Transcript External Plastering

External Plastering
Plain Float Finishes
Backgrounds
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Concrete blocks
Brick
E.m.l.
Cement boards
Suction Control
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Damp wall with brush and water
Reduces risk of cracking
Allows plasterer more time work with material
Prevents material from drying out too quickly
(curing)
Materials
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Sand
Cement
Plasticiser
Lime
Prepared laths
Clean water
Scudding
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Mix sand and cement at ratio 2.5 to 1
Mix to a wet consistency
Apply with a dashing spoon
Scud evenly no bare patches
Scud coat assists in prevention of blocks
showing through
• Provides grip for scratch coat
Scratch coat
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Mix at 3 to 1 with water proofer
Apply 10 mm thick approx.
Straighten with edge
Scratch immediately with wire scratcher (comb
key)
• Leave for a period of 72 hours before render coat
• Waterproofer regulates suction for finish coat
Plain coat finish
• Should be mixed at 3 sand 1 cement .25 lime
or 12:4:1
• Applied approx. 10mm
• Straighten with straight edge
• Fill out any “wants” or hallows
• Float when steady in a circular motion
• Float 1m square at a time
Reveals
• Patent, Plain, Band.
• Clean prepared laths
• Release oil
Nap finish
• Prepare background as with plain float
• Coat material 10mm approx.
• Float material while sprinkling water to bring
material to a “fatty” consistency
• Nap gently with a napping sponge
Plinths
• Recessed nail a 2*1 lath with top of lath along
damp coarse. Form a bell cast.
• Stepped nail a 2*1 lath with bottom of lath
along damp coarse.
• Stop beads can also be used.
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Dry dash
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Mix material 6 parts sand 2 cement 1 lime
Dashing coat should be “fatty”
White cement may be used for decorative effect
Colouring agents can also be used
Walls must be well dampened
Best carried out by 2 plasterers one applying
dashing coat and the other casting the pebbles
from a dashing spoon
• Pebbles size range from 6 to25mm
Dry dash
• Pebbles are cast when dashing coat is still wet
• Pebbles should be spread evenly on dashing
spoon no bare patches should be left
• If dashing a tall buildings joints should be cut in
saw tooth fashion to make less obvious
• Joints can be hidden in short areas such as doors
or windows
• A net should be left on the ground so that falling
pebbles can be collected washed and reused
• A dry dash receiver can also be used
Wet dash
• 2 Scratch coats one 1 comb scratched 2nd
scratched with yard brush
• Mixed at ratio of 4 chips 3 sand 1 lime
1cement
• Chips sand and lime can be mixed a day in
advance and cement added just before use
this is called “souring” and will stop material
from splashing
• Pebbles are included in mix