Is Polyurethane Waterproof?

If you’re looking into handling the upkeep of your wooden furnishings yourself, you may be looking for a sealant that you can apply easily. Polyurethane is a very common varnish choice, as it comes in multiple types and, according to manufacturers like Behr, it can “enhance the look and color of your wood surface.” But what is polyurethane, and is it waterproof?

Polyurethane is a chemical sealant for wood. It’s used to protect your wood floors and furniture from scratches, water damage, and other signs of wear and tear. There are two main types of polyurethane: oil-based and water-based. According to Nick O’Keefe, the owner of Oak City Coatings, LLC, water-based polyurethane goes on clear, while the oil-based kind has an amber tint to it. Read on to find out if polyurethane is waterproof.

Is Oil-Based Polyurethane Waterproof?

“Oil-based polyurethane can protect the wood surfaces from moisture very effectively as it forms a fine water-resistant barrier,” Jay Sanders, of Castle Dream Construction, says.

O’Keefe cautions that wiping up spills sooner rather than later is still best, since it’s technically water-resistant rather than waterproof. Still, oil-based polyurethane is a good choice for protecting your floors and furniture.

How long will oil-based polyurethane last/resist water?

According to Sanders, “Oil-based polyurethane can typically last for about 10 to 15 years. In fact, with proper maintenance, it can resist water for up to 20 years.” So, if you’re looking for something for your floors, which can feel like a huge undertaking, oil-based is a good option. With proper maintenance, you won’t have to refinish them as often.

Is Water-Based Polyurethane Waterproof?

“Water-based polyurethane is capable of resisting water and other liquids as it provides a protective finish,” Sanders explains. Like its oil-based counterpart, it’s water resistant, not fully waterproof. So, wiping up spills quickly is still recommended. But your floors and furniture will have a decent layer of protection from water damage.

How long will water-based polyurethane last/resist water?

According to Sanders, “You can expect water-based polyurethane to last for about 3-5 years. If applied and maintained properly, [it] can maintain its water resistance for up to 7 years.” He continues on, saying, “Although, in the context of durability, it is ranked lower than oil-based polyurethane, it is a great option for easier cleanup and faster drying times.”

Tips to Make Polyurethane Finish Last

Sanders has a few tips to make a polyurethane finish last:

• “Make sure that the site is prepared properly. Before applying polyurethane, sand and clean the surface thoroughly.” Don’t cut corners here; take the time to do things right.
• “Dont apply a single thick coat. Rather, apply multiple thin coats for better durability. Experts recommend applying 3-4 coats for optimal protection.” Patience is key; multiple thin coats will work better and look much nicer.
• “It is very critical to prevent the finished surface from direct sunlight. UV exposure can degrade polyurethane and may become yellow over time.” This piece of advice is key; you don’t want discoloration on your beautiful surfaces.
• “Regular maintenance is a must! Try to reapply the coat every 2 to 3 years to extend the lifespan of the finished surface. The key is to reapply the coating once you observe the signs of wear.” Keeping up with maintenance is the best way to get the most mileage out of your pieces.

If you follow the manufacturer’s directions and incorporate these tips into your application, your wooden furniture and floors are sure to look beautiful for a long time.

About the Experts

• Nick O’Keefe is the owner of Oak City Coatings, LLC.
• Jay Sanders is an MHIC licensed contractor and owner of Castle Dream Construction, a basement waterproofing company in Baltimore, Maryland. He’s been working on construction for more than 10 years.

Sources

• Behr: “Water Based Polyurethane | Interior Wood Stains & Finishes” (2021)