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Finish
Finishing normally begins about 7 to 14 days after installation.
This gives enough time for the installed floor to react to
the environment. Slight cracks and any raised edges that are
going to develop will have done so by then, and you can fill
and sand them for the best possible appearance. Longer periods
of exposure may subject the bare wood to job-site abuse and
moisture.
For starters, heart pine is naturally hard and dense, and
the new polyurethane finishes offers increased protection
wherever you install your wood floor. But there is a lot of
technical know-how needed for polyurethane or any other hardwood
floor finish. The finish industry is evolving rapidly to meet
strict new regulations and the increase in demand for wood
floors. If you have further questions, telephone numbers,
books, and articles are listed in the back of this guide,
all of which provide more detailed information.
Sanding
Just like site conditions are to installation, good
sanding techniques are critical in finishing. If the sander
leaves swirls or grooves these will become more noticeable
once the finish is applied. Sanding creates a lot of dust.
Wear a respirator, ear plugs, and shoes that do not hold dust
in the soles or leave scuff marks.
The job takes at least a couple of different machines. A
drum sander is used to level the floor, and a disc sander
to "screen" (or lightly sand) between each coat.
You might want an edger, a small floor sander that lets you
get close to walls, or you can sand these hard to reach areas
by hand. A professional floor finisher will have all of these
machines, or you may be able to rent them from your local
hardware store.
Seal off doorways, vents, and built-ins by taping plastic
over them. Just before sanding remember to check for loose
boards or squeaks and repair them with screws from underneath
the subfloor or nail through the floor into the joists. Set
any nails at least 1/16" deep and fill the holes with
wood putty.
Operating a drum sander takes some practice. The machine
is heavy but has to be moved along with a relatively "light"
touch. If held in place for even a few seconds it will leave
a dent in the floor. Sand in rows in the direction that the
floor runs from left to right across the room. The drum sander
takes a slightly deeper cut on the left side to allow you
to feather the edge on the right side as you move over to
the next row.
Turn on the machine and move forward as you lower the drum
to the floor so it does not dent the starting spot. You do
not have to bear down at all. About one foot away from the
wall, lift up. Put the machine down again as you begin to
move it backward over the same row. When you reach the spot
where you started, lift up and move over 2–4" for
each succeeding row.
The first "cut" (sanding) is to level the floor.
Use a drum sander with coarse-grit (20-36) paper. Fill any
nail or peg holes and sand again using medium-grit (50 to
80). Check for any more blemishes and fill them before the
final sanding with fine-grit (100-120) paper. Scrap the corners
and hard to reach places, then hand sand them to blend with
the rest of the floor.
You will not be able to get close to the wall behind you,
so plan to start a few feet away from the back wall and sand
to within a foot or so of the wall in front of you. Then turn
around and sand the few feet remaining to the other wall,
again starting from right to left. Take care to feather over
the line where you reversed directions. Use an edger to get
the area that the drum sander could not reach at walls and
under counters. You may need to use a hand scraper and hand-sanding
block for some areas.
After the first sanding, sweep well and change to medium
grit (60-80) paper and sand again. You may choose to use a
filler between sandings, usually used when refinishing old
floors. If you defects that you want to cover there are some
good latex fillers available. Use fine grit (100-120) sand
paper for the final sanding.
As soon as you have completely sanded the floor to a level
surface, vacuum thoroughly and then wipe it with tack rags.
Be sure to get all the dust from not only the floor and out
of the corners, but also off windowsills and mouldings. Remember
to clean out any vents as well. This will prevent sawdust
from falling into the finish and becoming a permanent part
of your floor.
"Wash" the floor with a rag or mop that has been
dampened with mineral spirits. This is an important step for
heart pine. It removes any oils or resins from the surface
of the wood that might prevent the finish from adhering properly.
The mineral spirits will dry within a few hours, unless applied
too generously. 
Supplies to Have On Hand for Finishing
Penetrating oil-based sealers can be applied by hand with
a rag, a brush, or a lamb's wool applicator. Surface finishes
are usually applied by applicator, or by brush in small areas.
Between coats of surface finishes you will need an abrasive
nylon screen, fiber buffing pad, or steel wool to lightly
sand the previous coat and help the next one adhere. Do not
use steel wool if you are using a water-based finish. The
steel fibers will rust and discolor the finish. If you use
brushes, clean them only with water or mineral spirits. The
distillates in some brush cleaners can slow the drying process.
Use a vacuum cleaner after each sanding or screening. For
large areas, clean vacuum bags frequently to avoid returning
any dust to the floor. You might even try wearing paper surgical
booties over your shoes to avoid tracking dust. Rags with
mineral spirits or water are also useful to clean up sweat,
dust, dirt, or oil if any drips on the floor while you are
applying the finish.
When do I Apply the Finish?
People generally prefer the natural look of finishes applied
in the home over a factory baked-on finish, and most fine
wood floors are sanded and finished on-site. For best results,
finish the floor after the wall coverings are in place and
painting is complete, except for a final touch-up coat of
paint on your base moulding.
Which Finish do I Use?
- Water-based (or water-borne) urethane is a good choice
for the environmentalist and is the easiest to apply. Water-based
is only slightly less hard than moisture-cure, and is less
likely to leave drying lines during application.
- Moisture-cure urethane is the hardest and most protective
finish, but it requires the most skill to apply. Generally,
it is not suggested for use by the non-professional.
