When did they start using metal lath?

Finish mainly for interior dividing walls and ceilings

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Lath and plaster is a building process used to finish mainly interior dividing walls and ceilings. It consists of narrow strips of wood (laths) which are nailed horizontally across the wall studs or ceiling joists and then coated in plaster. The technique derives from an earlier, more primitive process called wattle and daub.[1]

Lath and plaster largely fell out of favour in the U.K. after the introduction of plasterboard in the s.[2] In Canada and the United States, wood lath and plaster remained in use until the process was replaced by transitional methods followed by drywall (the North American term for plasterboard) in the mid-twentieth century.[citation needed]

Description

The wall or ceiling finishing process begins with wood or metal laths. These are narrow strips of wood, extruded metal, or split boards, nailed horizontally across the wall studs or ceiling joists. Each wall frame is covered in lath, tacked at the studs. Wood lath is typically about one inch (2.5 cm) wide by four feet (1.2 m) long by 1&#;4 inch (6 mm) thick. Each horizontal course of lath is spaced about 3&#;8 inch (9.5 mm) away from its neighboring courses. Metal lath is available in 27-inch (69 cm) by 8-foot (240 cm) sheets.

In Canada and the United States the laths were generally sawn, but in the United Kingdom and its colonies, riven or split hardwood laths of random lengths and sizes were often used. Early American examples featured split beam construction, as did examples put up in rural areas of the U.S. and Canada well into the second half of the 19th century. Splitting the timber along its grain greatly improved the laths' strength and durability. As Americans and Canadians expanded west, saw mills were not always available to create neatly planed boards and the first crop of buildings in any new western or northern settlement would be put up with split beam lath. In some areas of the U.K. reed mat was also used as a lath.

Temporary lath guides are then placed vertically to the wall, usually at the studs. Lime or gypsum plaster is then applied, typically using a wooden board as the application tool. The applier drags the board upward over the wall, forcing the plaster into the gaps between the lath and leaving a layer on the front the depth of the temporary guides, typically about 1&#;4 inch (6.4 mm). A helper feeds new plaster onto the board, as the plaster is applied in quantity. When the wall is fully covered, the vertical lath "guides" are removed, and their "slots" are filled in, leaving a fairly uniform undercoat.

In three coat plastering it is standard to apply a second layer in the same fashion, leaving about 1&#;2 inch (13 mm) of rough, sandy plaster (called a brown coat or browning (UK)). A smooth, white finish coat goes on last. After the plaster is completely dry, the walls are ready to be painted. In this article's photo ("lath seen from the back...") the curls of plaster are called keys and are necessary to keep the plaster on the lath. Traditional lime based mortar/plaster often incorporates horsehair which reinforces the plasterwork, thereby helping to prevent the keys from breaking away.

Historical transition

In addition to wood lath, various types of metal lath began to be used toward the end of the 19th century.[3] Metal lath is categorized according to weight, type of ribbing, and whether the lath is galvanized or not. Metal lathing was spaced across a 13.5-inch (340 mm) center, attached by tie wires using lathers' nippers. Sometimes, the mesh was dimpled to be self-furring.

In use as early as , rock lath (also known as "button board," "plaster board" or "gypsum-board lath"), is a type of gypsum wall board (essentially an early form of drywall) with holes spaced regularly to provide a 'key' for wet plaster.[3] Rock lath was typically produced in sheets sized 2 by 4 feet (610 by 1,220 mm). The purpose of the four-foot length is so that the sheet of lath exactly spans three interstud voids (overlapping half a stud at each end of a four-stud sequence in standard construction), the studs themselves being spaced 16 inches (410 mm) apart on center (United States building code standard measurements). By the late s, rock lath was the primary method used in residential plastering.[3]

Lath and plaster methods have mostly been replaced with modern drywall or plasterboard, which is faster and less expensive to install. Drywall possesses poor sound dampening qualities and can be easily damaged by moisture. Traditional lime based plasters are resistant to moisture and provide excellent sound isolation.

Advantages

One continued advantage of using traditional lath is for ornamental or unusual shapes. For instance, building a rounded wall would be difficult if drywall were used exclusively, as drywall is not flexible enough to allow tight radii. Wire mesh, often used for exterior stucco, is also found in combination or replacement of lath and plaster which serves similar purpose.

Traditional lath and plaster (including rock and metal lath varieties) has superior sound-proofing qualities when used with lime or gypsum plaster, which is denser than modern drywall.[2]

In many historic buildings lath and plaster ceilings play a major role for the prevention of fire spread. They are critical to the protection of horizontal elements such as timber joisted floors, including the flooring on top, which in terms of fire performance is often in a poor condition due to the presence of gaps.[4]

See also

References

• Plaster Base Installation, Building Construction & Finishing
• Preservation Brief No. 21 by the National Park Service. Contains detailed descriptions of Lath & Plaster construction and advisories on repairing and restoring these walls (especially in historic buildings).

