Finishing Wood Floors

Wooden floors used to be finished with shellac, a coating that dries rapidly, brings out a lot of depth in the wood and adds a warm amber coloring.

But shellac doesn’t wear well, so it was almost always waxed to reduce scuffing and extend longevity. Keeping waxed floors in good shape was a lot of work, however, so with the introduction in the 1960s of more durable, “no-wax” polyurethane finishes, shellac fell out of favor.

Today, there are a number of durable finishes that can be used successfully on wood floors, including oil-based polyurethane, water-based polyurethane, moisture-cured polyurethane and water-based finish with a catalyst (or “hardener”) added. Of these finishes, oil- and water-based polyurethanes are the most popular with do-it-yourselfers because these finishes are considerably less toxic and much easier to use.

Though both of these finishes are based in large part on polyurethane resin, they differ in several significant ways. Oil-based polyurethane is more durable (meaning more wear-resistant), has a slight amber coloring and dries slower than water-based poly­urethane, so application is easier.
Water-based polyurethane, on the other hand, has a much less irritating smell, is easier to clean up (with just soap and water), is non-flammable and doesn’t add color at all. Because of its lack of color, water-based polyurethane generally looks better on
“white” woods such as maple and woods that are whitewashed or “pickled.”

Clearly, there are legitimate reasons for choosing each of these finishes. But unless the non-yellowing characteristic of water-based polyurethane is very important to you, oil-based polyurethane is your best bet for a floor because of its better durability.

Once you’ve chosen the finish to use, you need to prepare the surface and apply the product. Finishing floors is like finishing any wood surface – with two rather significant differences. First, the surfaces to be covered are usually very large, so different tools are commonly used to increase speed. Second, there is a reduced need for perfection because flaws in the wood or in the finish aren’t noticed easily.

Preparing the Surface
Just as with newly made furniture, newly laid floors are always sanded before finishing. But already finished floors are rarely stripped. Instead, they also are sanded and the procedure is the same as with new floors.

Special, 100- to 200-pound stand-up sanders are used, and sandpaper grits are kept fairly coarse, ranging from 36-grit to 120-grit. (Sanding no finer than 80-grit is a good idea, for example, when whitewashing floors so that more of the white pigment becomes lodged in the deeper sanding scratches.)

Smaller “cut-in” sanders are used to sand right up to baseboards, and inside corners often are scraped and sanded by hand.

All of these tools, including the floor buffers mentioned below, can be rented at rental stores and some flooring-materials suppliers. These stores also stock the needed sandpaper, steel-wool pads and screens, and they can provide more detailed sanding instructions if you need them.