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Guide to whole house paint removal and recoating.
Update:
On a recent project, I've removed and reinstalled all
the siding back side out... Click here for info.
Homeowner's checklist for a lifetime
exterior paint job: rogcad.com/painting
Interior painting tips: rogcad.com/painting/interior.htm
Part I
Tools and techniques for using heat to completely remove
paint from siding and trim.
1. Ground Cover
2. Scaffolding
3. Face Mask and Clothing
4. Heat Guns
** NEWS FLASH ** Infrared heat largely replaces heat guns
(See item 4.5 further down)
5. Pro-Prep Scrapers
6. Setting Nails
7. Hand Sanding
Part II
Materials and techniques for coating bare wood.
8. Soaker Coat
9. Caulk
10. Acrylic Primer
11. Finish Coats
12. Encapsulation
Part III
13. Other paint removal methods
14. Coating mixed surfaces
15. Overpainting
I've been painting old houses in Minneapolis since 1976, with
an interest in the longevity of the paint job. I've done 100
percent paint removal and recoating on dozens of large houses,
most of them using heatguns, working by myself. Click on the
image to see a house which was stripped using heatguns.
Part I
Paint removal
1. Ground Cover
Protecting the health of your customers, their neighbors
and their pets is the motivation for containing lead paint
chips and dust.
Cover the ground with 4 or 6 mil plastic sheeting, cutting
and fitting tightly around bushes. Hang lightweight canvas
tarps over bushes, and remove these each night. Use plenty
of ballast to secure the ground cover. After paint removal,
slice it into manageable sections and roll it up.
Vacuum up any remaining chips using a wide diameter
vacuum hose with a tapered attachment. This will
prevent clogging the hose with chips and twigs.
2. Scaffolding
You'll be far more productive working off a plank
than off a ladder. Every house scaffolds differently,
and a lot of thought must be given as to exactly
how to implement it. Whether you rent or own your
scaffolding, you'll find adjustable stands and sidearms
for planks to be very valuable accessories.
Scaffolding will also provide a means for hanging
tarps to help direct chips and dust downwards to the
ground cover.
3. Face mask and clothing
The motivation here is to protect yourself with a mask,
and to protect people and pets you come in contact with
by changing clothes at the jobsite.
I've been using charcoal canister breathing filters.
These seem to be effective, since lead has a definite
odor, and these filters block out all such odor. There
is a filter called ULPA (Ultra Low Penetration Air)
which apparently is the ultimate protection against
lead fumes, but don't look for it at your paint store.
Eyes can also absorb lead fumes, so you might want to
consider full face protection.
4. The heatgun
** NEWS FLASH ** Infrared heat largely replaces heat guns
(See item 4.5 further down)
I've carefully measured stripping progress using single,
double and triple heatguns, and consistently find that
double heatguns strip at exactly twice the rate of single
guns, and triple heatguns strip at exactly triple the rate
of single guns.
Triple guns work well for siding. I buy the twenty dollar
guns at Menards or Home Depot, remove the plastic casing
from two of them, and through the use of electrical or
duct tape, achieve the configuration in the photo. By
doing this and by fastening the cords at your waist, you
will reduce the weight to exactly that of two heatguns.
A very important modification of the nozzle is to make about
a dozen snips and flare out the resulting sections as shown
in the photo. This will not only spread the heat out more
uniformly on the surface to be stripped, it will also allow
you to hold the nozzles right up against the surface and
keep them there. The biggest mistake workers make when
using heatguns is that they tend to keep backing the gun
away from the surface. The nozzles should rest on the
surface 100 percent of the time you are stripping.
Work in long strips. Heat spreads through the paint film
by conduction. If you work in short strips, you lose this
advantage of preheating. You also lose this advantage
every time you back the gun off the surface.
Double heatguns work well for trim and siding. Simply tape
two guns together.
Each heatgun requires a separate electrical circuit. Have
lots of cord on hand. Each 1000 watt gun costs seven cents
per hour to run. Thus, a triple gun costs less than two
dollars per day to operate.
