Abstract:
A rigid wire lath product having a backing material which may be used to reinforce coatings, such as stucco, applied to building surfaces. The product comprises a mesh of longitudinal wires and transverse wires having a plurality of spaced indentations. A layer of backing material having apertures which straddle the indentations is interwoven in the mesh by longitudinal retaining wires extending along the bottom of the indentations. A method of manufacturing the product by providing a mesh of longitudinal and transverse wires welded together at their intersections substantially in a plane, and forming rows of spaced indentations in the transverse wires. A planar material is overlaid on the mesh such that said portions of the indentations protrude through apertures in the material. A plurality of wires are welded along respective rows of the protruding indentations to sandwich the material between the mesh and the wires.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation in part of U.S. patent application Ser. No. 10/935,821 entitled Self Stiffened Welded Wire Lath Assembly by Abraham Sacks et al. filed Sep. 8, 2004, which was a continuation in part of U.S. patent application Ser. No. 09/927,544 filed on Aug. 13, 2001. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to building technology, and in particular to wire lath which may be used to reinforce coatings, such as stucco, applied to soffits and other building surfaces.  
       BACKGROUND OF THE INVENTION  
       [0003]     Some building construction techniques involve the application of a coating, such as stucco, to a surface. The coating may be desired, for example, to improve appearance, enhance fire resistance or to comply with building or fire codes. In the following disclosure the term “stucco” is used generally to apply to cementitious plasters or gypsum plasters, including stuccos as defined in applicable building codes.  
         [0004]     When applying a coating of stucco (or other similar material) it is generally desirable to provide a lath on the surface. The lath provides reinforcing for the stucco and holds the stucco in place while it cures.  
         [0005]     Typical construction usually involves wood or metal framing without sheathing, referred to as open frame construction. On vertical surfaces, horizontal strands of 18 gauge tautened wire backing are attached to the surfaces of the vertical supports. A weather-resistant barrier is then installed which is usually a Grade D asphalt building paper. For plaster cladding, wire fabric lath is then attached to the framing over the building paper and backing wires. The backing wires provide sufficient rigidity to permit proper plaster application without damaging the paper and achieving consistent plaster thickness between framing members.  
         [0006]     The building paper application starts at the bottom and each succeeding course overlaps the previous course by a minimum of 2 inches, and usually is approximately 4 inches. This ensures proper shingling of the paper to ensure that any moisture that penetrates the cladding is directed downward and away from the building structure. The wire fabric lath has to be lapped not less than one mesh at the sides and ends. Since the building paper and wire fabric lath are applied independently, there is no difficulty in achieving the proper overlapping of each element.  
         [0007]     This practice is referred to as a 3 step process—installation of backing wires, installation of building paper, and installation of lath. To overcome this inefficiency, paper backed lath products have been developed that are one step products. These products incorporate the backing wire, the building paper and the wire lath into a single product. An example of such a product is available from K-Lath Corp. of Fontana, Calif. referred to as Stucco Rite®. Stucco Rite® is a 2″ by 2″ welded wire mesh with a slot-perforated absorptive, separator paper, and with a sheet of Grade D building paper adhered to the separator paper. Another manufacturer, Davis Wire Corp of Irwindale, Calif. manufactures a similar product called Best-Lath “D” Welded Wire Fabric Lath.  
         [0008]     As seen in both of these products, a perforated separator paper is incorporated between the longitudinal and cross wires of the lath. The function of this separator paper is to provide a means of attaching the building paper to the lath. The building paper must remain intact so holes or perforations cannot be incorporated into the building paper itself. Therefore, the separator paper is required since it can be perforated so that it may be mechanically attached to the wire lath. This sheet provides a suitable base for attachment of the building paper.  
         [0009]     In the installation of these one step products, care must be taken to achieve the proper lapping of the building paper and of the wire lath. ASTM C-1063 “Standard Specification for Installation of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster” states in Section 7.8.3 “Where metal plaster base with backing is used, the vertical and horizontal lap joints shall be backing on backing and metal on metal”. To achieve this, the manufacturers of the above products have carefully sized the building paper sheet size and sheet location on the wire mesh sheet, so that proper lapping of both the building paper and the wire lath can be achieved. Since the building paper is adhered to the separator sheet, the interwoven wires are trapped between these two papers. As a result, the position of the papers in relation to the wire lath is maintained during handling and installation.  
