Sanding Plank Floors

From time to time, wooden plank floors need to be refinished.  Normal wear and tear, to say nothing of dogs and children, can make a floor's finish look dull.  This project is easy enough to complete as long as you can handle the sander.  They are very heavy pieces of machinery - the platform sander weighs about 125 pounds! 

The most important aspect of this project is the technique used when sanding the floor.  If you aren't careful while sanding, you can seriously damage the floor.  You have to keep the sander moving at an even speed with constant attention to what is happening.

This first step is to asses your floors and determine how much sanding is necessary.  There are two levels of floor refinishing:  The first is where the finish is damaged but the wood beneath is in good condition.  The second is where the finish and the wood are damaged.  The objective for both is the same: removing the damaged material while preserving as much of the wood flooring as possible.  Floors can only be sanded but so many times before they have to be replaced.

Dust is flying everywhere

Preparation for the Job

The first thing to do is to remove all furniture from the area you are sanding.  Do not try to sand around furniture, it will only cause problems.

The second thing to do is to seal off the area.  Sanding invariably produces lots of dust and it will travel to other rooms if allowed.  If there are doors to adjoining rooms, close  and tape around them.  If there are openings with no doors, seal them up with plastic or a drop cloth.  If there are registers for air conditioning/heating, remove them and tape over the duct.  Next use masking tape to protect baseboards from the edges of the sander.

Inspect the floors for exposed nail heads and other debris.  If there are exposed nail heads, you will need to use a nail set to drive them below the surface of the floor.  Clean any other debris from the floor as well.

Wipe down sanded surface with tack rag

Vacuum floor

Sanders and Sandpaper

There are two types of sanders that are commonly used.  The first type is the drum sander.  The second is the pad, orbital or platform sander.  Both kinds have their pros and cons.

Drum sanders are big, capable machines that are commonly used by professionals.  They must be used with care as they cut fast and you can seriously damage the floor if you don't use a steady, careful motion.  If there is significant damage to the wood, this sander will allow you to quickly remove it.  If you are simply trying to take up the finish, read on.

Pad (platform) sanders are normally rented at home improvement stores.  They are generally more forgiving than the drum sanders as they do not cut as fast as the drum sanders.  They also normally employ an orbital motion that makes them easier to use as they seem to "float" a bit.  These are recommended for Do-It-Yourselfers.  If you are just trying to remove the finish from a floor, the pad sander is a great choice.

Just as there is more than one type of sander, there is also more than one type of sandpaper.  There is sandpaper that looks like regular sandpaper and there is the sanding screen.

Normal sandpaper can be used for projects all the way from finish removal to defect removal.  They are available in many grits and can do it all.

Sanding screens are commonly used when removing the finish on the floor.  They are also used on the final sanding pass when you are trying to take out damage to the floor boards.

Pictures are courtesy of the Alto Corporation

Sanding the Floor

After you have selected the sander that you want to use, it is time to put on the sandpaper and get to work.  Always keep in mind that the objective is to remove as little wood as possible to get the job done.

Picking the Sandpaper

In general, you are going to start with a coarse-grit sandpaper and work your way up to a finer-grit sandpaper for the final sanding.  A good rule of thumb is to start with as fine a paper as will get the job done.  An easy way to determine the right grit is to test a small, inconspicuous patch with a fine or medium grit paper.  Generally 60 or 80.  If the paper is taking up the appropriate amount of material, keep using it.  If that particular grit isn't cutting enough or if the paper becomes clogged then you should move down a grade.  When moving between grits, it is a VERY good idea to vacuum the floor.

Sanding the floor with a DRUM sander

When sanding with a drum sander, only sand to within 4-6 inches of the wall.  Start in the middle of the room and sand one half at a time (see diagram).  On most drum sanders there is a lever that lowers the drum onto the surface to be sanded.  While slowly moving the sander forward, gently lower the drum against the floor.  Keep the sander moving forward, sanding WITH the grain.  As you approach the end of the floor, work the lever to lift the drum from the floor.  Pull the sander back to the center of the floor and position the sander so that the second pass will overlap the second pass by a couple of inches.  Continue to make passes until you finish up one half and then move to the other half.

Sanding the floor with a PLATFORM sander

The method for sanding the floor with a platform (pad) sander is the same as the drum sander.  The platform sander tends to "float" over the surface but continue to push the sander along with the grain of the wood.  A platform sander will also allow you to get closer to the edges.

Sanding the Edges

You can sand the edges with an edging sander or a small random orbital sander.  An edging sander will likely be faster.  Make sure that you sand down to the same level that the big sander left.

Floor sander

Sanding pattern

Edge sanding

Finishing the Floor

There are many different finishes available for the floor.  They include, but are not limited to, shellac, varnish, wax, oil and polyurethane.  For this article we will be sticking with polyurethane.  It is easy to apply and produces consistent results.

Water or Oil?

There is a fair amount of debate about what kind of polyurethane to use: water- or oil-based.  Most of it boils down to personal preference and ease-of-use.  The water-based variety smells less and dries faster.  Some people don't like the "cold" appearance of water-based polyurethane but this can be fixed by tinting the polyurethane (some of it comes pre-tinted).  The oil-based polyurethane looks "warmer" out of the can but smells more due to the solvents in the base.  If you are uncomfortable making a snap decision, purchase a little can of each and apply it to a scrap.  Regardless of the type you pick, make sure that you work with adequate ventilation.  Now is also the time to pick the gloss of the final finish.  Most people choose satin or semi-gloss.

Staining and Sealing the Floor

If you want to stain the floor, now is the time to do it.  Make sure that you use a stain that is compatible with the finish you are using.  Some water-based finishes have difficulty adhering to oil-based stains (the reverse is also true).  A lot of people like to use a natural colored stain.  Whether or not you stain the floor, it needs to be sealed.  You seal the floor by "cutting" the finish you are using and applying it to the floor.  If you are using water-based poly, cut it with water.  If you are using oil-based, cut it with a solvent.  In either case, check the instructions for the type and amount of solvent to use.  Apply the cut finish to the floor with a brush or painter's pad and allow it to dry.  If you are using water-based poly, you need to lightly buff the floor with an abrasive pad (or lightly sand the floor with a fine sand paper) to smooth the raised wood grain and remove imperfections.  If you are using oil-based polyurethane, then use fine steel wool to remove the imperfections (DO NOT use steel wool with water-based poly, the particles left behind may rust).  After the imperfections have been removed, vacuum the floor and wipe it down with a tack rag.

The next step is to apply at least two more coats of polyurethane to the floor.  Make sure you buff the floor with an abrasive pad (water-based) or steel wool (oil-based) between coats to remove the small dust bumps that appear.  Be careful how much you buff the final coat as more buffing reduces surface gloss.  If you want less gloss, buff more.

Apply finish

Continue working towards entrance

Second coat of finish