Fire hazards
Heat stripping does not need to be a risky procedure. The
most important thing is to carefully caulk all cracks,
holes and gaps between boards before using heat. Carefully
inspect under each siding board as well as all other boards
for gaps, holes or cracks.
Hidden fires in walls, eaves and under shingles start
in two ways:
1. Heat flowing into cracks, holes or gaps.
There is very dry wood or even dry wood dust in
walls, eaves, and at the roof line. This can
begin to smolder without your knowledge and erupt
into flames after you've gone home.
2. Sparks emitted from heat gun nozzles drift into
cracks, holes or gaps.
Bits of paint shavings fall into the nozzles and
come out as sparks, particularly when melting on
the underside of a horizontal surface, such as a
soffit, which at any rate is generally recommended
against.
You can nearly eliminate the risk of fire by using caulk to fill
in any cracks, holes or gaps prior to heat stripping. This
is my standard procedure. Never aim your gun at or below any
crack, hole or gap.
One place that cannot be caulked is where the roof shingles
meet the fascia board. Stay well away from the roof line
when heat stripping. Dry scrape the upper few inches of
the fascia board.
Whenever in doubt, turn the guns down to the low heat setting
or back them well away from the surface and use a little extra
scraping muscle.
Keep a water hose with nozzle attachment and crow bar near
you on your scaffolding. The hose should be left on at the
spicket. (A small fire extinguisher is very handy.) In the
event of a fire, do not pry up any board until you have the
hose in hand. Prying up a board gives the fire a burst of
oxygen and sudden life, causing it to spread rapidly.
4.5 Infrared heat (radiant heat) for paint removal
A lightweight infrared heater using just one electrical
circuit strips paint about as fast as my triple circuit
heat guns, provided there is reasonable continuity of the
paint film to be stripped. I've just started using infrared
heat this year after being alerted to it by a reader of this
website.
There is no fire hazard to speak of, and little or no need
of a face mask.
Why no one thought of this for paint removal 30 years ago is
hard to understand. The technology is at least that old.
There is now a commercial model available, but I didn't want
to spend $465 on the heavy commercial model when I could
make a lightweight model for about $35 in materials and
30 minutes of my time. I converted an old infrared room heater
for which I had paid about $50 into a very lightweight paint
remover. The replacement tubes are only $10 (and I have yet to
burn out a tube).
My tool works as well as the commercial model, based on
everything I've read about the testing others have done with
the commercial model. The working parts in my tool are the
same as in the commercial model - two quartz tubes.
Just go to wbmarvin.com for a listing of available infrared
heaters and the $10 replacement tubes. The model 5460
Steam 'n Heat at $79.95 looks like the current version of the
old Marvin heater I used to make my paint remover.
If I can locate a source for the ceramic terminals or find a
simple way to make my own ceramic terminals, I'll post
instructions for making one of these infrared strippers from
scratch. Bending some aluminum ($1), adding the tubes (2 X $10),
and fastening electrical cord and connectors ($6) would take
about an hour and the total cost for materials should be
about $35.
Make your own infrared paint remover and save the weight and
the high cost of the commercial model. The commercial model
(Silent Paint Remover) weighs 4 lb 3 oz. My infrared paint
remover weighs just 1 lb 12 oz. This includes the 12 oz
clamp being used for the handle. A lighter handle, such as
a simple L shaped piece of wood will bring the weight down
to just 1 lb 1 oz. Having stripped paint for a living for
the past 30 years using heat guns, I can assure you that
you'll appreciate this weight reduction and increased
productivity.
I refolded the aluminum reflector so that the tubes would
be spaced 2 1/2 inches apart, which is the average spacing
of narrow lap siding.
I'm also going to make a single tube model for doing narrow
architectural detail.
Niether the aluminum reflector or the clamp get too warm
to cause any problem. I casually lay the tool down facing
up and running (meaning plugged in - no switch needed) when
I'm not using it. You can lay it down on any surface such
as a wood plank, the ground, or a canvas tarp.
5. Pro-Prep scrapers
These scrapers will not only greatly boost your heat stripping
output, they will be your partner in all kinds of dry scraping
endeavors, from high speed outdoor dry paint removal to fine
interior wood refinishing projects, including furniture.
