INTERNAL
PLASTERING
Internal Plastering
Plastering helps provide better sound and
thermal insulation and fire resistance.
• A good plasterer should have a sound
knowledge of materials to use and their
characteristics.
• A plasterer should identify the correct
materials and their suitability for any given
situation.
• A good plasterer should be able to put right
any problems with their work and that of
others.
•
BACKGROUNDS
 The
background is the surface that
your first coat of plaster is applied to.
 The background needs to provide a good
bond for your plaster.
 Preparation of backgrounds is key to a
good standard of finished work.
 If a background is not suitable or
prepared well, your plaster will not stick
to it properly.
SUCTION
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A plasterer needs to check the rate of
suction of the background before applying
plaster.
Too much suction can cause the material to
shrink or crack and loose adhesion.
It can be difficult to rule in or get flat
because of the loss of water in the material.
The plaster will not reach its full strength
and could fall off.
Too little suction can cause the material to
slip down the wall making it hard to rule in.
High Suction Background
Can include Aerated
Block, old brickwork and
softer types of brick.
 Can be wetted before
plastering to control
suction.
 Can be controlled with
two coats of PVA , one
very wet to seal and a
50 / 50 mix for
adhesion.
 Use direct bond,
hardwall, render.
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Medium Suction Background
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Can include lightweight
aggregate concrete
blocks and clay
brickwork.
Generally has good
suction.
Make sure is dust and
grease free and clear of
mortar snots.
Can use all plaster
products.
LOW SUCTION
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Includes in situ
concrete, plasterboard,
painted surfaces.
Never apply render until
a good key has been
formed or it will fall
off.
Use spatterdash, gyp
bond for key.
Use Carlite bonding,
direct bond.
EXPANDED METAL LATHING
Can be used inside and
outside.
 Flexible so can be
curved.
 Fixed to wall plates to
provide a key and resist
movement.
 If fixing rib lath the
ribs should be in contact
with and at right angles
to the support.
 Needs pricking up coat
first.
 Use Carlite Bonding.
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COMPOSITE BACKGROUNDS
A background with a
range of materials.
 This can have
different rates of
suction.
 Use different
methods to create a
key eg pva, gyp bond,
spatterdash.
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PREPARATION
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1. Brush down the background to remove all
loose materials and dust etc. to give a good
sound background.
2. Remove all mortar snots from joints,
internal and external angles.
3. Make a key, if needed to the background.
4. Test the background for suction ( splash
some water on the surface and see how
quickly it gets sucked into the background).
5. Treat if necessary.
PREPARATION
 6.
Place drop boards at bottom of wall
to catch any material that is dropped.
This can then be re used.
 7. Fix EML to any timber wall and sole
plates as necessary. This stops the
plaster cracking and falling off the
wood.
 8. Fix any angle beads that are required.
 9.Set up the spot board and stand.
METHODS OF WORK
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BROAD SCREEDS.
Use on small areas.
Does not give the
highest standard of
work but better than
freehand.
Apply screed to corner
of wall and rule off.
Keep depth of material
to no more than 11mm.
Place another vertical
screed in other corner
and rule off.
BROAD SCREEDS
Don’t place any
screed in between
the two end ones.
 Form a horizontal
screed top and
bottom and rule off
using the vertical
screeds.
 Using the screeds to
rule off, fill in
between the
screeds.
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DOT AND SCREED
Can be used on long
or high walls.
 Use if the finished
work has to be
absolutely plumb.
 Gives the highest
standard for
tolerance purposes.
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DOT AND SCREED
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1. Place a dot of material near an internal
angle, place a lath in the dot.
Dot should be about 300mm away from
adjoining wall.
2. Place a second dot at the bottom of the
wall, place a lath into the dot.
Dots should be about 2.5m apart.
3. Plumb in the two dots using a floating rule.
4. Either tap in or bring the wood out until
the two dots are in line.
DOT AND SCREED
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5. Place another two dots at the other end of
the wall.
6. Place intermediate dots in the middle of
the wall.
7. Line the intermediate dots through
horizontally off the two perimeter dots.
8. Join the dots together as the Broad screed
system.
9. Fill in between the screeds and rule off.
APPLYING A KEY
Each progressive
coat of plaster
needs to be keyed.
 A key provides an
Inter Surface bond.
 The depth of key
used depends on the
weight of the next
coat of plaster to be
used.
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 After
the wall has been keyed before
skimming run the trowel over the wall to
remove any pick ups etc.
 All internal angles need to be ‘cut in’
using the trowel.
 Any plaster along external angle bead
needs to be cut back to allow room for
the skim coat.
FINISHING
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The finish coat provides the final, smooth
coat for decoration.
