HOME

TheInfoList



OR:

A lath or slat is a thin, narrow strip of straight-
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
ed 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 material for plaster. This includes metal wire mesh or
expanded metal Expanded metal is a type of sheet metal which has been cut and stretched to form a regular pattern (often diamond-shaped) of metal mesh-like material. It is commonly used for fences and grates, and as metallic lath to support plaster or stucco. ...
that is applied to a wood or metal framework as matrix over which
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 a ...
or
plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
is applied, as well as wallboard products called gypsum or rock lath.Ching, Frank. ''A visual dictionary of architecture''. New York: Van Nostrand Reinhold, 1995. 198. Print. Historically, reed mat was also used as a lath material. One of the key elements of lath, whether wooden slats or wire mesh, are the openings or gaps that allow plaster or stucco to ooze behind and form a mechanical bond to the lath. This is not necessary for gypsum lath, which relies on a chemical bond.


Etymology

The word is recorded from the late 13th century and is likely derived from the
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers in the mid-5th ...
word *, a variant of . This in turn would seem to stem from a
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic br ...
word *''laþþo'', from which have sprung words in many
Germanic languages The Germanic languages are a branch of the Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania and Southern Africa. The most widely spoken Germanic language, ...
, e.g. Dutch ,
German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...
. The root has also found its way into
Romance languages The Romance languages, sometimes referred to as Latin languages or Neo-Latin languages, are the various modern languages that evolved from Vulgar Latin. They are the only extant subgroup of the Italic languages in the Indo-European language ...
, cf. Italian ,
French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...
. The related German word ( gmh, lade) denotes a board, plank, sash, shutter, counter and hence also a shop. It is one of the few words in modern English to be close to a root going back to Proto Indo-European; for example words with the root ''lat'' mean a stick in various Indian languages.


Types of lath


Wooden

Wooden-slat laths are still used today in building construction to form a base or groundwork for
plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
, but modern lath and plaster applications are mostly limited to
conservation Conservation is the preservation or efficient use of resources, or the conservation of various quantities under physical laws. Conservation may also refer to: Environment and natural resources * Nature conservation, the protection and manageme ...
projects.
Tile Tiles are usually thin, square or rectangular coverings manufactured from hard-wearing material such as ceramic, stone, metal, baked clay, or even glass. They are generally fixed in place in an array to cover roofs, floors, walls, edges, or ...
s,
slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. ...
s, and other coverings on roofs and walls are often fastened to laths, sometimes also called battens or slats. Such strips of wood are also employed to form lattice-work, or are used as the bars of Venetian blinds, and window shutters. Lath is also used on many tobacco farms in the
Connecticut Valley The Connecticut River is the longest river in the New England region of the United States, flowing roughly southward for through four states. It rises 300 yards (270 m) south of the U.S. border with Quebec, Canada, and discharges at Long Isl ...
as a means to carry and hang the plant in barns. This is achieved by using one of two methods: hooking or spearing. A "spear" lath is a regular lath that is held in an upright position. A worker then mounts a spear on top and "spears" the tobacco onto the lath. The other form of lath is called "hook" lath, which has small hooks attached that allows workers to hook the stems of tobacco plants onto the lath, often between two lengths of twine attached to the lath and twisted mechanically. A lathhouse is an open structure roofed with laths in order to grow plants which need shelter from the sun. Laths were also used to fix reeds to a timber structure before plastering. In
Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer mont ...
, laths were used in the early 1880s for building wooden lobster traps. Historically there were three ways of making wood lath for plaster: riven lath, accordion lath, and circular sawn lath. Riven lath was traditionally split with the grain from chestnut, oak, and similar hardwoods, or from softwoods like eastern white pine. Individual laths were riven and nailed in place. Because they are split with the grain, riven lath is stronger than later forms of lath production. Accordion laths are thin, sawn boards that are partially split with a hatchet or axe. The splits are then spread apart to form gaps for the plaster to key into. The name derived from the spreading action, which is like pulling an accordion open. After the
circular saw A circular saw is a power- saw using a toothed or abrasive disc or blade to cut different materials using a rotary motion spinning around an arbor. A hole saw and ring saw also use a rotary motion but are different from a circular saw. ' ...
came into use in the early 19th century, lath for plastering was sawn in sawmills and delivered to the building site.


Counter-lath

Counter-lath is a term used in roofing and plastering for a piece of wood placed perpendicular to the lath. In roofing, a counter-lath is a slight piece of timber parallel with and between common
rafters A rafter is one of a series of sloped structural members such as wooden beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof shingles, roof deck and its associated ...
to give the lath extra support, or a lath placed by eye between every two gauged ones."Counter-lath" def. 1.b.''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009 When plastering, sometimes a counter-lath is placed perpendicular to the lath as a fillet (a thin, narrow strip of material) to space the lath off of the surface to allow the plaster to pass through the lath and create a key.


