What is the Plastering Process?

Plastering is a process of providing decorative and protective layers on the interior

and exterior walls. It should be noted that plaster shows both stiffness and
workability for attaining required strength and easy placement. The primary goal
behind plastering is to protect the surface from atmospheric influences such as
chemical attacks, to conceal defective masonry workmanship, to conceal porous
materials, and to provide a suitable surface for painting. It should be noted that the
properties of mortar are the most essential factor while doing the plastering work.
Hence, the requirement of good mortar is a must. The plastering process involves
several steps to create a smooth and finished surface on walls and ceilings. Here are
steps to Plastering process:

o Preparation: Clean the surface and repair any cracks or holes.

o Mixing the plaster: Combine plaster powder and water to create a smooth
paste.
o Applying the base coat: Spread the first layer of plaster evenly and
roughen the surface.
o Applying the finish coat: Apply a thinner, smoother layer of plaster for the
desired finish.
o Curing and drying: Allow the plaster to cure and dry completely.
o Finishing touches: Smooth out imperfections, prime, and paint or decorate
the surface.

Tools Used in Plastering

Various tools are used in the process of plastering. Here are some common ones:

o Trowel: A handheld tool with a flat, rectangular blade used for applying and
smoothing plaster.
o Hawk: A square or rectangular platform with a handle underneath, used to
hold and carry plaster.
o Plastering Float: A large, flat rectangular tool used for spreading and
leveling plaster.
o Plastering Darby: A long, straight-edged tool used for leveling and
smoothing larger areas of plaster.
o Plastering Brush: A soft-bristled brush used for wetting surfaces or cleaning
tools.
o Plastering Sponge: A damp sponge used for achieving a textured or
polished finish.
o Plastering Scratcher: A tool with sharp teeth used to create a rough surface
on the base coat for better adhesion.
o Bucket and Mixing Paddle: Used for mixing plaster and water to create a
consistent mixture.
o Plastering Rule: A straight, metal or wooden ruler used for measuring and
straightening plaster.
o Plastering Corner Bead: Metal or plastic strips used to reinforce and protect
plastered corners.

Purpose of Plastering
The purpose of plastering is to achieve several important objectives in construction
and finishing projects:
 1. Smoothing and leveling: Achieve a smooth and even surface on walls and
ceilings.
2. Protection and durability: Provide a protective layer and enhance the
structural integrity of the substrate.
3. Aesthetic enhancement: Enhance the visual appeal with various
textures, patterns, and decorative finishes.
4. Soundproofing and insulation: Contribute to soundproofing and provide
some thermal insulation.
5. Fire resistance: Act as a barrier against the spread of flames and offer
fire resistance properties.

Requirement of a Good Mortar

o A good mortar should show good adhesive properties with the surface it is
applied.
o It should develop the requirement of stress and should be able to withstand
them as well.
o It should show enough resistance to water from penetrating into its layers.
o It should be durable, cheap and easily workable. It should not affect the
durability of other materials it comes in contact with.
o For maintaining the pace of construction, it should set quickly.
o A good mortar should always be economical.
o Also learn about Portland cement in detail.

Materials for Plastering

The quality of materials significantly impacts the performance of plaster
finishes. According to ASTM C 926, proper materials selection includes:
1. Cement: Several types may be used:
 Blended hydraulic cement (ASTM C 595)
 Masonry cement (ASTM C 91)
 Portland cement (ASTM C 150)
 Plastic cement (UBC 25-1)2
2. Sand: Clean, sharp sand is essential for creating a workable mixture
with appropriate texture and strength1.
3. Water: Clean water free from impurities ensures proper chemical
reactions during setting.
4. Additives: Sometimes incorporated to achieve specific properties
or improve workability

Types of Plastering
Depending on where the plastering is being done, plastering is classified into two
major components:

o Internal Plastering
o External Plastering

Internal Plastering
As the name suggests, Internal plastering refers to plastering on interior walls in
which the process results in a firm and smooth finished surface. To some extent, the
plaster also acts as a thermal insulating layer as well as fire protecting layer.

