Trainees Hand-Book Plastering

Construction Training
Trainees Hand-Out Plastering Page 1
Heinz Ropertz
CONSTRUCTION
TRAINING
Plastering
Hand-out

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General Safety on building site
The site is the permanent working place for masons, concrete workers and others. While
masons and concrete workers are permanently on one site from the beginning to the end
other trades as painters, plasterers and tile layers are more or less short time workers and
will leave the site after their work is done.
With working place or area the whole building site including equipment, machines,
storerooms and places in meant. Apart from the general working place there is the personal
working place, where somebody is building up a wall for instance. Space is a rare good on
the site. All material and equipment has to fit in a limited area. Therefore it is crucial
necessary to keep strong order on site.
A neat and tidy site safes time, eases the work, avoids accidents. If things like not used tools,
battens, boards, stones, cables, steel bars etc. are laying around somebody may trip up and
fall down.
Care and order support the building process and avoid accidents
What means an accident?
Personally:

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For the company and society:
Colleagues are in Sorrow
Basic safety signs for personal protection
Proper equipped mason

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Safety equipment
Helmet
Protects from down falling items, it should be a must for everybody who works or moves on
a building site.
Ear protection
Protects ears from noise, continuously working on the building side, is very noisy
environment and harms ears. Once the eardrums are damaged there is no way of restoring
the sense of hearing again.
Safety boots
Safety boots are equipped with three safety measures. It must have:
1. Toes protection hood
A steel hood to protect the toes from down falling heavy thing
2. A steel layer inside the soles protects the carrier from stepping into a turned up
nail.
3. Petrol and oil resistant soles
Safety goggles
Necessary during chiseling and grinding work protects against chips sparking around from
the work piece.

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Behavior rules to avoid accidents
Keep order and neatness at the working place
Ware tight clothes during work
Ware safety boots
Ware helmet
Do not step under lifted loads
Use only proper and safe tools
Report safety deficiencies immediately
Obey safety signs and signals
Do not drink alcohol at work
Dangerous Behavior on Site
AGAIN:
- Never step under lifted loads
- Use safety measures
- Do not drink Alcohol
- Do not balance on the top tie beam without safety measures

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The use of Scaffolds and ladders
Scaffolds are structures, that course a lot of accidents. Especially when badly erected or
misused the Scaffolds are necessary when the high of work extends the hand range of the
people.
Scaffolds must
bear the load of
materials, tools
and persons safely.
They must have
tight stand, be
anchored against
shifting and
sufficiently braced.
In order to protect
the people against
falling down a
triple side
protection is
necessary. If the scaffolds height excides 2,00 m a three part side protection and anchoring is
necessary.
The proper side protection consists from: barrister handle, interim barrister and footboard.
The toeboard should avoid
Triple Side Protection of Scaffolds
materials and tools falling down.

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Local scaffolding and Formwork in Ethiopia
Working with Ladders
Ladders are measures to reach higher or lower points. Ladders are at site very important. A
very frequent reason for ladder accidents is, that they slip away during use. It is necessary to
find a stable and secure stand for the ladder. The ladder should be placed at an angle of
approx. 70 ˚.
In case of stepping over to another part of the building the lather has to exceed the top
point at least 1 m. (right site)
Working with ladder: approx. 70˚, 1 m over the highest
point

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The “ten commandments” in Using Scaffolding:
1. Check every scaffolding to structural stability
2. Only step on scaffolds that have side protection (when over 2 m height)
3. Only persons free from giddiness/ vertigo can use scaffolds
4. If you feel a trace of unsafe, leave the scaffold immediately
5. While working on scaffolds be concentrated and avoid hastiness.
6. Go slow on scaffolds. Do not run by any means
7. No unnecessary loads on scaffolds. Do not store material and tools on the
scaffolding.
8. Use a lather to go from one floor to another. Never use the winch for transporting
people.
9. No alcohol on the scaffolds
10. Caution is not cowardice and carelessness not bravery.
Electrical Equipment
Another source of hazards is electrical machines and equipment. On the one hand they ease
the work very much, but on the other hand they can course accidents, when not proper used
or handled.
Danger from touching the power
The human body conducts the current; if someone
touches the machine body his own body becomes
part of the circuit, so that the current can flow.
Starting from a current of 0.05 Ampere the power
can course dead.
An inappropriate use of a hand lamp and a confusing
cable lining is dangerous. If the Untidy terrible place

