On tilt-up wall surfaces, expandable metal lath may be fastened to the surface to reinforce the stucco adhesion providing a mechanical bond. The rigidity of the lath helps to maintain some of the structural integrity of the stucco cladding keeping the shape while the stucco is applied.Įxpanded metal lath also acts to reinforce smooth or worn surfaces or to provide a “bondable” surface for other products. In the Southwest where parapets are a part of the architectural design, metal lath is bent to form the desired shape and then fastened to the parapet area. It is also used to reinforce parapet locations.
This is a time proven cost saving procedure commonly used when a large amount of shapes are on a given elevation or building. Metal lath holds a bent shape and some contractors have taken to pre-bending metal lath to a given configuration and in large quantities, and then simply fasten them over the architectural shapes, rather than forming them in situ. Metal lath can be formed over foam (not wood) features or architectural embellishments we know as pop-outs. The edges of each sheet must overlap the adjacent sheet per ASTM C1063.īecause expanded metal lath is bendable, it can be used for other features and purposes.
#Metal lath code
In this assembly the WRB is placed over the code approved sheathing material and the metal lath is fastened over that to each stud member. Over a sheathed exterior wall assembly, a self-furring metal lath may be used. The wire fills the void between studs and acts to keep the WRB and metal lath in plane during application of the stucco. This is a time proven process where wire is strung horizontally along a wall and fastened to the studs. When metal lath is used over open framing the WRB may be given extra support between studs by line wire. The building codes do require a WRB on all exterior wall assemblies. A minimum 3.4 pounds-per-square-foot lath should be used and it can be directly fastened to the framing members, a cross furring member, or tied to a suspended metal furring channel assembly.įor the wall assembly, expanded metal lath can be applied over open framing or a sheathed substrate surface. The use of this lath on soffits and ceilings does not require a water resistive barrier, nor should it be applied to sheathing. Non-furring expanded metal lath may be used for soffits or ceilings, over open frame.
Expanded metal lath may be manufactured with a paper backing as well. Self-furring diamond mesh then has a 5/16 nominal thickness requirement. A self-furring version can be made by running the expanded sheet through another machine which adds dimples to keep the metal lath away from the substrate surface.
#Metal lath series
The sheet is then run through a series of cutters that stamp slits through the metal, and then the whole sheet is expanded, forming a diamond shape void. It is formed by first manufacturing a sheet of G60 coated metal approximately 12 inches wide (ASTM A653). C847 requires a nominal thickness of 1/8-inch, a minimum width of 27 inches, a minimum length of 97 inches, and weights of 2.5 or 3.4 pounds-per-square-yard. It is manufactured according to ASTM C847 standards.
This lath is probably one of the most recognized forms of modern lath. This month’s article will explore the various forms of lath used on the exterior walls and ceilings. To some of us believers, the lath also acts as a sort of spandex for the building, keeping the framework from bulging and twisting all the while maintaining its sleek architectural form.Īs with any construction product, technology ever moving forward has born new forms of this lath product utilizing new materials like spring steel and glass fibers, and through the years has been specially manufactured to perform in a variety of orientations. Yes it primarily holds the weight of the stucco cladding, maintaining the vertical plane, fighting gravity, but lath also works to gauge the thickness of the stucco. Some are welded into an engineered web, others stamped and expanded to create hexagonal shapes and yet others woven into octagonal nets, all designed to carry the weight of the cement cladding, stucco. Our modern forms of exterior lath are an intricate, sometimes artful, form of various configurations of metal. This stick and reeds was the first form of what we use today in our plaster environment, that binding framework known as lath. But there is historical evidence that early man, using mud as a form of plaster, applied it to a framework of sticks and interwoven reeds. Plaster has been applied for many centuries and in the earliest of times, was applied to a solid surface like a pyramid wall.