External Plastering

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Transcript External Plastering

External Plastering
Plain Float Finishes
Concrete blocks
Cement boards
Suction Control
Damp wall with brush and water
Reduces risk of cracking
Allows plasterer more time work with material
Prevents material from drying out too quickly
Prepared laths
Clean water
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
Mix at 3 to 1 with water proofer
Apply 10 mm thick approx.
Straighten with edge
Scratch immediately with wire scratcher (comb
• 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
• 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
• 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.
Dry dash
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
• 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