How to Sand and Refinish a Hardwood Floor

Buffing machine passing over hardwood floor

The Spruce / Margot Cavin

Project Overview
  • Working Time: 6 - 8 hrs
  • Total Time: 3 - 4 days
  • Yield: 10 x 10-foot room
  • Skill Level: Intermediate
  • Estimated Cost: $200 to $300

Refinishing a hardwood floor is a great way to revitalize the look of a room without the trouble and expense of installing brand-new flooring. The process involves removing the top layer of the covering material using a large sander, which removes the surface finish and digs down past any surface scratches, stains, or imperfections that might exist. The result is a fresh surface that is then stained and top-coated with whatever protective coating you prefer.

But be aware that sanding cannot be expected to remove very deep scratches, gouges, and stains. Even professionals advise homeowners to lower their expectations on what floor sanding can accomplish. Floor sanding removes at most about 1/16 inch of wood, and damage that is deeper than that usually will still be evident, though less obvious.

Before You Begin

Aggressive sanding and refinishing are best suited for solid hardwood floors—flooring comprised of solid maple, oak, or another hardwood throughout the thickness of the planks. Hardwood floors with 3/4-inch -thick planks can accept three or sometimes even four deep sandings over their lifespan.

But many floors are not solid hardwood, but instead consist of planks with a hardwood veneer layer glued over a core of plywood or another manufactured wood product. These products are often known as engineered wood. With these floors, you may be able to do only one sanding, and you need to be careful not to grind through the finish layer of hardwood and into the core layer.

Some floors that look like hardwood aren't wood at all. If you have laminate wood-look floors, sanding is not an option. However, bamboo floors (bamboo is technically a grass, not a wood) can be sanded in the same way as hardwood to remove surface imperfections. But bamboo floors are often very hard, so sanding may take a little more time.

While it is theoretically possible to sand floors with a hand sander, it is almost always done with a large upright drum sander—an expensive tool that is normally rented, not purchased. This tool is not easy to use, so make sure to get instructions from the store clerk on how to use it effectively and safely.

Safety Considerations

Large upright sanders make a lot of noise and throw up a lot of dust. Make sure to wear a protective mask, eye protection, and hearing protectors when using this tool. Where possible, open windows and ventilate with fans during the procedure. Mask off vent duct openings and passage doorways to prevent dust from traveling throughout your house.

Upright floor sanders are powerful tools. If used incorrectly, it is easy to create deep gouges or dips that ruin the floor's appearance. Take your time when sanding, making sure to use sanding belts or pads with the proper abrasive grit. Avoid tilting or rocking the sander, as this is guaranteed to gouge the floor.

When to Call a Professional

If you perform the work yourself, then you will have to rent a walk-behind, solid-wood sanding machine as well as hand sanding tools, which will cost roughly $200 per day. And it's easy to make mistakes that can irreparably damage the wood flooring surface. More than one homeowner has eagerly set out to save money by sanding a hardwood floor, only to end up spending a lot more to replace the floor entirely.

Refinishing hardwood floors is, therefore, no easy task, and if you're uncertain of your skills, it may be best to leave it to a professional service. A professional will charge $3 to $8 per square foot to refinish a hardwood floor, depending on the size of the job. The professional process includes sanding, plus the application of two or more layers of surface finish. The process will generally require three to five days, including cleanup.

What You'll Need

Equipment / Tools

  • Pry bar
  • Hammer
  • Eye, hearing, and breathing protection
  • Upright drum sander
  • Edge sander
  • Paint scraper
  • Under-radiator sander (optional)
  • Shop vacuum
  • Broom
  • Paint brush and roller
  • Brad nailer

Materials

  • Plastic sheeting
  • Painter's tape
  • Clean cloths
  • 40- or 60-grit sanding belts for upright sander
  • 40- or 60-grit sanding pads for edge sander
  • Wood putty
  • Fine-grit sandpaper
  • Tack cloths
  • Wood stain (optional)
  • Topcoat finish (sealer, polyurethane, or varnish)

Instructions

  1. Remove Trim Moldings

    Floor sanding will be easiest and give the best results if you remove the base shoe moldings, or even the entire baseboards, before beginning work. This will allow the edge sander to get very close to the walls.

    Take care when prying off the moldings to avoid cracking them. Some homeowners use this opportunity to install new moldings, which will give the refinished floor an even better appearance.