Proper sharpening and use of these scrapers is at the heart
of indoor and outdoor refinishing projects. The blades shown
above will be your primary ones for outdoor work (and most
indoor work). For heat stripping, I use the small sized
handles even with the large sized blades. This gives greater
clearance for shavings.
Buy large medium grade files by the half-dozen, or by the
dozen if you have a helper. A sharp file is the only tool
to use to sharpen your scraper. As soon as filing becomes
a bit of a struggle, throw the file away.
Place the scraper on a firm surface and file into the blade
edge. File at a 45 degree angle. Slightly round the corners
of the large flat blades as shown in the drawing, and for
dry scraping, very slightly arc the entire edge as shown.
Rounding the corners will help keep you from making gouge lines
on the surface you're scraping. Arcing an edge will give you
better bite for dry scraping.
Keep your file with you at all times. Dry scraping necessitates
resharpening as often as every half minute. Heat scraping
necessitates resharpening about every five minutes.
Use a variety of motions with your scraper - towards the guns
with the grain, away from the guns with the grain, perpendicular
to the grain, and diagonal to the grain.
Take your time and let the heat do most of the work, or
you'll end up with gouges on your wood surfaces. Clean up
all residue as you go along.
Heat assisted scraping is usually the best approach even
when just spot scraping. It's gentler on the wood and will
allow you to feather the paint as you go along.
Retire your blade as soon as it becomes a bit of a chore
to sharpen it. (You get to the thicker part of the blade
as you sharpen it.) The cost of the files and scraper
blades is small compared to the cost of struggling with
expended files and blades.
Here is a great dry scraping tip for fast paint removal,
especially when the paint is stubbornly attached: Use the
round edge of your blade to make channels in the surface.
Space these parallel channels about 1/3 of an inch apart.
Then come back over it with the flat blade. Presto, you
can strip any thick stubborn paint with very little muscle.
The only catch is that it sometimes leaves a somewhat crude
surface. Be careful of where and how you use this technique.
6. Sinking nails
Setting nails needs to be done after heat stripping and before
sanding.
I've found that I can't set nails for very long unless I use
vicegrips to hold the nail set.
These nail set holes are filled with a low shrinkage elastic
filler after the initial wood priming. A good general purpose
filler is CLEAR silconized acrylic caulk with Durham's
water putty (Durhams water putty) powder added to greatly
reduce the water content, which in turn greatly reduces
shrinkage. Two applications are typically needed. Allow at
least two days cure time before applying any coating over it.
Be sure to use the CLEAR caulk to minimize its capacity
to absorb moisture during its service life.
A less elastic filler is epoxy with Durham's water putty powder
added. While somewhat lacking in elasticity, this filler does
have the advantage of absorbing virtually no moisture even under
extreme conditions. This means that it won't release excessive
moisture during periods of rapid moisture evaporation through
the paint film, such as when a hot afternoon sun heats up a
dark colored topcoat. If that dark colored topcoat has much of
a sheen, it could blister where excessive moisture tries to
quickly escape.
Sometimes siding boards are so dense and the nail heads so
large that setting is impractical if not impossible. In
those cases the nail heads will need a very heavy spot priming
with red iron oxide rust primer prior to applying the wood
primer. They will also need a very careful finger-wipe
caulking after the wood primer is applied, or else water will
surely enter the surface here and cause premature paint
failure.
7. Hand sanding / Power sanding
60 grit floor sanding paper works well for all exterior hand
sanding tasks. Not only is it very long lasting, but it is
stiff and thus works very well on corners and narrow
surfaces. It can also be formed into a stiff rolled
shape for doing tight concave surfaces.
But for a little more money, you can avoid getting slivers
(no small issue) by using sponge sanding blocks. They are
also long lasting and come in coarse, medium and fine grit.
I now use these extensively, as I finally got tired of doing
deep surgery on my hands to remove slivers.
If you were gentle with the scraper and let the heat do
most of the work as you heat stripped, and if you carefully
scraped off all the residue as you went along, then a good
stiff hand sanding will complete the stripping task.