- Traditional oil-modified polyurethane finishes are used
today, though they will be regulated out of use in the future.
Wax is generally applied on top of this finish.
- Use a penetrating oil sealer for a natural but soft finish.
Buff the floor with steel wool between each coat, and then
wax over the sealer. This finish may be the correct choice
for some projects, but it requires extra maintenance and
offers less protection.
- There are completely natural finish products available
for people with chemical sensitivities or for those who
want to use totally non-toxic products. Organizations specializing
in the most healthful and ecological building materials
are noted at the back of this booklet.
The First Coat
We recommend that the first coat be an oil-based
sealer to help bring out the red tones for which heart pine
is so famous.
The oil-based sealer is a penetrating finish and soaks into
the wood, unlike surface finishes such as water-based or moisture-cured
polyurethane. The real beauty of the wood can be brought out
right away by one coat of the sealer.
Heart pine is renowned for its unique color and beauty. Many
heart pine lovers model the late Frank Lloyd Wright who said,
"I like wood left alone, for the sake of wood."
Stains may actually muddle the wood's strong grain patterns.
However, if your project has special needs you can get the
sealers in wood stain colors.
The finish is applied in parallel strips across the room
with the direction of the flooring. Always maintain a wet
edge and use a single gliding stoke along the length of your
strip, "feathering" into the previous wet area.
Work toward the light so that you can see your work, but do
not worry about retouching missed areas if the finish has
already begun to skim over. The next coat will fill in these
areas.
Make sure your floor is completely dry before you apply the
second coat since the sealer soaks into the heart pine. We
suggest thinning it with 1/4 to 1/3 Mineral Spirits to give
it maximum penetration. It has been our experience that this
coat may take longer to dry than the finish manufacturer's
directions. We often find that it takes at least 24 hours
for this sealer coat to dry. One customer says, "We think
the labels should read, 'dries in four hours unless you live
in Florida where it takes two days.'"
If you are in a hurry use a moisture meter to see if the
floor has returned to its pre-finish moisture content. Or,
check for a thumbprint by pressing your thumb firmly against
the floor (see Don Bolinger's book, Hardwood Floors, available
through Fine Homebuilding magazine).
After the First Coat
You have lots of choices for the second coat of finish.
Water-based is increasingly popular. It offers quick-drying
time, takes little maintenance, and is simple to recoat when
wear eventually begins to show. Moisture-cured and oil-modified
finishes are still used a lot today, even in this low VOC
(volatile organic compound) age. For a simple but soft finish,
wax on top of the sealer.
We generally recommend water-based urethanes because they
are safe, durable, fast drying, and offer good protection
for your floor. Water-based products are being continually
improved to decrease their VOC contents and increase their
durability. A water-based urethane used on heart pine over
an oil-based sealer applied in thin coats is a very pretty
finish. It looks similar to an "oiled" or hand-rubbed
finish. Some woodworkers may hate to admit this, but many
know it is -true and use this to their advantage. After the
first and between each succeeding coat of finish, use a floor
buffer fitted with a used 100-120 grit "screen"
(rub two together if you do not have a used one) or hand sand
small areas. You will have to hand sand corners and edges.
Lightly sand the "top" off the finish.
You do not want to sand into the finish, and one or two passes
over the floor is usually enough. All that is necessary is
to take the shine off the finish to help the next coat adhere
to the one before it. If the finish does not "powder"
while you are sanding, it is probably not dry. Vacuum the
floor and any sills and baseboards. Tack the floor again,
then let it dry completely, and start your next coat.
Additional tips for finishing your hardwood floors
- For the best possible adherence from coat to coat, use
high-gloss for all coats except the last one. Many types
of polyurethane are so hard that they do not adhere well
to themselves. The high-gloss adheres best, so even if you
want a satin finish use high-gloss. Use satin as your final
coat and you will get the low-gloss (or semi-gloss) finish
that you want with maximum adherence.
- You can apply as many coats of polyurethane as you want.
Usually two or three coats is enough, but we have had people
ask if they can use several coats. Just remember to let
each new coat dry a little longer than the previous one.
- It is important not to wax a wood floor that has a surface
finish (water-based or moisture-cured). If wax is used on
these finishes, it prevents the ability to simply retouch
the floor (screen or lightly sand to remove the shine and
recoat it). If you wax on top of a surface finish you must
sand the floor completely back to bare wood before recoating.
Special Floor Finishing Needs
If you are restoring a historic building, you may choose varnish
to match an old finish. We discuss varnishes in the section
on "Refinish." We can also provide you with reprints
of Old House Journal articles about historic finishes.
You might want to know about finishes for porch or outdoor
floors... or how to sand a parquet floor... or even how to
"pickle" your floor. There are many topics, and
we can only mention the basics in this short booklet. Do not
hesitate to call with questions. We will try to provide other
references.
There are many companies that make excellent finish products,
a few are listed in the back of this guide. No matter which
finish manufacturer you choose, follow their directions carefully.
These products are improving rapidly as are the ecological
standards they are required to meet.
Let us know if we can provide reprints of flooring manufacturer's
association guides on finishing to further assist you.
Other Finishes
We do not mention white floors nor do we discuss finishes
that contain formaldehyde in this guide. These finishes are
frequently used and many professionals have a great deal of
experience with them. If you need to know about them, we can
recommend sources.
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