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Sanding and refinishing a floor

MATERIALS: #8 finishing nails, wood putty, wood stain, 220-grit sandpaper or #000 steel wool, varnish, blue painter’s masking tape

TOOLS: Plastic sheeting, pry bar, hammer, nail set, putty knife, drum sander and sandpaper, vibrating sander and sandpaper, edge sander or random- orbit sander and sandpaper, dust respirator, shop vacuum, paint tray, lamb’s-wool applicator pads (for varnish), clean rags, paintbrush or foam brush, ventilating respirator

Hardwood floors typically last for the life of a home, but eventually they will need refurbishing or refinishing.

REFINISHING. If the floors are simply dirty from years of use but aren’t worn through to bare wood, you can probably clean them with household detergent and elbow grease, or you can rent a floor-buffing machine with an abrasive pad. Remove all the dirt and wax from the floor but not the finish itself, then apply a new finish coat.

REFURBISHING. If your floors are deeply stained, discolored, or damaged, you can often sand them back to their original state. Solid-wood-strip floors can be sanded and refinished several times. Some wood-strip floors, however, are made from laminated wood products and can be sanded only once and with great care. Examine an edge of the floor—under a threshold, for example— to determine the floor’s thickness. If the floor is laminated wood, leave the job to professionals.

If the floor is reasonably flat and free of dips and gouges, all you need to do is remove the finish with a vibrating sander. Vibrating sanders work on the same principle as handheld finishing sanders: A flat pad or plate with sandpaper on it vibrates and oscillates to remove the old finish. Floor models are bigger and heavier, of course, but work gently enough to control easily. If the floor is uneven or has scratches or deep gouges, you need to use a drum sander. If you’re not comfortable running the machine, call a professional to do the sanding, then do the finishing and staining yourself.

Refinishing saves the character of an old floor while giving it the shine of a new one.

TOO THIN TO SAND? Wondering whether the floor is too thin to sand? Pull up the floor vents or take off the threshold or the baseboard to reveal the edge of a floorboard. How far can you sand? Down to the tongue and groove, but no deeper.

Renting floor sanders - Drum and vibrating floor sanders and edgers are rental items. The drum and edging sanders are powerful, aggressive tools and take some practice to operate properly. Many rental companies offer a training demonstration, so take advantage of the opportunity. After class you're on your own. To minimize potential damage to your floor, start by using fine sandpaper on a small area to become familiar with the machine. Later switch to coarse paper and start the real sanding. Sandpaper comes with the sanders but you pay per piece. Get more than you think you’ll need-unused paper can be returned when you return the sander.

Keep the sander in motion to avoid gouging the floor.

1 REMOVE THE BASE MOLDING. A floor sander may bang against base molding, so remove it. Usually all it requires is removing the shoe molding—the quarter round that runs along the floor. Pry it off as shown, protecting the baseboard with a piece of scrap wood. If there is no shoe molding, either remove the base molding or take care not to damage it with the sanders.

2 CHECK FOR SQUEAKS AND NAIL LOOSE FLOORBOARDS. The best approach is to nail into a floor joist, not just the subfloor, with #8 finishing nails. Set the nails and fill the holes with latex wood putty. Set protruding nails that would tear the sandpaper.

3 CONTAIN THE DUST. To prevent dust from sifting throughout the house, close off doorways with plastic sheeting. Stick strips of masking tape around the edges of closet doors. If possible, pull the dust toward a window or door with a box fan. Wear a dust mask when sanding.

4 ROUGH-SAND WITH A DRUM OR VIBRATING SANDER. If the floor itself is in bad shape, start with a drum sander. If refinishing is all that's necessary, use a vibrating sander (Step 6) instead. Get advice from the tool rental company. When drum sanding, start with the coarsest sandpaper grit—typically 36- or 60-grit—then switch to 60-grit. Finish with 80- or 100-grit. Move the sander so that it travels along the length of the boards, with the grain of the wood. Work the drum sander forward and back over 3-foot to 4-foot lengths of floor, overlapping the strokes by at least one-third of the belt.

