Exterior
Paint Preparation
Introduction
A fresh coat of
exterior paint is a terrific way to give your home a "face lift." It
repels weather, protects the investment you've made in your
property, and adds curb appeal if you've decided to sell. Painting is a
relatively simple do-it-yourself project the whole family can help with.
And by inviting friends over, it becomes a social get-together that can be
fun. But before you get out the brushes and paint, there are some steps you
should take to prepare your house for painting. Following these easy "prep
steps" will help make sure you wind up with beautiful results that also
last a long time.
1. Start by thoroughly cleaning the outside of your home. Paint
won't stick to dirt, grease, grime or dust. You may be able to get by just
spraying the siding with a hose and nozzle. But you'll do a more thorough
job and get better results with a brush attachment for your hose. These
brushes often come with a reservoir for liquid soap. You can also wash by
hand with rags or sponges. If you do use soap, be sure to rinse the siding
after you've washed it. Start at the top and work your way down the sides
of the house. If your siding has areas of mold, mildew or discoloration,
wash it with an anti-fungal cleaner, available in most hardware and home
center stores.
2. On wood siding, fill in any gouges or holes with an
exterior-grade patching compound, sometimes called "plastic wood." If
damage is more extensive, replace the area with a new piece of siding.
3. Remove
even small areas of loose, flaking, chalky or blistered paint thoroughly.
If not too extensive, this can be done with a paint scraper, putty knife
and wire brush. Loose paint can also be removed with a power washer. Sand
the edges of the area of removed paint afterwards to help the new paint
cover and hide the edge.
4. To remove
larger areas of damaged paint, or multiple layers, you can use a heat gun.
This device, which looks a bit like a hair blower, generates temperatures
of 1000° F or more. Aim it at an area to soften the paint, and then scrape
away the paint with a putty knife. Use work gloves and keep your hands
away from the barrel of the gun. Never point the heat gun at anything
except the paint to be removed. Set the gun down on the butt plate
provided.
5. An
alternative to the heat gun is a rotary paint remover you attach to an
electric drill. Its stiff wire tines quickly remove large areas of paint.
Take care not to press too hard on the siding, or it may gouge the wood.
Practice on a board or other surface before you begin on the siding. Keep
the tool away from your face or other body parts when it is in motion.
6.
Caulk all cracks, seams and gaps with a top-quality, pintable exterior
caulk. This includes areas like the perimeter where siding meets windows
and doors, corners and the edges of exterior trim. Cracks and seams leave
edges where fresh paint can quickly begin to deteriorate. For detailed
tips and procedures see the separate Easy2.com tutorial on caulking.
7. Mask off
areas that are not to be painted. You may want to place masking tape along
the edge of house trim, and around window and door frames and trim, since
this is likely to be painted in a different color or with a higher sheen
paint. You can also tape newspaper or plastic drop cloth material over
windows and doors, including sliding glass doors, to protect them from
drips.
8. Place
plastic drop cloths over plants and shrubs, or where paint may drip on
porches, roof sections, sidewalks, driveways or other surfaces. Now you're
ready to go on to the Exterior Painting tutorial
Materials Needed
Caulk
Sandpaper
Rags and/or paper towels
Masking tape
Tools Needed
Garden hose
Power washer, or Hose brush attachment, or Sponges & buckets for wash water
Spray nozzle
Stepladder
Extension ladder
Paint scraper
Wire brush
Putty knives
Heat gun, or Rotary paint removing tool and electric drill
Caulk gun
Sanding block
Work gloves
Exterior Solid Color
Stains - Latex or Oil
Solid Color Stains may be applied to smooth or
lightly textured surfaces by brush, pad, spray or roller application, but
brush application is best. These stains act much like paint. One coat of
solid color stain is adequate, but two coats provide better protection and
longer service. Unlike paint, lap marks may form with a solid color stain.
Latex-based stains are faster drying and therefore more likely to show lap
marks than the oil-based stains.
Latex stain can be applied over freshly
primed surfaces and surfaces where an oil-base stain has already been used
and weathered. Where old surfaces are to be re-coated with latex a simple
test should be conducted first. After cleaning the surface, paint a small,
inconspicuous area with latex stain, and allow it to dry at least
overnight.
To test for adhesion, firmly press one end
of a "band aid" type adhesive bandage onto the painted surface. If the
tape is free of paint, it tells you that the latex paint is well bonded
and that the old surface does not need priming or additional cleaning. If
the new latex paint adheres to the tape, the old surface is too chalky and
needs more cleaning or the use of an oil-base primer.
Exterior Re-Painting Tips and Techniques
Remember
A coat of fresh paint will not glue down a coat of old paint
that's ready to crack and fall off. Paints are common coatings used on
wood and provide the most protection. Latex-based paints and stains are
water borne, and oil or alkyd paints are solvent borne. Paints are used
for aesthetic purposes, to protect the wood surface from weathering and to
conceal certain defects. Paints are applied to the wood surface and do not
penetrate it deeply.
