As a custom painting contractor in the Boston market, I've spent a
good part of my lifetime studying the way paint works. That
includes courses and seminars provided by the Painting and
Decorating Contractors Association, which I think every
professional painter ought to join (I'm the president of our local
chapter's residential forum; painters interested in best-practice
solutions are encouraged to visit www.pdcaresidentialforum.org).
Formal training is important — for example, we have all our
employees take the three-hour training course on CD from the Rohm
and Haas Paint Quality Institute (www.paintquality.com) each year,
and I often bring some employees along when I travel to an industry
conference. But experience is still the best teacher. And when you
think about it, painters are in a unique position to learn from
experience, because we get to revisit projects years after
construction is complete. Few builders get that opportunity: they
might go on and build a new project for a client, or they might
have a punch list at the end of a job for minor mistakes or things
that didn't get finished. But builders don't usually get a chance
to go back after five years, seven years, forty years, even a
hundred years to see what's working and what isn't working on a
home. We painters do — in fact, that's most of what we do: we
come along and fix things that are failing, and we get to learn
from that failure.
The source of most problems
No coating lasts forever, especially on wood. Depending on the
environment, you can expect a well-executed paint job to last
somewhere between 5 and 12 years. But often, paint begins to
experience trouble long before that. And from what I've seen, that
trouble is virtually never related to a flaw in the paint itself.
Manufacturers have had years to perfect their formulas, and they do
continual research and development. If you invest the dollars for
good-quality paint, rather than the cheapest can on the shelf, you
can expect excellent performance from the product.
So when I see problems, it's because of things other than the paint
or stain. Most commonly, problems go back to the way the house was
built. Less frequently, the issues relate to how the substrates
— the wood trim, siding, or window and door frames —
were prepped for paint. And least commonly, there was some problem
with how the paint was applied. In any case, the prep and the
painting are the painting contractor's job. But things the
carpenters do, before the painters even show up at the site, can
make all the difference to the endurance of the coating.
These days, most of my company's painting projects are likely to
involve some carpentry as well. I now have a few well-rounded
carpenters on my own payroll, in fact, and they sometimes spend
days replacing siding and trim, or even remodeling a porch, before
my prep crew starts to work. So the tips here aren't just kibitzing
— they're what our own carpentry crew does in the field. If
your carpenters do the same things on the next house you build or
remodel, they'll be helping to give the paint or stain a fighting
Top Tips for Trouble-Free
Use preprimed material. The minute you
put wood up on a wall, the sun starts to attack its wood fibers,
and it begins to experience swelling and shrinking as it gains and
loses moisture to adjust to the surrounding air (Figure 1). To
protect that wood, every piece of siding or trim that gets nailed
to a building should be primed first on six sides — that is,
on all four faces and on both ends. Factory-primed clapboards and
trim are easy to find in the market these days; if you use unprimed
material, you should prime it yourself before you nail it up.
Figure 1. Without back-priming, daily and
seasonal moisture cycling will soon cause beveled wood siding to
show cupping and warping (visible in the upper courses of siding on
this house), as well as cracking (visible at right). Moisture
migrating from inside the home through the backs of the clapboards
also attacks the adhesion of the paint or stain on the exterior
wood surfaces, causing premature loss of the coating. The new
preprimed clapboards at the lower right of this gable-end wall,
installed as part of a window replacement, will perform much better
That includes priming the back face. Although it doesn't face the
weather, the back of a board is often attacked by moisture coming
from within the house. Back-primed wood can resist that moisture,
but wood that hasn't been primed in the back will curl or cup. That
unbalanced movement stresses the nailed connections, and moisture
migrating toward the outdoors also attacks the bond between the
coating and the wood, causing early peeling or wear.
Don't over-rely on the factory primer. A
factory-installed primer serves to stabilize the wood during
shipping and storage, and it provides temporary protection when
siding, trim, or windows are first installed. But it's not usually
intended to be the primer for the material in service (Figure 2).
That's why the label on a new window or door will often warn you
that the unit should be primed again before it's painted. With
those components, and also with preprimed clapboards and trim, we
always reprep the surface and apply a field primer before we apply
the finish coating of stain or paint.
Figure 2. Factory-applied primer on new bevel
siding serves to stabilize the wood during shipping and immediately
after installation. However, it does not serve other functions of a
field-applied primer. For instance, factory primer usually will not
block bleed-through by extractive oils in cedar, as shown above. It
also will not provide the "tooth" that helps finish coats bind
strongly to the material. The author touch-sands and/or
power-washes the wall, spot-primes areas of bleed-through with an
oil-based stain-blocking primer, then primes the entire wall with
regular acrylic primer before applying a finish coat of paint or
In fact, even if wood is installed and primed, but then sits for an
extended period before the finish coating is applied, it may need
to be washed or even sanded again and primed again first. Primer is
not supposed to serve as a finish coat; it is supposed to help the
finish coat bond. And if it weathers before the finish coat goes
on, you can't count on it to do even that.