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Malvaney recently brought to my attention some very cool photos of the inner bowels of the Washington County Courthouse that have been made available on the MDAH HRI database.

Attic, Washington County Courthouse. Greenville, Washington County. JBaughn, MDAH 01-14-

Metal Lath, Washington County Courthouse. Greenville, Washington County. JBaughn, MDAH 01-14-

Metal Lath, Washington County Courthouse. Greenville, Washington County. JBaughn, MDAH 01-14-

Metal Lath, Washington County Courthouse. Greenville, Washington County. JBaughn, MDAH 01-14-

Attic, Washington County Courthouse. Greenville, Washington County. JBaughn, MDAH 01-14-

Metal Lath, Washington County Courthouse. Greenville, Washington County. JBaughn, MDAH 01-14-

These images show the metal lath that supports the plaster in the courtroom.  Our conversation quickly turned to pondering when this metal lath might date to, and how extensively was the courtroom remodeled in the work overseen by James Spain?  We ruminated between the thoughts that the metal lath implied the work actually gutted the courtroom completed to the studs, and the possibility that the metal lath actually date to the construction.

While the first metal laths were patented in , modern metal lath dates to the late 19th century.[1]  Its creation arose from the need to fireproof buildings by eliminating wood components, in this case it was replacing wood lath with metal.  Metal lath use really took off in the late s when iron and later steel production was capable of producing thin but strong metal sheets at a reasonable cost.  Most lath in the s & s was perforated which the Washington County Courthouse metal lath definitely is.   In the magazine the American Architect and Building News discussed the two kinds of commercially available metal lath.[2]  One was a 16 gauge wire mesh-a type precursor to modern expanded metal lath- and the other was &#;26 gauge metal crimped-up&#; or corrugated (Cincinnati Corrugating Company&#;s), with a series of perforations to make a clinch for the plaster&#;.

In their catalogue the Cincinnati Corrugating Company stated &#;We have patrons in every state and territory, and from Canada to Mexico inclusive.&#;  Assuming this was not hyperbole, that would mean their products were in use in Mississippi.  They also stated that at that time their metal lath was being used extensively in government buildings, which it might not be a big surprise that the Washington County Courthouse is one of those.  While the Cincinnati Corrugating Company did not have a monopoly on perforated metal lath manufacturing, they were seen as innovators due to using corrugated iron stock.  The corrigation had two benefits; acting as furring and to impart additional stiffness to the lath.  The corrugation acting as furring gave space between the lath and the studs along with allowing for &#;ample rest for the plaster&#;.  The strength from corrugation allowed for thinner , less weighty iron sheet stock to be used.  [3]

Metal laths would soon be exalted not only for their fire preventive-ness but also for the ease & speed of installation and low-cost vs. wood lath.  Expanded metal lath was well-known to architects by ,[4] and its installation was such a major industry by it necessatated the establishment of the Wood, Wire and Metal Lathers&#; International Union.  By the &#;s expanded metal lath was the industry norm as seen in the plethora of manufactures examples in the Metal Lath Hand-Book.[5]

So to conclude with the answer to our Washing County Courthouse metal lath question; what it looks like happened in the courthouse is that the perforated corrugated metal lath was the original and there was a cove to the ceiling in .  The ceiling and cove were ditched in , but the flat wall plaster was kept in place.

While perforated lath would continue to be used later on in the 20th century, it was only when a very rigid back was needed say as a backing for tile.[6]  Though old method and materials always hang on (and without seeing the building in person) I would wager to say that the lath we see would date closer to than .  Since we all cannot go see this attic space in person its great we have the MDAH HRI database sharing these images with the world.  Did this lath-ing matter test your metal?

1 McDonald, Marylee. United States. National Park Service. Preservation Brief 21: Repairing Historic Flat Plaster Walls and Ceilings.. Washington DC: , . Print.

2 Hill, George. &#;Slow Burning Construction.&#; American Architect and Building News. 21 04 : 28. Print.

3 &#;Iron Lath.&#; Catalogue of the Cincinnati Corrugating Company. Nov : 19. Print.

4 Kidder, Frank Eugene.  Building Construction and Superintendence, Vol. 1. . Print.

5 McMaster, H.B. Associated Metal Lath Manufactures.  Metal Lath Hand-Book Youngstown Ohio:, December . Print.

6 Concrete Steel Company of New York.  Havemeyer bars & building products.  New York:, . 30. Print.

Categories: Architectural Research, Courthouses, Greenville, Historic Preservation

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