Welded Wire Mesh: Types, Uses, Features and Benefits

USA1 - Self-stiffened welded wire lath assembly

RELATED APPLICATION

• This application is a continuation-in-part of U.S. patent application Ser. No. 09/ titled Self-stiffened welded wire lath assembly by Abe Sacks et al., filed on Aug. 13, .

FIELD OF THE INVENTION

• 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

• 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.

• 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.

• 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.

• 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.

• 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.

• 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's expanded metal lath products currently include:

• • &#;&#; Rib Lath (&#;Flat Rib&#;). This lath has eighteen ribs approximately &#; 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.
  • &#;&#; Rib Lath (&#;High Rib&#;). This lath has seven longitudinal ribs, each &#; 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 (&#;&#; 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 &#; inch high ribs is also available. Similar products have been available from California Expanded Metals Company (CEMCO.TM.) and others.

• 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.

• 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.

• 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.

• 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:

• 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.

• 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.

• &#;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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• Japanese patent application No. published on Sep. 9, (JP A2) discloses a multi-layer spray wall core body having a porous sheet between sheets of erected reinforcements. Japanese patent application No. published on Jul. 6, (JPA2) discloses another paper-backed wire lath.

• 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

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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

• In drawings which illustrate non-limiting embodiments of the invention:

• 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.

• FIG. 2 is a perspective view of a welded wire mesh lath in accordance with the invention;

• FIG. 3 is a cross-sectional view of the welded wire mesh lath of FIG. 2;

• FIG. 4 is a cross-sectional view of a welded wire mesh according to an alternative embodiment of the invention;

• FIG. 5 is a perspective view of a welded wire mesh lath according to the invention which incorporates a barrier layer;

• FIG. 6 is a cross-sectional view of the welded wire mesh lath and barrier layer taken along line 6-6 of FIG. 5;

• 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;

• 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,

• 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

• 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.

• 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.

• 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 P1 at truss locations 15.

• 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.

• 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 P1 at a first shoulder 16, extends outwardly at least to plane P2 and then bends back toward plane P1 to the point where it rejoins plane PI at a second shoulder 17. Certain ones of longitudinal wires 12 (indicated by the reference 12A) 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 P1.

• Longitudinal wires 12A 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 P1. Longitudinal wires 12A 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 P1 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).

• 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 12A and others of wires 12 which are not affixed at bent sections 20) lies generally in a first plane P1 (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 P2 which is spaced apart from plane P1 by a distance h. Preferably bent sections 20 of transverse wires 14 bend back toward plane P1 at a distance of approximately h from plane P1 (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 P1 to locations past plane P2 before bending back toward plane P1.

• The depth h of the truss 15 is preferably equal to the distance w between the two longitudinal wires 12A 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 &#; inches then the longitudinal wires 12A along its shoulders can be spaced apart from &#; inch to ¾ inch. In a preferred embodiment of the invention, the wires 12 in plane P1 are spaced apart by generally equal distances x (see FIG. 3) whereas wires 13 are spaced apart from adjacent wires 12A 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 12A extend along at least one of the shoulders of truss 15. Preferably each truss 15 includes a pair of longitudinal wires 12A, 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.

• 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:

• The spacing x between longitudinal wires 12 is in the range of about ½ inch to 2 inches;

• The spacing between adjacent transverse wires 14 is in the range of about 1 inch to 2 inches;

• The spacing between trusses 15 is in the range of about 1-{fraction (12)} inches to 6 inches.

• For soffit lath applications, preferably:

• The spacing x between longitudinal wires 12 is in the range of about 0.5 to 0.6 inches;

• The spacing between adjacent transverse wires 14 is about 1-½ inches; and,

• The spacing between trusses 15 is about 2 inches.

• In an example embodiment, lath 10 has:

• nominal spacing of about 0.6 inch between adjacent longitudinal wires 12;

• nominal spacing of about 1-½ inches between adjacent transverse wires 14;

• wires 12, 13 and 14 formed from 17 gauge (0.051&#;) diameter wire;

• trusses 15 having a depth (i.e. the dimension h) of about &#; inch; and,

• trusses 15 spaced apart from one another by about 2 inches.

• 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.

• 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.

• 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.

• 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.

• 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 14A of transverse wires 14 which extend between each wire 13 and an adjacent wire 12A extend steeply to plane P1. 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 12A could be provided along only one shoulder of each truss 15 instead of along both shoulders, as shown.

• 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.

• 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.

• A wire lath according to the invention can include a barrier layer 22, such as a layer of kraft paper, disposed between planes P1 and P2. FIG. 5 and FIG. 6 show a wire lath 10A which includes a barrier layer 22. Apart from the incorporation of layer 22, lath 10A 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.

• 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 P1 and plane P2 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.

• Wire lath 10A 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 10A. By orienting the apertures 24 parallel to transverse wires 14, the wires of lath 10A can slide sideways without crumpling layer 22. The amount of width reduction will be zero in the center of lath 10A 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 10A.

• 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 12A. The bends extend portions of transverse wires 14 out of, and then back into, the principal plane of the lath P1.

• 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.

• 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.

• 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.

• 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 10A. 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.

• As shown in FIG. 7, a wire lath 10B 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 10C according to another embodiment of the invention. Lath 10C differs from laths 10A and 10B 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 10C 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.

• Another advantages of using flattened shaped wires 12&#; is that appropriately shaped wires can help to direct stucco into lath 10C 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.

• 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 P2. The lath may then be installed, by attaching the furring spacers to a stud, for example, by nailing, stapling or screwing.

• 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 12 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.

• 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.

• The first longitudinal wires can be flattened and oriented with their wide dimension substantially parallel to the framing members.

• 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.