To refinish a hardwood floor, the first thing you need to do is sand off the old finish. You need a walk-behind floor sander, which you can rent. You also want to rent a handheld power edge sander for sanding tight against walls and in corners and doorways. Both units have a vacuum and dust bag system to minimize the amount of sanding dust left behind.

Sanding a Hardwood Floor

A walk-behind sander has a large rotating drum that evenly removes the finish — if you use the correct series of sandpaper grades and operate the sander properly. Rental stores have the three grades of sandpaper you need for successful floor refinishing: coarse, medium, and fine. For safety, wear a dust mask and eye and ear protection.

Once you have finished sanding, you fill any nicks or gouges in the floor. Use wood putty and a broad knife to fill any spots. Let the wood putty dry according to package directions and then lightly sand the areas smooth by hand with medium or fine sandpaper.

After you’ve completed all the sanding, you must remove all the dust from the floor, molding, and walls. Wipe down the walls and moldings once to get the dust onto the floor, and then use a damp rag on the moldings to remove any residue. You don’t want any dust falling onto the floor later, when the new finish is drying. Let the dust settle, and then vacuum. A standard shop vacuum with a dust filter will do the trick.

After you vacuum, wipe the entire floor surface with a tack cloth, a wax-impregnated piece of cheesecloth designed to pick up and hold dust residue. Plan to use several tack cloths — don’t overextend the cloths’ dust-holding capacity.

Types of Finishes for a Hardwood Floor

The type of finish you choose depends on the look you want for your floor. Durability is also an issue. Your choices are

• Polyurethane: Either oil- or water-based, polyurethane comes in various degrees of luster and has a sort of plastic look. Both finish types darken or even yellow wood, although some newer water-based products don’t darken as much. Poly finishes are excellent for high-traffic and high-moisture areas. However, if the finish gets nicked or gouged, it’s extremely difficult to spot-repair.

• Varnish: Varnish comes in a variety of lusters, from matte to glossy. The higher the gloss, the more durable the surface. Varnish often darkens with age. On the up side, you can make spot-repairs to varnish.

• Penetrating sealer: This offers a natural-looking finish that brings out the wood’s grain; however, it may darken over time. Penetrating sealer offers good protection, especially when waxed. However, it’s less durable than polyurethane or varnish. It’s the easiest of the three to spot-repair, though.

Ideally, you want to seal the floor on the same day you finish sanding to prevent the open wood surface from absorbing moisture. For best results, apply the stain (if desired) and sealer with a sheepskin applicator. Be sure to apply the sealer evenly, and use enough to cover the surface. But be careful not to apply too much. Excess sealer doesn’t soak into the wood — it pools on the surface. If you fail to remove it, it leaves an ugly, ugly spot.

Steps to Refinishing a Hardwood Floor

After the sealer has dried, follow these steps:

1. Buff the floor with No. 2 (fine) steel wool.
2. Vacuum and wipe the floor again with a tack cloth.It’s critical to remove all the dust between finish coats, or you’ll have a rough and ugly floor.
3. Apply the first of two coats of finish wax or other floor finish, such as polyurethane or varnish.Follow the directions on the finish container for drying time between coats.
4. Apply the final coat.Wait at least 24 hours after the final coat dries before moving furniture into the room.