From: macrakis@osf.org (Stavros Macrakis)
Subject: Re: Paint shavers
Organization: OSF Research Institute
Date: 15 Oct 92 11:50:57

In article <1bjrbgINNklu@usenet.INS.CWRU.Edu> wpc@po.CWRU.Edu (William P. Claspy) writes:

	   I will need to repaint my 85 year old house soon, and I think that
   there are some spots on it that have 85 years worth of paint on them.  I would
   like to take the paint off down to the wood this time around and am starting
   to look over options.

I assume you mean the _exterior_ of the house.  Chances are that there
is a lot of lead paint in there if it is 85 years old.  Lead paint is
not hazardous as long as it is attached to the house, but lead paint
dust or fumes (from heat stripping) are toxic.  So whatever you do,
you should be aware of this problem.

   One would be having the whole house professionally sand-blast
   stripped.

You don't say what your house exterior is made of.  If it is wood
(clapboard or shingle), sandblasting is a very bad idea.  It destroys
the wood surface, making it rough and porous.  The wood will not last
very long after that (not to mention destroying its smoothness).

The two standard ways of stripping are either heat or abrasion.

Heat guns and the like work pretty well.  They do create lead vapors,
which means you should wear a respirator (not just a dust mask).  You
have to be careful not to burn down the house, too.  This is a serious
risk, since there are often combustible materials behind the sheathing
(e.g. sawdust, paper, etc.) or in cracks.

Abrasion (sanding, etc.) also works, but is harder to do without
destroying the wood (belt or orbital sanders tend to gouge).  They
also produce huge quantities of toxic dust, which will then get into
your lawn, your house, etc.  In Massachusetts, it is illegal to sand
lead paint, and that is probably a reasonable restriction.

	   The other option is trying to do it myself, perhaps one side at a
   time.  I've seen ads in Old House Journal for a so-called paint shaver.  It
   looks sort of like a random-orbital sander, only it has three cutting blades
   on it that "shave" the paint off the wood.  The ad claims to safely remove
   1 sq. ft. of paint in 15 seconds.  It also claims to contain the chips in
   some kind of a vacuum system.

I have seen this ad too, but I have no idea how well this gizmo works.

The more conservative thing to do is not to strip at all, but just
scrape and pressure wash (caution, pressure washing can also pit wood
if not done carefully).  The result won't be as good as stripping, but
takes much less time and money, and causes fewer problems with toxic
materials.

See my painting FAQ below for further info.

	-s

----------------

As I was preparing to repaint the clapboard and trim of my
120-year-old house, I looked into paint specifications rather
extensively.  Here are my conclusions.

I cover the following subjects:

A) painting a house that has been badly maintained (like mine) for a
   long time;

B) adjustments to the specification for houses in better condition;

C) painting foundations

D) general notes on painting

E) houses which currently have asphalt, asbestos, or other siding on
   top of the original clapboard siding;

F) maintaining a painted house.

--- (A) Re-painting a badly maintained house

Here is the complete paint specification for our house, as I defined
it based on the information I collected.  Under each step, I give the
rationale for it.

0) (not painting, but a prerequisite) Inspect roof, gutters,
   downspouts, flashing (especially over windows), etc. and clean,
   repair, or replace as necessary.  Often roof leaks appear as
   alligatored paint several feet down the side of the house (where
   some cross-piece keeps the water from continuing downwards).  Be
   sure you don't have excess humidity in your house (e.g. vent
   bathrooms and clothes dryers to the exterior) -- such humidity is a
   major cause of paint failure.  Be sure you have effective vapor
   barriers, especially if the house is insulated.  In the absence of
   a continuous poly film under the wallboard or plaster, consider
   painting the interior with a vapor-barrier paint (Pratt & Lambert
   Lyt-All Double Duty Primer is one such).  Trim any shrubs or trees
   to a few feet away from the house, so that they not only don't
   touch, but allow a free flow of air.

   Rationale: humidity from behind is a major cause of paint failure.
   It is a waste of time and money to paint before you fix all sources
   of humidity.  In particular, badly flaking paint is ugly, but not
   dangerous; a leaky roof not only vitiates new paint, it may also
   cause other damage.  So fix the roof first!

