Plastering is the process of covering rough surfaces of walls, columns, ceilings and other building components with a thin coat of plaster matters to form a smooth and durable surface. The coating of walls, ceilings, columns, etc with mortar is called plastering.
Plastering on the externally exposed surface is called rendering.
Objective of Plastering
- To provide a smooth and finished surface.
- To give a decorative appearance.
- To protect the surfaces against atmospheric effects.
- To resist chemical actions.
- To cover defects in the structure.
- To make surface waterproof and durable.
Requirements for good plaster
The plaster material should fulfil the following requirement:
- It should be hard and durable.
- It should remain on the surface of the wall and column and protect from chemical attacks and weather.
- It should have good workability.
- It should have high strength and durability.
- It should be cheap and should easily available.
- It should protect from penetration of nature.
- Metal float( wooden flat / claying float)
- Plumb Bob
- Spirit level
Types of Plastering
There are two types of plastering work that are generally used; based on binding material.
When lime is mixed with the sand in the presence of the proper quantity of water, it is called lime mortar/ lime plaster. And the process of covering the surface of the walls and columns by using lime plaster is called lime plastering.
Plastering may be single coated or multi-coated. The proportion of lime and sand for lime plastering is generally taken as 1:3 to 1:4.
When cement and sand are mixed with the proper quantity of water; cement plaster is formed. And the process of co0vering the surfaces by cement plaster is called cement plastering. The generally used mixed proportion of cement and sand for cement plaster are 1: 4, 1:5 and 1:6.
Internal plaster – 1:6 or 1:5
External plaster – 1:4
Ceiling plaster – 1:3
The grade for cement plaster
|Grade Name||Mortar Mix (by Loose Volume)||Compressive Strength at 28 days (in N/mm2)|
|MM 0.7||1||8||0.7 to 1.5|
|MM 1.5||1||7||1.5 to 2.0|
|MM 3||1||6||3.0 to 5.0|
|MM 5||1||5||5.0 to 7.5|
|MM 7.5||1||4||7.5 to above|
Steps for plastering
- All joints on faces are raked out by pointing tools.
- All the base mortar and dust are brushed and the wall is washed and kept wet for a few hours.
- Joints are filled with lime or cement mortar with the help of a trowel.
- The mortar is well pressed into the joints to make solid contact with old mortars in joints.
- Finish pointing is kept wet for about 4 days for lime pointing and 10 days for cement pointing.
- The mortar is applied throughout the whole surface and levelled by the float.
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