Plastering Topics

• lath plaster
• pyramids in egypt
• plaster of paris
• hydraulic lime
• plaster walls
• uniform consistency
• design shape
• recent discoveries
• portland cement
• laths
• tudor times
• primitive man
• small stones
• plasterer
• joist
• gypsum
• timbers
• shingle
• egyptians

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The process of creating plasterwork, called plastering , has been used in building construction for centuries.

Evidence shows that the dwellings of primitive man were erected in a simple fashion with sticks and plastered with mud. The pyramids in Egypt contain plasterwork executed at least four thousand years ago, probably much earlier, and yet hard and durable, at the present time. From recent discoveries it has been ascertained that the tools of the plasterer of that time were practically identical in design, shape and purpose with those used today. For their finest work, the Egyptians used a plaster made from calcined gypsum just like plaster of Paris of the present time, and their methods of plastering on reeds resemble in every way our lath, plaster, float and set work. Hair was introduced to strengthen the stuff, and the whole finished somewhat under an inch thick.

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.

In Scotland it is termed "harling". It is one of the oldest forms of external plastering. In Tudor times it was employed to fill in between the woodwork of half-timbered framing. When well executed with good material this kind of plastering is very durable. Roughcasting is performed by first rendering the wall or laths with a coat of well-haired coarse stuff composed either of good hydraulic lime or of Portland cement. This layer is well scratched to give a key for the next coat, which is also composed of coarse stuff knocked up to a smooth and uniform consistency. While this coat is still soft, gravel, shingle or other small stones are evenly thrown on with a small scoop and then brushed over with thin lime mortar to give a uniform surface. The shingle is often dipped in hot lime paste, well stirred up, and used as required.

The pigments used for this work include Indian red, Turkey red, Antwerp blue, German blue, umber, ochre, purple brown, bone black or oxide of manganese for black. Combinations of these colors are made to produce any desired tone. Lime plastering is composed of lime, sand, hair and water in proportions varying according to the nature of the work to be done.

One coat work is the coarsest and cheapest class of plastering, and is limited to inferior buildings, such as outhouses, where merely a rough coating is required to keep out the weather and draughts. This is described as render on brickwork, and lath and lay or lath and plaster one coat on studding. Two-coat work is often used for factories or warehouses and the less important rooms of residences. The first coat is of coarse stuff finished fair with the darby float and scoured. A thin coat of setting stuff is then laid on, and trowelled and brushed smooth. Two-coat work is described as render and set on walls, and lath, plaster and set, or lath, lay and set on laths.

Wall screeds are plumbed and ceiling screeds leveled. Screeds are narrow strips of plastering, carefully plumbed and leveled, so as to form a guide upon which the floating rule is run, thus securing a perfectly horizontal or vertical surface, or, in the case of circular work, a uniform curve. The filling in, or flanking, consists of laying the spaces between the screeds with coarse stuff, which is brought flush with the level of the screeds with the floating rule.

Other differences is that walls intended to be plastered are hanged with "Blueboard" (named as such for the industry standard of the outer paper being blue-grey in color). This type of sheet rock is designed to absorb some of the moisture of the plaster and allow it to cling better before it sets. Plastering is also a one-shot one coat application; taping usually requires sanding and then adding an additional coat; since the compound shrinks as it dries. From a supply side the cost of plaster and drywall are approximately the same, but the labor costs of plastering is usually much greater.

Source: Wikipedia > Plasterwork