First, a word about paint
Peeling is rarely caused by bad
paint. The same paint that peels in
some spots will stick tenaciously
for 40 to 50 years in other spots.
Latex paints are the industry
standard for most exterior house
painting, and they continue to
improve. Long-term testing has
shown that 100-percent acrylic
latex lasts longest. Still, a few pros
still like oil-based paints because
they carry a slightly better sheen
and brush out more smoothly.
Finally, a caution: Scraping and
sanding paint that contains lead
can release hazardous lead dust. If
your home was built before 1979,
(lead in paint was banned in 1978),
contact your local health department
for detection and safe handling
One secret to paint longevity
Most paint dealers blame paint
peeling problems on poor prep
work. However, even the best routine
of cleaning, scraping, sanding
and priming won't stop paint from
peeling if water gets into the wood.
For this reason, inspect and repair
peeling areas annually.
Sure, this sounds like another
chore. But it pays off in three ways.
First, annual maintenance stops
localized peeling and keeps it from
spreading. Your house will look
better, and you'll protect the vulnerable
raw wood from rot.
Second, the cost of whole-house
repainting will be lower
when that time comes, because
you've kept the exterior in good
condition. It won't require much
And third, the paint that's in
good condition on your home will
last longer, because with longer
painting cycles it won't build up as fast. Thicker paint loses its flexibility
and cracks more easily, eventually
leading to a condition called
“alligatoring” (Fig. A). When the
paint gets that bad, you'll have the
huge job of stripping it all off and
If you don't have enough time
to do the annual maintenance
yourself, you'll still come out ahead
if you hire a pro for a day or two
every year to fix the problems.
Figure A: Peeling Paint
Peeling paint is usually caused by
moisture getting into the wood and
breaking the paint's bond with the
wood fiber. Most moisture comes from
outside, but sometimes it collects in the
wall and works its way outward.
A paint job is doomed when water
gets into the wood. Wet wood causes paint to peel. The process
goes like this: Moisture from high
humidity or rain works its way into
the wood and causes the fibers to
swell. The expanding fibers stretch
the paint film until it cracks. Once
the film is cracked, more water
from rain, dew and snow (and lawn
sprinklers!) readily seeps through
it, soaks the wood and breaks the
Water-induced, localized “spot”peeling is easy to identify (Fig. B).
Although all joints are vulnerable,
wood joints at window and door
sills are particularly susceptible. Water sits in the corners, is slow to
dry and eventually breaks through
the paint barrier. The end grain of
window and door frames, once
exposed, sucks up water like a
sponge, swells and further cracks the
paint, making the situation worse.
Peeling at wood joints could largely
be prevented by sealing the end grain
with primer. But carpenters rarely do
it. And contractors don't want to
bring in painters at this stage because
of the cost. But it's worth the effort if
you're the one installing the trim.
Otherwise, you're left with the
second-best solution: to rely on
flexible caulk to seal joints.
Sills and other horizontal surfaces
peel because water runoff is slow and
in the meantime can work its way
through any crack in the paint. Heat
from sunlight also drives the moisture
into the wood. Scrape, sand and
recoat these highly vulnerable areas as
soon as peeling begins. Some meticulous
painters reduce the problem by
applying a water-repellent preservative
or thinned, boiled linseed oil to
the bare wood to slow moisture penetration.
Then they let the wood dry
for at least five days before priming it.
When paint begins to peel off your soffits (Fig. B), one likely culprit is a
clogged or leaky gutter. The best prevention
is to clean your gutters twice
a year. Many veteran painters recommend
removing the gutters entirely
and eliminating both the peeling
paint and the cleaning chore at the
same time. Other painters disagree,
because gutters keep runoff from
splashing up, soaking and ruining the
paint on the lower siding. Despite the
cleaning chore, we generally recommend
gutters because they protect the
foundation from water damage.
If gutters aren't the problem,
check for a roof leak. Go up in the attic with a flashlight and examine
the underside of the roof for water
the roof quickly so that rot won't
damage the boards to the extent
that they won't hold paint. Poor
attic ventilation can also cause soffits
to peel. Soffit and roof vents reduce attic humidity,
which otherwise will dampen
the soffits and lift the paint. (For more on the subject, see Improve Attic Ventilation: Introduction)
Even with gutters, splashing
rain often soaks siding boards and
trim near the ground. Eventually,
they'll absorb water and peel.
There's no perfect cure. Maintain
your gutters, keep bushes
trimmed back from the house to
promote drying, and fix peeling
areas as soon as they appear.
Wood composites like hardboard
siding and plywood are especially vulnerable.
Keep edges well sealed.
Once they swell, they're almost
impossible to reseal.