Of particular importance is the rounding off of the
underside of each siding board, as well as the edges of
all trim boards.
A 5 to 10 amp random orbital sander or circular sander
often do a better job of cleaning up residue, smoothing the
surface, and providing a fresh wood surface than does
hand sanding.
Blow dust off the wood and out of nail holes with a reversed
vacuum, air compressor, or leaf blower before priming.
Part II
The Coatings
Outline:
* A conditioning soaking coat.
* Caulking and filling.
* A primer to complete the moisture seal.
* Finish coats primarily for sunlight protection.
* Encapsulation
Overview:
Start with a thin product with good sealing properties,
heavily applied in the shade. Follow with another coat
with good sealing properties to make sure the wood always
stays relatively isolated from outside moisture. Finish
with a topcoat with good permeability (good breather).
The topcoat is mostly for sunlight protection.
8. The Soaker Coat
I have a strong preference for a Pittsburgh Paints
acrylic product called Permanizer Plus as my initial
wood conditioner/sealer, but will include a discussion
here of oil based primers.
You get only one chance to penetrate the wood with a
soaker coat of primer. Once your initial prime is
dry, no other coating will penetrate the wood. The
key is to use a very thin product and apply it very
heavily. If using an oil based primer, you should
also consider applying it "wet on wet" for the deepest
penetration. This means recoating a section just as
soon as that section has mostly soaked in but not yet
dried. You should not apply the soaker coat in direct
sunlight.
Here's a good choice for an oil base penetrating coat:
I mix three parts alkyd primer to two parts mineral
spirits. (I recommend adding only a little or no
Penetrol, as it may interfere with the adhesion of
the subsequent latex coating.) Flood it onto the
surface with a 3" wall brush. Or mix it even
thinner and apply it "wet on wet" for the ultimate
soak. There should be runs. They won't have
enough body to be detectable after the primer is
dry. Since mineral spirits is a light oil, it will
increase the oil content of the primer. Allow at
least two warm dry days before applying acrylic
primer over this soaker coat.
If your wood is dried out, it would benefit from a
flood coat of Penetrol prior to oil based priming.
Only an oil based primer should be applied over
the Penetrol. Allow a few days of drying time
before applying latex primer or topcoat. There is
also much to be said for using a traditional oiling
process using boiled linseed oil thinned with mineral
spirits or turpentine. Les Woods of Maryland writes:
"I enjoy the feeding of the wood more than any
other part of the process, because it smells
(to me) heavenly! There is nothing like coming
back to the window after it has dried for a few
days, and catching the aroma of the oils having
mingled with the old wood. It's wonderful!"
Permanizer Plus is excellent as an initial wood primer.
It has good penetration, and has the additional property of
being able to stabilize old dry cracked wood. It does this
by sending its three dimensionally elastic molecules into
the pores of the wood and by winding its way through every
crack in the wood, forming a continuous elastic barrier
against water. This primer has created success where
oil based primers have failed.
Its urethane content also makes it surprisingly effective
against tanin bleeding from cedar.
When using an all acrylic priming system on new or completely
stripped wood, always start with Permanizer Plus, and be
absolutely certain to flood it onto the surface, and only in
the shade. Remember, you get only one chance to soak the
wood properly.
Do not accept any clear acrylic substitutes for Permanizer
Plus when using it as an initial wood primer. My testing
in the summer of 1999 showed that Permanizer Plus quickly
penetrated the surface of dry gray wood and stained it to
a rich brown, while Peel Stop from Zinsser did neither.
Speaking of dry gray wood - this is surface rot. Sand it
away if practical, since the wood fibers are very weak
when gray and can fail, taking the paint off with it
of course. A good penetrater such as Permanizer Plus or
Penetrol (penetrating oil) is often sufficient to overcome
this surface rot.
If you ever need a cold weather (sub 50) version of
Permanizer Plus, try this:
1/2 gal XIM Peel Bond
1/3 gal Sherwin Williams Clear Base Woodscapes
1 pint Penetrol (or Emulsa Bond)
1/2 gal water
The Peel Bond provides the appropriate amount of
acrylic resin. The Clear Base Woodscapes provides
the appropriate amount of urethane. The Penetrol
provides additional wood fiber conditioning. The
water provides better penetration.
