The more you learn about polyurethane, the more you find yourself asking – why can’t it be more like paint?
Or at least that’s how I felt when I first started. Everything about it seemed so complicated. Now, applying polyurethane is second nature to me, and I’m here to make it easier for you too.
In this article, you will learn:
- How many coats of polyurethane you should apply for different jobs
- Why you often need more than one coat
- If and how you should use one coat of polyurethane
- How long to wait between coats
So, first things first.
How Many Coats of Polyurethane Should I Apply?
For best results, apply at least two coats of polyurethane. When working on floors, tables, chairs, and furniture that will be used often, apply at least three coats. If you are using water-based polyurethane, you can apply up to four or five coats on floors and sheds.
If you’re looking to prime before painting, you can also learn how many coats of primer do you need on wood before proceeding.
Now, let’s get into the action.
What Is Polyurethane Coating?
Polyurethane is a coating type that can be either oil-based or water-based. Out of these two categories, oil-based polyurethane has been around for the longest time. Water-based has only just recently been developed. Polyurethane coating mixes polyurethane resin with alkyd resin in order to create the varnish formula that we are accustomed to.
Pretty much any varnish on the market, specifically the oil-type, has alkyd in its formula. By adding polyurethane resin in the mix as well, the coating obtains higher durability. This makes polyurethane coating heat-resistant, scratch-resistant, and water-resistant as well.
Water-based polyurethane also features polyurethane resin, but rather than mixing alkyd resin, it uses acrylic resin instead. The coating has a different formula, so it may have different levels of resistance – but at the same time, it has multiple comfort benefits. However, both have the same level of quality if chosen for the right purpose.
Water-Based vs. Oil-Based Polyurethane Coating
Water-based and oil-based polyurethane coatings have different purposes, based on your needs. It is essential that you understand the differences between the two so that you know exactly how to apply them.
– Oil-Based Polyurethane Coating
Oil-based polyurethane coating is a classic option that has been around for a long time. Not only is it strong and resistant to damage, but once it has cured, it can also resist all kinds of influences.
This type of polyurethane coating leaves a thicker layer, which may significantly influence the number of coats you will need. It also gets a very slight amber-like hue once it’s dried, which can add a bit of warmth to wood objects.
Due to its thicker formula, oil-based polyurethane takes a bit more to dry. So, it might not be a suitable choice when you are trying to get the project done fast. Also, it has higher VOC levels, which means the odor is stronger as well. It is mostly recommended to be used in properly ventilated areas.
– Water-Based Polyurethane Coating
Strong odors are not everyone’s cup of tea. This is where water-based polyurethane coating comes in, as it is a more environmentally friendly option. Releasing fewer VOC levels, not only is it better for the overall environment but is also a safer choice for your health.
The formula for water-based polyurethane is not as thick as with the oil-based kind, so usually, it dries a lot faster. On average, it takes about 6 to 12 hours for the surface to be ready – which is half the time you need for oil-based polyurethane coating.
With that in mind, the formula may not be as durable and may cause slight raises in the wood grain. As a result of this phenomenon, you will likely need more sanding and extra coats to cover that lift.
Water-based polyurethane applies in thinner layers, which means that it is less likely to drip. This makes the application much easier to handle even by beginner DIY painters.
Is One Coat of Polyurethane Enough?
Like I mentioned earlier, applying polyurethane can be a tricky affair. Different problems tend to arise after the first coat, such as brush marks (or lint when using a roller), dust nibs, and bubbles. As much as the flattening agents in polyurethane are meant to level out bubbles and brush marks, it rarely works on the first coat.
If these problems occur, you need to sand out the imperfections and then apply at least one more coat. After you apply the second coat, you will notice that the surface is smoother and has fewer imperfections.
If there are still bubbles or the wood doesn’t look glossy enough, then you need to learn how to apply polyurethane without bubbles.
Applying a third (and usually final) coat of polyurethane will do the trick. This will yield an excellent finish and will protect your wood from the elements for years.
Are 4 Coats of Polyurethane too Much?
In most circumstances, you only need three coats of oil-based polyurethane. You can use four or five coats of water-based polyurethane for hardwood floors, especially those that will see a lot of traffic or a lot of moisture. For all other projects, manufacturers usually recommend three coats, even for water-based applications.
When you are reviving old furniture that already has a finish on it, you won’t need more than two coats. However, if you sanded the old piece down to the stain, then you would need at least three coats of water-based polyurethane.
Whatever you are working on, you won’t go wrong with applying four coats of polyurethane. The only downside is that the project will take longer to complete, and it will cost more.
Actual Number of Coats for 11 Popular Polyurethane
The number of coats varies by brand and type of polyurethane. There are three main types: oil-based, water-based, water-based oil-modified formulations.