Spot peeling can also occur as a
result of moisture from the inside
(Fig. A), but the signs aren't always
obvious. Usually the cause is high
humidity in a room like a bathroom,
coupled with air leaks
through the wall or the absence of
a vapor barrier. Look for tip-offs
such as paint that peels around
only one window, or that peels
from siding in a pattern that outlines
a single room. If the problem
occurs outside a bathroom or
kitchen, you can usually solve it by
running a ventilating fan regularly,
plugging air leaks around
windows with caulk, and repainting
Figure B: Trouble Spots
Exterior paint peels where the wood is most likely to get soaked. The most vulnerable
spots include exposed horizontal surfaces, joints, wood close to the ground, and soffits.
Bad painting conditions
Although it's less common, peeling
paint can be caused by bad
painting conditions. Pros in particular, pressured by home purchase
closings, tight schedules and
bad weather, can get caught working
in less-than-ideal painting
weather. One veteran painter
recounts an occasion when his crew
completed the prep work late in the
fall, but freezing weather moved in
before they could paint. Two weeks
later in a surprise warm spell with
50- and 60-degree afternoons, they
got the job done. But in the spring,
large patches of paint fell off the
north side of the house. Thinking
back, they could only guess that the
north side simply never warmed up
enough. And they had a lot
of time to think as they
rescraped and sanded the entire
Such adhesion problems don't
often occur (Fig. C), but when they
do, causes are difficult to diagnose.
If you're puzzled, don't hesitate to
ask the manager of your local paint
store or a pro for advice.
Here are the most common
causes of adhesion problems:
- Skipping the cleaning step, so
that dirt, mildew and chalking cause
- Painting in temperatures below
50 degrees F. Sure, you might get
lucky. Some paints are formulated
for cool weather. But slower
drying times and complications
from dew and frost are
all tricky variables to manage.
Also, avoid painting
too early in the spring. The
air temperature might be
high enough, but the temperature
of the wood surface
may still be too low.
- Rushing curing times. Paint
sometimes feels dry to the touch
before it has hardened. A second
coat applied too soon can soften
the first and create a weaker bond.
The labels on paint cans specify
drying times, but humid or cool
conditions can lengthen them.
- Painting wet wood. Latex paints,
being water-based, can tolerate
mild wood dampness and still
adhere. But unless you have a
moisture meter, you won't know
the actual moisture content. Why
risk major league failure? Wait
until the wood looks and feels dry.
- Using spray equipment without
back-brushing. Most pros use
spray equipment for speed. But
sprayers can't ensure a good bond,
so a second painter should always
follow closely behind the sprayer
to brush the paint into the surface.
You also need to back-brush if
you're painting with a roller.
- Running afoul of unexpected
hazards. Insects, automatic lawn
sprinkler systems, direct hot sunlight,
high winds and other local
conditions can suddenly pop up
and ruin a nice job.
- Choosing the wrong paint. Generally
on the exterior, you can
safely cover oil paint with latex,
but not vice versa. In addition,
stick with the same brand of
primers and topcoats, because
some primers and topcoats aren't
compatible. As insurance against
future paint problems, ask the
paint dealer to write paint specifications
for your project, including
the brand and type of paint. Then
you'll have a record should the
topcoat peel from the one below.
Figure C: Paint separation
Figure C: Paint Separation
The problem of one
layer of paint separating
from another is called
intercoat adhesion failure.
It's often difficult to
diagnose. Common causes
include painting when it's
too hot, too cold or too
wet, a failure to clean the
old surface, choosing the
wrong type of paint or bad
paint and applying too
many coats too fast.
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Special peeling problems
If individual siding or trim boards
peel on your home while others nearby don't, examine their grain
pattern. Some types of wood
won't hold paint well. Wood used
for siding and trim usually has a
vertical grain pattern; that is, the
tree growth lines in the boards line
up close together (Fig. D). Moisture
won't affect wood cut this
way as much as it does flat-sawn
boards, that is, boards with wide
grain lines. The surface of flatsawn
wood moves so much that
paint will crack and peel after only
a few years if it's put in an exposed
spot. (Plywood also has wide grain
lines and won't hold paint either.)
Replace peeling flat-sawn
boards with boards that have vertical
grain, or sand all the paint off
and coat them with a paintable
water repellent before priming
and repainting. The water repellent
might stabilize them enough
so that they hold paint longer.
Use a primer over bare wood.
Some folks don't, or substitute a
thinned paint for the primer.
That's not good enough when you
want a high-quality job. Primers
are specially formulated to seal
and adhere to bare wood and
other materials. They aren't cheap
paint. A good one should cost
almost as much as a topcoat.
Finally, always read the manufacturer's
instructions for painting cementboard,
preprimed hardboard and other
wood composite products. The
primers on many of them were
designed to protect against moisture
while the products were being
handled and shipped. The primers
aren't always a suitable base for
paint. You might have to prime
the products again.
Figure D: Wood grain problems
Figure D: Wood Grain Problems
Paint usually won't
adhere long to boards with
a wide grain pattern if
they're exposed to rain.
They expand and contract
too much with humidity
changes. Vertical grain
wood holds paint better
because it moves less.