Abstract:
A self-furring wire lath comprises a mesh of transverse and longitudinal wires welded at their intersections. Stiffening trusses are formed by bent sections in the transverse wires and longitudinal wires attached to the shoulders of the bent sections. A barrier layer material is retained in the lath between the apex of the bent sections and the principal plane of the lath mesh. The barrier layer material has apertures that coincide with the intersections only at the bent sections to enable mesh size reduction without compromising the barrier layer but still allow the fabrication of the lath. The lath provides good embedment in the stucco, reduces cracking and wastage of stucco while remaining easy to work with.

Description:
RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 09/927544 titled Self-stiffened welded wire lath assembly by Abe Sacks et al., 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. Difficulties can be encountered in applying stucco to overhanging surfaces such as soffits (i.e. the area under building eaves) and the undersides of exposed roof areas, such as porticos. In such areas gravity tends to cause the stucco to sag after it has been applied.  
         [0005]     The framing for soffits is typically open where the framing members typically extend transversely across the soffit opening at regular spacings (for example, 16 inches or 24 inches center-to-center). A lath is applied across the opening and attached to the framing members. Stucco is then applied to the lath. The lath supports the stucco and, after the stucco dries, reinforces the stucco. Stucco may be applied in various ways including by hand trowel, or by spraying onto the lath. In either case significant pressures can be imposed on the lath.  
         [0006]     The lath must meet several requirements. First, it must be rigid enough to withstand the stresses of the stucco being applied. If the lath is deflected significantly during installation, then stucco in areas adjacent to the deflected area will be disturbed and will likely fall out. Second, the lath must provide adequate reinforcement so that the stucco coating on the soffit will be able to withstand maximum expected wind pressures. The lath should have features which provide good keying and embedment of the stucco over the entire area of the lath. Third, the lath should be designed in such a way as to assist in making the layer of stucco even in thickness. A stucco layer which is uneven in thickness can be prone to cracking.  
         [0007]     In many applications it is desirable to have a backing membrane integrated with the lath. A backing membrane prevents stucco from blowing through the lath. Such a membrane is especially desirable in applications where stucco will be pumped or sprayed onto the lath.  
         [0008]     Various types of lath have been developed for soffit applications. Specialty expanded metal laths are very widely used. Such laths have been produced by companies such as Alabama Metal Industries Corporation of Birmingham, Ala. under the trade-mark (AMICO.TM). AMICO&#39;s expanded metal lath products currently include: 
        ⅛″ Rib Lath (“Flat Rib”). This lath has eighteen ribs approximately ⅛ inch high, spaced {fraction (11/2)} inches on center to provide rigidity for horizontal applications. The lath has a large number of openings or “keys” which provide keying for either troweled or machine-applied stucco.     ⅜″ Rib Lath (“High Rib”). This lath has seven longitudinal ribs, each ⅜ inch deep and eight small flat ribs to provide additional rigidity for horizontal applications. A herringbone mesh is located between the ribs to provide keys for good bonding of the stucco to the lath. Cal Spray Rib (“⅛ Inch Flat Rib”). This is a more rigid lath which includes strips of kraft paper attached between the ribs. The added rigidity makes this product well suited for horizontal applications, such as soffits. The paper helps reduce the amount of plaster waste and is not intended to be moisture resistant. A version of Cal Spray Rib having ⅜ inch high ribs is also available. Similar products have been available from California Expanded Metals Company (CEMCO.TM.) and others.        
 
         [0011]     Expanded metal lath products such as those described above can provide good rigidity and stiffness for their rated spans. They also provide good keying and hang on surfaces. However, these products have some disadvantages. First, at the locations of the stiffening ribs, the stucco is much thinner than it is at other locations. Furthermore, the ribs present unbroken surfaces which do not provide opportunity for embedment and keying of stucco. This typically results in a series of cracks forming along each of the ribs.  
