Is Polyurethane Waterproof?

When you have hardwood floors in your home you do everything you can to ensure that they’re properly taken care of. Unfortunately, accidents happen and things spill onto floors. With tile or laminate floors in your home, you don’t really have to worry about a spill causing permanent damage to your floor, but that’s not the case when you have hardwood all throughout your home. The smallest spill could permanently damage the floor that you care so dearly for, which is why it’s important to take extra precautions to protect it. One of the best things you can do for your hardwood floors is to make sure that they’re coated with polyurethane. If you’re thinking about putting new hardwood floors in your home, or you have hardwood floors and haven’t done this yet, keep reading to learn about polyurethane and how it protects hardwood floors from water damage.

Is Polyurethane Waterproof?

No, polyurethane isn’t exactly waterproof, but it is capable of making wood water-resistant. Polyurethane repels water and prevents water absorption, but it can never fully block the water from penetrating something, which is why it isn’t 100% waterproof. This is the main reason why people use polyurethane to coat their hardwood floors, but it also protects hardwood from scratches and discoloration and it gives the wood that nice finished look we all know and love.

How to Polyurethane a Floor

Now that you have an understanding of polyurethane and why you should put it onto your hardwood floors, you may be wondering how you should go about applying it onto your floors at home. The process isn’t too difficult, which means even the novice do-it-yourselfer should have no problems completing this project.

Choosing a Type and Finish

There are a few different types of finish that you can choose from, and each one is used for a specific reason.

Water-Based Polyurethane

This type of polyurethane looks milky while it’s in the can, but it dries as a clear finish. Not only does it have a low odor, but it has a quicker drying time than the other options, so if you’d like to get the project done in a day, water-based polyurethane is for you.

Oil-Based Polyurethane

If you’d like your hardwood floors to have a deeper hue, then oil-based polyurethane is the way to go. This type of polyurethane adds a nice, warm hue to your natural floor, but unfortunately, it takes longer to dry than water-based polyurethane, and it has a very strong odor. On the plus side, depending on the kind of oil-based polyurethane that you get, you may be able to apply fewer coats to your floor.

Matte or Glossy Polyurethane

There are also matte, semi-glossy, and satin polyurethane finishes available, as well. Before you make a decision on which type of polyurethane that you’d like to use, take some scraps of wood, and test out all of the options that you’re considering. Make sure to let them dry before you make your mind up, and keep in mind that glossy polyurethane tends to show more fingerprints than other options.

Remember, polyurethane can let off some pretty nasty fumes, so take care to properly ventilate your workspace while working with it.

Prepping Your Floor

Before you can actually apply the polyurethane to your floors, there are a few steps you need to take to ensure that the area is properly prepped.

Sand the Floor (If Necessary)

Before you polyurethane the floor three times, unless you’re starting with a brand new, pre-sanded floor. Starting with 36-grit sandpaper, then 60-grit, and then finally 100-grit sandpaper, remove any imperfections there may be on your floor and smooth down the surface. Also, make sure to give plenty of attention to the corners of the room and the edges of the floor.

Vacuum the Floor

Using a commercial-grade vacuum, remove all of the dust and debris from the floor. There’s a good chance that your personal vacuum isn’t strong enough to get the job done, so you might want to consider renting a commercial vacuum instead.

Wipe Down the Floor

Using mineral spirits, wipe down the surface of the floor to remove any dust or debris that may have been left behind by the vacuum. Make sure to use a clean cloth, and pay close attention to the cracks, edges, and corners of the room. It’s important that you allow the floor to dry thoroughly before applying the polyurethane.

Tape Off the Room

Unless you’d like to get polyurethane all over your baseboards, it’s important to use masking tape to cover their edges.

Applying the Polyurethane

Now that you’ve prepped your floors, they’re ready to be coated with the polyurethane. Once again, it’s important to make sure that your workspace has sufficient ventilation at all times.

Stir the Polyurethane and Pour it Into a Paint Tray

Using a paint stirrer, thoroughly stir the polyurethane while it’s still in the can. The more you stir it up, the less chance of your floor having bubbles on it when you’re done. Also, never shake the can of polyurethane because that introduces more bubbles to the mix. Once you’re done stirring, pour the polyurethane into a paint tray.

Apply a Thin Layer

Using an 8-12 inch bristle brush and long, even strokes, apply a thin layer of polyurethane to your floors. You want a thin coat, so avoid putting too much polyurethane in one area. You also want to avoid going over the same spot multiple times because this can cause bubbles and imperfections.

Start at the Corner Farthest From the Entrance

You don’t want to step on an area that you’ve already applied polyurethane to, so start at the corner farthest from the entrance to the room. Working quickly, move from one of the room to the other.

It’s Drying Time

Look at the directions on the can of polyurethane to find out how long the kind you’re using takes to dry. Usually, you’re able to sand and apply another coat of polyurethane within 4-8 hours, but dry times do vary with different brands.

Sand Down Uneven Areas

Using 220-grit sandpaper, sand down any imperfections or bubbles on the floor. Take care to sand with the grain, rather than against it. Once you’re finished, wipe down the floor with a clean rag.

Apply a Second Coat

Your second coat of polyurethane should be thinned down using 10 parts polyurethane to 1 part mineral spirits (if you’re using oil-based) or 1 part water (for water-based). Apply another thin coat to the floor and allow it to dry.

Clean the Floor
Using grade 0000 steel wool, even out the entire surface of the floor. This is to remove any imperfections left behind by the second coat. As you did before, clean the surface of the floor with a rag before adding the final coat.

Add the Final Coat
Finally, it’s time to complete the project with the last coat. Using full-strength polyurethane, add the last coat. Allow it to dry for 24 before walking on it or putting your furniture back into the room.

As you can see, you don’t need to be a professional to put polyurethane onto your hardwood floors, but you definitely need patience. As long as you follow these simple directions, then you should have no problem completing this project!