         [0010]     Further, since the separator paper is only required to provide an adhesive base for the building paper, it need not extend all the way to the edges of the lath sheet. Therefore, it is sized so that it does not encroach on the overlaps and is not a hindrance factor in achieving the proper metal on metal contact. Usually, this separator paper is kept back two to three inches from all edges of the wire lath.  
         [0011]     Since the building paper provides support for the edges of the separator paper, there is no need to firmly attach the edges of the separator paper to the lath. When the product is applied on the wall, the building paper prevents the separator paper from being displaced into the wall cavity with the pressure of the applied plaster. Further, since the building paper extends past the lath overlaps in all directions, there are no gaps in the backing where plaster can flow past the lath into the wall cavity.  
         [0012]     However, there are applications where building paper is not required or not desired. Such applications would be on horizontal surfaces such as undersides of soffits or porticos, or on vertical surfaces such as rain screen walls. Rain screen walls are constructed with building paper installed over the framing and then a furring spacer, usually ¾ inch thick, is installed vertically over the building paper. A lath with backing is attached to these furring spacers. A lath with building paper is not desirable in this instance since any moisture traveling downward within the drainage cavity could be caught by the edge of the building paper and deflected out of the rain screen cavity. The design intent is to keep the moisture within the cavity and then discharge it at the bottom through a proper flashing.  
         [0013]     A lath as disclosed in U.S. Pat. No. 6,820,387 to Sacks et al discloses a lath with a separator paper only without the building paper which is intended for such applications. However, when the building paper is omitted, several deficiencies become evident. In the prior art as disclosed by Sacks, the separator paper (referred to as a barrier paper in the Sacks prior art) does not extend all the way to the edges of the wire lath. If the separator paper did extend all the way to the edge, it would firstly interfere with achieving metal to metal contact. Secondly, it would not be secured at the edges and would give way when plaster pressure was applied. This would result in uneven thickness of plaster which could cause a plaster fall out due to additional weight of wet plaster, or be the cause of potential cracks in the future. Further, since there is no building paper adhered to the separator paper, the separator is not held firmly in position relative to the wire. Therefore, since the paper may shift during handling and installation, it could the also interfere in obtaining metal to metal contact without any paper in between the overlapping joint.  
         [0014]     In addition, the longitudinal wires forming part of the Sacks truss extend across the slots thereby impeding to some extent the keying of the stucco through the slot. The elongated slots in the separator layer also result in movement or play between the separator layer and the wire mesh that can cause displacement of the separator layer.  
         [0015]     An additional problem arises from the use of paper backed lath arises from the manner in which the paper is terminated at the sides of the lath. The paper is provided with apertures for keying of the stucco. The areas between the apertures form interconnected webs of material. At the sides of the lath, the paper includes an unattached flap of material that does not provide effective resistance to the application of stucco, resulting in difficulty of application.  
         [0016]     It is the objective of the present invention to provide an improved backed lath with a barrier layer that avoids the disadvantages of the prior art paper backed laths.  
       SUMMARY OF THE INVENTION  
       [0017]     This invention provides a rigid wire lath product having a backing material that overcomes a number of disadvantages of prior art wire fabric laths.  
         [0018]     According to the invention, the principal plane of the wire fabric comprises a mesh of longitudinal and transverse wires forming columns and rows. The transverse wires have a plurality of spaced indentations. A planar barrier layer of material is interwoven in the mesh by longitudinal retaining wires extending along the bottom of the indentations. The barrier layer is provided with apertures enabling the indentations to be straddled by the apertures such that the material forming the barrier layer is retained between the principal plane of the wire fabric on one side and the longitudinal retaining wires on the other side. This arrangement allows all of the intersections of the principal plane of the wire fabric to be welded before applying the barrier layer and the longitudinal retaining wires. Preferably the apertures may be circular so as to more closely abut the indentations in all directions, thereby limiting relative displacement of the barrier layer in relation to the wire mesh.  
         [0019]     In one aspect of the invention, the longitudinal wires forming the principal plane of the wire fabric are arranged such that they do not extend across the apertures thereby ensuring that they do not impede the keying of the stucco into the apertures.  