         [0012]     Another disadvantage of prior expanded metal lath systems is that the keys are typically quite small. Correct installation practice requires the edges of adjacent sheets of lath to be overlapped. However, with small key openings it is difficult to force stucco adequately through the lath in the overlapping portions. This results in a weak zone in which the stucco is likely to crack at each point where sheets of the lath overlap.  
         [0013]     A third difficulty with expanded metal lath is that it is difficult to cut, especially if the ribs are high. When cut, expanded metal lath typically exhibits razor sharp edges. This makes current expanded metal lath products tedious and even dangerous to install.  
         [0014]     Another group of stucco laths sometimes used for soffits are wire fabric laths. Wire fabric laths typically comprise a rectangular mesh of wires which are welded at their intersections. Wire fabric laths have been available, for example, from the Georgetown Wire Company, Inc, of Fontana, Calif. under the trademark K-LATH.TM. Some examples of such laths include:  
         [0015]     Stucco-Rite™ standard. This product is a self-furring sheet of galvanized welded-wire-fabric lath, 16 gauge by 16 gauge, with 2 inch by 2 inch openings. A perforated absorbent carrier kraft paper is incorporated into the mesh, and a Grade D water proofed breather building paper is laminated to the back side of the kraft paper. A heavy duty version features an 11 gauge stiffener wire every 6 inches.  
         [0016]     Standard “Gun Lath”. This is a flat sheet welded wire lath, with 2 inch by 2 inch openings, 16 gauge by 16 gauge with a 13 gauge stiffener wire every  4  inches along length of the sheet. An absorbent, slot perforated kraft paper sheet is incorporated between the face and back wires. A heavy duty version features an 11 gauge stiffener wire every 6 inches on center.  
         [0017]     “Soffit Lath”. This product is similar to Gun Lath with 16 gauge by 16 gauge wires, but with grid spacing at 1.5 inches by 2 inches. The backing kraft paper has smaller perforated openings which are to provide a more positive keying for the soffit stucco.  
         [0018]     Wire fabric laths are more worker friendly than the expanded metal laths in that they are easy to cut, and do not present as many sharp edges when cut. They are also easy to overlap without blinding the openings at the overlap areas. This reduces cracking at overlaps of sheets. Further, there are no stiffening ribs that can cause cracking. Therefore, the overall finished stucco is much better since cracking is minimized.  
         [0019]     However, current paper-backed wire laths have two major disadvantages. First, the relatively large wire grid spacing provides little hang on surface area for the wet stucco to hang onto. The perforated backing kraft papers do prevent blow through, but do not have sufficient keying or suction capability to hang onto the wet stucco.  
         [0020]     A second disadvantage of current wire lath products is that they are not as rigid as is desirable. These laths tend to deflect as the plasterer applies force. After the force is removed the lath springs back. As this happens fresh plaster in adjoining areas can be dislodged and fall out. This exacerbates the stucco fall out problem. Therefore, plasterers must apply stucco to wire lath very carefully. This is a major disadvantage since it slows down speed of application. Even so, there is typically a high wastage of stucco.  
         [0021]     Rigidity can be increased somewhat by using larger diameter wires. However, increase in wire diameter does very little to increase stiffness. If wire diameters are increased enough to provide significant increases in rigidity then the large wires close to the stucco surface tend to cause the stucco to crack along the large wires.  
         [0022]     A third disadvantage of some current paper backed wire laths is that the installed stucco plaster has uneven thickness which may result in additional cracking of the stucco. This problem of cracking is exacerbated because the paper, which is tightly attached to the wire lath itself, prevents the stucco from totally surrounding the wires of the lath. As a result the attachment of the stucco to the lath is weaker than would be desired and the stucco can separate from the lath under certain loading conditions.  
         [0023]     Jaenson, U.S. Pat. No. 5,540,023 discloses an improved wire lath in which a layer of backing paper is held in place between two courses of horizontal wires. The backing paper is not tightly attached to the lath and allows good keying. However, this wire lath requires that the welds of the lath be made through perforated holes in the backing paper. The backing paper must have a hole at each intersection between two wires. As can be seen in  FIG. 1  (prior art), the perforations exist in the backing paper along each longitudinal wire and have significant size. These holes are a disadvantage for producing laths with smaller grid spacings, since the amount of hole area required to accommodate welding becomes very large, leaving less and less paper area. This is a major disadvantage for soffit applications since increasing the hole area results in increased blow-through. Further the kraft paper could easily tear between holes resulting in even more blow-through.  
