How To Apply Polyurethane On Floors? (With Images)

Polyurethane will protect floors from water, scratches, dents, and other damage. But, how to apply it on floors?

To apply polyurethane on floors, you must clean and sand the floor, and then apply it using a sprayer, roller, or rag. You must sand between coats with 320-grit sandpaper to help them stick better. 

You must wait 3 days for the sealant to dry before walking over it. You can use different types of polyurethane; oil-based, water-based, or exterior polyurethane. 

Things To Know

Polyurethane is strong enough to protect floors from moisture, water, scratches, dents, and other damage. When dry, it forms a top layer made of urethane plastic. The top layer acts as a “shield” and protects the surfaces underneath it.

Urethane plastic is a flexible compound that expands or contracts during temperature changes. This means the coating will withstand temperature changes without the coating cracking.

The hard plastic material on the top layer also makes the floor strong enough to withstand constant use, heavy furniture, and heavy foot traffic.

However, polyurethane isn’t waterproof, and if exposed to constant water, it will allow water to penetrate its coating. So, you shouldn’t apply it on bathroom floors.

Oil-based vs Water-based Polyurethane (For Floors)

What Type Of Polyurethane Should You Use On Floors?

You can use two types of polyurethane on floors: oil-based and water-based. Both types are durable and have similar qualities. However, they have different solvents (water and oil) that give each unique feature.

Clarity

Polyurethane has no paint pigments, so it forms a clear coat finish that reveals the grain of the wood underneath. Water-based polyurethane retains its clean finish longer than oil-based polyurethane. Oil-based polyurethane will start to yellow or have an amber tone finish after a  while.

The Dry Time

Water-based polyurethane dries faster than oil-based polyurethane. That’s because water-based poly uses water as its solvent, and water evaporates faster than oil. On average, water-based polyurethane will dry fully (cure) within 24 hours, while oil-based polyurethane will take up to 3 days to dry fully. 

Durability

Since oil-based polyurethane dries slower, the paint particles have more time to harden and bond to the surface. This means oil-based polyurethane is more durable than water-based polyurethane. 

Water-based polyurethane will chip and peel after a few years, while oil-based polyurethane won’t.

Cleaning and Maintenance

Oil-based polyurethane doesn’t require as much maintenance as water-based polyurethane. This is because stains on oil-based polyurethane often blend into the finish. The amber tone of the finish makes the floor hide stains easily. So you won’t need to take on much cleaning.

On the other hand, water-based polyurethane highlights stains on the floor due to its transparent finish. So, you must clean it more often. However, cleaning it easier since you can use soapy water. But, to clean oil-based poly you need to use a solvent. 

Number of Coats Needed

You need 2 -3 coats of oil-based polyurethane on your floor. Water-based polyurethane requires up to 5 coats for proper coverage, especially on a wood floor.

Final Verdict: Both types are great choices for your floor. But, oil-based poly is a better fit because it requires fewer coats and is more durable. 

How to Apply Polyurethane to Floors?

Applying polyurethane to floors isn’t hard, but you need to clean and prep the floor properly.

Also, you need the right tools and supplies:

  • A vacuum
  • 320-grit sandpaper
  • A floor or orbital sander
  • Clean rags
  • Mineral spirits
  • Paint applicator
  • Water or oil-based polyurethane
  • Wood filler
  • Primer paint (optional)

Note: If the wooden floor is already finished (sealed), you must remove the sealant first. If the floor is only painted (and not sealed), you can apply polyurethane over the paint. 

1. Prep The Wood Floor

Prep The Wood Floor

First, clean the wood floor. Cleaning will remove debris and filth from the surface. To do so, sweep it and use a clean rag to remove dust. For stubborn stains, use mineral spirits or rubbing alcohol to remove them. 

Polyurethane won’t stick if you don’t clean or remove dust from the floor. Also, dust and dirt will show through once the finish dries.

If the floor has cracks, holes, or gouges, repair them with wood filler. Apply the wood filler over the cracks, remove the excess filler compound, and allow it to dry before sanding it. If some floor planks are damaged, it’s best to replace them with new ones before sealing them. 