         [0020]     In another aspect of the invention, the barrier layer includes webs at the sides of a sheet between end rows of cells, each of the webs being folded over a common longitudinal wire and being secured back unto itself about the longitudinal wire thereby avoiding unattached flaps.  
         [0021]     In another aspect of the invention, the barrier layer includes a plurality of apertures overlapping the indentations and wherein each of the apertures in at least one row has a diameter substantial equal to or less than the maximum span of the indentations.  
         [0022]     In another aspect of the invention, at least one rows of apertures are smaller than the other rows of apertures and are sufficiently small that opposed edges of the apertures in the at least one row are in simultaneous contact with the indentation about which it is seated so as to retain the barrier material against transverse displacement.  
         [0023]     According to a method aspect of the invention, the manufacture of a welded wire lath comprises providing a mesh of longitudinal and transverse wires welded together at their intersections substantially in a plane, and forming rows spaced indentations in the transverse wires, the indentations having portions extending out of the plane. A planar material is provided, the material having a plurality of apertures being spaced from one another in a pattern corresponding to the locations of the indentations. The planar material is overlaid on the mesh such that said portions of the indentations protrude through the apertures. A plurality of elongated wires are then welded along respective rows of the protruding portions of the indentations to thereby sandwich the planar material between the mesh and the elongated wires.  
         [0024]     In a more particular aspect, the planar material is provided in sheets having end webs that are folded over a common elongated wire of the mesh and are secured to themselves about that wire.  
         [0025]     In a still more particular aspect, the planar material is provided with holes having a smaller diameter than the diameter of the apertures such that opposed edges of each hole are in simultaneous contact with its respective indentation to retain the planar support material against transverse displacement.  
         [0026]     The foregoing summary of the invention does not necessarily include all aspects of the invention. Further features and aspects of the invention will be more fully understood by reference the following description of the preferred embodiments and to the claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The preferred embodiment of the invention will be described by reference to the drawings in which:  
         [0028]      FIG. 1  is a schematic front perspective view of a welded wire mesh lath in accordance with the invention;  
         [0029]      FIG. 2  is a schematic cross-sectional view of the welded wire mesh lath of  FIG. 1 ;  
         [0030]      FIG. 3  is a diagrammatic side elevation of the manufacturing process of welded wire mesh lath according to the invention;  
         [0031]      FIG. 4A  is a diagrammatic plan view of a first part of the manufacturing process according to the invention;  
         [0032]      FIG. 4B  is a diagrammatic plan view of a second part of the manufacturing process according to the invention; and  
         [0033]      FIG. 4C  is a diagrammatic plan view of a third part of the manufacturing process according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     Referring to  FIGS. 1 and 2 , there is shown a lath  10  according to the preferred embodiment comprising a wire mesh  12  and a planar barrier layer of material  14 . The material  14  may comprise a suitable building paper, such as kraft paper, which may be surface treated to improve the adhesion of stucco. Alternatively it may comprise asphalt-coated paper or such an asphalt-coated paper adhered to another layer, such as kraft paper.  
         [0035]     Wire mesh  12  is fabricated by welding the intersections  18  of a plurality of transverse wires  20  and a plurality of longitudinal wires  22  that are perpendicular to the transverse wires  20 . The wires  20  and  22  and their intersections lie substantially in plane  24 , best seen in  FIG. 2 . Each of the transverse wires  20  has a plurality of spaced indentations  26  arranged in rows and columns across the lath. Indentations  26  are preferably generally V-shaped and provide rigidity to the lath.  
         [0036]     A set of longitudinal retaining wires  28  are welded to the indentations  26  at the apices of the indentations (as best seen in  FIG. 2 ) so that the indentations are formed in rows coinciding with the longitudinal retaining wires  28 . Each transverse wire  20  lies within a plane that includes indentation  26 . That plane, which is the plane of  FIG. 2 , is generally perpendicular to plane  24 . In the preferred embodiment, longitudinal wires  18  are located so as to avoid spanning the openings of the apertures  30  in the support material  14 , which apertures are described in more detail below.  
         [0037]     A wire lath  10  can be produced in any desired dimensions but is preferably provided in sheets of widths and lengths that can be easily handled. For example, the sheets may have a width in the range of 2 to 5 feet. Sheets of wire lath  10  can be compactly stacked together with the indentations  26  of one sheet being received within those of the next sheet in the stack.  
