Types of plaster and the method of cement plaster
The following types of plastering are utilized in buildings :-
- Lime plaster
- Cement plaster
- Mud plaster
- Stucco plaster
- Plaster on lathe
In this type of plaster, the lime is applied as the binding material. It comprises of hydrated lime, sand and water. It has similarity with lime mortar. Hydraulic lime is tougher and stronger. Mortar for lime plaster is generally made by blending sand and lime in identical proportions. To make it’s strength better, small quantity of cement is added to the mixer.
The surface to be plastered is arranged in same way as that of lime or cement plaster. Mud plaster is normally applied in two coats. The thickness of first coat is 18 mm whereas the thickness of second coat is 6 mm.
Stucco belongs to a decorative type of plaster that provides a superior finish. This type of plaster can be applied for inside and outside surfaces. It is usually placed in three coats which make the entire thickness of the plaster to roughly 25 mm. The first coat is known as scratch coat; the second as a finer coat or brown coat and the third is known as white coat or finishing coat.
In this type of plaster, the cement is applied as binding materials. It is very effective for damp condition. This type of plaster is provided in one coat. The thickness of coat varies from 12 mm, 15 mm, or 20 mm based on the site conditions and type of building. If the thickness of plaster exceeds 15 mm, 6 mm thickness of cement plaster and cement mortar in the ratio of 1:3 or 1:4 is suggested for cement plastering on RCC surfaces.
Method of cement plastering
- Average thickness should be 12 to 15 mm.
- Cleanse the surface with water and retain wet unless plaster is applied.
- Initial coat is provided on the surface to fill up void section of masonry.
- First coat should be kept with a thickness of 9 to 10 mm.
- Second coat should be provided after 6 hours and the thickness of second coat is 10 mm.
- The surface should be burnished with a trowel.
- If necessary, the third coat should be provided with maximum thickness of 3 mm.
- Finished plaster should be kept for 24 hours and drenched with sufficient water for minimum one week.
- Slow setting under greater humidity make the strength of the plaster better.