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Plastering is usually done on spruce lath, which comes 1/4 x 11/2 inches, and made in 4 foot lengths. As studding is spaced 16 inches apart this makes three spans, and all laths should be nailed to the studs at both ends. To cover 100 square yards will take about 1500 laths, and 10 lbs. of three penny nails. The plaster is usually applied in three coats, known as the scratch, brown and white coats. The first is applied directly to the lath, and consists of lime, sand and hair. Its surface is scratched with a stick to give good adhesion for the brown coats, which contains less hair, but is otherwise very similar. The white or finishing coat is usually composed of lime putty and fine beach sand in equal parts, to which plaster of Paris is added to make it hard and smooth. For 100 square yards, allow 10 to 12 bushels of lime, 2 bushels of hair, 1 1/2 cubic yards of sand and 100 lbs. plaster of Paris. If a sand-finished effect is desired, the plaster of Paris is omitted and ½ cubic yard of sand added. The surface is finished with a wooden float, so as to bring out the sand and produce a rough surface. Other types of plaster exist, based on the use of gypsum in the place of lime. They set more rapidly than lime plaster, and care must be taken to use them as directed by the manufacturers. Metal lath and plaster board are also much used in place of wood lath for reproduction corner guards (http://www.ferche.com). They increase the expense slightly, but reduce the fire risk. Whatever method is used, the plaster should be run back of dados and baseboards, as the open spaces add greatly to the fire risk. This is in fact required by the building codes of most cities. One man will lath about 100 yards in an eight-hour day, openings not deducted. With metal lath he can do from 100 to 150 yards, though if the plan has many corners his speed is greatly reduced. It has been estimated that a plasterer with one helper can do about 150 yards of the first two coats in a day, and about 90 yards of finishing coal. Cornices and ornamental pediment (http://www.ferche.com) add greatly to the cost, but are now far less common than they were a few years ago. Most ornaments are cast in the shop, while moldings are generally run on the job. When work of this kind is to be done, stock models should be used as far as possible. These are furnished by a number of manufacturers and can be ordered from their catalogues. When plaster board is used in place of wood lath, the first or scratch coat may be omitted. This greatly reduces the labor of plastering, but the plaster often tends to crack at the joints between the boards. For work that must be done quickly, a new type of gypsum board is now on the market, requiring no plastering, but finished ready for paint or paper. It is preferable to use paper, as with point it is hard to hide the joints. This material is only about 3/8 inch thick, while lath and plaster is 7/8 inch. It can be applied with practically no waste. There are also a number of makes of wall board, generally some sort of wood pulp composition. These shrink badly after application, and if they are papered the paper always cracks at the joints. The manufacturers recommend covering the joints with wooden corner protectors or strips, but this greatly limits the possible treatments, and makes an agreeable effect almost impossible. The gypsum board mentioned in the preceding paragraph is far preferable, and the cost is not much greater. Both types of wall board are made 4 feet wide, and almost any even number of feet in length. They are very easy to apply, and if 20% is added to the cost of the material it will usually cover the labor of nailing on. This, of course, is only for plain work, with few corners, and does not include wood strips or other woodwork.
Article Source: http://www.bharatbhasha.net Article Url: http://www.bharatbhasha.net/home_improvement.php/172163 Article Added on Tuesday, October 6, 2009 LD
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