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cable is broken and somebody touches the
bucket, trowel or iron bar or steps into the
water he will suffer a heavy electrical shock and may be dead.
The connecting cable of the mixer is broken and sets
the machine under power. The man who touches the
mixer stands in water and is a pretty good conductor
for the current. The power goes through his body into
the ground. We are not sure weather he has survived.
What Happened When Getting Contact to Earth?
Resume:
On every site there are a lot of electrical hand tools and machines employed and in use. The
purpose of every electrical tool is to ease the work, to accelerate the work process and to
better up the quality. The most common are drilling machine, concrete mixer, circular saw,
lamps, extensions cable, cutting machines, electrical vibrators etc. But when the tools,
machines and distribution board are not in safe condition, they can be a source of hazard to
anybody. A broken cable can set the body of a machine under power. If now somebody
touches the machine it will give a heavy electrical shock
Avoiding electrical accidents
Accidents can be avoided, when the distribution board is connected to the main course
according to the safety rules. A most important thing here is the RCD Residual Current
Device. This device cuts the power off immediately when a fouls occurs in the circuit. It is
therefore very important to safe lives on site.
The following has to be kept:
- Electrical tools and equipment must be in safe
condition
- Electrical tools and equipment must be
connected to the main board
- The RCD must be checked every day
- Do not use broken tools
- Flexible cables must be protected at exposed
points (lifted, covered)
- Illumination should be rain protected
Distribution Board in Good Condition

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Tools and Equipment
It is very important for everybody who wants to do decent work to keep his/ her tools in
perfect order. Tools ease and accelerate the work and improve the quality significantly. But
tools and equipment also represents highly valued assets. For this reasons it is crucial
necessary to handle tools and equipment with extra care. That means cleaning after use,
storing neatly, slightly greasing if necessary and regular maintenance.
Only carefully handled hand tools are safe tools
Measuring and Levelling Hand Tools
And instruments are precise devices and needed to be handled with extra care. Spirit level
e.g. should be checked every day before use!
Spirit level,
To erect horizontal and vertical walls, to check
the walls weather they are level and even. The
level demands always to be handled with care. It
should be checked from time to time weather it
is still working accurate.
Spirit level for horizontal and vertical
marking
Plumb bob,
The plumb is going to be hanged in the corner to
mark an absolute perpendicular line, when it
hangs without movement. Than it is fixed with
two nails to mark the line along which the tiles
should come closely.
Plumb bob for vertical marking & leveling
Nylon line, string
It marks the base line on the floor or wall and as the
line for every single row to be laid.
Mason line (fish line)

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Graphite Pencil
This is used for marking in wall construction. It is specially
produced for this purpose in such a way that it will not wear out fast.
Folding meter/rule-2/
For measuring length in wall construction, it is convenient to use rigid scales. Such a
measuring scale/ folding rule/ is made of 20cm separate wooden pieces joined together by
pins. The scale has subdivisions in cm and mm.
Hose level
Hose level to transfer meter score
It is a transparent PVC hose. It is used to transfer or mark vertical levels on surface of wall
when it is filled with water, but without any air bubbles. The water level in each end of the
hose is equal. It is an instrument to mark equal levels on site. It is very accurate but not
eases to handle.
Straight edge/Level/
This is a perfectly straight metal/aluminium/ with all
long and short edges parallel to its centreline. It is
employed to check straight alignments of walls. Straight edge
Its length ranges from 2m up to 4m. Together with
the sprit level, it can be used to bridge over the point to be checked. A straight edge/Level/
can also be made from a wooden plank with perfectly parallel edges.
Angle / Try square
It is used to measure a right angle (90º) of a corner. Used in
laying masonry units or blocks at corners of masonry wall.
Try square

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Measuring tape
Measuring tape
Tape is used to measure dimensions of building parts and distances in site. It is
manufactured from steel, plastic or fibre in lengths of 1m, 2m, 3m, 5m, 30m, etc. and 50m.
In using tapes for measurements, the two points should be aligned perfectly. In addition,
when long horizontal measurements are needed, care should be taken to avoid sag on the
tape meters.
Proper adjustment of measuring tape
Plastering Tools
Mason trowel
This is a tool, which every tile layer needs. Used for picking up mortar out of the barrel,
spreading mortar on the tile, the handle is used to knock the tile gently into place and
compact the mortar.
Mason trowel
Plasterer’s trowel

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Plasters spatula
Swiss float to score off the first coat
Wooden float, for scoring the plastered surface in the last
coat
Felt rubbing board to smoothen the last coat of the
plaster
Sponge board to smoothen the last coat of the plaster
Smoothing trowel for smoothing the last coat and scoring
mineral plaster

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Mason hammer
Tool for cutting and trimming bricks and blocks, removing
debris and to strike the chisel
Chisel
Chisel concrete, blocks and plaster. Cold chisel is
available in different sizes and is used together with a
club hammer and to remove extended material.
Mortar barrel/ drum
To prepare the mortar to the right consistence,
keep it workable and clean.
Mortar drum
Bucket
A Bucket is used to serve small amount of water or
material and to take the tools after work.
Bucket
Plasterers stool