         [0024]     Japanese patent application No. 06047691 published on Sep. 9, 1995 (JP 07233611A2) discloses a multi-layer spray wall core body having a porous sheet between sheets of erected reinforcements. Japanese patent application No. 09347789 published on Jul. 6, 1999 (JP11181989A2) discloses another paper-backed wire lath.  
         [0025]     Despite the wide variety of lathing systems that are currently available there remains a need for a lath which avoids the disadvantages discussed above.  
       SUMMARY OF THE INVENTION  
       [0026]     This invention provides a wire lath that can be made to be more rigid than current wire lath products, provides good keying, minimizes blow through, provides good embedment, and overcomes a number of disadvantages of expanded metal laths.  
         [0027]     Accordingly, in a preferred embodiment of the invention a welded wire lath comprising a plurality of generally parallel transverse wires lies substantially in a first plane. The transverse wires each depart from the first plane in a plurality of spaced-apart bent sections. Each bent section is defined between first and second shoulder portions. While the bent sections can have various shapes, a V-shape is preferred. The bent sections preferably have a height comparable to the width of the V-shape. The lath also comprises a plurality of generally parallel first longitudinal wires. The first longitudinal wires lie substantially in the first plane. They intersect with and are attached, preferably by welding, to the transverse wires. The first longitudinal wires include, for each of the plurality of bent sections, a longitudinal wire attached to each of the transverse wires in at least one of the shoulder portions corresponding to the bent section.  
         [0028]     The lath also comprises a plurality of generally parallel second longitudinal wires. The second longitudinal wires lie generally in a second plane parallel to and spaced apart from the first plane. The second longitudinal wires are attached to the transverse wires in approximately the middle of the bent sections. The second longitudinal wires in conjunction with the bent sections and those first longitudinal wires which are attached at the shoulders of the bent sections form trusses which provide rigidity to the wire lath. The trusses may also serve as furring spacers although separate furring spacers may be provided.  
         [0029]     In preferred embodiments of the invention the first longitudinal wires include, for each of the plurality of bent sections, a pair of longitudinal wires. One of the pair of longitudinal wires is attached to each of the transverse wires in a first one of the shoulder portions. The other one of the pair of longitudinal wires is attached to each of the transverse wires in the second one of the shoulder portions.  
         [0030]     While all longitudinal wires could be attached to all transverse wires to maximize the strength of the lath, several variations in the attachment locations are possible. In the first variation explained above, all longitudinal wires are attached to the transverse wires at each bent sections: two first longitudinal wires at the shoulders and one second longitudinal wires at the middle of the bent section. As a second variation, it is possible to include in the lath assembly, tertiary longitudinal wires located in the first plane and attached to the transverse wires at locations away from the bent sections and between the shoulder regions of adjacently located bent sections. As a third variation, it is possible to include some bent sections in the transverse wires at which, or near which, no longitudinal wires are attached. Yet another variation uses the bent sections as furring spacers. Other alternatives are possible that combine these four variations.  
         [0031]     The wire lath may incorporate a barrier layer disposed between the first and second planes. In the preferred embodiment apertures perforate the layer and the bent sections pass through the apertures. The barrier layer may comprise a suitable building paper, such as kraft paper, which may be surface treated to improve the adhesion of stucco. The barrier layer may have additional perforations, in the form of small apertures or slits, which do not coincide with intersections of the longitudinal wires and transverse wires. The additional perforations serve as “keys” for stucco.  
         [0032]     A backing layer, such as a layer of asphalt-coated paper may be adhesively affixed to the barrier layer. In this case the second longitudinal wires may extend between the backing layer and the barrier layer.  