Preparations for Internal Plaster

o Preparation of the surface is the first and foremost step before the actual
process can begin. There are various steps involved in the preparation of the
surface for internal plastering:
o For a good bonding between walls and plaster, the joints of mortars are
always kept rough.
o Extra amount of mortar should be removed and pointings should be made.
Pointing is the process of finishing the mortar joints after brickwork or
stonework.
o The surface of walls and joints should be cleaned thoroughly using a wire
brush.
o It should be made sure that no foreign substances like oil or grease remain on
the surface.
o The surface should not be left with any cavities or pores. If they exist, they
should be filled with concrete at least a day before.
o Before applying cement plaster, walls and mortar joints should be washed
properly. Efforts should be made to keep it wet for at least 6 to 7 hours.
o In order to save mortar consumption, if the projection on the wall surface is
greater than 12 mm, it should be knocked off to have a uniform surface.
o To ensure that the mortar adheres to the concrete surfaces like beams,
columns, and slabs properly, they should be properly hacked using hammers
and chisels.
o All electrical conducting works must be completed before plastering.

Plastering Process of Internal Walls

Internal walls plastering involves the following procedure:

o Plaster thickness varies from 9 to 15 mm in concrete masonry and is about 12

mm for brick masonry and blockwork.
o The ratio of cement and sand for plaster ranges from 1:3 to 1:6 depending on
the importance of the work.
o The ratio of mortars should be closely monitored to ensure durability and
economy.
o First only dry mortar is prepared using cement and sand, and then water is
added as per the requirements but the mixing of water should be done within
30 minutes.
o Plaster should be applied using a trowel between spaces formed by screeds.
o Wooden floats are used to level the plastering surfaces.
o At last, plastered surfaces should be left to set before the curing processes.

External Plastering
The term "external plastering" refers to plastering done for external walls in which
the masonry or blockwork is covered with a layer of cement-sand mortar, which also
serves as a damp-proof covering.

Preparations for External Plastering

Surface preparation for external plastering is more or less the same as internal
plastering. The additional procedures that are involved in external plastering are as
follows:

1. All the masonry works must be completed before applying plaster.

2. Scaffoldings are necessary while doing plastering works on external walls.

Scaffolding is a temporary platform that is used to raise workers and construction

materials. It is made up of one or more platforms that are of the required length and
width and have different types of supports, depending on the structure and intended
function. The vertical supports which are parallel to the walls are called standards
and the horizontal supports on which platforms are created are called ledgers.

Plastering Process of External Walls

o The surfaces and mortar joints must be cleaned using wire brush and they
should be free from oil, grease etc.
o A string is fixed from top slab to bottom level for all corners of the walls,
corners of windows, lines of R.C.C grill etc.
o After the walls have been leveled, the projected surface that is out of plaster
due to an uneven surface will be cleared.
o A rough surface is used to finish the external wall plaster.
o Groves are made in between the beam and column to avoid cracks in future.
o Primer is applied after the plaster has been set so that plaster does not
absorb moisture from the wall putty and also acts as protection against
severe climatic conditions.

Bullmark Procedure
Bullmark is used to ensure that the thickness of the plastering is uniform throughout.
BULLMARK is a plaster patch that is 10 cm x 10 cm in size and about 12 to 15 mm
thick. Bullmark is placed on the wall's one-end corner to provide a uniform thickness
of plastering throughout the entire wall surface.

Types of Plaster

Depending on the types of materials used for plastering, there are different kinds of
plaster.

1. Clay plaster
2. Lime plaster
3. Cement plaster
4. Gypsum plaster
5. Waterproof plaster

Clay Plaster
Clay plaster is a mixture of clay and sand. It is an eco-friendly alternative to
conventional plaster. Clay plaster has been in use since the origin of mankind. It is a
natural, non-toxic and aesthetically pleasing material. The pigments used to color
clay plaster also contain natural elements, unlike conventional paints which use
harsh chemicals. Clay plaster also helps in minimizing humidity, contributing to
better indoor air quality and acoustics.
Lime Plaster
Lime plaster is a mixture of sand, water, and lime. Lime used generally is non-
hydraulic for example slaked lime. First, a mixture is prepared with sand and lime
and then water is added mechanically to the mixture to obtain the paste of the
required consistency. The sand proportions in lime plaster control various properties
such as shrinkage, strength, porosity, and adhesiveness and fine sand is more
suitable for making the plaster.

