Refinishing Wood Floors: Screening, Sanding, and Finishes

Most hardwood floors are made of oak, but despite the durable nature of this wood, it only looks as good as the surface finish.

How Do You Make Old Hardwood Floors Look New?

Water stains, scratches, dullness and whole areas worn bare by household traffic are signs that it’s time to refinish the floor. In the past that meant sanding down to bare wood—a dust-producing, time-consuming process that’s risky if you don’t have experience or expensive if you hire a pro. Some floors require this level of work, but many others can be revitalized by screening.

What Is Screening Hardwood Floors?

Screening is a process that takes off the top layer of polyurethane but doesn’t remove any wood. This relatively inexpensive technique gives you the option of doing the work yourself with little risk and saves you the cleanup and hassle associated with floor sanding.

How Do You Recoat and Screen a Wood Floor?

Screens are clog-resistant sanding disks. Screening is done with a 16-inch floor polisher, which works like a giant oscillating sander. It won’t take off on you like a drum sander and doesn’t require a lot of strength. The weight of the floor polisher and a synthetic-wool pad hold the screen in place.

Screening removes the floor finish without cutting into the wood itself, so you should:

• Only screen a polyurethane finish, a non-penetrating plastic coating that sits on top of the floor.
• Only screen when the finish is worn, scratched or dull but the wood beneath is not stained or damaged.

How much Does Screening Cost?

If you want to do it yourself, renting one costs around $25 per day. The 60- to 120-grit disks used with this unit cost $6 to $10 each. If you can’t find the time to do the work yourself or don’t want to be around that much dust, hire a professional floor refinisher. This will cost 90 cents to $1.50 per square foot, depending on how much screening needs to be done and whether the floor needs one or two coats of finish.

Before You Start Screening

• Remove everything from the room you can—especially items that collect dust, such as furniture, carpets and paintings.
• Seal off all doorways with plastic sheeting and masking tape, seal off duct registers with plastic and tape around all cabinet doors.
• Weather permitting, open the windows and place a fan in one to blow dust out. With or without a fan in place, wear a respirator.
• Temporarily remove the quarter-round or base-shoe molding along the baseboard and countersink any flooring nails that stick up.

4 Tips for Screening Hardwood Floors

1. Before attaching the screen, take the edge off it with 100-grit sandpaper loaded onto a palm sander. This knocks down any high spots on the disk that can dig too deeply into the finish when the polisher first starts up.
2. You’ll be screening most of the floor with the floor polisher and screens. To be thorough, use four screening grits, from rough to smooth (60-, 80-, 100- and 120-grit). For corners and edges, use a palm sander or sanding pad fitted with sandpaper.
3. Once you have completely finished, sweep down walls and vacuum dust from all surfaces.
4. Then pick up remaining floor dust with a tack cloth, which is a 4-sq.-ft. treated cheesecloth ($2). Bag the sawdust and leave it outside, away from anything flammable (sawdust can spontaneously combust).

Do You Have to Sand Floors Before Polyurethane?

Sand floors down to bare wood if there’s a wax finish on top of the polyurethane, if the finish has worn through or if the floor has been stained or damaged.

Before Your Start Sanding Floors

Use the same preparations for screening, though you might want to create a double airlock (plastic on both sides of a door) to keep the dust confined — it really flies with a drum sander.

You may also want to think twice about doing this work yourself, particularly if it’s a large open area where any unevenness in the floor will be evident in the finish.

A drum sander can dig into the floor very quickly and leave unsightly gouges when operated by an inexperienced person. A professional will charge $1.50 to $3 per square foot, including finish application and cleanup. If you are going to do the work yourself, watch a how-to video (try a rental store or the local library) before you start.

How Much Does it Cost to Sand Floors Yourself?

You can rent a drum sander, which does the main floor, and edger for around $55 a day. Neither device reaches into corners fully, so you’ll have to scrape these areas with a razor-sharp floor scraper.

The disks for the drum sander typically cost $3 each; for the edger the disks run $2 each.

