How Many Coats of Polyurethane Should You Use on Stairs?

Polyurethane is considered the most durable yet easily-applicable protective hardwood finish. Polyurethane finishes come in two main types: oil-based finishes and water-based finishes. Choosing one or the other depends on your preferences and the specific project you're working on.

Generally speaking, oil-based polyurethane is a bit easier to apply. It is thicker as well, which means fewer coats are required. Depending on the type of wood and condition of the stairs, usually two or three coats of oil-based polyurethane are enough.

However, you need to be aware that it takes longer to dry. Also, it can add an amber glow to the wood, making it susceptible to brush marks. The odor of oil-based polyurethane is stronger than that of the water-based variety.

Taking all of the features into account, if you apply two or three coats of oil-based polyurethane to your stairs, the project may run much longer than if you use a water-based formula.

Water-based polyurethane can be more temperamental. The finish can raise the grain of the wood and is susceptible to watermarks. Additionally, water-based polyurethane is not as thick as oil-based polyurethane, so you may need to apply up to four or more coats.

On the other hand, it dries quickly and doesn't have such a strong odor. The color of water-based polyurethane is usually clear or neutral. Note that when applied it looks milky-white, but as it sets the finish becomes clear.

Now that you know how many coats of polyurethane you need on stairs to get the mirror finish, let's see how to properly apply them.

Sand the wood with 120- or 220-grit sandpaper. Some woods may require a wood-grain filler before you apply the first coat. You should gently sand the stairs before applying each coat. When you are done sanding, clean the stair thoroughly using a vacuum cleaner.

It is advisable to splurge a little on the brush. Use a fine-bristled brush or a foam brush. Take long brush strokes and follow the grain of the wood. Take out as many bubbles as you can. When it dries, repeat the process including the sanding.

The process is quite similar to oil-based polyurethane. Using a fine-bristled brush, work your way down the grain in long strokes.

Don't apply too much or the grain will rise. Water-based polyurethane dries in a couple of hours, so you should be able to apply the four required coats in one day. Applying this number of coats will insure your stairs are completely protected.

When in doubt, feel free to apply another coat, since some woods soak up more polyurethane than others.

Also, the number of coats of polyurethane required on stairs may depend on the condition of the stairs. The worse condition they are in, the more coats are required.