Metal lath

Metal lath dates from the late 19th century and is used extensively today with plaster and stucco in home and commercial construction. In addition to providing a matrix to which the stucco can adhere, metal lath adds strength and rigidity. . Metal lath can be stapled directly to studs, and is capable of bending to easily form corners and curves. Three coats of plaster are required when using metal lath. Several types of metal lath have been developed for a variety of applications: *
Expanded metal Expanded metal is a type of sheet metal which has been cut and stretched to form a regular pattern (often diamond-shaped) of metal mesh-like material. It is commonly used for fences and grates, and as metallic lath to support plaster or stucco. ...
lath is made by slitting and pulling apart a thin sheet of metal, which produces diamond-shape holes through which the plaster can form keys. * Ribbed lath is made from slit and expanded metal with V-shaped ribs which give it more stiffness, and is designed to span larger distance between framing supports * Self- furring lath is an expanded metal lath which is dimpled to hold itself off from a solid surface * Wire lath is made from welded or woven wires and is similar to hardware cloth * Paper backed wire lath is wire lath with building paper attached * Strip laths is metal lath that is several inches wide and is often used to reinforce joints and on corners * Corner lath is pre-bent for use in making corners * Wire mesh used on inside corners to prevent cracking is called Cornerite.


Gypsum lath

Gypsum lath (rock lath) consists of
gypsum plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
sandwiched between two sheets of absorbent paper. The finish side (to which plaster is trawled) is treated with
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
crystals for the plaster to chemically bond to and is sometimes perforated to allow mechanical bonding. It was commonly used in place of wood lath since it is noncombustible, easy to use, and can give better results. Gypsum board can be purchased in sheets of various sizes and screwed or nailed directly onto a building's studs. Due to its rigidity, it is most suited for use on straight walls. Gypsum board was improved in 1910 by the paper wrapping the edges and multiple variations were developed in the 1930s. Gypsum lath is available with a foil facing, which acts as a vapor barrier and heat reflector, and as a veneer base for
plaster veneer Plaster veneer (US terminology) or plaster skim (UK terminology) is a construction methodology for surfacing interior walls, by applying a thin layer of plaster over a substrate—typically over specially formulated gypsum board base, similar in n ...
.


Keys

Keys are formed by plaster that oozes through the spaces or gaps between wooden lath, or the holes in metal lath, and around to the lath's backside. This secures the plaster to the lath by creating a sort of hook. Wooden and metal lath depend on the mechanical bond created by keys to adhere the plaster to the lath.


Framing

Lath can be attached directly to the frame of a building, such as the studs of a timber structure. Alternatively, lath can be attached to a timber or metal frame called a furring, which is then attached to the building structure. Furrings are often used in masonry construction. Frames are also used when using lath and plaster to create decorative, curved, or ornamental work.


Lath failure

There are several reasons that a plaster and lath wall may fail. First, the lath itself can sometimes pull away from the frame on which it is mounted. This is generally due to the use of non-galvanized nails. The lath can also fail because of decay from moisture or insect damage. Moisture can also cause wooden lath to expand and contract, causing the plaster around it to crack. Additionally, failure can also occur in the plaster keys. Over time, the keys can deteriorate and crack, weakening their ability to hold the plaster onto the lath. The addition of hair in plaster helps to prevent this by adding strength. Problems can also occur in the keys if they were not properly formed to begin with, which can happen when laths are set too close together for plaster to travel though. Key failure often manifests as looseness and sagging in walls or ceilings, and in worst cases can lead to plaster breakage and collapse.


Repair methods

Repairing damaged lath and plaster walls is generally more economical than replacing it. Often, the plaster needs the repairs, and not the lath itself. As long as the lath and the first coats (brown coat) of plaster do not have any significant damage, minor cracks can simply be patched. For larger cracks, and when the brown coat is damaged, several base coats need to be applied prior to the patch coat. Metal lath can also be added to wooden lath prior to coating to add strength and increase keying. If the backside of the lath is accessible, it is possible to create new keys where they have failed. This is most often done by conservators when one wants to maintain the original finished surface of the wall or ceiling. After bracing the failing plaster in place, a bonding agent and a plaster are applied to the back of the laths and forced through the gaps to the backside of the original plaster.


Benefits of lath

Lath and plaster walls have several benefits, including fire and mold resistance,
soundproofing Soundproofing is any means of impeding sound propagation. There are several basic approaches to reducing sound: increasing the distance between source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound w ...
, and
heat insulation In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
. Though wooden lath can be susceptible to mold growth and decay, metal lath covered in plaster creates an environment that is inhospitable to toxic molds. Metal lath and plaster walls can be twice as resistant to fire than
drywall Drywall (also called plasterboard, dry lining, wallboard, sheet rock, gypsum board, buster board, custard board, and gypsum panel) is a panel made of calcium sulfate dihydrate (gypsum), with or without additives, typically extruded between thic ...
, and are capable of achieving a two-hour fire rating with a assembly. 2 inches of plaster and lath can also achieve the same
decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...
rating as of drywall.


See also

*
Garden trellis A trellis (treillage) is an architectural structure, usually made from an open framework or lattice of interwoven or intersecting pieces of wood, bamboo or metal that is normally made to support and display climbing plants, especially shrubs.
* Lath art *
Lattice truss bridge A lattice bridge is a form of truss bridge that uses many small, closely spaced diagonal elements forming a lattice. The lattice Truss Bridge was patented in 1820 by architect Ithiel Town. Originally a design to allow a substantial bridge to be ...
* Plasterwork#Laths


References

{{Wood products Building materials Wood products