         [0033]     The wires of a wire lath according to the invention do not need to be round. In some embodiments at least some of the first longitudinal wires are non-round in cross section. The non-round longitudinal wires may advantageously be flattened and oriented to lie generally in the first plane. This provides increased surface area for stucco adhesion, and also can facilitate the application of stucco.  
         [0034]     Further features, aspects and advantages of the present invention will be more fully understood when considered with respect to the following detailed description, appended claims, and accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]     In drawings which illustrate non-limiting embodiments of the invention:  
         [0036]      FIG. 1  is a schematic perspective view of the Jaenson prior art wire lath and backing paper showing large perforations overlaying all intersections of the wire lath.  
         [0037]      FIG. 2  is a perspective view of a welded wire mesh lath in accordance with the invention;  
         [0038]      FIG. 3  is a cross-sectional view of the welded wire mesh lath of  FIG. 2 ;  
         [0039]      FIG. 4  is a cross-sectional view of a welded wire mesh according to an alternative embodiment of the invention;  
         [0040]      FIG. 5  is a perspective view of a welded wire mesh lath according to the invention which incorporates a barrier layer;  
         [0041]      FIG. 6  is a cross-sectional view of the welded wire mesh lath and barrier layer taken along line  6 - 6  of  FIG. 5 ;  
         [0042]      FIG. 7  is a cross-sectional view of a welded wire mesh lath according to the invention incorporating a barrier layer and a backing layer adhesively attached thereto;  
         [0043]      FIG. 8  is a cross-sectional view of a welded wire mesh lath according to the invention incorporating flattened longitudinal wires, mounted on a horizontal wooden member; and,  
         [0044]      FIG. 9  is a cross-sectional view of stucco being applied to a welded wire mesh lath comprising concave longitudinal wires.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without some of these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.  
         [0046]     Referring to  FIG. 2  and  FIG. 3 , lath  10  according to a currently preferred embodiment of the invention comprises a plurality of first generally parallel longitudinal wires  12  which intersect with a plurality of generally parallel transverse wires  14 .  
         [0047]     Wires  12  lie substantially in a first plane PI (best appreciated by reference to  FIG. 3 ). Similarly, wires  14  lie substantially in plane PI, save that wires  14  are bent out of plane P 1  at truss locations  15 .  
         [0048]     Wires  12  and  14  are welded together at their intersections  11 . Wires  12  and  14  preferably extend generally perpendicularly to one another. The spacing of wires  12  and  14  can be such that square or rectangular grid openings are created. A set of second longitudinal wires  13  is also welded to transverse wires  14  as described below. Wires  12 ,  13  and  14  may be made of any suitable materials, such as steel, aluminum, or the like. If made of steel, the wires are preferably galvanized. Wires  12 ,  13  and  14  are preferably of the same or similar diameters. Preferably wires  12 ,  13  and  14  have cross sectional areas which differ from one another by 25% or less.  
         [0049]     Longitudinally extending trusses  15  are formed at spaced locations across lath  10 . Transverse wires  14  have bent sections  20  at the location of each truss  15 . In each bent section  20  the transverse wire  14  bends out of plane P 1  at a first shoulder  16 , extends outwardly at least to plane P 2  and then bends back toward plane P 1  to the point where it rejoins plane PI at a second shoulder  17 . Certain ones of longitudinal wires  12  (indicated by the reference  12 A) are affixed in a shoulder portion at each of shoulders  16  and  17 . Preferably transverse wires  14  bend sharply away from plane PI at each shoulder  16 ,  17  with a bend radius of no more than a few diameters of the transverse wires  14 . Preferably the radii of the bends at shoulders  16  and  17  are less than 5 diameters of transverse wire  14  and most preferably less than 2 diameters of transverse wire  14 . In each truss  15 , a longitudinal wire  13  of a plurality of second longitudinal wires is affixed to transverse wires  14  on bent sections  20 . Bent sections  20  are preferably generally V-shaped, as shown in  FIG. 2  and  FIG. 3 . In preferred embodiments of the invention each transverse wire  14 , including bent sections  20 , lies in a plane which is generally perpendicular to plane P 1 .  