If you don’t repair or replace the wood, the damage will be seen through the transparent finish, making your it look amateurish.

2. Sand The Wood Floor

Sand The Wood Floor

Sand the floor using 150-grit sandpaper and work your way to finer-grit sandpaper (240-grit). You can also use sanding pads or blocks instead of a power sander.

Sanding will remove imperfections and smooth the floor so the polyurethane can stick better. After sanding, remove the dust. 

4. Apply The Polyurethane

Apply The Polyurethane

The best applicator for water-based polyurethane is a synthetic bristled paintbrush or a microfiber paint roller. The best applicator for oil-based polyurethane is a lambswool paint roller or a natural-bristled paintbrush.

You can also spray both types of polyurethane, but you must thin them, prime the sprayer, and spray correctly to avoid overspraying. So, spraying it is harder than rolling it. You can also use applicator pads to apply it. Applicator pads are fitted in long poles, allowing you to cover larger areas. 

To apply polyurethane:

  1. Use a paint roller, applicator pad, or paint sprayer. 
  2. Ensure to cover the entire floor with the first coat.
  3. You can use a paintbrush to apply it on tight corners. 
  4. Wait for one coat to dry before applying the next one.
  5. While waiting for polyurethane to dry, place your paint roller into a refrigerator to avoid clogged paint. 

5. Recoat It

Recoat The Polyurethane

After the first coat dries:

  1. Sand it with ultrafine-grit sandpaper.
  2. Remove dust from the coating. 
  3. For water-based polyurethane, apply 4 more coats (5 in total).
  4. For oil-based polyurethane, apply 2 more coats (3 in total).
  5. Wait until one coat dries, sand it, and then apply the next one.
  6. Don’t sand the final coat.
  7. Wait until the final coat dries fully (1-3 days) before walking over it. 

it takes water-based poly 24 hours to cure, and oil-based poly 3 days to cure. When the finish cures, the coating has dried fully and hardened enough to withstand foot traffic and furniture weight. If you use the floor before the finish dries, it will take longer to dry or turn sticky.

Staining The Floor Before Polyurethane

You don’t have to stain the floor before applying polyurethane. That’s because polyurethane can be applied over bare wood too. However, if you want to add beauty and color to your wood floor, you can apply wood stain first. 

Polyurethane has a transparent coat, meaning it doesn’t add color to a surface. Instead, it will reveal the texture and wood grain. But, if you stain the wood floor, it will reveal the stained wood color, making the finish look better.

Polyurethane is a tropical sealer, meaning it sticks over stains and other paints. You can also paint a wooden floor, wait for the paint to dry, and then seal it. Polyurethane will protect the paint or stain from moisture, water, or other damage. 

How Long Does Polyurethane Last On Floors?

Polyurethane lasts between 5-20 years on floors. However, how long it lasts depends on the condition and type of the floor and the room type.

For instance, polyurethane will last longer in a bedroom than on a bathroom floor. That’s because a bathroom floor is exposed to constant water that can damage the finish, while the bedroom isn’t.

The durability of finish depends on the type of polyurethane. For example, oil-based polyurethane will last longer than water-based polyurethane.

Polyurethane Alternatives

Here are some other types of sealants you can use:

  1. Varnish: There are different types of varnishes you can use, including acrylic, oil, exterior, and spar varnish.
  2. Wood oils: Wood oils like Tung oil, Linseed oil, and Danish oil protect your floor and give it a nice luster.
  3. Lacquer: Lacquer is similar to polyurethane in terms of durability and protection, but you must pick the right type for floors.
  4. Shellac: Shellac is another hard and strong alternative. However, shellac isn’t weather-resistant. 
  5. Wax: You can also use wax on your floor. But, you must buff the wax regularly to retain the finish.

Final Words

You can apply polyurethane over floors using a paint roller or sprayer. However, before applying it, you must clean, prep, and sand the floor properly. Sanding will remove imperfections and make the floor ready for sealing.

You must sand between coats of polyurethane (except for the final coat) to allow each coat to stick better. After applying the final coat, you must wait 1-3 days before walking on the floors. 

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