No, polyurethane cannot make hardwood waterproof, but it can make wood waterproof. Polyurethane provides protection for hardwoods. It can repel water and prevent water absorption, but it will never completely block water, so it will never make it 100% waterproof. Polyurethane can also protect wood from scratches and discoloration. And, of course, it makes the wood look complete.
Only one layer of polyurethane is not enough. Polyurethane is a thin layer and is discontinuous (with small holes). If there is only one layer, even small scratches and scrapes will allow water to penetrate the surface. Moreover, wood will of course expand and contract, which creates more weaknesses.
As you add more polyurethane coating, it will make the wood semi-impermeable because the polymer layer will be thicker and more cohesive. The protection effect will be better and the service life will be longer...This means you don't need to sand and repair for a long time.
What happens to polyurethane over time? Has the water resistance decreased?
Over time, the wood will expand and contract, thereby generating more penetration, and the polyurethane will wear out due to natural wear (or even just walking on the wood).
In addition, when you add polyurethane to the floor, it will not cover all 4 sides of the wood.
Therefore, naturally, if there is water on the polyurethane floor, even if the water penetrates from the side, the water will eventually penetrate into the wood.
This can cause polyurethane to swell, warp, wear, and discolor (for example, the wood turns gray and eventually black).
How to make hardwood floors more waterproof?
Although no hardwood is waterproof, here are 7 ways to make hardwood more water resistant.
1. Use white oak instead of red oak
Ways to make hardwood more water-resistant due to its honeycomb structure, white oak flooring is more water-resistant than red oak. Many pores are blocked by tylos, making them more elastic to water. This is why it is often used in boats and canoes. It is best to use white oak in the kitchen, entrance and front door bends and other household areas that are easily affected by water.
2. Use harder wood (and avoid using looser wood, such as pine and bamboo).
How to make hardwood floors have better waterproof performance Hardwood is often more resistant than softwood because the wood fibers are more tightly packed together. Softer woods such as pine trees absorb more water; moreover, bamboo looks like grass, absorbs a lot of water, and has many pores for water penetration. The water resistance of bamboo is extremely poor, and it can even become black due to a small amount of water spilled from the dog bowl or the back door.
3. Add more polyurethane layers
More layers means more protection (to a certain degree). I usually recommend 3 layers of Polyurethane Waterproof Coating(never more than 4 layers). If you apply too much polyethylene coating, it will make the floor yellower and even a little sticky (the floor will take longer to cure). Therefore, it would be wiser to make three coats first, and then apply another coat after 3-4 years (see screen and recoat below).
4. Hire professionals to polish and repair your hardwood
Is it polyurethane waterproof? I know some people want to polish and repair themselves. They think this can save them a lot of money. News Flash: No! Please hire professionals.
Repairing hardwood floors is not a good DIY job. It will only save you some money, and of course, it will take longer to complete the work compared to hiring a professional (so you will spend more time away from home). Moreover, it is important that your floor does not stick out, and it will not last long.
You will see that the machines used by professionals are better than the machines you can rent. And, of course, professionals have honed their skills. Mosquito nets, floors are better, and when you hire professionals, polyurethane can better penetrate and adhere to wood. And, naturally, your floor will be better supported and more resistant to water and moisture.
5. Screen and re-lay the floor regularly
This is a little-known secret, most homeowners don't even know. Sieving and recoating (sometimes called buffing) is a preventive maintenance step that helps to make the floor last longer.
Basically, you can polish the floor and add an extra layer of polyethylene. This can provide you with more protection and may increase the wear value of the floor for 3 years. This is just a day's process, you may only need to operate in areas with heavy traffic (such as the first floor, kitchen + family room, etc.). Learn more here: What is a screen and repainting?
You want to do this before the floor is worn and before the color is scratched.
6. Remove spills (and pet accidents)
How to protect hardwood floors from water and scratches I think this is obvious-wipe off all liquids as soon as possible because it will wear the polyester and penetrate the wood. This includes snow may migrate (use entrance mats both inside and outside the doorway). Clean the floor frequently and vacuum once a week (this is the level of vacuum I recommend for hardwood floors).
7. Avoid using wax or products that restore luster.
Many people don't realize that certain cleaning products are actually hurting their hardwood floors. Avoid using products that restore luster or gloss. The wax contained in these products will temporarily make your hardwood floors look better. However, they will actually degrade the polyurethane on the floor...so you need to repair it faster and the water will penetrate more easily.