Trainees Hand-Book Plastering

Construction Training

Trainees Hand-Out Plastering

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.

Tools waiting for workers



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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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Transcript of Trainees Hand-Book Plastering