Preparing Walls for Paint
SURFACE PREPARATION IS THE KEY TO A LASTING
PAINT FINISH.
Here’s what to do for each surface:
RAW WOOD
Before you add a pretty colour to your raw wood, there are a few basic
steps that need to be observed to ensure the paint bonds to the wood.
This preparation is not suitable if you want to varnish the wood or
paint a clear coat.
- Clean
the surface to remove dirt, dust and mildew.
- If
it’s a piece of furniture, fill and cover nail holes with wood filler,
then sand smooth, or coat exposed screws with metal primer to prevent
rusty spots or discolouring.
- If
you find unevenness in the wood, repair and smooth over with wood filler.
- To
smooth unevenness in the wood (or after wood filler is applied) use
100-grit sandpaper and either an orbital sander or multi sander.
It is advised to sand the wood in the direction of the grain (running
along the lines in the wood). This will give the surface a smooth finish, which
is much easier to paint. Dust the surface off after sanding. If the raw wood
has knots, it is especially important to seal these with a primer.
- Paint
the surface with one coat of wood primer (two coats if it’s going to be in
severe weather outdoors) using a brush or a roller and leave to dry
thoroughly between each coat. An oil-based primer is best for outdoor use.
A water-based primer such as that made by Harlequin is good for indoors
and easy to clean.
- Once
your primer has dried, give it a light sanding to remove the hairy bits.
- Finish
with the paint colour and coating of your choice.
PREVIOUSLY PAINTED WOOD
- Don’t
just slap new paint on previously painted wood. It needs a bit of prep
first.
- If
the surface is in poor condition, remove the old paint or varnish with a paint
stripper or by scraping peeling paint off with a scraper and sanding the
surface with sandpaper.
- Fill
and repair holes in the wood with wood filler.
- Sand
the filled areas to remove unevenness and dust the surface before applying
primer to the exposed wood.
This will also smooth out any irregularities of colour, such as water
stains.
- For
the best adhesion, use one coat of oil-based universal undercoat.
- Once
dry, give the surface a light sanding with fine grit paper to remove any
hairy bits.
- Finish
with the paint colour and coating of your choice.
RAW BRICK
- Clean
the bricks thoroughly using a firm sponge and sugar soap in warm water.
For deeper insets and loose mortar, use a stiff brush.
- If
it is an expansive wall, a pressure washer is advised.
- If
it is an exterior wall, mildew might be a problem, and can be treated with
a diluted bleach solution (one part bleach and three parts water). Soak
the affected area for an hour and scrub the mildew with a firm brush.
- Rinse
the area with fresh water.
- After
cleaning, leave the brick to dry for at least a day (in cooler climates at
least 48 hours) before painting.
RAW CONCRETE
- Brush
the wall or floor with a stiff-bristled brush or broom to remove any dust
and dirt.
- Scrub
the surface with a scrub brush and a concrete-cleaning solution.
- Allow
the surface to dry completely.
- Test
interior floors and walls for excess moisture. Tape a piece of plastic
(such as a black bag) to the wall for a day (or at least 24 hours).
- Check
the outside of the plastic facing away from the wall. If there is
moisture, the humidity level in the room is high. If there is
moisture present on the side against the wall, then it’s either not dry
yet or is absorbing a heavy amount of moisture from the ground
beneath it.
- Treat
the cause of the moisture. The wall must be dry (for at least 30 days)
before applying a plaster primer and then paint.
PLASTER
- Plaster
is only ready to paint when it’s completely dry.
- The
drying time can vary depending on the weather, temperature and the surface
it was applied over. Usually it’s ready to paint over within two to three
days.
- When
painting fresh plaster, start with a mist coat. This will show any
blemishes or unevenness in the plaster. If you notice imperfections you
can fill and sand roughness.
- The
mist coat can be diluted slightly with water and is normally the cheapest
white PVA paint you can find. Apply diluted with water, roll it with a
normal roller. The plaster will soak up the paint and will dry very
quickly.
- The
mist coat gets drawn into the wall and seals the wall.
- Paint
the wall with one to two coats of plaster primer. Oil-based primer is best
for outdoors, indoors you can use water-based plaster primer. All
mouldings and ceiling roses need to be primed with oil-based primer before
being painted.
TILES
- Clean
tiles thoroughly with a sponge using a tile cleaner or sugar soap to
remove any soap scum, grease and dirt. (Remember to wear rubber gloves!)
- Rinse
thoroughly with fresh water to remove all traces of soap and allow to dry.
- Mask
off all areas that should not be painted using painter’s tape.
- Apply
one coat of tile primer to the tiles and grout, ensuring that all areas
are evenly covered and leave to dry completely before applying the paint.
Tip: Allow longer recoating times in cool and wet
weather conditions.
MELAMINE
- Using
a scraper, fill the holes of the melamine surface and other defects with
crack filler and allow to dry.
- Wipe
down and clean with Builders sugar soap using a sponge. (Remember rubber
gloves!)
- Remove
all traces of the sugar soap. Allow to dry. Sand the melamine surfaces
lightly with 150-grit sandpaper to provide a key. Dust off.