  2. Cover Ducts and Doorways

    Use plastic sheeting, secured with painter's tape, to cover doorways and vent ducts. This will prevent sanding dust from traveling throughout your home.

  3. Clean the Floor

    Completely clean the surface of the floor. It should be swept or vacuumed to thoroughly remove any dust or debris that may be present. A slightly damp mopping, preferably by hand with a cloth rag, may also be useful to get rid of loose particles.

  4. Make Any Necessary Repairs

    Examine the floor for protruding nails and pound them down using a hammer and nail set. Protruding nails will quickly ruin sanding belts or pads when you begin sanding.

    Damaged or missing flooring boards should be replaced or repaired before you begin sanding.

  5. Sand the Floor

    Install a 40- or 60-grit sanding belt on an upright drum sander. While wearing protective gear (eye, hearing, breathing), sand the entire floor, moving parallel to the direction of the boards—not across the wood grain. Sand in a series of long passes, overlapping each pass by 2 to 4 inches. Get as close to the walls as possible, but don't touch the baseboards with the tool.

    How you start and stop the sander is crucial. Make sure the drum is raised off the floor when you turn the machine on, then lower it down onto the floor as you begin moving with a long forward stroke. When you reach the far wall, raise the drum before you stop moving the sander. Failure to follow this method can result in dips and severe damage to the floor.

    drum sander to sand wood floors
    BanksPhotos/E+/Getty Images
  6. Sand the Edges and Corners

    Using a hand sander fitted with 40- or 60-grit sandpaper, sand the edges and corners of the room, up to the baseboards. In corners, you may need to use a paint scraper to remove the last bits of finish.

    Sanding machine passing over hardwood floor by hand and door frame corder

    The Spruce / Margot Cavin

    Tip

    To sand under radiators, consider renting a specialty sander with a flat sanding head that fits into tight spaces. Or, you can also sand by hand in these areas.

  7. Examine the Floor

    Once you have completed sanding the floor using power tools, you can work on any areas that remain, using medium-grade sandpaper. This can also help to smooth out any rough patches that may have occurred during the process. If gouges are present, they can be filled using wood putty, which should be left to dry for at least 24 hours and then sanded with fine-grit sandpaper and wiped clean with a tack cloth.

  8. Clean the Floor

    The vacuum attachments included in most power sanders will suck up the majority of the dust generated by the refinishing process. However, it is still important to sweep and/or vacuum the room thoroughly before proceeding. Afterward, use a tack cloth to wipe the floors and walls.

  9. Stain the Wood (If Desired)

    If you wish, the wood can now be stained whatever color you want. A variety of stains and dyes are available, but one easy method is to use a rub-in stain that is applied with clean rags.

    Make sure the stain dries completely (usually overnight) before proceeding to the topcoat application.

  10. Apply a Topcoat

    The term varnish is often used generically to refer to any topcoat layer, but there are several options to consider:

    • A simple sealer is a thin, protective liquid that goes over hardwood, both seeping into the pores of the material and creating a clear surface coating over its top. It allows the natural color and grain of the wood to shine through, but it also provides the least protection and may need to be reapplied every six to 12 months depending on traffic use.
    • Polyurethane is now the most common topcoat finish for hardwood floors. A clear, almost plastic-like substance, polyurethane is applied with a standard paintbrush and is available in a variety of finishes, from matte to glossy. Its purpose is to create a clear, protective layer over the top of the wood that resists stains and scratches. 
    • Traditional varnish is similar to polyurethane, except that it has a more dramatic effect on the wood, darkening it noticeably. The advantage of this substance is that it is thinner, so spot repairs can be more easily made when future damage occurs.

    Whatever finish you choose, make sure to follow label directions exactly, especially when it comes to safety measures and drying time. With many topcoats, you can expect to apply at least two coats, allowing each coat to dry overnight before proceeding to the next.

    Polyurethane protective coating applied by long roller on hardwood floor

    The Spruce / Margot Cavin

    Tip

    Polyurethane finishes are available in both water-based and oil-based formulations. Water-based poly is easier to use and dries quicker, but it has a tendency to show imperfections. Oil-based poly is slow-drying and smelly, but this slow-drying characteristic allows the finish to achieve a very smooth, elegant look.

  11. Replace the Moldings

    The final step is to install the base shoe or other moldings along the walls, covering the edge of the newly finished flooring. These molding are easy to tack into place with a brad nailer.