Generally not more than 3mm thick but can be
up to 5mm.
Always applied in two coats for the best
finish result.
If matching to a lime plastered surface the
finish used will be lime putty / fine sand mix.
Finish coats should not be over trowelled as
this can prevent the paint sticking to it.
METHODS OF WORK
 TROWEL,TROWEL
 This
is the most commonly used method
of work for skimming.
 1. first coat is the scratch coat.
 2. each stroke should overlap the
previous one.
 3. fill any hollows, joints etc. with the
scratch coat.
TROWEL,TROWEL
 4.
Once scratch coat has picked up –
apply laying down coat.
 5. this should be slightly tighter than
scratch coat.
 6. When laying down coat has picked up
enough, apply first dry trowel.
 7. Trowel twice more with just enough
water to lubricate the trowel and to
work the plaster.
TROWEL,TROWEL
Any hollows, marks etc. should be filled with
the first trowel (fat). Any later than this the
fat will be too watery and has no strength.
 8. Clean angles out at final trowel and use
brush to clean angles and beads.
 9. Cross trowel at right angles to trowelling
strokes to remove any water or fat marks.
 10. Clean skirting line of excess plaster
material (lips)
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TROWEL,FLOAT,TROWEL
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This method is useful on uneven backgrounds.
1. Apply scratch coat with trowel.
2. Apply second coat using a float.
Because the float is more rigid than a trowel,
it will straighten out any irregularities in the
floating coat.
3. When the second coat has picked up, apply
thin laying down coat with the trowel.
4. Trowel the work as before.
BEADS
Float ( angle ) bead.
 Used to form external
angles.
 Galvanised or stainless
steel.
 Fix using dabs of
material.
 Need to be plumb, level
and straight along their
length.
 Make sure wings are
behind finished edge.
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STOP BEAD
Reinforces and
finishes edge of
plaster where no
other material
meets it.
 Can be used to finish
plaster if butting up
to another material
if there is no cover
being used eg. No
arcitrave.
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FEATURE BEADS
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Used to form
shadow gaps along
skirting board.
MOVEMENT BEADS
Fixed over any
movement joints in
the background to
prevent cracking of
the plaster.
 Fix with dabs.
 Can be formed with
two back to back
stop beads and
mastic filler.
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MATERIALS
Carlite Bonding
 Undercoat plaster
for low suction
backgrounds eg.
Concrete and
plasterboard or
surfaces treated
with a bonding agent.
 Purple bag.
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THISTLE HARDWALL
Undercoat plaster
with high impact
resistance.
 Quicker drying
surface.
 Use on medium to
high suction
backgrounds.
 Blocks,
bricks,thermalite.
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THISTLE TOUGHCAOT
Undercoat with good
impact resistance.
 Use on medium to
high suction
backgrounds.
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CARLITE BROWNING
Undercoat for
backgrounds of
moderate suction
with a good key.
 Make sure suction is
controlled when
applying.
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DRI COAT
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A cement based
undercoat for re plastering after
installation of damp
proof course.
LIMELITE RENOVATING
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Lightweight cement
based backing plaster.
Contains waterproofing
and salt inhibiting
additives.
Used in re- plastering
after installation of
damp proof course or in
the renovation of old
solid wall properties.
BOARD FINISH
Finish for low to
medium suction
backgrounds.
 Plasterboards, Dri
Coat.
 Class B hemi
Hydrate.
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MULTI FINISH
Can be used on all
suction backgrounds.
 Good choice where
both solid and
plasterboard
backgrounds are
involved.
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DURA GRADE
Specially formulated
to produce a hard
finish.
 Used in high traffic
areas.
 Can be used on
plasterboard, Dri
Coat, Gypsum
backgrounds and
cement based
backgrounds.
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HIGH IMPACT FINISH
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High impact finish is used to finish Limelite
products.
This is a Class D anhydrite plaster.
Gives a very hard and high quality of finish.
All of the water is driven off when the
powder is produced.
The plaster crystals take longer to form when
the water is added when mixing.
An accelerator is added to kick start the
reaction.
The slower forming crystals give a harder
more durable finish coat.
RE CAP
 Aerated
blocks and old bricks are …………
suction backgrounds.
 Concrete and plasterboard are ………..
suction backgrounds.
 If plastering to a low suction
background Carlite …………… should be
used.
 If re plastering after damp proof work
the backing coat should be ……………….
RE CAP
After forming the perimeter dots on a wall
the intermediate dots should be …………… in.
 Internal angles should be ………. in after
floating.
 Different types of key are used dependant on
the ………….. of the subsequent coat.
 Angle beads should be fixed to concrete with
dabs of Carlite …………………..
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