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Brush and Broom
Used for cleaning the joints of the tiles and to clean the tools. Multipurpose tool
Plasterers brush
Sponge
To clean tiles after scratching and broom, and to clean
the tools after work

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Pliers
To create different shapes of a tile, to pull nails and whatever is necessary.
Plastering hooks to fix boards or battens on the wall
Plastering nail
Clup hammer
Knee pads
To protect the knees during long time kneeling
Gloves to protect the hands from the aggressive
attack of the cement, very important

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Equipment/Machinery
Extension cable
To connect all machinery and electrical equipment in a proper way
Concrete/ Mortar Mixer
Concrete mixers are available in from of different capacities.
Small mixers can produce 250Lit. of mortar or concrete and
the big ones produces more and more, up to 6000Lit.; widely
used, small mixers up to a capacity of 1000Lit. Mixers are
driven with diesel, benzene engine or electrical power.
Gravity Mixer 250 lit they can be distinguished into
Free-fall or gravity mixer consists from a rotating drum with
metal blades inside
Compulsory mixer, here is the drum fixed and the blades alone are rotating
Advantages of Mixers:
In case where a large quantity of mortar or concrete is to be produced, hand mix becomes
costly even if the labour is cheap. Hence machine mixing becomes essential and the mix
(mortar or Concrete) can be thus being produced at faster rate, at a lesser cost and of better
quality.
Wheelbarrow
Wheelbarrow /85Lit is used to dispose disposal materials
from working place, to transport or serve materials and
tools during construction activities in the site. It is the most
efficient way in transporting materials or items. In
comparison to a barilla, (commonly used in the country), a
wheelbarrow is much more efficient.
For this reason, it is operated by one person and can be carried up to 100 kg at once. So that
it saves operation cost; it is time effective and therefore in general.

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Angel grinder
Grinders are available as one hand and two hands. They are operating with high speed
rotary cutting discs. The protecting hood must not be removed by all means. A grinder is
very useful for cutting hard material like concrete, steel, natural stones or tiles. It is effective
to cut blocks or bricks perfectly than cutting with hands.
Angle grinder
Drilling machine
It is used to make or drill holes in concrete, stones and other
building elements or material. Drilling holes is depending up
on the size and materials to be drilled, i.e, the drill bits are of
different size and types. Types of drill bit can be classified as
bits for metal, wood and stone or concrete).
Electrical drilling machine
Lamp to illuminate the working place

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Selecting Material
General Building Technology knowledge
Production of cement
Cements are fine milled hydraulic binding agent of mortar
and concrete. Cement hardens/ sets on air or under
water.
The raw material for cement is lime- and clay marl/ stone
in different combinations. After breaking the material in a
pit it is fine milled and combined in the right dose (ration
lime stone: clay 3:1).
In a rotating kiln the cement raw powder in burned at a
temperature of 1450 ˚C at the sintering limit (melting
point). During this process the burning goods are
migrating through the sloping rotating kiln, of a length
from some times more than 100 m.
After the process the material is called cement clinker.
These are now small bowls from a diameter of approx. 1
cm. Now the cement clinker is fine milled together with
3% gypsum. The finer the cement grains the bigger is the
reaction surface, the faster is the chemical reaction when
it is set under water. Fine milled cement reach higher
compression strength after 28 days. But at the end after
2-3 years the compression strength is almost the same.

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Properties of cement
Cement is a hydraulic bonding agent. The bonding process, once it has started continuous
under water. The most important property of cement is the compressions strength. Usually
cement is named and distinguished after his compression strength after 28 days, but for the
on-going building process the strength after 2 and 7 days is also important.
When we put the compression strength after 28 days as 100 % we get the following table
Initial hardening time is 60 minutes
Final stetting should be after 12 hours
The than following hardening time is been taken after 2, 7 and 28 days but the cement will
gain strength more and more through the years
Hardening of cement
Kinds of cement
Portland cement
Portland cement has a medium rate per cent hardening and is suitable for the most types of
work.
Rapid Hardening Portland cement
Similar constitution like Portland cement except the
strength is developed most rapid. Good for construction
grate floor slabs and road construction.
Pozzolan Cement
Like Portland cement but the strength is developed slower, but after a certain tile the final
strength is the same.
Good for water proof buildings