The one exception is factory-primed wood shingles. Many companies
now apply both a permanent primer and a durable top coat to
shingles, under ideal factory conditions and with controlled drying
and curing. That's the best coating a wood shingle or shake can get
— better than any field-applied coating. If you're going to
use wood shingles, I'd advise you to go that route.
Field-prime all cut ends. Whether you use
factory-primed material or prime it yourself, make sure to prime
every cut end or edge. That's easy to do — just keep a can of
primer and a brush at the chop-saw station, and have the carpenter
who's doing the cutting prime each end before he passes it to the
carpenter who's nailing.
If you don't prime the cut ends, you're leaving open the part of
the wood that is most open to moisture entering: the end grain.
Nature intended wood to draw water into the end grain. In service,
unprimed ends will absorb water and swell, and paint will start to
come off the wood at that location first (Figure 3). If painters
arrive to paint or stain a house that is sided with clapboards
whose cut ends are unprimed, or trimmed out with boards whose ends
are unprimed, there is very little we can do to address the issue.
So it's up to the people installing that wood to make sure that the
ends are primed (Figure 4).
Figure 3. Here, carpenters have installed
factory-primed window casing material without sealing the ends.
Stain was applied without any sanding or repriming. Failure has
begun at unprimed ends and flat grain (far left), and at unsealed
knots (middle). At the bottom of one piece, water has entered
unprimed end grain and caused the piece to check (left). If the
carpenters had primed all cut ends, and if the original painters
had prepped the wood and applied a fresh field primer, the onset of
failure could have been postponed for years.
Figure 4. Carpenters have several convenient
choices for primers to apply in the field during siding
installation. Above, stain-blocking primers come in small cans for
brush application or in spray cans. The author prefers the brush
method (above right) because it gives thick coverage without
overspray or environmental concerns. A pocket-sized sponge
applicator bottle is handy too; a carpenter can keep it in his
pouch, ready to use (right). However, it takes repeated swipes with
the bottle to achieve thick primer coverage (far right).
Take special care with finger-jointed
material. Many wood windows and doors are now
assembled with finger-jointed wood. We also see a lot of
finger-jointed siding and trim these days. If the wood has a
factory primer applied, it may hide those joints, but it doesn't
protect them from the weather. So it's very important to prime
finger-jointed material again as soon as possible after installing
it. If those joints start to open up and let moisture in, they may
not hold up the way they're supposed to, and they'll start to look
bad as well.
Some finger-jointed material uses very small pieces of wood and
lacks a good match between one section and the next. Pieces with
different grain density and grain orientation move in different
ways, and they also accept paint or stain in different ways (Figure
5). If you use this kind of material, you should make sure your
customer can accept the way it looks: coatings on sections with
flat grain will wear or come loose sooner, and the joints and
variations may quickly become apparent to the eye. While the
material may be economical, the results may not be to everyone's
Figure 5. These finger-jointed clapboards
appear to be made with very short sections of wood with different
sawing and grain patterns. Some finger-jointed boards are even made
with pieces from different tree species. Here, we see that the
flatsawn grain of some sections holds stain very poorly. The author
advises carpenters to reject pieces of siding that show such
dramatic differences from section to section.
Use ring-shank or spiral-shank nails.
When siding and trim are nailed with smooth-shank nails —
even galvanized nails — daily and seasonal wood movement can
work the nails loose from the material over time, leaving nails
standing proud (Figure 6). On repaint jobs, our prep crew usually
has to pull a lot of nails that are high, and we always replace
them with ring-shank nails (either hot-dipped galvanized or
stainless steel). There's no good reason for a carpenter in new
construction not to use ring-shank nails in the first place. In my
experience, I've never found a ring-shank nail that has worked its
way high of the siding or trim.
Figure 6. As the wood expands and contracts
with changes in moisture, smooth nails may gradually work proud of
the board surface (right). Nails like this should be pulled and
replaced with stainless steel ring-shank nails, which hold better
and won't work loose.
Be careful to drive nails just flush with the top surface of the
wood, or perhaps just a hair lower. Good carpenters get a feel for
how to set the nails just right with the final tap of the hammer.
But gun nails are harder to control, and carpenters may get in the
habit of driving the nail heads into the wood (Figure 7). That's
bad practice — it provides a place for water to pool and
attack end grain, and it creates a surface condition that is hard
for primer to seal.
Figure 7. When carpenters overdrive gun nails
beneath the surface of a board, water finds a place to collect and
penetrate exposed wood fiber ends. The coating has started to peel
next to this nail hole, even on the shady north side of the
There's a lot more to say about a durable paint job. Good surface
prep and good application technique are important factors in the
success of a coating. But those measures are really the painter's
job to implement — and if you choose a well-qualified
painting contractor, they'll be done properly. And they're no more
important than the tips I've provided here: if your crews use the
careful priming and nailing techniques I've described when you're
building the house, you could add years to the lifetime of the
coating your painter applies.
Nigel Costolloe owns and operates Catchlight
a full-service custom painting company in Boston, Mass. All photos
by Ted Cushman except as noted.