1) Scrape thoroughly.  Bag and dispose of scrapings properly (lead
   scrapings are hazardous waste).  It's a good idea to dispose of the
   dry scrapings before you power wash, so they won't be weighed down
   by the water.  Keep doors and windows closed during this step to
   avoid filling your house with lead dust (and wash off your shoes
   before entering the house).  Also, be sure to have wide, solid drop
   cloths; cloth is better than plastic, but if you do get plastic,
   get the heaviest grade.  The thin grades tear much too easily to be
   of any use.

   Rationale: The goal is to get rid of badly-adhering paint, which
   will sooner or later come up.  In fact, new paint may actually pull
   badly-adhering paint off the surface -- this is especially true of
   latex paint.  Some people recommend stripping a house if it is
   painted with lead paint, but lead paint is only a hazard if
   ingested.

2) Power wash with detergent (there are special detergents made for
   power wash machines).  For a deluxe job, scrub with a hard brush as
   well.  Bag and dispose of scrapings properly.  (If it is lead
   paint, it needs to go into a low-level hazardous waste dump.)  The
   power wash not only cleans, it also removes whatever loose paint
   you missed in step (1).  Try to avoid forcing water up between
   clapboards or other joints.

   Since most old houses will have lead paint, it is NOT advisable to
   dry-sand, because this will create lead dust, a health hazard
   (especially for children), illegal in some states (e.g.
   Massachusetts).  You could wet-sand, but it is a pain.  It might be
   worthwhile to feather rough edges where scraped areas meet paint by
   wet-sanding.

   If the paint is _very_ thick, it may be necessary to completely
   remove it before painting.  This is because subsequent layers
   (especially of latex) will have a tendency to lift it off the
   substrate.  This can be done with chemical removers or electric
   radiant heaters (not torches or forced-air heat guns, which may
   start fires in tinder-dry material in building interstices).  This
   is really an awful task.

   (steps 1 and 2 can be done in the opposite order, but that leaves
   you with a lot more wet paint scraps, which are much heavier than
   dry paint scraps)

   Rationale: paint will not adhere properly to dirty or greasy
   surfaces.

3) Rinse with clear water.

   Rationale: paint will not adhere properly to detergent, either.

4) Let dry for at least three days of warm, dry weather.  More is
   better.

   Rationale: paint will not adhere properly to wet surfaces (most
   latexes tolerate some moisture).

5) Kill any mildew (dark, dusty-looking spots) by scrubbing with
   chlorine bleach diluted with water (1:3).  Some power-wash
   detergents take care of this.  Rinse well.

   Rationale: mildew prevents adhesion, and can sometimes grow through
   new layers of paint.

6) (carpentry work) Replace any split clapboard, or cupped clapboard
   which cannot be nailed back (using hot-dipped galvanized nails).
   (This step is done after scrape and strip because you can see the
   condition of the wood better, but you can also do it with other
   preparation in step (0); for that matter, you might have to do it
   at both times....)  Replace popped nails with slightly larger
   nails.

   Rationale: see (0).

7) Caulk all vertical joints between clapboard and trim, after
   removing loose old caulk.  Polysulfide caulk is the most highly
   recommended, but hardest to use.  Silicone-reinforced acrylic latex
   caulk (the 25-year kind, e.g.  DAP) is next-best.  Paintable
   silicone is excellent caulk, but apparently doesn't paint up all
   that well.  You can use _clear_ silicone AFTER painting.  Although
   silicone has the longest life (50 years), you will certainly
   repaint (and recaulk) before any of these caulks breaks down.  Some
   painters caulk under each clapboard, but this is a bad idea, as it
   holds moisture in.  If you _do_ caulk under clapboards, be sure
   that (1) you have zero leakage into the wall (from the roof,
   gutters, etc.); (2) you have at least a moderately effective vapor
   barrier (e.g. vapor barrier paint on interiors; and (3) that you
   haven't missed any spots (where water could creep in under areas
   which _are_ caulked and cause mischief).

   Rationale: see (0).

