Lath And Plaster
   HOME

TheInfoList



OR:

Lath and plaster is a building process used to finish mainly interior dividing
wall A wall is a structure and a surface that defines an area; carries a load; provides security, shelter, or soundproofing; or serves a decorative purpose. There are various types of walls, including border barriers between countries, brick wal ...
s and ceilings. It consists of narrow strips of
wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
(
lath A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work. ''Lath'' has expanded to mean any type of backing m ...
s) 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 Wattle and daub is a composite material, composite building method in which a woven lattice of wooden strips called "wattle (construction), wattle" is "daubed" with a sticky material usually made of some combination of wet soil, clay, sand, and ...
. Lath and plaster largely fell out of favour in the U.K. after the introduction of plasterboard in the 1930s.Jeff Howell
''On the level: is the old plaster best?''
The Telegraph (London), May 10, 2006. Retrieved 2012-03-30.
In
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
and the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, 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.


Description

The wall or ceiling finishing process begins with wood or metal
lath A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work. ''Lath'' has expanded to mean any type of backing m ...
s. These are narrow strips of
wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
, extruded metal, or split boards, nailed horizontally across the wall studs or ceiling
joist A joist is a horizontal structural member used in Framing (construction), framing to span an open space, often between Beam (structure), beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joi ...
s. Each wall frame is covered in lath, tacked at the studs. Wood lath is typically about wide by long by thick. Each horizontal course of lath is spaced about away from its neighboring courses. Metal lath is available in by sheets. In
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
and the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
the laths were generally sawn, but in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
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 . 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 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. Metal lath is categorized according to weight, type of ribbing, and whether the lath is galvanized or not. Metal lathing was spaced across a center, attached by tie wires using lathers' nippers. Sometimes, the mesh was dimpled to be self-
furring In construction, furring (furring strips) are strips of wood or other material applied to a structure to level or raise the surface, to prevent dampness, to make space for insulation, to level and resurface ceilings or walls, or to increase the be ...
. In use as early as 1900, 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. Rock lath was typically produced in sheets sized . 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 apart on center (United States building code standard measurements). By the late 1930s, rock lath was the primary method used in residential plastering. 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 damping 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 Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and ...
, 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. 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."Fire Resistance of Historic Fabric" by Peter Jackman - http://www.buildingconservation.com/articles/fireresist/fire_resistance.htm


See also

*
Lath A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work. ''Lath'' has expanded to mean any type of backing m ...
s *
Stucco Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and ...


References


External links

{{Commons category
Plaster Base Installation
Building Construction & Finishing

by the National Park Service. Contains detailed descriptions of Lath & Plaster construction and advisories on repairing and restoring these walls (especially in historic buildings). Building engineering Building Plastering