. A flashing material according to claim 6, further comprising an elongate flexible wedge secured to a rear edge portion of said underside of said membrane to provide said membrane with a forward slope from its rear edge toward its front edge.

8. A flashing material according to claim 7, wherein said elongate wedge has opposite ends defining opposite end sections of said membrane, and wherein said filaments extend in a direction substantially from one end section of said membrane to said opposite end section of said membrane.

9. A flashing material according to claim 8, wherein said wedge is made of an openwork mat of polymeric filaments.

10. An assembly of a building opening, comprising: framework defining an opening in an exterior wall of a building, said framework including a sill member extending between opposite upright framing members;one or more outer sheathing members applied to the wall surrounding said opening; anda flexible water-resistive membrane applied over said sill member and being folded over a front edge of said opening onto said outer sheathing member, said membrane having a series of separate, laterally spaced-apart, elongate spacers bonded to an upper surface of said membrane, said elongate spacers being polymeric filaments and defining an air space and drainage paths across said upper surface of said membrane;each of said filaments extending generally in a direction from said one upright framing member to said other upright framing member along the length of said sill member of said opening.

11. An assembly according to claim 10, wherein said filaments are of a thickness that projects to a predetermined height above said upper surface of said membrane and that defines a thickness of said air space above said upper face of said membrane, and wherein said filaments have a series of depressions formed therein that do not extend to said predetermined height and that provide said drainage paths which extend transversely across said filaments.

12. An assembly according to claim 11, wherein said series of depressions are located at spaced intervals along a length of each filament and are formed by flattened sections of said filaments, herein each filament is continuous and consists of an alternating array of said flattened sections and non-flattened full-size sections of said filament, and wherein said filaments do not intersect.

13. An assembly according to claim 12, wherein said membrane has a multi-layer construction and includes an upper layer made of a sheet of polymeric material having a textured upper surface to which said filaments are thermally bonded and a lower adhesive layer providing said membrane with a self-stick property.

14. An assembly according to claim 13, wherein said underside of said membrane is adhesively secured to said sill member and said outer sheathing by said adhesive layer.

15. An assembly according to claim 14, further comprising an elongate wedge or backdam secured to said sill member underneath a rear edge portion of said membrane to provide said membrane with a forward slope from its rear edge toward its front edge.

16. An assembly according to claim 15, further comprising a window installed within said opening over said sill member and said membrane, and wherein said air space and said drainage paths are provided between said membrane and a lowermost framing element of said window.

17. An assembly according to claim 16, further comprising: at least one additional membrane identical to that applied over said sill member that is applied over a window flange extending from said window adjacent at least one of the jambs or header of the window; andan exterior window trim member applied over said at least one additional membrane.

18. A method of assembling a window opening in a wall of a building, comprising: installing framework defining an opening in an exterior wall of a building, the framework including a sill member extending between opposite upright framing members;applying outer sheathing members to the wall about the opening; andsecuring a flexible water-resistive membrane over the sill member and folding a front edge of the membrane onto the outer sheathing member extending below the sill member, said membrane having a series of separate, laterally spaced-apart, elongate spacers bonded to an upper surface of the membrane, the elongate spacers being polymeric filaments and defining an air space and drainage paths across the upper surface of the membrane, each of the filaments extending generally in a direction from the one upright framing member to the other upright framing member along the length of the sill member of the opening.

19. A method according to claim 18, further comprising a step of installing a flanged window within the opening over the sill member and the membrane.

20. A method of making a flashing material for a sill of an opening in an exterior wall of a building, comprising the steps of: bonding a series of separate, laterally spaced-apart, elongate polymeric filaments on an upper textured surface of a flexible water-resistive membrane; andflattening said filaments at spaced intervals to create drainage paths extending transversely across said filaments.

21. A method according to claim 20, wherein said water-resistive membrane is made of a polymeric material, wherein, during said bonding step, said extruded polymeric filaments are thermally bonded to said membrane, and further comprising the step of applying a layer of adhesive on an underside of said membrane and thereafter applying a release sheet to the underside of said membrane to cover said layer of adhesive.