Cement Plaster
Cement plaster is a mixture of portland cement, sand and water in a definite
proportion. It is used on interior and exterior walls to have a smooth, regular,
uniform, clean and aesthetically beautiful surface. Cement being a stronger material,
can be applied in a single coat of thickness 12 mm, 15 mm or 20 mm depending
upon the strength requirements. The only drawback of applying cement plaster is
that sometimes it becomes time-consuming and ultimately costly. It requires a
minimum of 7 days otherwise shrinkage cracks and efflorescence may develop.

Gypsum Plaster
Gypsum plaster is an eco-friendly substitute for traditional sand-cement plaster for
application on internal plastering surfaces. It is a quick method because it does not
have any curing period like in cement plaster.

Waterproof Plaster
To avoid the intrusion of water and thereby reduce the possibility of dampness,
waterproof plaster is applied. Generally, cement and sand are mixed in a ratio of 1:2
with pulverized alum added at the rate of 12 \(kg/cm^3/) of sand. Soft soap is mixed
with water at the rate of 75 gms per liter. It is the reaction of alum and soap that
results in the sealing of the pores in plaster.

Curing of Plaster
Curing should be initiated after 24 hours of plastering, the objective behind curing is
listed below:

o To maintain the required moisture content as loss of moisture results in

shrinkage cracks.
o To maintain the required temperature for the hydration reaction to take place.
o Proper curing helps in the development of desired properties of plaster.
o To prevent premature drying out of the plaster because of winds, sun etc.

Methods of Curing

There are different methods employed in curing, for eg. spraying, wet coverings,
shading etc.

Methods of Process Involved

Curing
Spraying By the application of water through spraying using pipes.
Wet coverings By using wet gunny bags, wet jute bags etc
Shading By preventing the exposed surface from direct sunlight and heat which cause
moisture loss.
Floor screed is composed of cementitious materials and sand blended based
on a suitable mix design and applied to provide a leveled surface for the floor
finish which is introduced to the surface of the floor screed. So, floor screed is
the base for the floor finish and greatly influences the performance of floor
finish. In this article, different aspects of floor screed will be explored.

Fig.1: Details of Floor Screed

Fig.2: Floor Screed Construction

Following points regarding flooring screeds are
discussed:
 Types of floor screed
 Floor screed materials
  What are the requirements that a floor screed should meet?
 Floor screeding procedure
 How a successful screed floor can be constructed?

Types of Floor Screed

There are different types of floor screed that is specified based on the
requirements and applications and the functionality of the floor:

 Unbonded screed floor (Figure 3 and Figure 6)

 Bonded screed floor (Figure 3 and Figure 4)
 Floating screed floor (Figure 3 and Figure 5)
 Heated screed floor (Figure 3 and Figure 7)

Fig.3: Different Types of Floor Screeds; (A) Bonded Screed,

(B) Floated Screed, (C) Unbonded Screed and (D) Heated
Screed

Fig.4: Bonded Screed Floor

 Fig.5: Floated Screed Floors

Fig.6: Unbonded Screed Floors

Fig.7: Heated Screed Floor

Materials for Floor Screed
Following are the materials used for construction of floor screeds:

 Cement
 Clean and sharp sand
 Water
 And occasionally additives are added to obtain specific properties.
Polymer materials or metal mesh or glass are likely to be introduced to
reinforce the screed.
The above components are adequately blended based on the prepared
material proportions. If the thickness of the floor screed does not exceed
40mm, then the recommended mix is 1 Portland cement: 3 sands or 1
Portland cement: 4.5 sand. However, 1 cement: 1.5fine sand: 3 coarse
aggregate (10 mm maximum aggregate size) should be considered if the
floor screed thickness is greater than 40mm. It should be known that drying
shrinkage gets reduced as the proportion of cement to sand is decreased.
Suitable amount of water should be specified to provide required workability
since excessive water would reduce floor screed strength and inadequate
water quantity lead to poor compaction.

