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Lath and Plaster
The following description appears to be
American in origin, and certainly does not represent the
situation in Britain, or perhaps Europe.
Lath and plaster is a building process used mainly for
interior walls. In many areas its use began to decline in
the late 1950s as drywall began to replace it.
The process begins with wood laths. These are narrow strips
of wood nailed horizontally across the wall studs. Each wall
frame is coverd in lath, tacked at the studs. The lath is
typically about two inches wide, by four feet long, by a
quarter inch thick. Each horizontal course of lath is spaced
about a quarter away from its neighboring courses. Next,
temporary lath guides are sparsely vertically to the wall,
usually vertically at the studs. 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. 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.
It is standard to apply a second layer in the same fashion,
leaving about a half inch of rough, sandy plaster (called a
brown coat). A smooth white finish coat goes on last. After
the plaster is completely dry, the walls are ready to be
painted. In the photo, "lath seen from the back, brown coat
oozing through," those curls of plaster are called "keys"
and are important to keep the plaster on the lath.
Insufficient "keying" and the plaster will fall off the
lath. In Scotland horse-hair was used to help bind the
plaster to the laths.
Eventually the wood laths were replaced with rock lath,
which is a type of gypsum wall board available in sheets
size 2 by 4 feet. The purpose of the four-foot length is so
that the sheet of lath reaches exactly across three wall
studs, which are spaced 16 inches apart on center (American
building code standard measurements).
In addition to rock lath, there were various types of
diamond mesh metal lath which 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 center,
attached by tie wires using lathers' nippers. Sometimes the
mesh was dimpled to be self-furring.
Lath and plaster has been replaced altogether with drywall
(also a type of gypsum wall board, although a bit thicker),
since no plaster is applied afterwards.
Although plastering as a building process has all but
disappeared, there remain still a few skilled professionals
(plasterers) who are employed mainly to do small jobs and
patchwork in older buildings where drywall may not as easily
match the existing finish.
A possible advantage of using lath is for ornamental or
unusual shapes. For instance, building a room with rounded
corners would be difficult if drywall was used exclusively.
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Sample
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Citation
The above was extracted from Wikipedia on
11/15/06.
Lath and plaster. (2006, November 8). In
Wikipedia, The Free Encyclopedia. Retrieved 21:35,
November 15, 2006, from
http://en.wikipedia.org/w/index.php?title=Lath_and_plaster&oldid=86459255 |
