Types and methods of plastering

Plastering is a blend of lime or gypsum, sand and water, often with fiber included that is applied to coat walls and ceiling.

Features of a good plastering :-

1. Good resistance capacity against fire and sound.
2. Offer a smooth, non permeable and washable surface.
3. Should be weather resistant.
4. Should efficiently check the penetration of moisture from the surfaces.
5. Should be free from volumetric changes at the time of setting and drying.

The following materials are required for plastering : Cement, Lime or clay, Aggregates, Water, Accelator, Admixture.

The following types of plasters are generally found : Lime plaster, Cement plaster, Mud plaster, Stucco plaster, Plaster on lathe.

Lime plaster – If lime is utilized as the binding material it is known as lime plaster. It comprises of hydrated lime, sand & water. Hydraulic lime is harder and stronger. Mortar for lime plaster is generally formed by blending sand & lime in same ratios. Small quantities of cement can be included to make the strength better.

Mud plaster – The process is similar to lime or cement plaster. Mud plaster is usually used in two coats, the first coat is 18 mm thick whereas the second coat is 16 mm thick.

Stucco plaster – It is attractive type of plaster that offers an elegant finish. This type of plaster is suitable for interior and exterior surfaces. It is generally placed in three coats to retain the complete thickness of plaster to 25 mm. The first coat is known as scratch coat, the second coat is known as finer coat or brown coat and the third coat is known as white or finishing coat.

Cement plaster – In this type of plaster, cement is applied as the binding materials. This type of plaster is very effective for damp condition. Cement plaster is provided in one coat. Based on the site conditions and type of building, the density of plaster differs from 12 mm, 15 mm and 20 mm. For cement plastering on RCC surfaces, the density of cement plaster should be 6 mm and the ratio of cement mortar should be 1:3 or 1:4.

Plaster of lath – Lathing comprises of wood or expanded material. Wooden lathe contains thin strips of well seasoned wood with width 25 mm and length 90 to 120 cm.

Method of cement plastering :-

1. Average thickness for cement plastering should be kept 12 – 15 mm.
2. Cleanse the surface with water and retain it wet until plaster is used.
3. Initial coat is utilized on the surface to fill out void section of masonry.
4. First coat is provided with a thickness of 9-10 mm.
5. Second coat should be used after 6 hrs and the thickness of second coat is 10 mm.
6. A trowel is used to polish the surface.

7. If necessary, third coat should be used with minimum thickness of 3 mm.
8. Completed plaster should be kept for 24 hours and drenched with water for minimum one week.
9. Slow setting under greater humidity enhance the durability of plaster.