         [0050]     Longitudinal wires  12 A are preferably attached to each transverse wire  14  at a point which is as close as practical to a point at which the transverse wire  14  bends out of plane P 1 . Longitudinal wires  12 A should be attached to transverse wires  14  at points which are spaced away from the points at which transverse wires  14  begin to bend out of plane P 1  by no more than about 5-8 times the diameters of transverse wires  14  (and preferably no more than 1-2 times the diameters of transverse wires  14 ). The term “shoulder region” includes those points which are close to shoulders  16  and  17  (i.e. are spaced away from the points at which transverse wires  14  leave plane PI by no more than about  8  times the diameter of transverse wires  14 ).  
         [0051]     It can be seen that lath  10  includes longitudinal wires in two groups. A first plurality of generally parallel longitudinal wires  12  (which includes wires  12 A and others of wires  12  which are not affixed at bent sections  20 ) lies generally in a first plane P 1  ( FIG. 3 ). A second plurality of generally parallel longitudinal wires  13  are affixed to transverse wires  14  on bent sections  20  and lie generally in a plane P 2  which is spaced apart from plane P 1  by a distance h. Preferably bent sections  20  of transverse wires  14  bend back toward plane P 1  at a distance of approximately h from plane P 1  (so that second longitudinal wires  13  are located at the “peaks” of bent sections  13 ). However, this is not essential. Bent sections  20  could extend away from plane P 1  to locations past plane P 2  before bending back toward plane P 1 .  
         [0052]     The depth h of the truss  15  is preferably equal to the distance w between the two longitudinal wires  12 A on either side of the truss, but may be have a dimension up to twice w in some applications. For example, if a truss  15  has a depth of ⅜ inches then the longitudinal wires  12 A along its shoulders can be spaced apart from ⅜ inch to ¾ inch. In a preferred embodiment of the invention, the wires  12  in plane P 1  are spaced apart by generally equal distances x (see  FIG. 3 ) whereas wires  13  are spaced apart from adjacent wires  12 A by a smaller distance y. Preferably y is roughly ½ of x. In another embodiment of the invention x and y are equal. Each truss  15  has at least one longitudinal wire  13  which is displaced out of the plane of the other longitudinal wires  12 . Longitudinal wires  12 A extend along at least one of the shoulders of truss  15 . Preferably each truss  15  includes a pair of longitudinal wires  12 A, one attached to transverse wires  14  in the shoulder region on one side of the truss and the other attached to the transverse wires  14  in the shoulder region on the other side of the truss.  
         [0053]     It can be seen that trusses  15  enhance the rigidity of lath  10  in the longitudinal direction. Trusses  15  also make lath  10  self-furring. The number and depth of trusses  15  and the thickness of wires  12 ,  13  and  14  may be selected to achieve a desired strength. Preferably:  
         [0054]     The spacing x between longitudinal wires  12  is in the range of about ½ inch to 2 inches;  
         [0055]     The spacing between adjacent transverse wires  14  is in the range of about 1 inch to 2 inches;  
         [0056]     The spacing between trusses  15  is in the range of about 1-{fraction (12)} inches to 6 inches.  
         [heading-0057]     For soffit lath applications, preferably:  
         [0058]     The spacing x between longitudinal wires  12  is in the range of about 0.5 to 0.6 inches;  
         [0059]     The spacing between adjacent transverse wires  14  is about 1-½ inches; and,  
         [0060]     The spacing between trusses  15  is about 2 inches.  
         [heading-0061]     In an example embodiment, lath  10  has:  
         [0062]     nominal spacing of about 0.6 inch between adjacent longitudinal wires  12 ;  
         [0063]     nominal spacing of about 1-½ inches between adjacent transverse wires  14 ;  
         [0064]     wires  12 ,  13  and  14  formed from 17 gauge (0.051″) diameter wire;  
         [0065]     trusses  15  having a depth (i.e. the dimension h) of about ⅜ inch; and,  
         [0066]     trusses  15  spaced apart from one another by about 2 inches.  