         [0038]     The combination of the longitudinal and transverse wires welded at their intersections forms a mesh comprising rows of cells, including opposed end rows  32 ,  34  at opposed transverse ends  36 ,  38  of the mesh. The cells comprising end row  32  share at least one common longitudinal wire  40  while the cells comprising end row  34  share at least one common longitudinal wire  42 . In the preferred embodiment, wires  40  and  42  are the endmost ones of longitudinal retaining wires  28 , i.e. they extend along the apices of indentations  26  in a plane  44  that is defined by the plurality of longitudinal retaining wires  28 .  
         [0039]     Lath  10  may be applied over framing members, which are typically 16 inches or 24 inches on center. It can be attached to the framing members at the bottom of indentations  26 . In horizontal applications, building codes generally require that a lath be attached every 3 inches. In vertical applications, the codes generally require attachment to the framing members every 6 inches. In either case, a 3 inch spacing of the indentations  26  allows appropriate attachment points. Lath  10  is preferably applied in an orientation such that the side of lath  10  bearing longitudinal retaining wires  26  faces the framing members, each of the longitudinal retaining wires crosses a plurality of the framing members, and longitudinal wires  22  are spaced from the faces of the framing members by the indentations  26 . The portions of lath  10  between the framing members can be substantially unsupported.  
         [0040]     A planar barrier layer of material  14  is disposed between plane  24  and plane  44 . Barrier layer  14  includes apertures  30  through which the indentations  26  protrude to allow the longitudinal wires  22  to lie on one side of support layer  14  and longitudinal retaining wires  28  to lie on the other side of layer  14 . The barrier layer  14  is thereby interwoven with the mesh, straddling the indentations  26  and being sandwiched between the principal plane  24  of the mesh and the longitudinal retaining wires  28 . This arrangement allows all of the other intersections of the mesh to be welded and the indentations  26  to be formed in advance of applying the barrier layer  14  and welding the longitudinal retaining wires  28  to the indentations  26 .  
         [0041]     According to the prior art approach disclosed in U.S. Pat. No. 6,820,387, certain ones of the longitudinal wires  22  are provided on the shoulder portions of the indentations  26 . This sometimes results in such longitudinal wires spanning and obstructing a portion of the opening of the apertures  30 . However, according to the present invention, the longitudinal wires  22  are positioned in relation to the indentations  26  so that none of them spans the apertures  30  as best seen in  FIG. 1 .  
         [0042]     In the known prior art, the perforations in the barrier layer are elongated to form slots. This can result in displacement or floating of the support layer in relation to the wire mesh in the direction of elongation of the slots. In order to avoid such effect, the present invention provides apertures  30  that are circular so as to more closely abut the indentations in all directions, thereby limiting relative displacement of the support material in relation to the wire mesh. Preferably, all of the apertures  30  have diameters substantial equal to or less than the span D of the indentations at their base, i.e. where the transverse wires  20  begin to leave plane  24 .  
         [0043]     In the preferred embodiment, at least one of the rows of apertures comprises holes  46  that are smaller in diameter than the maximum span D of the indentations (at the base of the indentations). This results in holes  46  snugly engaging the indentations at some point between the base and the apices of the indentations, thereby more effectively resisting displacement of the support material in relation to the wire mesh. In the preferred embodiment, holes  46  are between ¼″ and ¾″ in diameter, preferably about ½″ in diameter, while the apertures  30  are between ¾″ and 1¼″ in diameter, preferably about ⅞″ in diameter. Such an arrangement of two sets of apertures allows snug retention of the support material to the wire mesh on the one hand, by means of the smaller holes, while also allowing effective mushrooming of the stucco through the larger apertures.  
         [0044]     The arrangement of apertures  30  in the barrier layer forms a matrix of interconnected webs of support material between the apertures. It will be appreciated that the longitudinal retaining wires  28  span portions of these webs to retain the barrier layer  14  between the longitudinal retaining wires  28  on the one hand and a combination of the transverse wires  20  and the longitudinal wires  22  on the other hand. The barrier layer of the preferred embodiment has two opposed ends  48  and  50  that extend generally to the opposed sides of the wire mesh. At least one of such ends, for example end  50 , comprises a row of end webs  52  extending between a plurality of end openings  54 . The end webs  52  are folded over and secured to themselves about and around common longitudinal wire  56  and each of said end webs  52  is secured back onto itself around common longitudinal wire  56 . Preferably the same is done at opposed end  48  of the support material.  