This blend makes a suitable replacement for Permanizer
at all temperatures between 35 and 90.
For surfaces that are a complex mixture of bare wood
and existing paint, making spot priming impractical,
an alkyd primer works when the existing paint is alkyd
or oil base, but an acrylic primer should be used when
the existing paint is latex. It's always a risk to
apply alkyd primer or alkyd paint over latex paint.
The reasons for this are not chemical incompatiblity
but rather mechanical considerations: You don't want
a coating which is a very poor breather over a
coating which is a good breather, as this can lead
to moisture buildup in the good breathing coat and
ultimate failure. You also don't want a coating
with little elasticity over a coating of high
elasticity, as this can lead to alligatoring.
For a longer discussion about these mixed surfaces
see bottom of page.
9. Caulk
The caulking is performed next, allowing you to apply
two film forming coats over it.
My two favorite all-purpose caulks are DAP 35 year clear
siliconized acrylic and White Lightning 40 year clear sili-
conized acrylic. The DAP is lower water content, stiffer,
and can be painted over a little sooner. Caulk every little
crack, tiny hole and end joint, however tight the joint may
be.
You might prefer a polyurethane caulk such as Vulkem, PL, or
Sherwin Williams for high movement "architectural joints".
Allow plenty of drying time.
Another excellent use for the DAP 35 year caulk is as window
glazing. I resisted this method for years because I was
proud of my traditional glazing skills. But caulk will
outlast glazing by dozens of years, will remove far more
easily should you need to replace a window pane, will save
an enormous amount of time right up front, and will
look virtually identical to traditional glazing once you
become proficient at applying it. It's been my standard
method for many years. Cut the nozzle wide and at a
30 degree angle. Be sure to prime the window wood prior
to caulking or glazing.
10. Second coat - The Acrylic Primer
After caulking you are ready for your second coat of
primer, as the penetrating coat alone is not adequate
moisture protection for the wood.
I don't use any alkyd products beyond the penetrating
coat. I prefer that any coating which forms a substantial
film on the surface be elastic.
This is especially important whenever the wood has a high
degree of unstability, such as in the case of old dry
cracked wood, plywood, poor cut wood, broad soft boards,
or pine. In fact in these cases, you should definitely
use an all acrylic priming system, beginning with Pittsburg
Paints Permanizer Plus clear acrylic wood stabilizer.
A pigmented acrylic primer such as 1-2-3 by Zinnser
works well over the penetrating coat. This primer
will provide pretty good film build, providing both
moisture protection and the beginning of sunlight
protection. This coating needs to be applied heavily
if it's going to do its work. Be very careful to not
brush it beyond what is necessary. Window sills need
an extra coat.
If there is bleeding present after the Permanizer Plus has
been applied, a coat or multiple light coats of 1-2-3 would
handle that as well. Yellow oxide, red oxide, or zinc oxide
added to a tinting base of 1-2-3 makes it more effective
against tannin bleeding in cedar.
My current favorite product for the second coat of primer
is a 1:1 blend of Permanizer Plus and the finish paint,
the nature of which I'll discuss next.
11. Finish Coats
Sherwin Williams exterior finish coats
I use Sherwin Williams Duration Lifetime Coating almost
exclusively. The best Sherwin Williams paints have always
had the best ingredients in the optimum percentages.
Sherwin Williams Duration Lifetime Coating is a higher build,
better bonding, more flexible coating than previous premium
acrylic coatings and is the ultimate finish coat for exterior
painting. It even works okay as a bare wood primer in a pinch.
This product performs well down to 35 degrees. I do not rely on
it for bare wood priming, since most situations call for better
penetration, sealing or stabilization. It can be used as a two
coat system over Permanizer Plus, but using 1-2-3 as the next
coat over Permanizer Plus will provide better moisture
protection, as well as bleeding protection as mentioned above.