5 SWEEP AND VACUUM BETWEEN SANDINGS. The sanding dust eventually gets in the way of the sanding process and has to be swept and vacuumed. Always sweep and vacuum before starting with the next grit of sandpaper. It not only makes the floor cleaner, it picks up any grit that may have been left by the sandpaper—grit that would scratch the job of the finer-grit paper.

6 FINE-SAND WITH A VIBRATING SANDER (optional).

7 SAND CORNERS AND EDGES WITH AN EDGE SANDER. The edge sander usually comes as part of the rental. Use 80-grit paper to reach areas that the large sanders cannot reach: corners, under radiators, in small closets, etc. Edge sanders can be difficult to control; practice on a hidden area, such as the inside of a closet, until you get the hang of it.

8 A RANDOM-ORBIT SANDER IS EASIER TO CONTROL THAN THE EDGER. Use it to finish tight places such as corners. Random-orbit sanders are less aggressive and less likely to gouge, and they do an excellent but slower job.

A DIFFERENT DRUMMER - A sander drum is usually made of rubber wedged between two discs held in place by a nut. To lock a roll of sandpaper in place, tighten the nut, squeezing the sides of the drum together. This increases the diameter just enough to prevent the sandpaper from slipping off. Loosen the nut to remove the sandpaper.

9 APPLY A WOOD STAIN [optional). When the sanding is done, clean up all the dust with a vacuum and tack cloth. Apply wood stain with a foam applicator pad. Work one manageable area at a time—4 square feet, for example. Always stain in the direction of the wood grain.

10 WIPE OFF THE EXCESS STAIN AS YOU GO. Most manufacturers recommend removing excess stain as you go—usually after a few minutes. Use clean cotton cloths or paper towels. Try wiping the floor with a cloth wrapped around a dry applicator pad.

11 APPLY A CLEAR FINISH. Allow the stain to dry as recommended before applying the first coat of varnish. Polyurethane, either oil-based or water-based, is a reliable finish for floors. Apply the finish with a lamb’s-wool applicator. Sand the floor lightly with 220-grit paper, or #000 steel wool. Vacuum up the dust. Sand and apply three coats of oil-based finish, or four coats of water-based finish.

SANDING PARQUET - Parquet floors require a special technique or a special machine. Unless you're a pro, use the machine. To create a parquet pattern the tile is made of several strips with the grain running in different directions. As a result, sanding across the grain is unavoidable, and the sandpaper leaves noticeable scratches. Rent an orbital floor sander, which has a pad that moves in a random semi-circular pattern that doesn't scratch the grain. Use a 36-grit sandpaper to remove the finish. Change to a 60-grit paper for a first pass over the floor. Make a second pass with 80-grit, and a final pass with a 100-grit sandpaper. Sand around the edges of the floor with a hand sander, using the same progression of grits.

OIL-BASED VS. WATER-BASED POLYURETHANE - Oil-based polyurethane is reliable and has been around for years. It imparts warmth to most wood colors, darkening them slightly. Use a brand that is recommended for flooring and has a warranty. Some brands dry slowly, requiring a full day between coats. Others are fast-drying (A hours is about the minimum), which allows you to get two, even three, coats on in a single day. Good ventilation is a must, and you should wear a ventilating respirator. Water-based polyurethanes dry quickly and are nearly odorless. They're also virtually clear when dry, an advantage if you don’t want the finish to darken the wood. Many professionals use commercial water-based polyurethane that holds up well, but reports are mixed on the water-based varnishes available to consumers. Quality seems to vary from brand to brand. Check warranties and discuss your choice with knowledgeable floor-finish experts.

OIL-SOAKED RAGS ARE A FIRE HAZARD - The heat from dry, oily rags can set the rags on fire, especially if they are bunched together. Hang the rags outside, away from any structures, and allow them to dry thoroughly before you throw them out.

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