8) (optional) For best results, use exterior spackle to smooth the
   surface.  This is only worth doing on the most visible parts of the
   house.  A deluxe job uses set finish nails and fills the nail holes
   with spackle.

   Rationale: aesthetic.

9) Now, inspect the wood.  If there are places where it is _heavily_
   weathered (2 years or more without paint) it will have turned from
   brown to grey.  Such areas--where lignin has been leached out, and
   you can dent the wood with a fingernail--need reinforcement to
   accept paint properly.  SPNEA recommends using an oil product
   called Kyanize Kyanoil 21 as a pre-primer on such areas.  This is
   the modern equivalent of boiled linseed oil.  Use enough to
   pentrate the wood, and brush off any excess -- the goal is NOT to
   create a film over the wood, but to soak into the wood itself.  Let
   this dry.  (I do not know what the equivalent is in other brands.
   Kyanize can be reached at 1-800-522-2565.  Their westernmost
   distributor is in Colorado.)  Instead of Kyanoil, some
   manufacturers recommend using two primer coats, the first one
   thinned about 25% for better penetration (perhaps Penetrol would be
   good here: see below).  Let me reemphasize that the Kyanoil
   treatment is only for _very_ badly weathered wood.

   In places where the trim is split or cracked, either replace the
   trim or fill it with an epoxy filler, which is expensive, but very
   effective.  Epoxy filler is a superior material for such patching,
   because it doesn't hurt the wood, and can be cut and sanded like
   wood.

   Clean and oil your gutters while you're at it.  Wooden gutters
   should be oiled with boiled linseed oil annually (on the inside).
   If you've bought Kyanoil 21 for the clapboard, use it for oiling
   the gutters, too: it should be better than linseed oil.

   Rationale: paint won't adhere well to weathered wood.  Also, the
   Kyanoil actually strengthens the wood.

10) Now, prime with a brush, being sure to get it into all nooks and
   crannies.  Alkyd primer and acrylic latex primer are considered
   equally good by the experts (as long as you always stick to the
   top-quality product of the good brands), but to be conservative,
   use a breathable oil-rich alkyd or oil primer, which is thought
   imperative by all contractors I've talked to.  Primer should be
   close to the finish coat color if possible; some manufacturers
   (e.g. Ben. Moore) have deep-base primer or grey or red primer, most
   manufacturers have only white.  Since you shouldn't overload primer
   with pigment, you can probably only get pastel colors from a white
   base.  You need to prime where wood is exposed or paint is badly
   chalked, not over intact paint (remember, you have already taken
   off any loose paint).  But if you've exposed more than 30% bare
   wood, you might as well prime everything.  Many painters add
   Penetrol (a brand name) to the primer; Penetrol increases
   penetration of primer by thinning it a bit, while not destroying
   its properties (as straight thinning would).  I don't know why
   manufacturers don't use such additives themselves.

   Rationale: primer is designed to bind well both to the substrate
   beneath it and the paint over it.

11) Two coats of paint, not too long after priming (a month maximum).
   Benjamin Moore is a universally respected brand (by painters,
   architects, Consumers' Reports).  If you use other brands, use 100%
   acrylic latex.  Be sure it is really 100% acrylic and not vinyl
   acrylic.  Pratt and Lambert and California also have excellent
   reputations.  Stay away from house-brand paint.  Stay away from the
   "professional" lines from the large manufacturers: this is usually
   a code-word for lower quality and price.  Some painters tint the
   primer and use one coat of paint, but two coats should last
   considerably longer, unless most of the surface has an intact
   existing paint surface.  Other painters use two coats of tinted
   primer, and one finish coat, which doesn't make sense to me, since
   primer and paint have quite different functions.  If you spray, be
   sure your coats are thin enough that they don't drip and sag; you
   may well need three sprayed coats instead of two brushed coats to
   get full coverage.