Latex paints are generally easier to use since water is used in
clean-up. They are also porous and, thus, will allow some moisture
movement. In comparison, oil-based paints require organic solvents for
clean-up, and some are resistant to moisture movement. Paints are the only
way to achieve a bright white finish. However, they, especially oil based
paints, are subject to peeling where moisture is a problem.
If a new paint coat is to be successful over a problem area, moisture
problems must be eliminated. Good surface preparation is also essential.
If the wood has been completely stripped or is being painted for the first
time, it should be brush treated with a pintable water-repellent
preservative or water repellent.
After the water-repellent preservative or water
repellent has dried for at least two warm days, following manufacturers
specifications, apply an oil-base primer or a stain blocking latex primer,
followed by at least one top coat of high quality acrylic latex paint. One
top coat of paint should last four to five years, but two top coats can
last up to 8 or 10 years.
If only isolated areas of the paint coat have failed by peeling to the
bare wood, spot painting may be the best alternative.
First, scrape away
all loose paint. Sandpaper or "feather" the edges of any remaining paint
left smooth with bare wood.
Clean the old painted surface by scrubbing
with a sponge or bristle brush. Rinse the scrubbed surface with clean
water. Wipe the surface with your hand. If the surface is still dirty or
chalky, scrub it again using a detergent, and rinse it with clean water.
After the surface has been thoroughly dried, apply one coat of a
pintable
water repellent preservative or water repellent to the bare wood, being
careful to liberally treat end and lap joints. Any water- repellent
preservative or water repellent on the painted surface should be wiped dry
with rags. At least two warm days should be allowed for the
water-repellent preservative or water repellent to dry before painting.
All too often, exterior finishes for wood
are short lived in durability or fail completely. Failure is usually the
result of selecting the wrong kind of finish being applied to the wood
surface or of not following recommended application procedures.
Exterior Paint Problems and
Failures
Peeling
Moisture
can penetrate a paint coat and result in cracking, peeling, discoloration
and premature paint failure, these problems may be observed in both heated
and unheated buildings and are more pronounced on edges and ends of boards
and are also observed where water is held on the surface.
Proper construction and maintenance will eliminate most exterior water
problems. Ice dams occur in northern climates when snow on the upper
warmer parts of a roof melts and runs downward. With repeated thawing and
freezing on the roof more water moves to the roof edge and an ice dam
begins to build up.
The melted water may penetrate the roof and
drain into the exterior walls, thus causing moisture and associated paint
problems. Ice dams can be reduced or eliminated by adequate insulation in
attics and by proper attic ventilation. Inside moisture (water vapor) can
destroy paint on the outside of a building by diffusing through the walls.
Water vapor from cooking, dish washing,
clothes dryers, bathing and normal respiration by an average family of
four can contribute three gallons of water per day to the humidity. If the
inside of all exterior walls does not have a vapor barrier or if the vapor
barrier is improperly installed, water vapor passes into the walls during
cold winter weather and condenses to a liquid.
The water eventually soaks into the siding
and wets the paint. This is a common cause of blistering and peeling. The
problem is particularly pronounced around bathrooms, laundry rooms,
kitchens and other areas of high humidity.
Blistering
Temperature blisters are bubble-like swellings that occur on the surface
of the paint film as early as a few hours or as long as one to two days
after painting. They occur only in the last coat of paint, they are caused
when a thin dry skin has formed on the outer surface of the fresh paint
and the liquid thinner in the wet paint under the dry skin changes to
vapor and cannot escape.
A rapid rise in temperature, as when the direct
rays of the sun fall directly on freshly painted wood, will cause the
vapors to expand and produce blisters. Usually only oil based paint
blisters in this way. Dark colors which absorb heat and thick paint coats
are more likely to blister than white paints or thin coats.
To prevent temperature blisters, avoid painting surfaces that will soon be
heated. "Follow the sun around the house" for the best procedure. Thus,
the north side of the building should be painted early in the morning, the
east side late in the morning, the south side well into the afternoon, and
the west side late in the afternoon. However, at least two hours should
elapse before the fresh paint film cools to the point where condensation
will occur.
If blistering does occur, allow the paint to dry for a few days. Scrape
off the blisters, smooth the edges with sandpaper and spot paint the area.
Moisture blisters are also bubble-like swellings on the surface of the
paint film. They may occur where outside moisture such as rain enters the
wood through joints and other end grain areas of boards and siding. Paint
blisters caused by outside water are usually concentrated around joints
and the end grain of wood aloe.
Cracking
Cross-grain cracking occurs when paint coatings become too thick. This
problem often occurs on older homes that have been painted several times.
Paint usually cracks in the direction it was brushed onto the wood. Once
cross-grain cracking has occurred the only solution is to completely
remove the old paint and apply a new finishing system.
To prevent
cross-grain cracking, follow the paint manufacturer's recommendations for
spreading rates. Do not repaint un-weathered, protected areas such as
porch ceilings and roof overhangs as often as the rest of the house.
If
possible, repaint these areas only as they weather and require new paint.
However, if repainting is required, be sure to scrub the areas with a
sponge or bristle brush and detergent in water to remove any water-soluble
materials that will interfere with adhesion of the new paint.
|
