Plaster Work In Building Construction. Types of Plaster.

 

Plaster Work:-

Plastering work is a thin layer of mortar, applied over the masonry and it acts as a damp-proof coat over the brick masonry work. Plastering work also provides a finished surface over the masonry that is firm and smooth hence it enhances the appearance of the building. The main objectives of plastering are to protect the surface from atmospheric influences, to cover the defective workmanship in masonry, to conceal porous materials, and to provide a suitable surface for painting.

Plastering is done mainly for the following purposes:

i) To protect the surface from harmful atmospheric effects such as rain, wind, sun, snow, etc.
ii) To create decorative effect as well as to improve the aesthetics.
iii) To hide defective and poor workmanship.

Types Of Plaster

Conventional types of plaster are as follows:

·         Cement plaster
·         Lime plaster
·         Mud plaster

 

1. Cement Plaster

Cement plaster is the most common type of plaster in the construction industry. Cement plaster is a mixture of cement, sand, and suitable amount of water.

Proportions of cement and sand may vary according to the requirements of the plaster. But, the usual proportion are 1:3 and 1:4 which gives the best results.

Cement plaster is used on the interior walls and exterior walls, ceilings, and other building elements. For interior walls, a single coat of plaster is usually enough to achieve the desired surface.

For exterior walls, another coating is required depending on the thickness of the plaster and the nature of the surface. The thickness of cement usually ranges between 12 and 20 millimeters, depending upon the type of wall or ceiling surface.

The cement plastered surface requires proper curing with water for a minimum of 7 days. Improperly cured walls may develop cracks.

It provides improved adhesive and tensile properties to the plaster. Types of plaster are now being replaced with cement plaster.

2. Lime Plaster

 

Lime plaster is a type of plaster made of sand, water, and lime, usually non-hydraulic hydrated lime (also known as slaked lime, high calcium lime, or air lime). Ancient lime plaster often contained horse hair for reinforcement and pozzolanic additives to reduce work time.

When lime is used as a binding material in making mortar for plastering purpose, it is called lime plaster.

The sand proportions in lime plaster control various properties such as shrinkage, strength, porosity, adhesiveness & fine sand is more suitable for making the plaster.

3. Mud Plaster

This is the cheapest type of plaster. It is made up of suitable proportions of clay and sand. The clay content should be free from grass, roots, organic matter, stone pebbles, etc.

Chopped straw, hay, or hemp is also used in the mixture at the rate of 30kg/m3 of earth content. Mud plaster is mostly used in villages and temporary constructions.

Special Types Of Plaster

Besides the above plastering materials, there are some special types of plasters. They are as follows:

1. Waterproof Plaster

As the name suggests, this type of plaster protects the masonry wall from ingress of moisture and thereby eliminating or reducing dampness of the wall.

The mortar for waterproof plaster is prepared by mixing cement, sand (1:2), and pulverized alum at the rate of about 12 kg/m3 of sand content.

Water to be used in the mix is not normal water but the water is prepared by dissolving 75gm of soft soap per liter of water.

2. Gypsum Plaster

Gypsum plaster is a factory-made product produced by partial or complete dehydration of mineral gypsum. It is available in powder form and in white color.

Dry gypsum powder is mixed with a suitable amount of water to form a ready paste that can be easily applied to the ceiling and wall surfaces.

The thickness of gypsum plaster is usually 6 mm- 20 mm. It dries very fast, so painting on the plastered surface can be started 72 hours after application.

It gives a very good smooth finish and level surface with excellent proper angled corners. This type of plaster can only be used in the interiors of the building, not suitable for external plastering. It can also be used to fabricate ceiling cornices and mouldings.

It is fire resistant and a good thermal insulator. Another good advantage is there is no shrinkage during setting and hence it does not develop cracks.

3. Acoustic Plaster

It is a gypsum product that is mostly used as a final coat. During final coat finishing small pores are left on the surface to absorb sound.

4. Asbestos-marble plaster

It is prepared by mixing finely crushed marble, asbestos, and cement. It gives a beautiful marble-like finish on the surface.

5. Stucco Plaster

Stucco plaster is a type of decorative plaster that provides excellent finishing. This type of plaster is usually done in three coats with a thickness of about 25 mm.

Each coat needs to be dry completely before applying the next coat. The first coat in stucco plaster is called scratch coat.

The second coat is called finer coat or brown coat and the final coat is known as a white coat or finishing coat. Stucco plaster can be used for internal as well as external walls.

• Also Read: What Is Flooring ? Types of Flooring.
• Also Read:  : What is waterproofing ? Various Kinds of Waterproofing. Steps Engaged with Waterproofing. Advantages & Disadvantages .