What are the Requirements that a Floor

Screed Should Meet?
Floor screeds should have adequate thickness which is based on the screed
type and application frequencies. Recommended floor screed thickness
based on the type of the screed floor and the construction conditions are
provided in Table-1. Table-1: Recommended Floor Screed Based on the
Type of Screed and Construction Condition
Recommended
floor screed Floor screed type and construction condition
thickness, mm

For monolithic construction. In this case floor screed

will be placed no longer than 3 hours after the
12 placement of concrete. This will guarantee a
satisfactory bond between floor screed and placed
concrete beneath it.

For screed floor placed on hardened concrete. The

concrete should be cut by appropriate means then
40 cleaned, wetted and finally screed is placed. Not
only will this ensure good bond but also make the
screed to dry slowly and prevent cracks.

For floor screed placed on impermeable damp proof

membrane. In this case a bond between the screed
50
and the layer below it would not exist and hence
shrinkage is unrestrained.

65 For screed installed on compressible course of

 sound or heat insulation material. This is
recommended for domestic application only,
otherwise the thickness of the screed should be
increased. Lesser thickness will suffer from crack
development.

For screed installed on compressible course of

sound or heat insulation material. This is advised
75 for applications other than domestic utilization.
Lesser thickness will suffer from crack
development.

 Floor screed strength should be 20MPa for domestic application and

30MPa for industrial utilization
 It should be solid and compact so as to provide satisfactory base for
the floor finish
 It should be curried properly to prevent shrinkage and rapid drying
which lead to cracks. So, it should undergo almost all shrinkage, which
floor screed might experience, prior to applying floor finish. This will
lead to prevent the initiation of cracks.
 Finally, floor screed surface should be flat and smooth.

Procedure of Floor Screeding

1. Site Preparation: Before starting, it's essential to measure the
area accurately and develop a comprehensive plan. This includes
determining the required screed thickness and preparing for any
specific site conditions4.
2. Substrate Preparation: The base layer must be properly
prepared. For unbonded screed, reinforcement of the substrate may
be necessary. For bonded screed, exposing the aggregate and
applying a bonding agent is required. All surfaces should be cleaned
of dust and debris before proceeding4.
3. Material Mixing: The screed materials must be mixed according to
the appropriate design specifications to ensure proper consistency
and strength5.
4. Application: The screed mixture is applied to the prepared surface
and spread to the required thickness. Proper leveling techniques
ensure a flat, even surface4.
5. Finishing: The surface is finished according to the requirements of
the subsequent flooring material. This may involve smoothing,
texturing, or other techniques depending on the final floor
covering4.
6. Curing: The screed must be allowed to cure properly, which
involves controlling the drying process to minimize cracking and
ensure optimal strength development4.
How a Successful Screed Floor can be
Constructed?
 Choose right and suitable screed contractor
 Select suitable screed floor type
 Produce right and suitable floor screed mixture
 Construct floor screed using appropriate and acceptable screed
placement process
 Consider right approaches for floor screed protection
all rendering is the application of a cement mixture to exterior walls to
create a smooth, textured, or decorative finish. Similar to plastering but
typically applied to exterior surfaces, rendering serves both protective
and aesthetic functions. It shields the underlying masonry from weather
damage while improving the appearance of the building6.

Materials and Mixtures for Rendering

The typical rendering mixture consists of:
1. Sand: Provides bulk and texture to the render6.
2. Cement: Acts as the binding agent, creating strength and
durability6.
3. Lime: A crucial addition that increases flexibility and reduces
cracking. Even a small amount ("a pinch") improves the render's
performance significantly6.
4. Water: Added to achieve the right consistency for application6.
The proper mix ratio is essential for success, with lime being particularly
important for adding strength and preventing cracking in exterior
applications6.

Wall Preparation for Rendering

Before rendering begins, several preparatory steps are necessary:
1. Surface Assessment: The wall must be inspected to ensure it's
suitable for rendering6.
2. Cleaning: All surfaces should be free from dust, loose material, and
contaminants that might affect adhesion6.
3. Damping: Depending on the wall material and weather conditions,
the surface may need to be dampened to prevent it from drawing
water too quickly from the render6.
4. Corner Beads: Installing exterior corner beads helps achieve
straight, clean edges and reinforces vulnerable corners6.