   As for the vexing latex vs. alkyd debate, it turns out that almost
   all the experts nowadays, from the paint companies, to our local
   historical commission, to the Society for the Preservation of New
   England Antiquities (SPNEA) conservation department, agree that
   100% acrylic latex is a better product than alkyd or oil paints,
   especially for deeper colors.  It lasts as long, but keeps its
   color and sheen better.  The only advantage of alkyd is that window
   sash won't stick (this is called `blocking', a typical problem with
   latex paint; the best brands don't have too much of a problem with
   this; this might be a reason to use alkyd for trim and sash, but
   latex for siding).  Alkyd does brush out and level somewhat better,
   leaving fewer brushmarks, but this is not really an issue on
   exteriors (even on interiors, good-quality latexes can be brushed
   out to an excellent surface).  Ben. Moore makes an alkyd-modified
   vinyl-acrylic which is probably as good as 100% acrylic.  However,
   local contractors are split: some recommend alkyd, others recommend
   latex.  As for primer, the experts are split about alkyd vs. latex,
   and all contractors recommend alkyd primer.

   Latex is quite breathable; most alkyds are water-vapor-resistant.
   You might think that impermeability is desirable, but in fact
   breathability is more important to the longevity of the underlying
   clapboard and framing.

   Rationale: paint protects the wood against moisture, and of course
   gives the color you want.

12) For highly exposed trim, such as sash and sill, you might try a
   polyurethane- or epoxy- reinforced latex such as California AllFlor
   (a floor paint), although high-quality alkyd gloss paints
   ("enamels") such as Pratt and Lambert Effecto also have excellent
   reputations.  Sill often is heavily weathered, so it's probably not
   a bad idea to skim-coat it with epoxy filler.

--- (B) Houses in better condition

For houses in better condition, many of the steps go faster, but the
procedure is basically the same; even if you're just changing the
color on intact paint, it can't hurt to inspect thoroughly and treat
incipient problems.  Step 0 is essential in any case (inspection and
repair of potential leak sites).  Step 1, scraping, need only be done
where you see flaking or peeling paint.  Step 2, washing, is always a
good idea, but you could wash by hand instead of by power washer
(still, you do want to get rid of accumulations of dirt, soot, etc.,
which inhibit paint adhesion).  Step 3, rinsing, is essential.  Step
4, drying, can go faster if you haven't exposed bare wood during
scraping.  Steps 5 and 6 (mildew removal and clapboard repair) will go
fast -- but do make sure to inspect your clapboard and nail it back as
necessary.  Step 7 (caulking) is important; do check all the caulk,
pull out deteriorating caulk if any, and replace with fresh caulk.
Step 8 probably won't be necessary.  Step 9 will surely not be
necessary (except for wood gutter oiling).  Step 10 (priming) is only
necessary where you've gotten down to bare wood.  Steps 11 and 12
(paint) are of course necessary.

--- (C) General notes on painting

Never paint wet wood (except with certain special products formulated
specifically for this).  Never paint when it threatens to rain.  Let
wood dry at least a day after rainfall before continuing to paint.

Do not paint in the sun; this dries the paint too fast.  In the
morning, paint the west or north side, in midday, the east, etc.

Box your paint, i.e. if you have multiple containers of paint, mix
them together so that the color is uniform.  As a general rule, it is
best to do a "surface" in a single session.  If you have to break, do
it where there is some natural boundary, such as vertical trim or
between clapboards.  Do not paint the left side of a well, then a few
weeks later the right side -- you will see a line down the middle.

High-gloss paint is somewhat stronger than semi-gloss or flat, as a
general rule.  Experienced painters claim that high-gloss does NOT
have the effect of showing up defects on exteriors as it does on
interiors.  I do not understand this claim, and am not sure I believe
it.

Use good-quality materials and tools.  I've mentioned the importance
of good-quality paint.  Use good brushes, too, and the right kind for
each paint.

--- (D) Painting foundations:

My house has a fieldstone foundation below grade, and a brick
foundation above grade.  The brick has been painted.  There is a good
chance, in fact, that it was always painted, since paint protects
brick against moisture, and thus allows the use of lower-grade brick
without spalling.