Below is a table depicting the actual polyurethane coats for several popular brands so you can have a rough idea of how many coats to apply.
|Product||Number of coats||Hours between coats||Best for|
|Minwax Wipe-On Poly||Three||2 to 3||Carved or profiled surfaces|
|Minwax Stain-and-Poly Combo||Two||6||Furniture, cabinets, trim|
|Minwax High-build||Two||4 to 6||Tabletops|
|Minwax Fast Drying||2 to 3||4 to 6||Cabinets, floors, furniture|
|Minwax Polycrylic||Three||2||Light-colored woods|
|Water-based oil-modified||Three||2||Doors, cabinets, furniture|
|Oil based Spar urethane||Three||4||Exterior doors, trim|
|Water-based spar urethane||Four||2||Doors, trim, and furniture|
Is One-Coat Polyurethane Good?
Due to the long drying time of polyurethane, a few manufacturers have been trying to come up with quicker and easier solutions. An increasingly popular alternative is a product called one coat polyurethane.
Just as the name implies, you only need one coat to get an excellent-looking finish on any wooden object. Or at least, that is what they say. Another name it goes by is triple-thick polyurethane. These products are usually water-based.
The one coat or triple thick poly is noticeably thicker than oil-based polyurethane. As a result, it is more difficult to apply, and I am yet to meet any professional who would rather use this than go through the hassle of applying other coats three times.
The main reason is it is near impossible to get a smooth finish with just one application of one coat. As it does not level out as it dries, you will see a lot of brush marks on the one coat. You, therefore, need to sand it and apply a second coat before it becomes smooth.
Ironically, you might still need a third coat of the so-called one-coat poly. For a product that costs more, it really isn’t worth the trouble.
The one instance where I recommend the one coat is when you are building something that does not need to be aesthetically pleasing. Shelves in your garage, for example, or children’s toys built for destruction.
One coat is quite durable and can withstand more abuse than regular poly, making it ideal for these types of construction.
Number of Polyurethane Coats By Surface
– How Many Coats of Polyurethane on Wood countertops?
You need at least two coats of polyurethane on wood countertops. If this is a surface that is going to be used a lot, then apply a third coat. If you are using water-based polyurethane and it raises the grain of the wood, you may need more than three coats.
– How Many Coats of Polyurethane on Kitchen Table?
You should use at least three coats of polyurethane on a kitchen table. Just like floors, kitchen tables will go through a lot of abuse – liquid spillage, cutlery constantly scratching and pots banging -, so it needs more protection. With three coats, you won’t need to refinish the table anytime soon.
– How Many Coats of Water-based Polyurethane on Hardwood Floors?
Most manufacturers recommend three to four coats of water-based polyurethane on hardwood floors. You’ll only need more coats if you’re using a water-based finish not made for floors, or you overdiluted the poly. However, if you haven’t gotten a smooth finish by the fourth application, sand it over and apply another coat. Keep going until you get the desired result.
– How Many Coats of Polyurethane on Stairs?
Stairs are high-traffic areas, so you should apply at least three coats of polyurethane. The same is true for water-based and oil-based poly alike. If you applied a sealer coat, you may only need two coats of water-based polyurethane., but as always, keep going until you get a smooth finish.
How Do I Apply the Polyurethane Coating?
Applying a polyurethane coating is quite simple, as long as you follow the right steps. Here is what you’ll have to do:
Step 1: Prepare the Surface
Whether it’s an item, a cabinet, or the floor, the surface needs to be completely clean before you apply the polyurethane. If dust or debris remains, it will create lumps under the polyurethane.
Step 2: Stir the Formula Gently
The polyurethane may have arrived prepared, but some compounds may have separated while it stood in the can. Before you apply, make sure to gently stir everything together so that the mix is smooth. A clean paint stick should do the trick just fine.
Step 3: Apply the First Coat
Use a stiff brush to apply the first polyurethane layer. This layer doesn’t have to be particularly thinned out, as it allows the polyurethane to adhere properly to the wood. Only thin it out if the surface was already coated with polyurethane before.
Step 4: Allow Drying Time
Even if the polyurethane boasts a 30-minute drying time, allow at least 6-12 hours for water-based polyurethane and 24-36 hours for oil-based polyurethane. Once this time passes, you may proceed with the next step.
Step 5: Sand the Surface
Once the first layer of polyurethane has dried, take some light grit sandpaper and begin sanding the surface. Do it gently; you don’t want to take off the whole layer of polyurethane after just applying it. Make sure that you clean the surface properly after sanding it and that you do not leave any stray dust or debris behind. Use a lint-free cloth to gently wipe everything away.
Step 6: Apply the Second Coat
With the first layer of polyurethane having dried and sanded, it is time you proceed with the second layer. You don’t necessarily have to sand if you must apply more than two coats. Starting with the second coat, keep the layers thin.
Tips for Applying Polyurethane
When applying the polyurethane coating, you must be very careful about the procedure. Here are some tips that you’ll want to keep in mind:
- Stir the mix rather than shaking it.When you shake the polyurethane mix, there’s a good chance that bubbles will form. Stirring will prevent that from happening.
