4.
Preparatory Work
4.1 PLANNING with project specification. For verification of the paint
colour, uniformity and compatibility of the paint
Quality control starts with good planning and
system, it is a good practice to have a mock-up unit
management. An Inspection and Test Plan, ITP (refer
for the approval of the architect or owner before the
to Appendix D) which lists down the project’s
commencement of the actual works.
inspection and testing requirements should be
prepared to detail the checks required to achieve
good workmanship. The plan should cover the
responsibilities of each party, inspection methods,
4.2 SURFACE PREPARATION
requirement references and frequency of inspections. Good surface preparation is critical for the paint system
Checklists for the in-process and final inspection to function effectively. As the performance of the paint
on painting works should also be prepared (as in system depends largely on its adhesion with the
Appendix E and F). substrate, and paint adheres best to surfaces that are
clean and sound, it is essential to establish the required
Prior to starting any painting work, it is important for standard and level of surface preparation works. The
the parties involved to plan and agree on the receiving surfaces should be dry, and free from foreign
compatible paint system as per project specification, and unstable matters such as dust, dirt, rust, spatter,
surface preparation method, sequence of work, drying salt, grease, oil, loose paint film and so forth before
out time and method of access. proceeding with the painting work.
preparatory work
In general, the schedule of painting works should be Works by other trades that might affect the painting
planned in relation to the work of other trades, so as should be satisfactorily completed. The applicator
to ensure that the surfaces to be painted are prepared should inform the designer of any change in the nature
on time and that the subsequent construction works or condition of the receiving surfaces, which may
will not damage the paint work. necessitate modification of the specifications.
The applicator should confirm on the type and number Refer to Table 4.1 to Table 4.4 for more details on
of coats, location of application, surface preparation surface preparation for various types of surfaces.
method and application method are in accordance
Table 4.1 Preparation of Concrete/Cement Plaster Surfaces
Condition Tools/Methods Remarks
Uncoated Surface Coated Surface
Moisture – Checking with moisture meter – To ensure moisture – To ensure moisture
content not exceeding 6% content not exceeding 6%
(or refer to (or refer to
manufacturer’s manufacturer’s
recommendation) recommendation)
– Allow drying after – To check for source of
plastering for minimum dampness
of 21 days (in compliance
with CP22)
Surface – High pressure water jetting – To remove foreign and – To remove loose particles
Contaminants unstable matters such and existing paint with
such as as construction soot, flaking, dirt or chalking
construction soot, concrete/cement etc
algae, loose paint- splashes, cement
film (for coated salts etc
surface only) etc
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Condition Tools/Methods Remarks
Uncoated Surface Coated Surface
Surface – Manual cleaning by chipping, – To remove foreign and unstable matters such as
Contaminants scrapping or wire brushing construction soot, algae, concrete/cement splashes,
such as cement salts, loose paint film etc
construction soot,
algae, loose paint-
film (for coated
surface only) etc
– Brushing or sweeping – To remove foreign and unstable matters such as
construction soot, algae, concrete/cement splashes,
cement salts, loose paint film etc
Surface Treatment – Fungicidal wash – To kill fungal/algae spores and roots
Microbiological
growth, e.g. algae
or fungi growth
preparatory work
Surface – Sanding/grinding/skim coating – To reduce roughness
Imperfections followed by rinsing with clean
(i) rough, open- water and wiping dry – To improve adhesion to substrate/existing coating
textured or
coarse-grained – To remove foreign and unstable matters such as
surfaces construction soot, algae, concrete/cement splashes,
cement salts etc
(ii) hairline cracks, – Patching – Use fillers that contain a resin/binder system e.g. acrylic
nail & screw based putty or cement with additives
holes, open
joints, cracks and – Water sensitive types e.g. gypsum-based fillers are
similar local not recommended as they may dissolve in water
cavities, deep and
shallow – Prime surface before patching if oil-based fillers are used
depressions
– Patch in two stages if cavities are deep
– If applied immediately beneath finishing coats, shrinkage
and variations in gloss, sheen or colour may occur
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Table 4.2 Preparation of Timber Surfaces
Condition Tools/Methods Remarks
Uncoated Surface Coated Surface
Moisture – Checking with moisture meter – To ensure moisture content not exceeding 15% (or refer
to manufacturer’s recommendation)
Surface – Sanding manually or – To improve adhesion to substrate/existing coating
Contaminants mechanically with sandpaper
such as dirt, grime, followed by wiping with damp – To remove foreign and unstable matters such as dirt, grime,
loose paint-film cloth loose paint-film etc
etc
– To provide a smoother and better finish
– Stripping by paint remover NA – To strip off defective paint
preparatory work
accompanied by scraping works
– Chlorinated/alkaline
paint remover
not recommended
Surface – Patching with wood putty or – Use wood filler for painting with transparent coatings
Imperfections filler
(i) nail & screw
holes, cracks
and similar
local cavities,
deep and
shallow
depressions
(ii) rough surface – Sanding/grinding/skim coating – To provide a smoother and better finish
followed by rinsing with clean
water and wiping dry – To improve adhesion to substrate/existing coating
Surface Treatment – Priming – Prime all surfaces including abutting surfaces, e.g.
doorframes.
