UNIT - VI
Building Finishes
• Plastering: Methods, tools used, Mortars, Defects, Plaster types: Lime
plaster, cement plaster, gypsum plaster, Plaster of Paris and
applications
• Pointing: Purpose and Types of pointing, Methods of pointing.
• Paints : Types and applications , Textures, Apex, Plastic emulsion
• Wall cladding: Materials, method of fixing, wall papering and glazing
work
• Damp proofing: causes, effects, prevention, and treatments,
• Fire resistant construction: Fire resistant properties of common
building materials, requirements for various building components.
Building Finishes Means ?
• Building finishes such as plastering, varnishing, dis-tempering, white-
washing, coloring, etc. basically perform two functions as pointed
below.
They give a protective coating to the surfaces which protects them from
weather effects such as rain water, frost, heat etc., and
They provide decorative effects which add to the appearance of the surfaces
and building as a whole.
Plastering
• Plastering is the process of covering rough walls and uneven surfaces in
the construction of houses and other structures with a plastic material,
called plaster, which is a mixture of lime or cement concrete and sand
along with the required quantity of water.
• REQUIREMENTS OF GOOD PLASTER
It should adhere to the background and should remain adhered during all climatic
changes.
It should be cheap and economical.
It should be hard and durable.
It should be possible to apply it during all weather conditions.
It should possess good workability.
Before Plastering and After Plastering
Mortar
• Mortar is a bonding agent which is generally produced by mixing
cementing or binding material (lime or cement) and fine aggregate
(sand, surki, sawdust, etc.) with water.
• Mortar is used to bind different building blocks like bricks, stones, etc.
It can also add a decorative pattern in brick or stone masonry.
• Mortar is being used from the dawn of civilization. 2000 years ago,
the Egyptians used lime mortars.
• Types of Mortar
• Cement Mortar
• Lime Mortar
• Gauged Mortar
• Mud Mortar
• Cement Mortar
Cement mortar is a type of mortar where cement is used as binding material and sand is
used as fine aggregate. Depending upon the desired strength, the cement to the sand
proportion of cement mortar varies from 1:2 to 1:6.
• Lime Mortar
• Lime mortar is a type of mortar where lime (fat lime or hydraulic lime) is used as binding
material and sand is used as fine aggregate. The lime to the sand proportion of cement
mortar is kept 1:2. The pyramids at Giza are plastered with lime mortar.
• Gauged Mortar
• Gauged mortar is a type of mortar where cement and lime both are used as binding
material and sand is used as fine aggregate. Basically, it is a lime mortar where cement is
added to gain higher strength. The process is known as gauging. The cement to the lime
proportion varies from 1:6 to 1:9. Gauged mortar is more economical than cement
concrete and also possesses higher strength than lime mortar.
• Mud Mortar
• Mud mortar is a type of mortar where mud is used as binding material and sawdust, rice
husk or cow dung is used as fine aggregate. Mud mortar is useful where lime or cement is
not available.
Cement mortar
Lime /mud/Gauged
Tools required for Plastering
• Gauging Trowel
Gauging trowel tools are used to gauge small quantities of materials and apply cement mortar to
corners, moldings, etc.
The physical appearance of this plastering tool can either be pointed or bull-nosed on one end, as
we can see in the below image.
• 2. Spackle Knife
• A Spackle knife is small in size but can play a significant role in plastering work; before using this
tool or any repair, one must ensure to run a sturdy knife on cracks and uneven surfaces to use this
tool smoothly.
• Following the above procedure will remove chips of old plaster and high points and give a clean
and smooth surface to apply plaster evenly with a spackle knife.
Gauging Trowel Spackle Knife
• 3. Spirit Level
• This tool is essential and very useful during plastering work, As the spirit level
helps to achieve an even and flat finish.
• It consists of a water tube through which the surface level can be known. It
also allows you to increase your work quality and attain evens from all sides.
• 4. Straight Edge
• A straight edge is a plastering tool used to even off rendered floors that can
cover a large area in a short period. Generally used for leveling the concrete
surface or plastered surface and also used to measure distance.
• 5. Float
This tool is used for applying and spreading the cement mortar on the
surface. It is a flat wooden or metal board with a handle on a flat surface.
There are two types of floats based on the type of material used to make it.
1. Metal float
2. Wooden float
Straight Edge
Spirit Level
Metal Float Wooden Float
• Plumb bob
• Plumb bob is a level-checking tool that
is used to check the vertical levels of
the wall. The appearance of this
plastering tool is usually a solid cone
shape bob with a pointed one end and
a thread tied on the other end.
• Tube Level
• A tube level is used to level the upper
part of the plastered surface to attain
an equal and clean finish. A tube level
is a transparent plastic tube or small
pipe filled with water without a bubble.
It works on the principle that water
seeks its level.
Defects in Plastering
1.Cracks on Plastering
• Cracks can be broadly classified as structural cracks and non-structural cracks.
• Non-structural cracks include crazing where a network of fine cracks like spider web with
hairline depth appear due to rich cement content in mortar or due to the presence of excess
dust in the sand or due to improper curing. Cracks due to shrinkage (loss of moisture content
from the plaster) also fall under non-structural cracks.
• Cracks which are visible on plaster resulting from cracking of walls are known as structural
cracks. These can be caused by differential movement of the foundation and thermal
movement of the roof slab and this type of cracks often forms a straight vertical line or
horizontal line or in steeped diagonal lines. Structural cracks are the one to be worried about,
which need immediate evaluation for the root cause and correction guidance from the
experts.
2.Blistering of Plastered Surface
• Blistering is the formation of small patches of plaster, swelling out beyond the plastered surface, arising
due to late slaking (addition of water to lime) of lime particles in the plaster. This defect is usually
caused due to the uneven mixing of plaster.
• How to prevent it: This can be prevented by ensuring appropriate mixing between cement and it’s
components used to form plaster.
3. Plaster De-bonding
• De-bonding occurs when a plaster is separated from the wall. It can be caused by an excessively
thick plaster layer, inadequate substrate preparation or may be due to a dusty, oily or dry substrate.
• How to prevent it:
• Remove dust & oil from the substrate before plastering.
• Allow substrate to reach correct moisture content.
• If necessary you should use bonding chemical.
4.Efflorescence on Plastered Surface
• When a newly constructed wall dries out, the soluble salts are brought
to the surface and they appear in the form of a whitish crystalline
substance. This is called efflorescence.
• Efflorescence is formed on plasters when soluble salts are present in
plaster making materials as well as building materials such as bricks,
sand, cement etc.
• Even water used in the construction work may contain soluble salts.
• It seriously affects the adhesion of paint with the wall surface and
causes further problems.
• How to prevent it:
• All Construction materials used for wall should be free from salt.
• Ensuring that the surface is moisture-free.
5.Falling Out of Plaster
• This defect can happen in two forms – Flaking of plaster and peeling off plaster.
• Flaking of plaster: The formation of a small loose mass on the plastered surface is known
as flaking. It is mainly due to bond failure between successive coats of plaster.
• Peeling off plaster: The plaster from some portion of the surface comes off and a patch is
formed. This is termed as peeling. It is also mainly due to bond failure between successive
coats of plaster.
• How to prevent it: Both defects can be prevented with proper material selection and
surface preparation. Imperfect adhesion can be minimized by good workmanship.
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.
2. Lime Plaster
Lime plaster consists of lime, sand. and water. The proportion of lime and sand is
equal. Sometimes, little amount of cement may also be added to improve the strength
of the plaster. In lime plaster mostly fatty lime is used. Hydraulic lime results in
blisters on the plastered surface.
