page_title: Plasterer
section_title: Laths
hierarchical_section_title: Plasterer / Tools and materials / Laths
caption_attribution_description: Laths seen from the back with plaster visible between them
context_page_description: A plasterer is a tradesman who works with plaster, such as forming a layer of plaster on an interior wall or plaster decorative moldings on ceilings or walls. The process of creating plasterwork, called plastering, has been used in building construction for centuries.
context_section_description: Wood laths are narrow strips of some straight-grained wood, generally Baltic or American fir, in lengths of from two to four or five feet to suit the distances at which the timbers of a floor or partition are set. Laths are about an inch Lathing-wide, and are made in three thicknesses; single (1/8 to 3/16 inch thick), lath and a half (1/4 inch thick), and double (3/8-1/2 inch thick). The thicker laths should be used in ceilings, to stand the extra strain, and the thinner variety in vertical work such as partitions, except where the latter will be subjected to rough usage, in which case thicker laths become necessary. Laths are usually nailed with a space of about 3/8 of an inch between them to form a plaster key. Laths were formerly all made by hand. A large quantity, however, are now made by machinery and are known as sawn laths, those made by hand being called rent or riven laths. Rent (riven) laths give the best results, as they split in a line with the grain of the wood, and are stronger and not so liable to twist as machine-made laths, some of the fibers of which are usually cut in the process of sawing.
  Care should be taken to check the PH value of the wood; oak contains tannic acid which attacks the lime, this can compromise bond strength.
  Laths must be nailed so as to break joint in bays three or four feet wide with ends butted one against the other. By breaking the joints of the lathing in this way, the tendency for the plaster to crack along the line of joints is diminished and a better key is obtained and it provides restraint for the timber frame. Every lath should be nailed at each end and wherever it crosses a joist or stud. All timbers over three inches (76 mm)  wide should be counter-lathed, that is, have a fillet or double lath nailed along the centre upon which the laths are then nailed. This is done to preserve a good key for the plaster. 
  Walls liable to damp are sometimes battened and lathed in order to form an air cavity between the damp wall and the plastering.
  Lathing of metal, either of wire or in the form of perforated sheets, is now extensively used on account of its fireproof and lasting quality.  There are very many kinds of this material Metal made in different designs under various patents, the best known in England being the Jhilmil, the Bostwick, Lathing, and the Expanded Metal lathing. The two last-named are also widely used in America. Lathing nails are usually of iron, cut, wrought or cast, and in the better class of work they are galvanized to prevent rusting. Zinc nails are sometimes used, but are costly.
caption: Lath seen from the back with brown coat oozing through
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