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Table 4.3 Preparation of Ferrous Metal Surfaces
Condition Tools/Methods Remarks
Uncoated Surface Coated Surface
Surface – On site: mechanical wire – Wire brush till surface is free from rust (compliance
Contaminants brushing with ST 3 standards or equivalent)
(i) mill scale, rust
– Off site: blasting – Compliance with SA 2.5 – If condition allows,
standards (bare metal compliance with SA 2.5
with only traces of slight standards (bare metal
stains in spots or stripes) with only traces of slight
stains in spots or stripes)
(ii) joints/welded – Manual cleaning by chipping, – To remove foreign and unstable matters such as grease,
areas/spot scraping and/or wire brushing oil, loose paint film, abrasive residue etc
rusts, oil,
grease, dirt,
loose paint
film, abrasive
residue, debris
etc
preparatory work
– Manual or mechanical washing – To remove foreign and unstable matters such as grease,
down with solvent or detergent oil, loose paint film, abrasive residue etc
solution
– Blasting – Compliance with SA 2.5 – If condition allows,
standards (bare metal compliance with SA 2.5
with only traces of slight standards (bare metal
stains in spots or stripes) with only traces of slight
stains in spots or stripes)
– Stripping by paint remover NA – To remove loose paint
film
– Alkaline paint remover
may be used
Surface Treatment – Washing with clean water and – To improve adhesion/existing coating
allow it to dry
– Priming exposed steel – To prevent corrosion
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Table 4.4 Preparation of Non-Ferrous Metal Surfaces
(include aluminium, aluminium alloys, magnesium alloys, zinc and treated steel such as galvanised surfaces, anodised aluminium etc)
Condition Tools/Methods Remarks
Uncoated Surface Coated Surface
Surface – Wiping with cloth dampened – To remove grease and oil
Contaminants with solvent
(i) oil, grease
– Mechanical washing down with – To remove grease and oil
solvent or detergent solution
– Degreasing – To remove grease and oil
(ii) loose paint- – High-pressure water jetting – To remove foreign and unstable matters such as loose
film, dirt, rust followed by sanding paint film, abrasive residue etc
etc
– Stripping by paint removers NA – Rinse thoroughly with
clean water after stripping
to avoid chemical
reaction with metal. Mild
detergent should be used
to remove residue
preparatory work
– Sanding – To remove foreign and – White rust need not be
unstable matters such as removed if found stable
loose paint film, abrasive
residue etc
Surface Treatment – Coating the exposed surface with – To ensure good adhesion – To ensure good adhesion
an etching primer.
– Spot prime exposed
surfaces immediately
after cleaning
4.3 PAINT PREPARATION Mixing should be carried out in compliance with the
specifications and manufacturer’s recommendation.
Proper paint preparation is important in delivering
No unauthorized thinning or adulteration should be
quality work. Refer to Table 4.5 for details on
carried out and no addition of driers is permitted.
preparation of paint.
Where additions are authorized, the correct proportions
should be strictly observed.
In mixing of paint, the following factors should be
considered:
There should be sufficient stirring until uniformity of
the paint is achieved. The pigment in paints is heavier
• mix ratio;
than the vehicle and tends to settle at the bottom of
• type of thinner used;
the container. Failure to stir the paint properly is a
• induction time;
common cause of unsatisfactory results. It is, hence,
• pot life; and
essential that the paint is completely uniform
• ageing time
throughout the container.
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Table 4.5 Preparation of Paint
Condition Methods/Tools Remarks
Confirmation of Visual checking – Inspect name of paint, colour,
Specification location of application and numbers
of coats
Settling of solid Stirring: – Stir continuously until no solid
constituent in paints a) Manual settlement remains
– Long, broad-bladed stirrer
– Boxing (i.e. pouring from one – Refer SS CP22 on ‘Mixing &
container to another several times) Thinning of Paints’
– Used for small quantities
b) Mechanical – Used for large quantities
– use of mechanical equipment
High viscosity paint Thinning – To assist workability
– Use type and proportions of thinner
in accordance to manufacturer’s
recommendations
preparatory work
– Thinning to be carried out under
supervision
Mixing different brands Not recommended Not recommended
or types of paints
Using 2-pack materials Mixing of two components – Use the correct proportion in
accordance to manufacturer’s
recommendation
– Check the following:
• Induction Time
• Pot Life
• Age-ing Time
– Use paint within the pot life
4.4 PROTECTION WORKS BEFORE
PAINT APPLICATION
It is a good practice to plan the sequence of works All surfaces not intended to be painted must be
such that the final coat will be painted only after the protected. Doors, furniture, light fittings and similar
completion of other trades such as installation of items should be covered. Care should be taken when
doors and carpentry works. This will ensure that the protecting surfaces that are sensitive to adhesive tapes.
final coat of paint will not be stained during the
execution of other trades.
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Air Conditioner – Fan Coil Unit Window
preparatory work
Building Materials Electrical Wirings
Floor, Sliding Door Frame and Railing Lift Button Panel and Cabinet
Figure 4.1 Examples of protection works before paint application
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4.5 SAFETY
Applicator should be equipped with safety attire/ Proper access such as scaffolding and gondola should
equipment, including proper working clothes, footwear be provided to facilitate external painting works.
and helmet. A safety belt should be used where painting Applicator should also make sure that there is adequate
is being carried out at heights. Protective accessories ventilation and illumination when carrying out
such as goggles or masks should be worn where painting works, especially for internal areas.
necessary.
preparatory work
Figure 4.2 Proper access and safety measures for surface preparation and external painting works
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