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Exterior
painting - surface preparation
Surface
preparation is without question the most important step in
obtaining an attractive, long-lasting painted finish, it
is generally the least performed.
Many do-it-yourself painters are not aware that the life
of a painted surface, is directly proportionate to the
care taken during surface preparation.
Regardless of whether you are repainting or working with a
previously unpainted surface, take the time to correct
basic problems and prepare surfaces properly. Even though
a new unpainted surface tends to pose fewer problems
(primarily because there's no guesswork in deciding what
type of finish has already been applied), the appropriate
surface preparation is still crucial to ensure
trouble-free results.
Before starting your exterior painting project, run a
quick inspection tour to check out likely trouble spots.
These include window and door frame areas, steps, siding,
downspouts, under-eave areas and anywhere else moisture is
likely to collect.
If there's cracking or peeling of the old coating, use a
wire brush to remove the original paint. If you discover
extensive moisture damage over a large area, you'll need
to sand the entire surface area to ensure the new coating
will adhere. In either case, be sure to feather edges with
sandpaper to provide an even appearance after painting.
If the old coating is slated for removal, a pre-painting
prime job is a must. Ask your local paint store
representative which primer is best suited to the surface
in question. Remember that the entire coating 'system'
should be treated as a unit. Just as your primer should be
suitable for the surface, the top coat you choose must be
compatible with the primer.
A CLEAN SURFACE
A clean surface is another must for any painting job -
paint cannot adhere to dirt, grease, chalk, wax or other
surface contamination. Use a mild detergent or trisodium
phosphate solution to remove accumulated surface residues.
After a thorough scrub-down, rinse the area well with
clean water and allow to dry completely before priming or
painting.
Any mildew growth on exterior surfaces must also be
removed before repainting or the mildew will continue to
feed on edible materials in the paint and eventually
destroy the new coating. Since moisture is the single most
important factor in mildew growth, the discoloration is
usually found in damp, dark areas such as northern
exposure sites. To determine if mildew is present, drop a
small amount of household bleach on the discolored
surface. If it's mildew, the bleach will destroy and
whiten the fungus. If not, nothing will happen.
The most effective way to remove mildew is to scrub the
surface with a soft brush using a solution of one cup
non-ammonia detergent, one quart of household bleach and
one gallon of water. For maximum protection, use a
mildew-resistant primer and paint. A generous topcoat will
provide a further safeguard against penetration of the
mildew fungi.
BEFORE BEGINNING TO PAINT
Before beginning, patch any nail holes and caulk open
joints in siding and other exterior wood surfaces. By
priming these areas first, you can prevent the vehicle or
binder in the caulking or patching compound from being
absorbed into the wood and thus extend the life of the
compound.
A FINAL POINT
The type of paint you choose can sometimes have a
significant effect on the type or degree of surface
preparation required. For example, if you select an
exterior latex like BREEZE ACRYLIC LATEX to apply
over an exterior gloss house paint, you will need to sand
or otherwise reduce the gloss of the existing surface to
ensure the new latex will adhere. If you're unsure about
the preparation required for your painting job, check with
your local paint store representative. In the long run
you'll be glad you did! |
