thin each coat with 10% mineral spirits. Oil-
based polyurethanes dry slowly, so apply only
one coat per day, unless the manufacturer
recommends otherwise. Here again, sanding
between coats is not imperative unless you
wait a week between coats—or you need to
528 Chapter 18
sand down imperfections. Before waxing an
look you like; typically, two or three coats do the
oil-based poly, be sure to wait a week after the
trick. Oil finishes offer the least protection but
last coat dries.
are easiest to reapply.
shellac doesn’t have the water resistance of poly-
urethane, but it dries quickly, has a wonderful
Painting the Exterior
old-fashioned sheen, and adheres well to earlier
Exterior paint jobs can last 10 years or more if
shellac coats, so it can be touched up repeatedly.
you’re fastidious about prep work and attentive
If wood is new or recently stripped, apply a sealer to water-related building details. Key factors
coat of thinned-down shellac. If you’ll be staining include proper flashing of windows, doors, and
the wood, first brush on a sealer of 1 part shellac
roof junctures; maintaining gutter systems;
to 4 parts denatured alcohol, allowing it to dry.
caulking gaps in exterior siding; and adequately
Otherwise, brush or wipe on a coat of 1 part shel-
venting excess moisture from interior spaces.
lac to 2 parts denatured alcohol, wiping off the
excess and allowing the coat to dry for two hours
before sanding lightly with 320-grit sandpaper.
Thereafter, apply two or three coats, thinned with
10% denatured alcohol. If the surface is smooth,
ladder saFeTy
there’s no need to sand between coats. Wait one
day between coats and three days before waxing.
if you’re painting a whole house, the job will go much faster if you rent scaffolding.
Because shellac dries so quickly, don’t attempt to
however, if you decide to use an extension ladder or two, follow these safety rules:
rebrush it.
don’t place ladders near incoming electric service lines. When the air is moist,
Oil finishes include boiled linseed oil, tung oil,
electricity can arc to nearby objects or people, so keep your distance.
and the so-called Danish oils like Watco®. Using
Securely position the ladder. never ascend a ladder that lists to one side. On
a nylon pad or a rag, rub a generous amount
uneven ground, use a ladder with adjustable leveling feet, as shown on p. 44.
of oil onto the wood. Let that soak in for 10 to
Place the bottom of the ladder out from a building no more than one-quarter the
15 minutes before rubbing off the excess with a
ladder’s height.
clean, dry cloth. With each coat, the wood will
Wear hard-soled shoes so your feet won’t tire quickly on the ladder rungs.
darken slightly. Allow each coat to dry for
24 hours, then reapply the oil until you get the
P R O T I P
shellac mixed from dry flakes
is a terrific finish with better
water resistance and clarity than
premixed shellac. also, it’s a
good idea to check the label for
an expiration date. old shellac in
the can won’t dry properly.
Sheet peeling is caused by excessive moisture migrating through a wall—in this case, an unvented
bathroom wall.
Painting
529
WhY Paint Fails
Wrinkling is caused by applying paint too thickly,
painting an exterior that is too cold, failing to
Before you sand or scrape anything, figure out
thin paint sufficiently, applying paint before ear-
why the paint is failing . . . and where.
lier coats are dry, or letting the paint get rained
blistering is usually caused by painting over
on before it cured adequately. Use a power sander
damp wood or an earlier coat of paint that isn’t
to even out the surface before repainting.
dry. Blisters often contain water vapor, although
alligatoring, or cross-grain cracking, is caused
“temperature blisters” are largely hot air, caused
by too many layers of paint, usually old, oil-based
by painting a surface that was too hot. Scrape
paint. The thicker the paint, the less it can flex as
and sand blisters, allow the wood siding to dry
siding expands and contracts. So the paint
thoroughly, and spot prime.
cracks—sometimes all the way down to bare
Peeling off in sheets is blistering on a grand
wood. Alligatoring may also be caused by paint-
scale—sometimes an entire wall. This is most
ing over an undercoat that didn’t dry completely.
common on older homes lacking vapor or air
In either case, it’s big trouble because you’ll need
barriers and occurs especially on siding outside
to strip the paint down to bare wood and seal it
bathrooms or kitchens, when excessive moisture
with a primer-sealer before repainting. It may be
migrates through the wall. If your old house has
easier to replace the siding.
been retrofitted with insulation and a vapor bar-
Chalking is a normal occurrence and isn’t a
rier, peeling may indicate moisture trapped
problem unless it’s excessive, usually the result of
inside the walls and, possibly, rotted framing. At
cheap paint. Because new paint won’t adhere
the very least, add ventilator fans to exhaust
well to a powdery residue, you must scrub and
water vapor. And on outside walls, drive thin
rinse the old surface and allow it to dry before
plastic wedges behind the lap siding to help
repainting.
moisture escape.
rusty nail stains are common where siding
intercoat peeling, a new coat of paint separat-
nails are not galvanized. The fastest fix is
ing from the old, is a classic case of poor prep
sanding each stain lightly and priming with a
work. Typically, chalky old paint was not
rust-inhibiting primer like Kilz® stain blocker.
scrubbed or sanded and thus new paint could not For a longer-lasting repair, sand until you expose
adhere. Or, less often, the painter waited too long each nail head, use a nail set to sink each one
P R O T I P
between the prime and finish coats. Scrape failed 1⁄8 in. below the surface, prime with stain blocker,
paint, sand, and wash the surface well, letting it
and fill with wood filler. Then sand and spot-
although white pigmented
dry before repainting.
shellacs such as b-i-n® are
prime before painting.
terrific for blocking stains
on interior surfaces, they’re
not advisable for priming
exteriors. hot sun softens
and degrades shellac.
Alligatoring, or cross-grain cracking, is caused by too many layers of old, inflexible paint.
530 Chapter 18
Where a random-orbit sander won’t fit, use a
palm sander, as shown, with
60-grit or 80-grit sandpaper. A palm sander is also handy for scuff-sanding
old paint in good condition so new paint will adhere better.
Hand-scrape nooks and crannies that power tools can’t
reach or could damage. Here, heat guns and chemical
scrapers also make sense.
To maximize adhesion, spot-prime
seams and gaps before caulking them
with an exterior-grade, paintable
acrylic or multipolymer caulk. Paint
won’t stick to pure silicone caulk.
Tannin bleed-through, a widespread brown
four years. If that sounds like too much mainte-
staining, occurs when waterborne resins in
nance, prime the siding with an oil-based primer,
woods, such as cedar and redwood, bleed
and switch to paint.
through porous latex primers. Scrub the surface
mold and moss are common in humid climates,
well, and prime it with one or two coats of an oil-
on north-facing and foliage-shaded walls, and
based (alkyd) primer such as Kilz or Benjamin
where lawn sprinklers hit the house. Siding that’s
Moore Fresh Start®. Paint what you like—latex
constantly damp can lead to structural rot. For
or oil based—over that. At this writing, stain-
starters, cut back foliage and adjust the sprin-
blocking acrylic latex primers show promise but
klers. Scrub moss off by hand, using a wire
don’t yet have the track record of oil-based stain-
brush. Remove mold by applying a cleaner/
blocking primers. Get a second opinion from an
mildewcide such as Zinsser® Jomax® before
up-to-date paint supplier.
scrubbing or power washing the surface (but see
graying wood is a natural response to sunlight
the cautions later in this section). After the exte-
when siding is left unfinished or has been sealed
rior has dried for about a week, prime as needed,
with a clear finish that degrades. Never leave
and repaint with a paint containing a mildewcide.
wood siding exposed to the elements—both
because bare wood quickly degrades and because
PreParing the exterior
paint or clear finishes don’t adhere well to
Houses built before 1978 may contain lead paint,
degraded wood. Sand and wash the surface, and
so before starting prep work, be sure to review
reapply a clear finish with a UV-blocking agent.
Clear finishes need to be reapplied every two to
Painting
531
A mechanical scraper with a vacuum
using a garden pump sprayer. A dilute solution of
attachment is the tool of choice
TSP is often recommended, but urban houses
when you’ve got to strip exterior
may need a cleaning agent with a degreaser that
paint. But set the nail heads first, or
will cut soot, automobile exhaust, and the like. As
you’ll chew up expensive scraper
noted earlier, if there’s mold present, use a clean-
blades. Eye protection is a must.
er with a mildewcide. Once the cleaner has had
time to work, rinse it off with a garden hose and
allow it to dry thoroughly for a week or so before
painting. That’s a minimal wash.
To thoroughly wash and rinse an exterior, rent
a pressure washer, which has a small boiler and a
high-pressure electric pump. The rental company
will recommend a detergent suitable for the unit
and explain how to use it safely. For most clean-
ing jobs, 1,800 psi to 2,500 psi is specified—for
softwoods such as cedar or redwood, use 1,000 psi
to 1,500 psi. Tip sizes range from 0º (concentrat-
ed pressure that can easily damage siding) to 40º
(a wider fan of water favored for light cleaning).
In general, start with a low-pressure setting until
you are familiar with the machine, and keep the
spray wand moving. Note: Always spray down-
ward if you’re cleaning lapped siding. Otherwise,
you’ll force water underneath.
scraping, sanding, spot-priming, caulking.
Once the siding has dried, hand-scrape the loose
this chapter’s earlier sections on equipment and
paint. For this, use a large scraper with a 3-in.-
lead-paint safety—and test for lead (see p. 515).
wide blade, preferably one with a forward grip
Even though you’re working outside, wear a
over the blade. Be sure to scrape the lower edges
respirator when sanding or scraping paint and
of the clapboards and beneath the windowsills.
when working with solvents or paints of any
For hard-to-reach areas when siding abuts trim
kind. Likewise, when applying cleaning solutions or where trim is curved or intricate, use a hand
(which can be caustic), wear rubber gloves and
scraper with interchangeable blades. If paint
eye protection.
doesn’t come off easily, that’s a good sign—it’s
Prep work is prodigiously messy, so spread
well adhered. However, if isolated areas of paint
drop cloths out 8 ft. from your house to protect
are too thick or obscure ornamental details, use
your lawn and shrubs. Otherwise, you’ll be pick-
a chemical stripper or a heat gun to remove
ing paint scraps out of your grass for years or—
more paint.
even worse—exposing kids and pets to lead-based
After scraping loose paint, use 80-grit sand-
paint. If it’s hot and sunny, don’t cover your
paper to feather out the edges of the remaining
plants with plastic drop cloths; the plants will
paint, smooth uneven surfaces, and scuff up sur-
cook. Instead, use fabric drop cloths, which
faces so new paint will adhere well. For this
shade plants, won’t tear, and are far less slippery
work, an electric palm sander or random-orbital
to walk on. But if tests indicate lead paint, cap-
sander is a good tool, powerful yet light enough
ture the debris in heavy 6-mil plastic tarps,
to use all day. If you’re prepping painted stucco,
which you can roll up and discard at the end
brick, or concrete, instead use a wire brush.
of each day.
When you’re done, brush off the dust with a
hand broom.
Washing surfaces. Before installing new wood
If the paint is largely intact, you may not
siding, apply primer-sealer to the front and back
need to prime it, but you should spot-prime all
faces and to all edges. When that coat is dry,
areas you’ve scraped down to bare wood, plus
scuff-sand it with 100-grit sandpaper, and dust it
exposed nail heads and cracks, gaps, and holes
off with a whisk broom. Then install the siding
you intend to fill or caulk. Spot-priming blocks
before applying the topcoats.
nail stains, seals wood from moisture, and pro-
However, if the siding is already painted—
vides a better surface for filler or caulk to adhere
even if the
paint is in good shape—wash it first.
to. Use either an exterior-grade polyurethane, a
Start by applying a house-cleaning solution,
532 Chapter 18
paintable acrylic, or a multipolymer caulk; don’t
reach, use hand scrapers, a chemical stripper, or
use silicone caulk because paint won’t stick to it.
small mechanical scrapers like the Metabo®
This is also a good time to set and fill nail
Lf724S. When you’ve finished stripping, use a
heads. Because wood filler shrinks as it dries,
palm sander or a random-orbit sander with
slightly overfill the holes. When the filler is dry,
50-grit to 80-grit sandpaper to smooth out the
sand it flush.
rough spots before washing, caulking, dusting,
Where wood is badly deteriorated, you should and priming.
replace it. If the trim has only localized rot and
Chemical strippers are most appropriate where
would be difficult to replace, scrape the loose
trim is intricate or where you want to remove
matter away and impregnate the remaining area
lead paint without dispersing particles into the
with an epoxy filler, such as the one shown in the air and soil. Strippers vary in strength, environ-
photos on p. 163.
mental impact, working time (4 to 48 hours), and
method of application. See the sidebar on p. 526
stripping exterior paint. Stripping exterior
for a list of solvent-free strippers. Typically,
paint is a nasty job. Fortunately, only a few paint
chemicals are brushed thick—roughly 1⁄8 in.—
conditions require stripping. One of those condi-
and allowed to work.
tions is alligatoring, in which many layers of old,
Given enough time, chemical strippers should
cracked, oil-based paint resemble the skin of an
remove all paint layers in one application,
alligator (see the photo on p. 530). In that case,
although solvent-free strippers may take repeated
before stripping to bare wood, get a bid to
applications. Methods of application vary widely,
replace the siding. Labor costs should be less, to
so follow the instructions on the label carefully.
say nothing of the cost, mess, and health con-
One example: To keep its stripper from drying
cerns of stripping lead-based paint. But if you
out while working, Dumond Chemicals’s Peel
decide to strip, wear a respirator, eye protection,
Away® system comes with plasticized paper that’s
Renovation 4th Edition Page 123