         [0067]     Lath  10  may be applied over framing members, which are typically 16 inches or 24 inches on center. Lath  10  can be attached to the framing members at the bottom of trusses  15 . 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 2 inch spacing of the corrugating ribs allows appropriate attachment points. Lath  10  is preferably applied in an orientation such that the side of lath  10  bearing second longitudinal wires  13  faces the framing members, each of the second longitudinal wires crosses a plurality of the framing members, and first longitudinal wires  12  are spaced apart from faces of the framing members by the distance h. The portions of lath  10  between the framing members can be substantially unsupported.  
         [0068]     A wire lath  10  can be produced in any desired dimensions but is preferably provided in sheets of widths of sizes that can be easily handled. For example, the sheets may have a width in the range of 2 feet to 5 feet. It can be appreciated that sheets of wire lath  10  can be compactly stacked together with the trusses  15  of one sheet being received within the trusses  15  of the next sheet of wire lath  10  in the stack.  
         [0069]     A wire lath  10  may be made by making a sheet of welded wire mesh and then bending transverse wires  14  at predetermined locations to form bent sections  20  such that trusses  15  are formed. Where each truss  15  is formed, a longitudinal wire  13  is displaced out of the plane of the longitudinal wires  12 .  
         [0070]     It can be appreciated that the provision of trusses  15  can make a lath according to this invention significantly more rigid than prior wire laths. This can be achieved without using jumbo-sized wires which can tend to cause cracking. Further, since trusses  15  are open, stucco is continuous at trusses  15 . This is a major advantage over prior ribbed expanded metal laths in which the ribs cannot be fully embedded in stucco.  
         [0071]     The wire lath of  FIG. 2  and  FIG. 3  may be varied in various ways within the scope of the invention. By way of example only, bent sections  20  may have shapes other than V-shaped. For example, bent sections  20  may be U-shaped, trapezoidal, square, generally rectangular, semi-circular, or the like. It is preferable that the sections  14 A of transverse wires  14  which extend between each wire  13  and an adjacent wire  12 A extend steeply to plane P 1 . Preferably angle υ is 45 degrees or less. Most preferably angle υ is 30 degrees or less. While it is not as structurally sound, a longitudinal wire  12 A could be provided along only one shoulder of each truss  15  instead of along both shoulders, as shown.  
         [0072]     More than one longitudinal wire  13  may be provided on each truss  15 . If two closely-spaced longitudinal wires  13  are provided on each truss  15  then lath  10  may be fastened to a building structure with fasteners such as nails or screws inserted between the two longitudinal wires  13 .  
         [0073]     In the embodiment of  FIG. 3 , longitudinal wires  13  are on the opposite side of transverse wires  14  from the first longitudinal wires  12 . Conversely as shown in  FIG. 4 , longitudinal wires  13  could also be located on the same side of transverse wires  14  as first longitudinal wires  12 . Similarly, all of longitudinal wires  12  and  13  could be on the same side of transverse wires  14  as bent sections  20 .  
         [0074]     A wire lath according to the invention can include a barrier layer  22 , such as a layer of kraft paper, disposed between planes P 1  and P 2 .  FIG. 5  and  FIG. 6  show a wire lath  10 A which includes a barrier layer  22 . Apart from the incorporation of layer  22 , lath  10 A is the same as lath  10 . Layer  22  has apertures  24 . Bent sections  20  pass through apertures  24 . Longitudinal wires  13  are on one side of layer  22  and longitudinal wires  12  are on the other side of layer  22 . Barrier layer  22  may comprise a layer of paper. The paper is preferably absorbent and may have a surface treatment such as sanding or microperforation to enhance its adhesion to stucco.  
