Plastering Work | cement plaster

Plastering Work in Construction : Procedure, Objectives & 2 Types of Plaster Used

 

Plastering is the process of covering the rough surfaces of walls, columns, ceilings, and other building components with a thin coat of plaster to make the surface smooth and durable. 

Plastering on the externally exposed surface is called rendering.

Generally, cement plaster and lime plaster are used for plastering work.

Curing

 


 

  1. Objectives of Plastering  

Some objectives of plastering are:

a. To provide a smooth and finished surface.

b. To protect the surfaces against atmospheric effects.

c. To resist chemical actions.

d. To cover defects in the structure.

e. To give a decorative appearance.

 


 

  2. Requirements for Good Plaster Material  

The plaster material should fulfill the following requirements:

a. It should be hard and durable.

b. It should remain on the surface and should protect from chemical attacks and weathering actions.

c. It should have good workability.

d. It should have high strength and durability.

e. It should be cheap and should be easily available.

f. It should protect from penetration of nature.

 


 

  3. Tools Used in Plastering  

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Names Images Uses
1. TrowelTrowelUsed for plastering and smoothing surfaces.
2. Spackle KnifeSpackle KnifeUsed for scraping surfaces or spreading material such as plaster in various construction trades.
3. Spirit LevelSpirit levelUsed to indicate how parallel (level) or perpendicular (plumb) a surface is relative to the earth.
4. Straight edgeStraight edge Used for ruling, cement render screeding, tiling, and as a general construction straight edge.
5. FloatFloatUsed for making plaster smooth and flat.
6. Plumb bobplumb bobUsed to establish a vertical reference (called a plumb line).
7. Floating RuleFloating RuleUsed to check the level of the plastered surface between the successive layers.
8. Paddle MixerPaddle Mixer Used for ideal for quick and convenient mixing of paint, plaster, and more.
9. HammerHammerUsed to chip out chunks of plaster and to re-secure or remove problematic pieces of lath.
10. Plaster SpongePlaster Sponge Used for providing a final coat and finishing touch on plastered surface.

 

11. HawkHawk Used to carry mortar or plaster from the mixing table to the surface that’s being worked on.
12. Tube LevelTube LevelUsed to transfer a vertical level across a distance.
13. Water BrushWater BrushUsed during the final smoothing stage of your plaster job.
14. ThreadThreadUsed for checking the level of plaster of different structures.
15. BucketBucketUsed to transport/carry mortar.
16. BroomBroomUsed during the final smoothing stage of your plasterwork.
17. ShovelShovelUsed to mix the cement, sand, and water.

These are 17 construction tools list used in plastering work.

 

Read Also: Ferrocement

 


 

  4. Types of Plasters Used In Plastering Work  

There are two types of plaster used in plastering work. They are:

 

a. Gypsum Plaster 

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O). It is generally found in the form of rock and is white in color.

Gypsum plaster is a paste formed by mixing the gypsum powder and water in a suitable proportion.

gypsum pointing | Gypsum plaster

No sand is used in gypsum plaster. Only mixing of gypsum powder and water is done to prepare gypsum plaster.

This plaster is only used for interior plastering work.

 

b. Lime Plaster  

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, slabs, and columns by using lime plaster is called lime plastering.

lime plaster

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.

This plastering is commonly used for interior works rather than the exterior.

 

c. Cement Plaster  

When cement and sand are mixed with the proper quantity of water; cement plaster is formed and the process of covering the surfaces with cement plaster is called cement plastering.

Difference Between Cement and Lime Plaster

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

Different grades for cement plaster are: 

Grade NameMortar Mix (by Loose Volume)Compressive Strength at 28 days (in N/mm2)
CementSand
MM 0.7180.7   to 1.5
MM 1.5171.5 to 2.0
MM 3163.0 to 5.0
MM 5155.0 to 7.5
MM 7.5147.5 to above

 

 

d. Mud Plaster 

This plaster is prepared by mixing an adequate percentage of clay and sand content. A small amount of cow dunk is also added to this plaster to receive a better surface.

This type of plaster is environmentally friendly and repairing work is also very easy and inexpensive.

 


 

  5. Plastering Procedure  

Plastering work should be done in the following steps:

Plastering Work | cement plaster

a. The application surface should be made rough by raking out.

b. In case of the presence of cavities or holes; fill it in advance with suitable material.

c. All joints and application surfaces are cleaned out with the help of water and a wire brush. No traces of oils or greases should be left.

d. The application surface should be wet for at least 6 hours before the application of plaster.

e. For obtaining the uniform surface level; patches of plaster of size 15 mm * 15 mm and having a thickness of about 10 mm are used( Patches are also known as fixed dots ). Patches are fixed at an interval of 2m.

f. Verticality of fixed dots is checked with a plumb bob and screeds are formed between dots.

g. Then, a base coat is applied to the surface between screeds using the trowel. The thickness of the base coat may vary between 9 to 15 mm.

h. The surface is leveled using a wooden float.

i. Let the base coat set but not let it dry.  Then roughen the base coat by scratching.

j. Then surface or finishing coat is applied over the base coat.

k. The thickness of the finishing coat may vary between 2 mm to 3mm.

l. Finishing coat is leveled uniformly utilizing a wooden float.

m. Let the plastered surface dry and after 12 hours; start the curing.

n. Curing should be done for at least 7 days to prevent problems like cracking in the future. As cement need, 28 days for complete hydration, curing for 28 days is best.

 

The plastering process of exterior and interior surfaces is the same. The only difference is that a waterproofing admixture is commonly added to the plaster to be used on exterior surfaces.

High-grade plaster is preferred to external plastering. 

( Note: Plaster should be always done from top to bottom. )

 

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