         [0045]     Prior to being folded over, the end openings  54  comprise apertures bounded by a closed curve, however it is contemplated that prior to being folded over, the end openings  54  may simply present unclosed gaps in the end of the support material. In the preferred embodiment, end openings are larger in their aperture area than aperture  30 . When the end openings are folded over themselves, there is a possibility that the webs of material between the openings will not line up perfectly so that the facing webs combine to increase the surface area available to obstruct the passage of stucco. This may be compounded when adjacent sheets of lath are brought into edge to edge engagement during installation. Thus it is desirable to have openings that are as large as feasible to maximize the keying of stucco once the webs are folded over and secured to themselves.  
         [0046]     It will be appreciated that various modifications to the preferred embodiment may be practised without changing the underlying structure and effectiveness of the invention. For example, additional longitudinal or transverse wires might be added and additional apertures might be provided in the barrier layer. Other such changes can be made that do not depart from the principles of the invention.  
         [0047]     The manufacture of the lath  10  of the preferred embodiment will now be described by reference to  FIGS. 3, 4A ,  4 B and  4 C.  
         [0048]     A matrix of perpendicular transverse  60  and longitudinal  62  wires are welded ( 64 ) at their intersections  66  in a continuous process to produce a rectangular mesh  68 . Transverse wires  60  are spaced about 1.6″ from one another while longitudinal wires  62  are nominally spaced about 0.6″ from one another. At regular intervals of three longitudinal wires, one of the longitudinal wires is omitted as indicated by the numeral  70  so that gaps are provided between groups of otherwise equally spaced longitudinal wires. The gaps  70  left by the omitted wires are made to be of such dimensions that when a fur indentation  72  is made in the transverse wires by indentation former  74 , the groups of longitudinal wires are drawn towards one another across the gaps so that the spacing between the groups is brought to approximately the regular longitudinal interval spacing of 0.6″. The drawing in of the longitudinal wires is shown at  76  in  FIG. 4A . Each of two transverse feed strands is turned back on itself at the sides of the lath to form adjacent transverse wires at a spacing of about 1.6″. The turning back on themselves at the sides of the lath results in the formation of ears  78  (shown in  FIG. 1  as ears  37 ,  39 ).  
         [0049]     The resulting mesh  68  is then formed as at  74  to provide fur indentations  72  at spaced intervals along the transverse wires  60 , the indentations  72  corresponding in position to the omitted longitudinal wires from gaps  70 .  
         [0050]     A support material  80 , preferably kraft paper, having apertures  82  and  84  corresponding to the pattern of indentations  72  is then applied over the mesh workpiece such that each of apertures  82  and  84  straddles one of the fur indentations  72 .  
         [0051]     A plurality of longitudinal retaining wires  86  are then welded ( 88 ) to the apices of the indentations  72  to sandwich the support material  80  between the principal plane of the mesh and the longitudinal retaining wires  86 .  
         [0052]     Pinch feed rolls  95  draw the mesh along to a shearing station  90  where the mesh is sheared into sheets  92  having approximately the desired dimensions of the lath  10 .  
         [0053]     Glue is then sprayed ( 94 ) by an applicator  96  onto the end webs  98  of the sheets  92  and the sheets are then fed to a folding station  100  where the end webs  98  are folded over and around the terminal longitudinal retaining wires  102  that are at the sides of the sheets. Additional feed pinch rolls  104  deliver the sheets to a stack  106  for transport.  
         [0054]     It should be appreciated that the invention as described herein comprising a number of aspects, each of which might independently be applied. For example, the aspect of the invention involving the folding over of the end webs of the barrier material may be practised on a mesh that does not necessarily include indentations or furring spacers. Similarly, the method of manufacturing involving the formation of a planar mesh, followed by the formation of indentations and the application of longitudinal retaining wires over a barrier layer may be practised without necessarily folding over the end webs of the barrier layer. Further still, providing a mesh wherein the longitudinal wires do not span the apertures may be practised without necessarily including the other aspects of the invention.  
         [0055]     As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.