         [0075]     It can be seen that layer  22  does not prevent stucco from fully embedding longitudinal wires  12  or transverse wires  14  due to the furring provided by the bent sections. The furring creates a space between plane P 1  and plane P 2  so that stucco can embed wires  12  by forcing layer  22  against longitudinal wires  13  as the stucco is applied. It can further be seen that layer  22  requires relatively few apertures  24 . Layer  22  provides protection against blow-through of stucco. Apertures  24  may be elongated. If so, then preferably apertures  24  would be oriented to be generally parallel to transverse wires  14 .  
         [0076]     Wire lath  10 A may be fabricated by first welding the plurality of first longitudinal wires  12  to transverse wires  14 , applying layer  22  and subsequently welding longitudinal wires  13  to bent sections  20  of transverse wires  14 . Bent sections  20  may be formed while applying layer  22  and welding longitudinal wires  13  to transverse wires  14 . Forming bent sections  20  reduces the width of the sheet of lath  10 A. By orienting the apertures  24  parallel to transverse wires  14 , the wires of lath  10 A can slide sideways without crumpling layer  22 . The amount of width reduction will be zero in the center of lath  10 A and will increase progressively towards the two outer edges. This can be accommodated by making apertures  24  in the form of elongated slots having lengths which are greater for trusses  15  located toward the outer edges of lath  10 A.  
         [0077]     If bent sections  20  could be fully formed before applying layer  22  then apertures  24  would not need to be elongated and could be, for example, round. This would serve to limit the overall size of the apertures and provide greater control over the keying of the stucco through the apertures. Accordingly, the preferred method of fabricating the lath according to the invention involves first producing a welded lath mesh that is substantially flat. The resulting lath is then processed through a continuous roll forming machine so as to provide spaced bends in the transverse wires  14  corresponding to shoulder wires  12 A. The bends extend portions of transverse wires  14  out of, and then back into, the principal plane of the lath P 1 .  
         [0078]     A sheet of a suitable barrier paper is provided in which a limited number of apertures are pre-cut in the paper to correspond only to the bent areas of transverse wires  14 . The lath and paper are then presented in overlapping relationship to a welding machine such that the pre-cut apertures in the paper overlap the bent sections of transverse wires  14 . Backing wires  13  are then welded to transverse wires  14  through the apertures to retain the paper onto the lath.  
         [0079]     It will be appreciated that whereas the first mentioned approach above requires apertures in the form of slots to avoid crumpling of the backing paper during the furring process, the preferred approach avoids the need for elongated apertures. Each approach however, avoids the need for an aperture at each wire intersection, such as is found in the prior art paper web welded lath structure exemplified by Jaenson U.S. Pat. No. 5,540,023. The preferred approach requires apertures only at the intersections of the transverse wires  14  and the backing wires  13 . A reduction in the mesh size of the Jaenson lath results in the apertures of each intersection being closer together and ultimately running into each other. This reduces the effectiveness of the barrier layer in limiting the amount of stucco flow-through. It also weakens the barrier layer and makes it more prone to tearing, particularly when subjected to the pressure of stucco being applied. The preferred embodiment of the present invention avoids such disadvantage by providing fewer apertures.  
         [0080]     In addition, the Jaenson design represented an improvement over the previous prior art in that two out of three longitudinal wires were fully exposed to the stucco. However, every third longitudinal strand of Jaenson is on the back side of the backing paper. According to the present invention, all of the longitudinal wires  12  are on the outer (stucco) side of the backing layer. This enhances the ability of the lath to provide to fully embed in the stucco as compared to Jaenson.  
         [0081]     Layer  22  may optionally include a series of additional perforations  25 . Perforations  25  provide further keying and assist in holding wet stucco to layer  22 . Perforations  25  may be extremely small, from micrometer to sub-millimeter size, or they could have larger dimensions up to the mesh grid size. When stucco is being applied, some of the stucco can force its way through perforations  25 . The perforations  25  trap some stucco, which will tend to mushroom out on the rear side of layer  22  (i.e. the side of layer  22  toward longitudinal wires  13 ). The blob of stucco on the rear side of layer  22  locks around the edge of perforation  25  thereby promoting adhesion of the wet stucco to lath  10 A. In one embodiment of the invention, perforations  25  comprise slits formed by cutting layer  22  without removing any material. Perforations  25  could be X-shaped, as shown, H-shaped, semi-circular, or some other shape. Perforations  25  could also comprise holes of various shapes in layer  22 . For example, the holes could be round, oval, elongated or other shapes.  