Application Techniques
The rendering process typically involves:
1. First Coat Application: The initial layer (base coat) is applied to
the prepared wall. This coat provides the foundation for the finish
and helps level out any minor irregularities in the substrate6.
2. Reinforcement: For additional strength, reinforcement materials
may be incorporated into the render to prevent cracking6.
3. Leveling: Using tools such as a featheredge, the render is leveled
to ensure a flat surface. This step is crucial for achieving a
professional finish6.
4. Second Coat: If required, a second coat is applied after the first
has set but not completely dried. This helps ensure good bonding
between layers6.

Finishing Methods
Various finishing techniques can be employed depending on the desired
aesthetic:
1. Floating: Using a float tool to create a flat, smooth surface. The
technique involves working the tool in circular motions across the
surface until the desired flatness is achieved6.
2. Sponging: A sponge float is used to create a textured finish by
working it over the surface of the nearly-set render6.
3. Scraped or Roughcast: Creates a more textured finish for
aesthetic interest or to match existing finishes6.

Keying and Pointing in Masonry

Definition and Purpose of Pointing
Pointing refers to the process of filling and finishing the mortar joints
between masonry units such as bricks or stones. This technique serves
several critical purposes: it enhances the wall's weather resistance,
improves its appearance, and contributes to the structure's overall
durability. Properly executed pointing prevents water penetration, which
could otherwise lead to damage from freeze-thaw cycles, efflorescence, or
internal moisture problems78.

Types of Pointing
Various pointing styles are used in masonry work, each with distinct
characteristics:
1. Weather Struck Pointing: In this technique, the mortar is filled
and pressed to match the face of the brick masonry, then the top
edge is pressed inward to create a slope of approximately 10mm
compared to the bottom corner. This sloping effect allows rainwater
to drain rapidly, minimizing water retention on the masonry
surface7.
 2. Flush Pointing: The mortar is applied flush with the face of the
masonry units, creating a flat surface across both brick and mortar.
3. Recessed Pointing: The mortar is set back slightly from the face of
the masonry units, creating a shadow line that emphasizes the
pattern of the brickwork.

Materials for Pointing

The mortar used for pointing must fulfill several requirements:
1. Structural Adequacy: It should be strong enough to meet
structural requirements without being so strong that it inhibits
movement of the masonry8.
2. Weather Resistance: The mortar must provide a weathertight seal
to protect the wall from moisture infiltration8.
3. Aesthetic Compatibility: For architectural purposes, especially in
restoration work, the mortar should match the color and texture of
the original mortar8.
According to ASTM C 270, pointing mortar typically comprises:
 Cement
 Sand
 Lime (often included to improve workability and flexibility)
 Water8

Pointing and Repointing Procedures

The process of pointing new masonry or repointing existing walls involves:
1. Joint Preparation: For repointing, deteriorated mortar must be
carefully removed to a uniform depth (typically 1/2" to 3/8") or until
sound mortar is reached. This removal should not exceed one-third
the depth of the masonry unit above. The void should be
rectangular in shape, not "U" or "V" shaped, to ensure proper
bonding8.
2. Cleaning: After raking out old mortar, loose particles should be
removed by brushing, rinsing with water, or using compressed air8.
3. Mortar Preparation: According to ASTM C 270, pointing mortar
should be prehydrated to reduce shrinkage after placement:
 Dry ingredients (sand, cement, lime) are thoroughly mixed
 Half the normal amount of water is added
 The mixture is mixed until it holds shape when formed into a
ball
 The mix hydrates for one to two hours
 Additional water is added to achieve workable consistency8
4. Application: The mortar is applied to the prepared joints, pressed
firmly to ensure complete filling, and tooled to the desired finish8.
5. Curing: Proper curing is essential to prevent rapid drying, which
can cause shrinkage cracks and poor bonding8.
Quality Control in Pointing
Several factors influence the quality of pointing work:
1. Proper Joint Preparation: Inadequate preparation can lead to
poor adhesion and premature failure8.
2. Mortar Composition: The mortar must be properly proportioned
and mixed to achieve the desired properties8.
3. Application Technique: Careful filling and tooling of joints ensures
complete coverage and proper compaction8.
4. Matching Existing Work: In restoration projects, matching the
appearance of the original pointing is often critical to maintaining
architectural integrity8.
5. Weather Conditions: Temperature and humidity affect the curing
process and must be considered during application8.