5 Tips for Sanding Hardwood Floors

To ensure a more even floor, keep the following tips in mind:

1. Using the drum sander and working with the grain of the wood, make at least two passes in each direction with 60-, 80- and 100-grit sanding disks.
2. Keep the sander moving; stalling it in one place will result in a noticeable swale.
3. Move at a steady, even pace to take off a uniform amount.
4. Don’t muscle the sander.
5. Don’t drop the sanding drum down on the floor too quickly after picking it up to make a turn, or you’ll gouge the floor. Again, bag the sawdust and leave it outside, away from anything flammable.

What is the Best Finish for Hardwood Floors?

Polyurethane is the most popular finish for floors. It’s tough enough to handle constant traffic and is resistant to almost everything. There are two types of polyurethane finish: oil-based (solvent borne) and water-based (waterborne). Each type has its strengths, and neither is a poor choice.

Oil-based vs. Water-based

Oil-based polyurethane will turn a light amber color with age whereas water-based stays clear. If you want to preserve the creamy-white look of maple, for instance, use waterborne polyurethane. (For a red-oak floor or a stained floor, use either type of finish.)

Another advantage of waterborne polyurethane is how quickly it dries — you can apply two coats in three hours and walk on the floor in your socks after seven hours. However, because it dries quickly, you must work fast to maintain a “wet edge” during application or you’ll end up with visible lap marks where wet polyurethane was applied over dried or partially dried finish. And you can’t go back and work waterborne polyurethane, even when it’s wet, or you’ll leave marks in the finish.

Oil-based polyurethane dries slowly, which means you can’t walk on the finished area for 24 hours or more after coating. It also emits noxious fumes. But it can be worked when wet, which means you can go back and correct mistakes — a crucial advantage for the beginner.

As for durability, Lance Hemsarth, technical director for Minwax, a leading maker of polyurethane, maintains that oil-based polyurethane is still the standard for performance, especially for high-traffic areas.

Water-based polyurethane runs about $40 per gallon, enough to cover 600 square feet of floor space. A gallon of oil-based poly costs around $25, enough for 400 square feet. In either case, follow the manufacturer’s application instructions carefully.

6 Tips for Wood Floor Finishes

1. Before applying any finish, vacuum twice and use a tack rag on the entire floor.
2. For edges and corners, use a painting pad to apply a water-based finish; on open floor, use a synthetic-wool applicator.
3. With an oil-based finish, use a china-bristle brush for edges and corners and a lamb’s-wool applicator for open floor.
4. As you apply the finish, move the applicator with the grain of the wood from wall to wall, angling it slightly.
5. For a truly smooth finish, sand lightly between coats with a pole sander using 100-grit sandpaper. Then use the vacuum and tack rag again with care before adding another coat of finish.
6. Don’t sand the final coat — just appreciate how it reflects the light and know that you have a finish that will last for years.

What are the Types of Floor Finishes?

There are three general types of floor finish: polyurethane, penetrating oils and sealers, and waxes. It’s important to know which you have because not all finishes are compatible. If the old and new finish don’t mix, you’ll have to sand down to bare wood before refinishing.

1. Polyurethane

Today, most floors are finished with polyurethane, a durable, moisture-resistant oil-based or waterborne plastic coating. You’ll know your floor has a polyurethane finish if it looks as though it’s covered with a plastic film and you can’t scrape up any gummy residue.

If you’re not sure, get advice — other surface finishes like shellac, lacquer and varnish resemble polyurethane but require special treatment. For more information on these finishes, go to nofma.org.

2. Penetrating oils and sealers

These primarily solvent-borne finishes, including old-fashioned sealants like linseed oil, soak deeply into the wood pores. Many of these floors are then waxed.

These finishes are typically not compatible with a topcoat of polyurethane and have to be treated with the original finish or stripped completely.

3. Waxes

Some floors have wax as the only finish, or the wax is applied over polyurethane or a penetrating sealer. If you can scrape up a gummy, waxy residue, especially in corners, your floor has a wax finish.

A waxed floor also gets a hazy look when wet. Before you put down any finish on a wax-only floor, the wax has to be removed.

Ways to Make Spot Repairs and Remove Stains

For a Water Stain on a Waxed Floor

Rub the wax lightly with No. 1 (medium grade) steel wool, being careful not to rub through the wax. Then reapply the wax with a solvent-based wax. If the stain remains, remove all the wax on and around the stain with floor-wax remover and clean with No. 1 steel wool and mineral spirits. After the floor dries, apply more wax and buff to a high sheen.

