Self-stiffened welded wire lath assembly

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....

AI Technical Summary

Benefits of technology

[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.

[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.

Problems solved by technology

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.

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.

A stucco layer which is uneven in thickness can be prone to cracking.

The paper helps reduce the amount of plaster waste and is not intended to be moisture resistant.

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.

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.

This makes current expanded metal lath products tedious and even dangerous to install.

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.

This exacerbates the stucco fall out problem.

This is a major disadvantage since it slows down speed of application.

Even so, there is typically a high wastage of stucco.

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.

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.

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