- Use a synthetic brush to apply water-based polyurethane coating. Check out the best roller for polyurethane if you’re looking to roll on polyurethane.
- Apply a thin coat if you want to prevent dripping. You can always add another layer once it dries. For thin coats, use sprayers or wipes.
- If you are short on time, thinning the layers will also work. The thinner the layer, the faster it will dry.
- Don’t thin out the formula if it’s the first layer. The first polyurethane layer should be slightly thicker, as it needs to stick to the wood and create an even surface to work with.
- If you decide to use a brush in order to apply oil-based polyurethane, make sure that you use a high-quality brush. If you use a low-quality one, you may end up with streaks and/or bubbles.
- Don’t wipe the brush on the edge of the can. If you want to get rid of excess polyurethane, simply tap the brush over the container. This will prevent the formation of bubbles.
- Brush the polyurethane along with the wood grain so that it seeps into the pores. This will give you an even surface.
- When applying polyurethane, keep the brush into a solvent, such as water or mineral spirit. This will make it easier for you to clean the brush when you are done.
- When sanding between polyurethane coats, use fine-grit sandpaper. This way, you can be certain that there won’t be any awkward streaks underneath the final layer.
- Never apply a new layer of polyurethane on surfaces that are not completely dry. Not only will this lead to streaks, but it might also cause drips to occur. Only apply once it has dried completely.
Prepping the wood before applying the polyurethane is essential. However, if you follow the tips above, it should be fairly easy for you to apply the polyurethane without any issues. Pay attention to your technique, and the final surface should be streak-free, drip-free, and bubble-free.
Can I thin Polyurethane?
Yes, you can thin polyurethane. As a matter of fact, thinning polyurethane makes it easier to use. This is because the poly levels better, so brush marks disappear better.
You may also choose not to thin polyurethane, especially water-based polyurethane. Some people say thinning helps the poly bond better, but that isn’t true. The most significant benefit is that it dries quicker, thus reducing the time between sanding and reapplication.
How Should I Thin the Different Types of Polyurethane?
The best product for thinning oil-based polyurethane is mineral spirits, while water should be used for water-based polyurethane. However, as mentioned earlier, you can do without thinning water-based finishes.
Another alternative for thinning oil-based polyurethane is paint thinner. Paint thinner is technically mineral spirit, but it has more impurities, so it should only be used if you can’t find mineral spirits.
Naptha is another mineral spirit you can use, but it is highly flammable.
How Long Should I Wait Between Coats of Polyurethane?
You can apply the next coat of water-based polyurethane, usually within 2-6 hours. Despite the instructions by some manufacturers, you should wait for at least 24 hours when using oil-based polyurethane.
However, you can apply another coat of fast-drying oil-based polyurethane within 4 to 6 hours. One factor that determines the wait time is if and how you have thinned the product. Thinning significantly reduces the wait time, but try not to overdo it, or you’ll end up needing more coats.
Can You Apply the Second Coat of Polyurethane Without Sanding?
Even if you use a water-based polyurethane coating that is on the self-leveling side, applying a second coat without sanding is not a very good idea. Read what happens if you don’t sand between coats of polyurethane to learn more.
Once you apply the second coat, it will look unsightly and far from flawless and smooth. Also, it doesn’t make the polyurethane last for a longer time. If you sand the surface, not only do you prevent any drips and runs, but you also ensure the final coat will look even and smooth.
How Quickly Should the Coats of Polyurethane Dry?
This depends on the polyurethane coating that you use. If you are using water-based polyurethane coating, then the whole thing should be dry in about 6 hours. However, oil-based polyurethane can take as long as 24 hours to dry. Factors such as ventilation, humidity, temperature, and thickness of the layer may also influence how quickly they should dry.
Do I Need to Sand the Final Coat of Polyurethane?
While there is no problem with sanding the first coat (in fact, it is actually recommended), sanding the final coat of polyurethane isn’t a good idea. Instead, try spraying it or layering it as smoothly and evenly as possible. The final layer will be the base that remains visible, so sanding it might just ruin the whole look.
Can You Add Too Many Coats of Polyurethane?
With everything, there is such a thing as too much. Remember that the more coats you add, the longer it may take to dry. Four coats may be fine in certain circumstances, but more than that can be problematic. There is indeed a chance that it will look fine – but at the same time, it might peel or turn yellow. Three coats of polyurethane should be more than enough.
How Many Coats of Polyurethane For Your Next Project?
No matter how tricky it might seem to use polyurethane, its advantages outweigh any disadvantages. It may take some getting used to, but it is a skill worth mastering for personal and professional reasons.
Now that you know how many coats of polyurethane you need on your project, it’s important to get the timing right. Check out our quick response on How Long to Wait Between Coats of Polyurethane?