         [0082]     As shown in  FIG. 7 , a wire lath  10 B according to another embodiment of the invention has a backing layer  30  of building paper or the like may be applied behind longitudinal wires  13 . Layer  30  may be affixed to layer  22  with a suitable adhesive. Layer  30  may comprise, for example, an asphalt-saturated-type building paper or one of the various building wraps. Where a backing layer  30  is provided then perforations  25  in layer  22  are not advantageous.  FIG. 8  shows a wire lath  10 C according to another embodiment of the invention. Lath  10 C differs from laths  10 A and  10 B in that longitudinal wires  12  are replaced with shaped wires  12 ′. Shaped wires  12 ′ have shaped cross sections instead of circular cross-sections. Wires  12 ′ may be, for example, flattened, oval, square, half-round, concave or other non-round formed shapes. Lath  10 C has the advantage that the surface areas of wires  12 ′ is increased. This provides enhanced grip when stucco is applied. A further advantage of this embodiment is that the process of shaping longitudinal wires  12 ′ can work-harden wires  12 ′. This can increase their strength. Thus, a lath using shaped wires  12 ′ may use smaller wire sizes to obtain similar strengths. This, in turn, makes such a lath easier to cut to size, lighter and potentially less costly in materials. The lath of  FIG. 8  is shown attached to a transversely-extending stud  36  by way of a nail  38  which captures longitudinal wire  13  against stud  36 .  
         [0083]     Another advantages of using flattened shaped wires  12 ′ is that appropriately shaped wires can help to direct stucco into lath  10 C as it is troweled into place.  FIG. 9  illustrates an embodiment of the invention wherein shaped wires  12 ′ are flattened and have their edges curved slightly downwardly. As stucco  40  is troweled across lath  10 C using trowel  45 , in the direction indicated by arrow  42  shaped wires  12 ′ cut through the flowing stucco and tend to cause part of the stucco to flow upwardly, as indicated by arrows  44 .  
         [0084]     In the laths described above, trusses  15  play the dual role of providing rigidity and serving as furring spacers. It would be possible to add other furring spacers to transverse wires  14  at locations away from trusses  15 . The furring spacers may comprise, for example, additional bent sections in transverse wires  14 . Where the lath comprises a backing layer  22  the furring spacers pass through apertures in backing layer  22  in substantially the same manner that bent sections  22  pass through apertures  24 . The separate furring spacers provide points for attachment of a lath according to the invention to a building structure and are located away from trusses  15 . The use of separate furring spacers thus reduces the risk that trusses  15  may be damaged while a lath is being installed. The furring spacers may be formed, for example, by creating bent sections in transverse wires  14  such that selected ones of longitudinal wires  12  is displaced into or behind plane P 2 . The lath may then be installed, by attaching the furring spacers to a stud, for example, by nailing, stapling or screwing.  
         [0085]     This invention also includes a building structure comprised of parallel transverse framing members to which the lath constructed as described above, is attached such that the second longitudinal wires of the lath are crossing, and are adjacent to, the parallel transverse framing members, and the first longitudinal wires are spaced apart from the framing members. The framing members could be spaced apart by more than  1 2 inches leaving the wire lath substantially unsupported in its portions between the framing members. Such building structure could be located on an underside of a part of a building.  
         [0086]     The building structure could also comprise stucco such that a layer of solidified stucco encases the first longitudinal wires and at least substantially filling a space between the barrier layer and the first longitudinal wires. If perforations are made through the barrier layer, the stucco would flow through these perforation when it is still wet and would therefore extend beyond the barrier layer.  
         [0087]     The first longitudinal wires can be flattened and oriented with their wide dimension substantially parallel to the framing members.  
         [0088]     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. For example, a lath according to the invention could include additional longitudinal or transverse wires. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.