For a Shallow Burn Mark on a Polyurethane Floor

Scrape it up with an extremely sharp chisel or scraper. Then apply a dollop of oil-based polyurethane. A burn mark that has gone through the finish must wait for a full-floor drum sanding, and it must be sanded out by hand.

For a Burn on a Waxed floor

Try No. 1 steel wool moistened with soap and water. Let the floor dry thoroughly and rewax. Any burn that has gone through to the wood needs to be sanded out by hand when the floor gets drum sanded.

For Heel Marks and Deep Scuffs on a Polyurethane floor

See if the scratch has penetrated the finish by wetting it with your finger. If the wood darkens along the scratch, it has penetrated completely and you must apply more polyurethane. You can sand and spot-apply polyurethane, though you risk an obvious patch. The alternative is to screen and recoat the entire floor. To get rid of heel marks and scuffs on a waxed floor, polish the mark with 000 (extra fine) steel wool and hardwood-floor cleaner. Wipe the floor dry and rewax.

Water Stains on a Polyurethane floor

Indicate that water has gotten beneath the finish and into the wood, a difficult problem to fix. First, try a hardwood-floor cleaner (about $4) and buff with a clean cotton rag. If the stain remains, you’ll have to sand off the polyurethane and perhaps sand the wood itself. You can spot-sand down to bare wood with 100-grit sandpaper, and spot-recoat with polyurethane matched to the gloss of the existing finish (use an oil-based polyurethane to patch an existing oil-based finish, and a water-based poly to patch an existing water-based finish). However, expect the patch to be a different color and sheen than the surrounding area. Consider screening the entire floor or a discrete section.

Water Stains on a Waxed Floor

Often are just on the wax surface. Start by rubbing the wax lightly with No. 1 steel wool, being careful not to rub through the wax. Then reapply the wax with a solvent-based wax. If the stain remains, remove all the wax on and around the stain with floor-wax remover and clean the spot with No. 1 steel wool and mineral spirits. Then let the floor dry and apply more wax. Buff to a high sheen.

Pet Stains on Hardwood Floor

Pet strains are tough to remove from a hardwood floor, especially if the stain is old. Try a hardwood-floor cleaner or mineral spirits, but you’ll probably have to sand the floor. Some stains are so deep you may have to replace the flooring.

For an Oil or Grease Stain on a Waxed Floor

Try trisodium phosphate (TSP). Buff the wax with a clean cotton rag. On a polyurethane floor, wipe the stain with mineral spirits. Then dry with a clean cotton rag. Wax buildup can look cloudy, so remove it with wax remover or mineral spirits (the fumes are flammable, so extinguish all open flames such as a pilot light). Use 00 (very fine) steel wool and cotton rags to pick up the old wax. Seal the used cloths in a metal can and dispose.

Chewing gum, Crayon or Candle wax

Scrape up chewing gum, crayon or candle wax after you freeze the material by placing ice in a double plastic bag on top of it.

Where to Find It

Armstrong World Industries
Box 3001
Lancaster
PA 17604
Armstrong
800-233-3823

Armstrong-Bruce-Hartco-Robbins Floors
16803 Dallas Pkwy
Dallas, TX 75248
Armstrong-Bruce Floors
800-722-4647

US Plank Flooring
9597 State Rte 125
W. Portsmouth, OH 45663
888-472-3261

Leslie Bros. Lumber Co.
Box 609
Cowen, WV 26206
304-226-3844

Memphis Hardwood Flooring Co.
1551 N. Thomas St.
Memphis, TN 38107
901-526-7306

Missouri Hardwood Flooring
15455 Conway Road, Ste 320
Chesterfield, MO 63017
636-519-0400

Minwax
101 Prospect Ave
Cleveland OH 44115
Minwax
800-523-9299

National Oak Flooring Manufacturers Assn
Box 3009
Memphis, TN 38173-0009
NOFMA
901-526-5016

National Wood Flooring Assn
1688 Westwoods Business Park
Ellisville, MO 63021-4522

Stuart Flooring Corp
655 Dobyns Road
Stuart, VA 24171
Stuart Flooring
276-694-4547

Zickgraf Hardwood Flooring
Box 1149
Franklin, NC 28744
Zickgraf Flooring
800-243-1277