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Kinds and properties of Lime
Introduction
Similarly like Cement, It is finely ground cementations material having adhesive and cohesive
properties which solidify when mixed with water and is one of binding materials used in
masonry work and other related works in construction.
The raw materials from which building limes are obtained are limestone and chalk. Both of
these materials are largely composed of calcium carbonate and were formed over a period
of millions of years by calcium deposits from marine life in the ocean of the world. As a
result of later earth movements, layers of limestone are to be found inland in many
countries of the world.
Classification of Limes
Most of the limestone or chalks quarried contain impurities such as silica, alumna, iron oxide
and sulphur. The lime retains these impurities after manufacture from calcium carbonate,
and their presence will greatly affect the setting times, working properties and strengths of
the resulting slaked limes. Limes of this type do not depend upon carbonation for setting
and are capable of setting out of air even under water. This property is termed hydraulic
The classification of limes is based on the degree of hydraulic follows.
(a) Non-hydraulic limes
This is the purest type of lime containing upon 98% calcium oxide. This produces a putty
lime, which has high plasticity and workability, and sets slowly by carbonation. It is also
known as high calcium lime.
(b) Semi-hydraulic limes
These limes contain sufficient impurities to impart feebly or mildly hydraulic tendencies.
(c) Eminently hydraulic limes
These contain a high proportion of impurities, which give the resulting slaked lime
properties.
(d) Hydrated lime
This should not be confused with hydraulic lime. Hydrated lime is obtained by slaking high
calcium lime under controlled conditions in a manufacture’s plant to ensure efficient slaking,
after which the excess water is dried off. The resulting powdered hydrated lime is sold in
bags. Hydrated lime, soaked in water overnight, will produce lime putty with improved yield
and workability. Hydrated lime is a ready product and it is not necessary to soak the lime
before use. Soaking the hydrated lime may spoil/decrease/ the ability of bonding. Hydrated
lime is most common and widely used in construction and is available in the market.

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Production of lime
The limestone or chalk is quarried, crushed and heated in kilns, at
900ºC, to drive out the carbon dioxide content. The resulting
material withdrawn from the kilns is calcium oxide, known also as
burnt lime, lump lime, and quick lime or simply as lime. The
materials are then slaked with water to from slaked lime (calcium
hydroxide), also known as lime putty.
Lime putty sets by a process of carbonation as a result of loss of
water and also by combining chemically with carbon dioxide from
the atmosphere. In doing so, it reverses the chemical actions,
which took place during the manufacturing process.
Manufacturing process of lime

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Gypsum
The raw material for the production of gypsum
is natural gypsum. The natural gypsum is going
to be ground and burned at a low temperature
of 300 ºC and at high temperature of
1000ºC.Durinf this process the crystal water is
deducted partly of totally.
With gypsum the workability period is very
short. From the beginning of mixing to the
beginning of hardening a period of 8 to 20
minutes is available
With the beginning of hardening the gypsum has already reached 40 % of its final strength.
From the beginning of hardening the gypsum should not be used any more. Especially the
adding of water should be avoided.
The hardening period can slow down by chemical additives. As well a small portion of
hydrated lime can do this job.
High temperatures will accelerate the process as well as remaining of gypsum in the mixing
water work as initial crystals.
Properties of gypsum
Gypsum sticks good to smooth and plan surfaces.
Gypsum does not shrink during hardening process so it can be used without sand.
Gypsum plaster can take and give up water
Gypsum is not water resistant continuously contact to water will spoil the matrix.
The contact from gypsum to metal is a problem metal in direct contact to gypsum must be
protected
Gypsum protects, because of its property of giving up the water when heated, construction
members against fire

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Sand
The biggest part of the mortar is sand; therefore it is advisable to keep an eye on the sand.
There are 3 properties sand should have
1. The sand should not be too porous so that the water
stays with the cement
2. The sand should have a good grain size distribution
curve. This safe cements and makes the mortar strong
3. The single grain should have a rounded shape. This
ensures workability of the mortar and eases the work.
Good grain structure through good grain size distribution and rounded grains
Aggregate and sand is the stable skeleton of the plastering mortar. Cement alone will shrink
too much and develop cracks.
Mortar section (magnified)

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Angle beads
To create even and flat surfaces the best
way is to use plastering beads. The beads
are going to be fixed on every corner with
gypsum or other fine mortar. Gypsum out
site is impossible.
The beads are to create a plan and even
surface and to protect the corner against
chipping off.
Corner Beads
For the area fast plastering beads are available to
indicate exactly the finished surface.
Application of Angle Beads Beads for the Area

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Storing plastering Material
Good storing
Cement and lime are binding material, if water is added a chemical action takes place
(cement and lime setting hard)
Therefore bags have to be stored well in dry air- tight place to keep its original strength.
Store the entire bags in a shed and on a dry floor. Cover it with a plastic waterproof foil or in
a dry store.
Storing of stones and bricks
- Bricks and stones should be piled near where they are needed
- They should be handle carefully to minimize breakage
- They should be plied on edges a layer crossing over the previous
- The piles should be stable

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Doesn’t store like this! Proper storing of HCB
Storing tools, equipment and aggregates
Shelf storing Tools hang up on a board
Storing tools and equipment Storing sand and gravel in bunkers
Scaffolding, wheelbarrows, planks e.g.

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Tools ready for work
Metal scaffolding should be stored inside to them free from rusting
Systematically stored tools and equipment are ease to find and safes
money.

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Estimating required Materials
Standard units
Standard units according to ISO 10 424 are a worldwide agreement how long a meter is or
how much weight has one kilogram.
1. Meter
The meter for instance is exactly 1/10 000 of the quarter of the earth circumference. The
first and original Meter lies in Paris and all meter in the world go back to this meter.
2. Kilogram
It is similar with the Kilogram. It was decided that the weight of 1 liter of water, which is 1
dm x 1 dm x 1 dm, at a temperature of 4 ºC at a certain air pressure should be called
1 kilogram kg
All other units are differenced from these Grand units.
We divide the meter as follows
1000 mm → 1 meter
100 cm→ 1 meter
10 dm → 1 meter
1 m → 1 meter
0.001 km → 1 meter
1000 m → 1 kilo meter
In construction business one, two and three-dimensional calculations are necessary.
When you want to measure the length of the skirting board of a room you simply measure
the entire walls and add them up.
Length
The length is a one-dimensional line. The unit of length is meter “m”.

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Exercises:
1. Change to the given units!
Write in m!
200 mm; 3 dm; 1397km; 12.5 cm; 1232 mm;
30cm; 0.02 km; 357 dm; 0.5 cm; 1224 mm
Changing Table
Write in cm!
34 m; 12.4 km; 123 mm; 98 dm; 0.45 mm;
1.74 m; 0.0043 km; 0.4 dm; 0.005 m; 3 mm
Write in mm!
20 cm; 1.374 m; 20.55dm;
12m; 0.0054 km; 53,9 cm;
12.909 m; 0.45 dm; 1 km;
247 cm.
Calculate the length of needed skirting board!
2 x 4.51 + 2 x 3.76 – 0.885 = 15.66 m
Floor plan of a room
Read from left
to right mm cm dm m
mm 1 10 100 1000
cm 0.1 1 10 100
dm 0.01 0.1 1 10
m 0.001 0.01 0.1 1

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Area
An area has always two dimensions. The unit for an area is
meter square “m²”.
Change to the give unit!
Write in dm²!
2.75 m²; 24.80 m²; 0.8 m²; 0.935 m²; 248 cm²; 968.46
cm²; 23.5 cm²; 56 cm²; 1200 mm²; 5902 mm²
Area Calculation
Write in m²!
8 km²; 5254 dm²; 245 dm²; 27652 cm²; 0.5 km²
120000 mm²; 86431 mm²; 240 cm²; 987 cm²
Write in cm²
0.5 m²; 23 dm²; 2340 mm²;
93 mm²; 1.2 m²; 9.345 dm²;
20094 mm²; 3.2 m²
Calculate the area of the room beside
4.51 m x 3.76 m = 16.96 m²
Floor Plan of a Room
Read from left
to right mm² cm² dm² m²
mm² 1 100 10000 1000000
cm² 0.01 1 100 10000
dm² 0.0001 0.01 1 100
m² 0.000001 0.0001 0.01 1

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Volumes
The volume has then following the logic of length
and area three dimensions length, width and
height. The unit of volume is meter cube “m³”.
Change to the given unit!
Write in dm³!
26 m³; 24.364 m³;
23076 cm³ 2395 cm³;
2034954 mm³
Write in cm³
2983 mm³;
7893 mm³;
0.083 m³, 35 dm³;
95.3 dm³; 0.2 m³
Volume calculation
Write in m³
5254 dm³; 245 dm³; 27652 cm³; 0.5 km³
120000 mm³; 86431 mm³; 240 cm³; 987 cm³
Calculate the volume of the room above assuming
the height is 2.60 m!
4.51 m x 3.76 m x 2.60 m = 44 09 m³
Volume Calculation
Read from left
to right mm² cm² dm² m²
mm² 1 1000 1000000 1000000000
cm² 0.001 1 100 10000
dm² 0.000001 0.001 1 100
m² 0.000000001 0.000001 0.001 1

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Mortar consumption of finishing work
In plastering and tile laying the most obvious calculation are layers of mortar. A certain area
to understand the formula it is necessary to know, that a layer of 1 m² area and a thickness
of 1 mm has the volume of 1 liter = 1 dm³
Proof: 10 dm x 10 dm x 0.01 dm = 1 dm³
1. Calculate in dm
The following formula contains the following letters
A Area in m²
t Thickness of the mortar in mm
1.92 Mix-in measure and waste * Density of cement (1.2*1.6)
s Sand content in the ratio
The result of the equation is the cement in kg
Example:
Screed: Area to be screed 30 m²
Thickness in average 45 mm
Mortar ratio 1 to 5
30 * 45 * 1.92 / (1 + 5) = 432 kg Cement
432 / 50 = 8,64 bags → 9 bags of cement

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Exercise
Compute the cement and sand consumption for the
screed of the room. The screed should be 5cm thick
This formula applies to all mortar layers like
plastering, tiling and Screed

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Prepare Mortar
Mortar in General
Ordinary mortar consists from sand, cement and water. These three things are going to be
mixed in different ratios.
.
But this procedure depends on certain conditions.
1. The sand should be sieved and cleaned
2. The mortar should not be to poor
3. The mortar should not be to rich
4. The sand should have the right grain size, not to rough and not to smooth.
Sieving and washing
Sand for mortar should be sieved and washed. Simple machines for this purpose are shown
below
Simple throw-through sieve Simple sand washing machine

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Find the correct ratio
To find the right ratio of the mortar is very important. The sand is not the same in the
various areas. Some sands demand more cement and some less. To find the right ratio, to
achieve the best connection between the wall and the mortar is one of the previous tasks.
MIXING
Mortar for plastering is usually mixed at the site, and mixing may be manually and
mechanically
The amount of cement is very much
depending on the sand. A test when
news sand is delivered is necessary.
The mixing ratio can due to the above-
mentioned reasons differ from 1:4 to
1:5. If the sand is very fine and loamy
the ratio is very poor 1:6. If the sand is
very rough and has not much fines
than the ratio is relatively rich 1:4.
The plastering mortar has no
structural bearing, meaning its only
purpose is to hold its self on the wall.
So the ratio, although is seems to be
to poor, provides by fare enough strength for tile plastering work.
A very rich mortar like 1:1 or 1:2 is very harmful to the connection of mortar and wall,
because the shrinkage rate of this kind of mortars in so high, that the tile will shear off after
some time from the mortar.

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Manually
In this method, mixing is done on a water tight steel plate or on a clean hard surface.
The method is resorted to when the quantity of mortar needed for is small the work
The mortar is prepared dry, first.
The right amount of material is measured and hipped up
Shovelled from one site to the other
Wetted with the right amount of
water
Shovelled through again until the
water is distributed equally
Transported to the plastering place
But it must been known, that this
kind of mixing provides the poorest
result concerning the mixing quality.
Better is to use a proper mixing
machine.
Machine Mix Modern preparing of mortar by the use of mixer
Preparing mortar on site

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It is used when large quantity of mortar is required continuously at fast rate. In this method,
mixing of the ingredients of mortar is done in a machine, which is known as Mixer. Binding
materials, cement and lime, in specified proportion are put into the drum of the mixer and
then required of water is added immediately before revolving the drum. After this, the drum
is revolved for sufficient a period to form uniform mixture of required consistency.

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Preparing back ground for plastering
Clean the back ground
All mortar droppings and dust should be removed with the help of broom and masons
hammer
Level the wall area with nails
- check plainness of the wall by placing floating rule horizontally, vertically and diagonally at
different locations
Do the followings
Mark three parallel lines are on the wall
At a height of 120 cm above the floor surface the levelling nails A and B are nailed.
Nails C and D are fixed at a joint approximated 10 cm above the floor level. They are then
plumbed with nails A and B by means by means of floating rule and sprit level

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Level the wall areas with nails
The diagonal control over the nails A-D & B-C is conducted. Wet the back ground using water
and brush.
Two and Three- coats
In the three coat plastering the first coat is known as rendering coat; the second coat is
known as floating coat and the third coat is known as setting or finishing coat.
Two -coat plaster
The following procedure is adopted.
 Raking the joint to a depth of 20 mm and cleaning the surface and well watering it
to prepare the back ground
 If the surface to be plastered is very uneven, a preliminary coat is applied to fill up
the hollows, before the first coat.
 The first coat or rendering coat is of plaster is applied, the thickness being equal
to the specified thickness of plaster less than 2 to 3 mm. In order to maintain
uniform thickness of plaster, screeds are formed of plaster on wall surface by
fixing dots of (15*15) cm. Two dots are formed in vertical line at a distance of
about two meters and plumbed by means of plumb bob as shown below.
 A vertical strip of mortar, known as screed, is then formed. A number of such
vertical screeds are formed at suitable spacing. Cement mortar is then applied on
the surface between the successive screeds, and the surface is properly finished.

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Three- coat plaster
The procedure for applying three- coat plaster is similar to two-coat plaster except that an
intermediate coat, known as floating coat, is applied. The purpose of this coat of plaster is to
bring the plaster to an even surface. The rendering coat is made rough. The floating coat is
applied about 4 to 7 days after applying the first coat. The finishing coat may be applied
about 6 six hours after the application of floating coat.
Applying rendering coat
The mortar is forcibly applied with mason’s trowel pressed well in to joints and over the
surface. The thickness of the coat should be suitable to cover all inequalities of the surface
with normal thickness of 12 mm. This is allowed to slightly harden and then scratched
crisscross with the edge of trowel. The surface is left to set at least for 7 days. During this
period, keep it damp and allow the surface to dry completely.
Detailed procedure
 Mix lime mortar
 apply mortar between plastering aid
o To insure best bondage the mortar must be applied with swing. This forces
the mortar to penetrate the pores of the plastering area. More over the base
coat absorbs some of the lime solution resulting in the formation of small
dowels which facilitate the bonding of the mortar. The plastic mortar is
applied starting at the bottom next to the aids and proceeding up wards.

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Strip mortar over the plastering aid. The excess mortar used to fill hollows. The process is
repeated until the surface of the fresh mortar is completely levelled.
1. Trowel the surface the surface of the plaster. The fresh mortar surface cannot be
towel immediately. It must be let to set a little bit until it is not possible to smash it
in with the thumb any more. The trowel is guided in a circular motion applying a
light pressure at the same time.
Should the mortar have set too much, it can be wetted lightly using the floor brush. One of
the activities is to produce a clean finish at the wall-floor joint. This can be achieved by
moving the wooden float horizontally applying a small pressure at the same time.

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During towelling the surface is continuously checked for plainness using the floating rule.
PREPARATION OF SURFACES, MORTAR, DOTS AND SCREEDS
PREPARATION OF SURFACES
Clay Bricks
Sweep the surface, and then wet it sufficiently to control the suction. Due to variation in
materials, your instructor will demonstrate to you the degree of wetness required.
The wall can then be rendered with the material specific for the job. On large areas it is
advisable to scratch coat the wall a few days before rendering. Even suction is then
achieved.
Clay bricks that have been silicon dipped should be swept clean, then scratch coated with
sand/cement slurry.
Masonry Blocks
Sweep the surface clean then apply a splash coat (a very fluid mix of two (2) parts sand, one
part(1) cement (type A) and water). Flick the mix onto the wall with a trowel or brush. Leave
the wall to dry for 24 hours before plastering
Concrete
Concrete should be sparrow picked to remove laitance, paint, curing agents and form oil.
Sweep the wall clean and then brush slurry of water and neat cement into the wall. While
the slurry is still wet, apply a scratch coat.
If sparrow picking is not required, a bonding agent of 4 parts bonding agent to 1 part water
is applied and the wall then scratch coated. The bonding agent should be still tacky when the
scratch coat is applied. This will enhance adhesion.

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PREPARATION OF MORTARS
Mortar is a mixture of lime, sand and water or cement, sand and water, or a mixture of both.
Because of its adhesive properties, mortar will provide an even bedding to unite the
materials to be fixed into one mass. The properties of a good mortar are:
It should be easily workable to reduce the labour of applying and spreading it, and to make
sure that it stiffens quickly enough to avoid any delay to the work;
It should develop “sufficient strength” for the job on which it is used; and it should be
durable and should not affect the durability of other materials.
Basic Materials
Cement
The cement used in mortars is ordinary Portland cement
Lime
Lime is generally used in Australia are non-hydraulic lime. As they are lacking substantial
proportions of silicates and aluminates, which hydrate in the presence of water, they will not
set under water. Building limes are marketed as: Quicklime and Hydrated lime
Quicklime possesses a great affinity for water and is highly caustic. It must be slaked before
it is used. It is important that this slaking is completed before the lime and sand is made up.
For this reason it is common to specify that lime shall be “slaked until all lumps disappear”,
and the mixed
Lime mortar is to “stand for fourteen days before use”.
Hydrated lime is a dry powder obtained by treating quicklime with just enough water to
satisfy its Chemical affinity.
Hydrated lime is more convenient to use than quicklime, but does not give plasticity equal to
that of well-slaked quicklime. It is also less economical on large jobs. Fattier mortars result if
the hydrated lime is made into a putty or paste prior to use (best practice), even an
overnight soaking is beneficial. Hydrated lime may be mixed dry, but the expansion, which
develops, will harm the adjacent mortar.
Sand
Sand used in mortar should be clean and sound. The presence of dust and dirt may interfere
with the setting and hardening of the mortar and impair its strength, adhesion and
durability. Salty sands should not be used, as the presence of soluble salts may lead to
efflorescence.

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Types of Plastering Mixes
Composition Mortar
A plastering mix composed of cement, lime and plasterer’s sand 1:1:4 is a typical compo mix
Cement Mortar (Render)
A plastering mix composed of a cement and sand. A small quantity of lime may be included
as a plasticiser.
PREPARATION OF DOTS AND SCREEDS
When walls exceed 3m in length, it is necessary to fix “dots” to the area to be plastered to
ensure accuracy in the plumbing and lining on the horizontal.
Take a small amount of mortar or compo and lay it about 50mm from each internal angle, or
as close as possible to any external angle and about the same distance up from the floor
level (see Figure 15).
The top dots are placed at your reach height (approx. 2m). Press a strip of tile or hardboard,
measuring approximately 150mm x 25mm, vertically into the bed of mortar or compo (see
Figure 16) allowing for a render thickness of about 12-18mm. If a thickness in excess of
20mm occurs, a scratch coat should have first been applied.
The next step is to fill in between the dots to form the screeds. Screeds are the guides for
floating.
The plaster is laid on about 150mm wide to coincide with the dots. It is then ruled down until
perfectly in line with the dots, which are then removed. The voids are then filled level with
the existing screed.
Points to Observe:
Dots should be in the plane of the finished wall.
Mark the position of the dots.
Screeds should be ruled flush with the dots and be flat.
Common errors with beginners include ruling screeds hollow, and ruling unevenly by putting
uneven pressure at the top and bottom of the screed.

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THE DOT AND SCREED METHOD OF
PLASTERING A WALL
AN ENLARGED VIEW OF A DOT

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Carrying out plastering work
Stresses on Plaster
Inside plaster as well as outside plaster
is exposed to stresses and has to fulfill
certain tasks.
Outside plaster should protect the wall
from sucking water during rain and
getting wet. Wet walls create a bad
climate inside the house and make the
inhabitants thick.
Stresses on Plaster
On the other hand the plaster must allow the moister to pass the wall from the inside.
Otherwise the wall will get wet either
Outside plaster must stand the alternating temperature and moister without cracks and
separating through shearing off from the wall.
Last but not least the plaster ensures a nice appearance of the whole building
To fulfill all the motioned tasks the plaster is
mostly applied in three layers.
An old saying goes:
Never tough on weak
It means: from the inside to the outside never
apply a layer on the previous, which is tougher
than the one before.
Mounting of Plaster Layers

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Checking and Cleaning the Surface
The Background
Before you can apply plaster onto a background you have to check it very well. There are
certain conditions the background should meet.
The background should be
1. Tough
2. Stable
3. Sound
4. Not too smooth
5. Free from oil paint
6. Free from oil or grease
7. Free from dust
8. Not brittle no loosen substances
9. Free from gypsum lumps
10. Straight and even
11. Closed masonry joints
12. Tension cracks
Brittle background
Different backgrounds require different
treatment. Here are some examples of possible
backgrounds.
1. New concrete
2. Old concrete
3. Brickwork, block work
4. Plaster, render
5. Screed
6. Gypsum plaster board
Sloppy grouted block work

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Checking of level and evenness
The deviation
from a straight
line should not
exceed 10 mm
per m as shown
in the picture.
Applying the first coat
The first coat or splash coat is a
fine and rich mortar from rough
sand the first coat is to ensure
the best connection of mortar
and wall. The wall itself must
meet the requirement motioned
above.
It is prepared as slurry and
thrown on the wall.
Applying first coat
The application of chemical primer is not necessary for cement or compo mortar. Because
the surface is too rough, and the primer will not have any duty

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Hacking and chiseling
Is necessary on concrete surfaces, because of the common use of burned oil as separation
agent for the formwork
It can be avoided, when
 The use of a proper lubrication is introduced
 The plastering layer is slimmed down to at least to 10 – 15 mm
 The conduction of the concrete work is more accurate
 The plastering mortar performs more flexible and weak
But in the meantime chiseling stays necessary!
Fixing of Corner Beads
If angle beads are available they are fixed with a fine mortar outside and/ or with gypsum
inside. See picture
They act as a metal gage to indicate the exact level and direction of the finished plaster
works.
Fixing of angle bead

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Working with Plastering Guides
First fix a siring or line on top of the wall to be plastered. Along this line dots are fixed to
mark the straightness. From this dots down mortar gages are installed perfectly in vertical
level see pictures. Instead of the mortar gages it is also possible to fix small metal or wooden
guides, which can be de-installed and the trenches filled up after plastering the wall.
The traditional
way is to make
gages from mortar
with a distance of
approx. 1.50 m
After the first coat
is hardened the
second coat can be
applied. There is
no vital difference
between the
different kinds of
mortar when it
comes to the
application
techniques.
 The space between the gages is going to be filled with mortar
 After the mortar is stable enough the surface is pulled-off with a straight edge to
remove to surplus mortar down to the level of the gages.
 Remaining holes are filled and pulled-off again
 When the surface is nearly closed it is scored with a wooden float to close the
surface.
 After scoring the surface is treated with a steel float to be finished

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Applying mortar
Pulling-off surplus mortar

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Use of wooden float to close the surface
Finishing with steel float
Enjoy your Hand- Out and keep it clean and all the time by hand

Trainees Hand-Book Plastering

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