When it comes to sealants, you need to apply the right amount of coats so the finish can come out fine and smooth. So how many coats of polyurethane do you need?
You need to apply between 2-5 coats of polyurethane on a surface. On surfaces that don’t need much protection, such as room decor, apply two light coats. On surfaces that are used heavily, such as tables or desks, apply 3 coats.
The minimum amount of polyurethane coats is 2, while the maximum is 5. Apply more or less than this and you won’t get a smooth finish.
Why Does it Matter?
The number of coats matters because polyurethane is a clear sealant, so if you add too many coats, it will affect the clarity of the finish. Polyurethane by design is meant to produce a clear and glossy top film when it dries.
The sealant durability is also determined by how much you apply. For instance, if you apply fewer coats, polyurethane won’t be able to produce a strong or moisture-resistant layer over the surface. You need at least 3 coats for proper protection.
Applying too many coats can also make oil-based polyurethane turn yellow. That’s because there will be too many oil deposits on the surface that can turn yellow.
Applying too many layers can also lead to a poor finish. That’s because the sealant will take longer to dry, so dust and debris will accumulate over its coating. This means the finish will be riddled with dust and debris, and won’t be as moisture-resistant.
You need 2-3 coats of oil-based polyurethane. For wooden surfaces, you don’t need more than 2 coats, unless you are applying it over a high-traffic surface. High-traffic surfaces require up to 3 coats.
You don’t need many coats of oil-based polyurethane because the sealant is thick and its solvents produce a glossy finish. So, applying too many coats isn’t necessary.
Most DIYers believe that the more coats of oil-based polyurethane that they apply, the extra protection the material gets. This is false. Applying more than 4 coats isn’t recommended because it increases the chances of the finish yellowing over time.
When the oily solvent in oil-based polyurethane is evaporated, it leaves deposits that can turn yellow if there is enough of it. So if you apply more coats, the oily deposits will increase and your finish can start to yellow in a few months.
However, if you apply fewer coats, the finish won’t be durable. So, always apply between 2-4 coats for oil-based polyurethane.
You need 2-5 coats of water-based polyurethane. On average, apply 3 coats of it for surfaces that wouldn’t see much use, such as room decor. For high-traffic surfaces, apply 5 coats.
Since water-based polyurethane uses water as its solvent, you can apply more coats since it won’t leave oily deposits behind. So, the chances of the finish yellowing are less.
However, you shouldn’t apply more than 5 coats as it increases the chances of the finish becoming cloudy. Plus, applying that many layers can be time-consuming due to the required time to wait.
Asides from that, it will also take longer for the sealant to dry and cure. The longer the sealant remains wet or sticky, the more likely it is to accumulate dust.
Most people feel water-based polyurethane is not as durable as oil-based polyurethane which is why you need more of it when covering a surface. This is false. They have exactly the same formula (except for the solvent) and offer the same level of protection.
Dry Time Between Coats
It takes oil-based polyurethane 24 hours to dry enough for a re-coat, while water-based polyurethane dries between coats within 8 hours. The water-based polyurethane dries faster because it uses water as its solvent, and water evaporates faster from the coating.
If you re-coat too soon, the finish won’t dry properly. It will remain tacky for several days, and when it dries, the finish won’t be as clear as it should be.
The solvent or thinner must completely evaporate before you can re-coat the sealant. If the solvent remains in the coating while you lay another layer, the solvent will become trapped between layers. Since the solvent can’t evaporate, it will begin to bleed through to the top layer of the polyurethane, making it turn sticky.
Let’s check out common surfaces the sealant is used on and how many layers you need for each.
For floors, you need 3 layers of oil-based polyurethane and 3-5 layers of water-based polyurethane. Don’t apply more than 4 layers as the finish will become blurry.
For low-traffic floors, such as bedroom floors, you can apply 2 layers only. This is because they don’t see much foot traffic, so they don’t need much protection.
For indoor wood, apply 2 coats of polyurethane since the wooden surface isn’t exposed to high-trafic. For outdoor wood, you need 3-4 coats since the surface is exposed to moisture, rain, and other outdoor elements so it needs more protection.
For outdoor surfaces, it’s recommended to use exterior polyurethane as it contains additives, such as UV-blockers, so it can thrive outdoors.
Wood is a porous surface so it can absorb too much sealant, it’s advised to apply 1-2 coats of paint (or primer) to prevent over-absorption.
For trims, use 2 layers of polyurethane. This is because baseboard trims are usually positioned at the base of the walls and aren’t affected by high traffic or other elements. So, they don’t need much protection.
For exterior walls, apply as much polyurethane as you can without ruining the finish. Usually, you’ll need 4-5 coats of exterior polyurethane.
For stains, apply 3 layers of polyurethane. That’s because stairs are exposed to high-traffic and need a lot of protection. Always ensure to sand and prime before applying the sealant. That’s because stairs are usually riddled with dust and debris, so you must remove them before sealing.
You should apply 2-3 layers of polyurethane on pine walls.
You should apply at least 3 layers of water-based polyurethane on a table.
Things To Know
If you apply just one coat, the finish won’t be as durable. This won’t be as noticeable if you apply it on a decorative surface, but if you apply it on a high-traffic surface, the surface underneath will be exposed to different elements.
Sand Between Coats
You don’t have to sand between coats of polyurethane, but it’s recommended to. If you do, the next layer will stick better and the overall finish will be more durable.
2 vs . 3 Coats
For low-traffic surfaces, apply 2 layers of the sealant. And, for high-traffic surfaces apply 3 layers of the sealant.
Varathane comes in two types; oil-based and water-based polyurethane. You should apply more than 2 coats of oil-based varathane and more than 4 coats of water-based varathane,
In summary, the number of layers of polyurethane depends on the surface and how much it is used. For high-traffic surfaces, apply 3-5 coats while for low-traffic surfaces apply 2 coats.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,