Next year (probably), I'll be working on the foundation.  First step
is repointing the mortar where it's deteriorated.  This involves
digging out mortar with a special tool, and replacing it.  The main
tricks here seem to be (1) not hurting the brick (2) using the right
mortar and (3) finishing the mortar correctly.  To avoid hurting the
brick, do _not_ use the trick of running a circular saw along the
mortar tracks.  There is a good chance that you'll cut into bricks
(note that the exterior skin of bricks is much tougher than the
inside).  Also, NEVER sandblast brick, especially exterior brick.  The
right mortar should not be too strong, or it will break the brick over
time.  Modern mixes are too strong, and need more sand.  I don't have
the formulas with me.  Finally, the finished pointing of the mortar
should be such that water runs out of the joint, and ice doesn't crack
it.  There are many kinds of point, but the simplest sound ones are
either completely flush (probably best if you intend to paint anyway)
or beveled outwards, that is, set in at the top of the joint, and
flush at the bottom.

To take off peeling paint, use a wire brush.  Then get special masonry
paint.  Color will make a difference in the final effect.  Don't make
the mistake of using too-bright a red, which will look garish and
unnatural.  A very earthy red is probably a good choice, as are shades
of dark brown or grey.  If you want to make it look like brick, you
could take a sample of unpainted brick to a paint store with a
color-matching computer (but you presumably won't be painting the
joints a different color...).  Another color to match might be the
color of the bark of any shrubs planted in front of the foundation.

--- (E) Dealing with asphalt, asbestos, etc. siding

Many old houses were covered with asphalt or asbestos shingle in the
40's and 50's.  (Some houses newly built at that time used this as
their primary siding.)  This was done for the same reason that more
recently many old houses are covered with vinyl or aluminum imitation
clapboards, namely the promise of lower maintenance.  Although it is
true that all these products last longer than a coat of paint, they
have other problems, the most serious of which is that they tend to
hold moisture in, and therefore accelerate the degradation of the
underlying wood (some of the newer imitation clapboards are better
vented than older varieties).  The other serious problem is that they
look awful, and usually destroy any character the house originally
had.

It is perfectly feasible to remove these products and restore the
original clapboard.  This is done in three steps: 1) removal; 2)
repair; 3) repainting.  Removal is easy--you just yank it off with
(e.g.) a flat crowbar or roofer's tool ("Wonderbar").  It takes time,
but is easy.  Don't be shocked if the paint is in bad shape
underneath: that's why they put up the siding!

Repair is the hard part.  You need to identify bad clapboard and trim
and replace it.  This should be done by a competent carpenter (which
you may well become yourself, of course).  The sad thing is that
original trim was often torn or sawn off to make installing the crummy
siding easier (this is especially true of vinyl and aluminum, which
are easier to install if all the vertical edges are straight, and the
horizontal runs are long).  If possible, you should try to restore
this trim.  Now you should let the house `rest' for several months of
warm, dry weather.  This is important, because the siding has held
moisture in over time.  You want to let the wood breathe and return to
a more normal level of humidity.  Thus the usual recommendation is to
remove the old siding in the spring, and re-paint in the fall.

The very worst case is if there has been water leaking into the wall
over a long period of time (bad gutters, bad roof) and the framing is
damaged.  If this is the case, you will probably see water stains on
the inside of the house.  Of course, if the inside walls are covered
with paneling or something, you may not be able to tell.  But you
should be suspicious, because maybe they were covered with panelling
precisely to hide water damage.

Now follow the specification in section (A), being particularly sure
step (0) has been done thoroughly.  You will probably want to spackle
all the nail holes left by the installation of the siding.

Remember, the usual cause of paint failure is not the paint, but the
underlying surface.  And the usual problem with the underlying surface
is moisture.

--- (F) Paint maintenance

Now that you've painted the house, you shouldn't ignore maintenance
until the next complete repainting.  Don't forget to oil wood gutters
before the winter.  Be on the lookout for leaks, and repair them.  And
whenever you get flaking or peeling, scrape, prime, and repaint.  On
highly exposed trim, such as sills, you may have to do this annually,
but fortunately most such trim is easy to reach without a ladder.  If
there are patterns of flaking or peeling, the problem is not the
paint, but the substrate.  You probably have a source of moisture,
either leaking water, or vapor (from, e.g., a bathroom).

--- (G) Contract

This is the contractual language I used with my painter.