Update: As mentioned just two paragraphs ago, I'm currently
favoring a 1:1 blend of Permanizer Plus and Duration as my
second coat of primer.
I use eggshell or satin finish latex whenever I can,
as opposed to flat, semigloss or gloss finish latex.
"Satin" or "eggshell" finishes have just the right
resin/pigment ratio to allow the paint to both breath
and shed water. Ideally, the topcoats should breath
better than the primer(s) in order to avoid moisture
trapping. See further down (item 15) for information
about hydrostatic pressure and paint film failure.
Eggshell or satin finish latex paints also tend to have
more ideal elongation (elasticity) properties.
There is a strong tendency for people to overbrush latex
coatings and to spread the coating too far. The idea is
to apply a film of protection on the surface, not to
just color the surface. The goal is to transfer the
acrylic substance from the can to the surface in a
uniform film with as little disturbance of the resin as
possible.
There should be a minimum of three coats of film forming
product everywhere (except well shaded soffits). This
might take the form of a conditioning coat followed by
two coats of Duration, or a conditioning coat followed by
an acrylic primer, then Duration.
Anything less does not adequately seal the surface.
When moisture penetrates into the wood often, the surface
wood fibers lose their integrity and the film fails at
the wood surface, ultimately as the result of hydrostatic
pressure acting on what has become a poor bond.
A four coat system is recommended: Permanizer Plus, then
a 1:1 blend of Permanizer Plus and Duration, then two
coats of Duration. Adequately sealing the surface is
important even for short term success.
Soffits require less protection. For well shaded soffits
that have only a small percentage of bare wood exposed
after scraping, you could actually get by with just a one
coat process: mix one part Penetrol or Emulsa Bond with
three parts acrylic finish coat. This gives the coating
better sealing and surface wetting properties. (Penetrol
mixes with latex paint just as well as Emulsa Bond and
provides the same long term performance. I always have
Penetrol in stock and therefore use it exclusively.)
Review:
I favor the all acrylic systems even when the old paint is
entirely oil based. I've come to rely on Permanizer Plus
as a whole house initial primer, over bare wood of course,
but also over chalky paint and checked paint (if sound).
It binds any residual dirt on the surface that pressure
washing leaves behind and even helps rejuvinate the old
paint film. I follow this with a 1:1 blend of Permanizer
Plus and Duration, then two coats of Duration. And remember,
yellow oxide, red oxide, or zinc oxide added to the second
coat of primer makes it more effective against tannin bleeding
in cedar.
12. Encapsulation
Encapsulation can be regarded as stabilizing a substrate,
whether the substrate is bare wood or old paint.
Problem boards
Boards with horizontal hairline cracks as well as larger
cracks need to have a high stretch caulk troweled into their
cracks.
There can be over a hundred such areas on a house with these
types of lumber problems, and replacing all such boards can
be cost prohibitive, especially when dealing with fascia
boards and crown molding, the very boards that most frequently
have long running cracks.
Old checked paint
(This section is highly optional. It examines the concept
of layering coatings for optimal encapsulation. I don't
always follow this routine myself.)
First of all, one needs to learn to recognize the difference
between stable and unstable old paint. Generally speaking,
if the paint is not seperating from the substrate or even
hinting at it, then the paint is stable, even if heavily
checked.
But such paint can become unstable if not encapsulated
correctly:
It's desirable to use a very elastic final coat over the
checked paint, or else the checking will transmit through
it in time.
Unfortunately, a coating which is sufficiently elastic to
accomplish that might also pull the old coating loose from
the substrate through repeated expansion and contraction
with temperature changes.
Applying an oil based primer over the checked paint
prior to an elastic coating will not solve the problem,
because the elastic coating will still do work on the checked
paint by virtue of transmitting its force very effectively
through the relatively inelastic coat of new oil primer.
What to do? The secret is in using a go between coating
that is not elastic enough to flex the checked paint loose,
but elastic enough to force the elastic topcoat to do much
of its work on the go between coating. The flex force of
the elastic topcoat is largely dissipated in the go-between
coating.
I find the definition of the paint film attribute "elongation"
to be misleading: A paint film with an elongation factor
of 1 means it will stretch to 2 times its own length before
tearing. An elongation factor of 2 means it will stretch to
3 times its original length before tearing. So I use a term
called "stretch factor" to distinguish it from the industry
defined term - "elongation", even though it's the exact same
concept.
A coating with a stretch factor of 1 means that the coating
will tear upon trying to stretch it beyond its original length
of 1 unit. A coating with a stretch factor of 2 means it will
tear when stretched to double its original length.
Here are some examples among quality coatings:
Sherwin Williams Superpaint flat 1.3
Benjamin Moore Moorlife flat 1.5
Benjamin Moore Moorgard eggshell 1.5
Zinsser 1-2-3 acrylic primer 1.6
Sh Wlms Superpaint satin (eggshell) 2.1
Sherwin Williams Duration flat 2.5
Sherwin Williams Duration satin 3.1
These numbers are approximate values, based on averaging
test samples using white or light colors.
I've had great success in longterm encapsulation using
paint or primer with a stretch factor of between 1.3 and
1.6 as my buffer coat, but prefer the low end of this range.
It must be applied heavily or in two coats (1.3, then 1.6)
to be most effective. Start with Permanizer Plus as an
initial sealer, especially if there is any bare wood
mingled with the checked paint. It's function is to
seal the wood and bind any dust on the surface. It's thin
film will not play a role in the stability of the checked
paint one way or the other. It has a stretch factor of 1.5.
Duration is of course my choice for the final coat over
the buffer coat(s).
I've yet to see failure upon returning to inspect old job
sites where this method was used.
There are also heavy bodied encapsulation coatings
available, but take a look at their elongation
properties before commiting to their use.
Part III
Other Methods
13. Other removal methods
Many people have written inquiring about other methods of
paint removal. I would never say never to other methods,
but here are my impressions:
1. Water blasting. Makes a big mess as lead paint chips
end up everywhere, and leaves a lot of precariously attached
paint on the surface. It must be followed by intense scraping.
I'm not sure it's ever a cost effective method of maintaining
a house.
2. Chemical stripping. Works well more often than not.
You'll need to know whether the particular stripper you're
using will require the surface to be nuetralized after
the stripping. Much slower than heat stripping, and the
stripper is expensive.
3. Mechanical siding stripper (rotary carbide blade). Just a
bit hard on the siding, since it takes away some wood and
tends to leave waviness on the bottom edge of siding boards.
You need to follow up with a power sander. Both steps are
noisy and dusty. And you still have the ends of siding boards
and trim to deal with. The painters I've talked with who use
this system don't bother with the unwieldy vacuum attachment.
They tent the house and wear sophisticated respirators.
Quite a messy operation. There's a chance of getting
lead dust into the house. Also might be hard to contain
regarding the outside, even when tenting. I nearly killed
someone's pet dog in my early years with lead sanding dust.
I generally recommend against powered mechanical stripping
on all counts.
So heat stripping and chemical stripping are the quiet, clean
methods.
14. MIXED SURFACES
(An expanded discussion on how to approach surfaces
that are a mixture of bare wood and old paint.)
Another highly optional section. You can ambitiously read
through these scenarios, or just skip down to the dotted line
and read the punch line, which simplifies everything.
Four basic situations exist:
I. None of the existing paint is latex and the intermingling
of old paint and bare wood is such that spot priming is
not practical.
Viable options:
1. Soaker (thinned product applied heavily) coat of alkyd
over the whole works, followed by another light coat of
alkyd primer, then heavy coat of Duration.
2. Unthinned coat of alkyd primer, followed by heavy coat
of Duration.
3. Heavy coat of 1-2-3 mixed 3:1 with Penetrol, followed
by heavy coat of Duration. (Might need a coat of
straight 1-2-3 prior to Duration to control bleeding.)
4. Heavy coat of Permanizer Plus applied not in
direct sunlight, followed by heavy coat of Duration.
(Might need a coat of straight 1-2-3 prior to
Duration to control bleeding.)
II. None of the existing paint is latex and
spot priming is practical.
Viable options:
1. Spot prime with alkyd soaker coat, followed by
priming the whole works with a light coat of
alkyd primer or with a coat of 1-2-3. Then
a heavy coat of Duration.
2. Spot prime with unthinned alkyd primer or with
a heavy coat of 1-2-3 mixed 3:1 with Penetrol or
with a heavy coat of Permanizer Plus, followed by
a heavy coat of Duration.
3. Any of the four options listed under situation I.
III. The existing paint includes at least one layer of
latex, and spot priming is not practical.
Viable options:
1. A heavy coat of 1-2-3 mixed 3:1 with Penetrol,
followed by a heavy coat of Duration.
(Might need a coat of straight 1-2-3 prior to
Duration to control bleeding.)
2. A heavy coat of Permanizer Plus followed by
a heavy coat of Duration.
(Might need a coat of straight 1-2-3 prior to
Duration to control bleeding.)
IV. The existing paint includes at least one layer of
latex, and spot priming is practical.
Viable options:
1. Spot prime with soaker coat of alkyd, followed
by spot priming again with a light coat of alkyd,
followed by heavy coat of Duration.
2. Spot prime with soaker coat of alkyd, followed
by spot priming with 1-2-3, followed by a heavy
coat of Duration.
3. Spot prime with unthinned alkyd, followed
by a heavy coat of Duration.
4. Spot prime with 1-2-3 mixed 3:1 with Penetrol,
followed by Duration.
(Might need a coat of straight 1-2-3 prior to
Duration to control bleeding.)
5. Any of the options listed under situation III.
--------------------------------------------------------------
I favor the all acrylic systems even when the old paint is
entirely oil based. I've come to rely on Permanizer Plus
as a whole house initial primer, over bare wood of course,
but also over chalky paint and checked paint (if sound).
It binds any residual dirt on the surface that pressure
washing leaves behind and even helps rejuvinate the old
paint film. I follow this with a 1:1 blend of Permanizer
Plus and Duration, then two coats of Duration. And remember,
yellow oxide, red oxide, or zinc oxide added to the second
coat of primer makes it more effective against tannin bleeding
in cedar.
15. Overpainting
When paint separates from the substrate, there is always
hydrostatic pressure involved. This is the pressure of
water evaporation. To reduce the possibility of this occuring,
you must use coatings with a favorable ratio of adhesion to
permeability, you must apply them in the correct order, and
you must not overcoat a surface. When the permeability of the
overall coating system reaches a certain low point, the film
will separate at the weakest link, usually at the surface of
the wood, especially if the initial primer did not penetrate
deeply enough into the wood or did not enhance the wood fibers.
To review what was said earlier about primers and topcoats:
Start with a thin product with good sealing properties,
heavily applied in the shade. Follow with another coat with
good sealing properties to make sure the wood always stays
relatively isolated from outside moisture. Finish with a
topcoat with good permeability (good breather). The topcoat
is mostly for sunlight protection.
When encapsulating old paint, there is risk of creating
hydrostatic pressure beyond what the old coating can resist,
but that can sometimes be a good risk management decision,
considering the cost of paint removal.
Update:
On a recent project, I've removed and reinstalled all
the siding back side out, running each piece through
a table saw to remove the paint from the bottom edge.
98% of it was symmetrical enough to allow reversal.
I hand sand or power sand the face to freshen it. The
total time required was no more than that for stripping
with the triple heat gun as described above. If you are
handy with a flat pry bar, you can remove all the siding
with no damage. It's important to grind down your flat
pry bar until it is very sharp and has a very slim profile
over the first couple of inches.
Reversing the siding works only if your house has
vertical corner boards, or if you are willing to
install corner boards. Otherwise the bevels at the
corners will be backwards. (Or you could do some
carpentry, patching in some new fairly short lengths
of siding extending to the corners.)
Mark the locations of each siding board on the adjacent
window frame or corner board prior to removal. Scrape
the edge of the window frame or corner board clean of
paint so that you can pry off the siding boards without
binding.
Work from the top down. The first board will be a bit
of a struggle and you might damage it, but after that
it is smooth sailing.
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