0) Painter shall inspect existing conditions.  If they are not
   suitable, he shall not begin work.

1) Scrape thoroughly, removing all blistered, peeling, and scaling
   paint to a sound substrate.  Remove all old caulk and putty.  Use
   drop cloths to prevent scrapings from reaching soil.  Dispose of
   scrapings properly.  Keep doors and windows closed.  Sand all new
   clapboard, gutters, and trim with coarse sandpaper.  Do not sand
   existing painted surfaces.

   Scrape window sills thoroughly, all the way back to stool.  When
   scraping with window open, either block off interior or scrape wet.

2) Power wash with detergent, with nozzle no more than 6' from surface
   (don't wash upper floors from the ground).  Do not erode wood
   surface.  Power wash brick foundation, but do not scrape or paint.
   Power wash interiors of old gutters.

3) Kill any mildew with mildewcide.

4) Rinse with clear water.

5) Let dry for at least three days of warm, dry weather.

6) Inspect woodwork.  Nail back any cupped or loose wood.  DO NOT
   remove any woodwork, even rotten, without approval from owner.

7) Where wood is heavily weathered (grey), pre-prime with Kyanize
   Kyanoil 21.  Use only enough to penetrate the wood, and brush off
   any excess.  Pre-primer _must not_ form a film.  (If it does, sand
   it off.)

GET SIGNOFF FROM OWNER BEFORE CONTINUING.

8) Brush-prime with Benjamin Moore Moorwhite house primer (grey).
   Prime complete surface of house, including areas which are new
   wood, old wood, or old paint.  Let dry 48 hours before finish coat.

9) Caulk all joints between clapboard and trim, and between trim
   elements.  Use 25-year silicone-reinforced acrylic latex caulk (NOT
   grey).  DO NOT caulk under clapboards.

10) Use exterior spackle to smooth the surface and nail holes in the
   following areas: woodwork around doors; clapboard between front
   door and window; clapboard next to rear door (both sides).  Fill
   window sills with epoxy wood paste, and sand smooth when dry.  Fill
   nail and screw holes in window frames.  Fill other cracked trim as
   necessary with epoxy wood paste.  

11) Two coats of asphaltic roof paint on the interiors of all wooden
   gutters.  Gutters must be dry before starting.

GET SIGNOFF FROM OWNER BEFORE CONTINUING.

12) Spot-prime over new spackle, caulk, and wood paste.  Provide
   sample area of finish colors for approval.  Two coats of Benjamin
   Moore MoorGard Latex House Paint.  One color for all clapboard and
   the inside of "framed" areas (including insets and the spaces
   between brackets); another color for trim.  Sash to be black.
   Downspouts to be painted on the ground.  Each coat must dry
   overnight before recoating.  First coat shall have slightly
   different color from second coat (to be specified).

   Sides of window frames may be painted body color.  Sides of corner
   boards and window sills shall be painted trim color.

   Do not paint pressure-treated wood (fire escape, rear stair posts).
   Paint treads of rear staircase with two coats of California AllFlor
   floor paint.

GET SIGNOFF FROM OWNER AFTER FIRST COATS.

13) Remove all equipment and debris.  Clean windows thoroughly,
   including paint spatters, glazing compound, dirt, etc.  Remove
   paint that has been misplaced.

--- General notes

All materials shall be applied free from runs, sags, wrinkles,
streaks, shiners, and brush marks.  All existing work shall be
protected (in particular, the brick driveway and trees' bark).  No
materials shall be thinned.  Manufacturer's recommendations shall be
followed.  All materials must be delivered to the job site in
manufacturer's original containers.

Do not paint when surface is wet.  Do not paint when it is raining or
drizzling, or when rain is forecast.  Allow surface to dry before
resuming painting.  Do not paint when air or surface temperature is
below 50 degrees.  Do not paint in direct sunlight.

Painter may store equipment and materials in the rear room of the
basement.

The contract amount shall cover all the labor and materials to execute
the work as specified above.

----------------
Copyright 1992 by Stavros Macrakis <macrakis@osf.org>
Usenet distribution authorized when I post it.
Redistribution to Usenet or other networks forbidden.
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU