When it comes to sealants like polyurethane, 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 average, 3 coats of polyurethane are needed to seal and protect a surface.
On materials that do not require much protection like room decor, you can apply two light coats of polyurethane. On materials that would be used heavily like chairs, tables, and desks, you should apply 3 light coats of polyurethane.
On materials that would be walked on like patios, walkways, and floors, it’s advised to apply 3 coats of polyurethane.
You can apply more coats of water-based polyurethane than oil-based polyurethane. Also, you should never apply just one coat of polyurethane, why? Let’s find out.
Why Does The Number Of Coats Matter For Polyurethane?
The number of coats matters for polyurethane because polyurethane is a clear sealant. Polyurethane by design is meant to produce a clear and glossy top film when it dries. If you apply more coats of polyurethane than needed, it can affect the clarity of the finish.
The number of coats also matters for polyurethane because the finish is designed to be strong, durable, moisture, and chip-resistant. If you apply less than the required coats of polyurethane, the finish will not be as strong or moisture-resistant as it should be.
Polyurethane is a tough plastic finish meant to protect the material it is used on. A coat of polyurethane on your wood will protect it from scratches, dents, and moisture. But your wood doesn’t get any of this protection unless you apply the right number of coats. Too many coats and the polyurethane will easily turn yellow. This is common with oil-based polyurethane.
Also, less than the required number of coats and the polyurethane will not be as strong or water-resistant as it should be.
Oil-Based Polyurethane: Number of Coats
You need 2 or 3 coats of oil-based polyurethane on the material. On wood, you don’t need more than 2 coats unless you are painting over a surface to be walked on or an item to be used frequently. Chairs, tables, desks, walkways, and patios all require 3 coats of polyurethane.
Oil-based polyurethane is water-resistant and durable. So if you are applying it over an item that won’t see much use, you should apply just two coats of oil-based polyurethane. If you want to paint an item that would be used frequently or one that would be walked on, 3 coats of polyurethane are needed.
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 of oil-baed polyurethane isn’t recommended because it increase 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 in the paint coating if there is enough of it. So if you apply more than the required number of coats of oil-based poly, the oily deposits will increase and your finish can start to yellow in a few months.
Also, if you apply less than the required number of coats, the oil-based polyurethane will not be very durable. Unless there is a sealant under the polyurethane.
Water-Based Polyurethane: Number of Coats
You need 2-5 coats of water-based polyurethane. On average, 3 coats of water-based polyurethane are advised for surfaces that wouldn’t see much use like room decor. On surfaces that would be used heavily or be walked on, you can apply up to 5 coats of water-based polyurethane.
The reason you can apply more coats of water-based polyurethane than oil-based polyurethane is because of the solvent. With water-based polyurethane, there is no oily deposit being left behind as the paint dries. So the chances of the polyurethane yellowing over time are reduced.
You shouldn’t apply more than 5 coats of water-based polyurethane because it increases the chances of the finish becoming cloudy. Plus, Applying polyurethane can be time-consuming due to the required time to wait between coats. So if you want to apply more than 5 coats of water-based polyurethane, it will take longer to finish applying the paint.
Asides from that, it will also take longer for the paint to dry and cure. The longer the polyurethane 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.
The reason you can apply more coats of water-based poly is because there are no oily deposits left behind as water-based polyurethane dries so the finish is less likely to turn yellow with more coats. As you already know, this is not the case with oil-based polyurethane.
Dry Time Between Coats Of Polyurethane
You should wait until the existing polyurethane coating dries before applying another coat. It takes between 4 and 24 hours for polyurethane to dry between coats. You can re-coat water-based polyurethane in less than 12 hours. Oil-based polyurethane can take up to 24 hours to dry enough for re-coat.
If you don’t leave enough dry time between coats of polyurethane, the finish will not dry properly. The paint will remain sticky for several days and when dry, it will not be as clear as it should be. Water-based polyurethane can turn cloudy while oil-based polyurethane will seem dirty.
The solvent or thinner in the polyurethane needs to be completely evaporated before you can re-coat polyurethane. If the solvent remains in the paint coating while you lay another coat, the solvent will become trapped in the polyurethane. Since the solvent can’t evaporate after you primed and sealed the material, it will begin to bleed through to the top layer of the polyurethane.
If it’s a water-based polyurethane, the solvent or water that bleeds through will make the finish cloudy. If it’s oil-based polyurethane, the solvent or oils will stain the clean polyurethane. So always wait for the right time before re-coating polyurethane.
How Many Polyurethane Coats For Different Surfaces?
Let’s check out common surfaces polyurethane is used on and how many coats you need for each.
For floors, you need 3 coats of oil-based polyurethane and 5 coats of water-based polyurethane. However, you can get away with only 3 coats of water-based polyurethane too. But, don’t apply more than 4 coats of oil-based polyurethane.
For low-traffic floors like the bedroom floor, you can apply 2 coats of polyurethane. This is because these floors don’t see much foot traffic. Also, high heels and other footwear aren’t used in the bedroom so there are fewer chances of a dent or hole in the polyurethane.
For indoor wood, you can go with 2 coats of polyurethane since the wooden surface wouldn’t be exposed to the elements. For outdoor wood, you need 3-4 coats of polyurethane since the wooden surface would be exposed to the elements.
Rainfall, UV rays, light, and dust will affect the polyurethane if used on outdoor wood, so you need enough weather resistance. Always go for exterior or outdoor polyurethane if you want to paint on wood outdoors.
Exterior polyurethane is formulated with the best weather resistance qualities. The coating also contains additives like UV blockers so it can thrive in harsh exterior environments.
If you are painting on decorative wood like wall frames, 2 coats of polyurethane is enough. For chairs, desks, and other surfaces that will see heavy use, you need at least 3 coats of polyurethane.
Wood is porous and can suck polyurethane making you require additional coats. So before applying the polyurethane, you apply 1-2 coats of primer.
For kitchen cabinets, 3 or 4 coats of polyurethane are enough. You need more coats on the kitchen cabinet because the cabinets aren’t only affected by touch or the weather but also by the heat in the kitchen.
Heat can also damage wood, so you need enough protection on the wood. Accompanied by the heat in the kitchen is steam, which is a source of moisture on the kitchen cabinets. So you need enough water resistance as well.
For trims, you can go with 3 coats of polyurethane. This is because baseboard trims are usually positioned at the base of the walls.
That means it’s closer to the floors and can also be affected by footprints, dust, and weight so enough protection is required.
For exterior walls, you should apply as much polyurethane as you can without ruining the finish. Usually, you’ll need 4 coats of exterior oil-based polyurethane. Or, 5 coats of exterior water-based polyurethane on exterior wood.
You should go for exterior polyurethane when picking a choice for exterior surfaces. Exterior polyurethane is formulated with UV blockers and special additives to help the finish thrive under the harsh exterior environment.
Interior polyurethane doesn’t have these additives. So, even if you apply 6 coats of interior polyurethane, the finish will not last long outdoors.
You need at least 3 coats of polyurethane on the stairs. This is because stairs are high-traffic areas. The stairway will see a lot of running, stamping, and pointed heels. So you need enough protection.
Always ensure to sand and prime before applying polyurethane, especially on already used stairs. This is because stairs are usually packed with dust, debris, and dents that need to be removed before painting.
You should apply 2-3 coats of polyurethane on pine walls. You have to wait until the polyurethane dries properly before you add the next coat. If you don’t wait, the polyurethane will peel off.
You should apply at least 3 coats of polyurethane on a table. It’s recommended to use water-based polyurethane for a table because water-based polyurethane is more suited for indoor use. You should sand between coats of polyurethane when applying over a table to allow the polyurethane to stick better.
What Happens If You Apply Too Many Coats of Polyurethane?
When you put too many coats of polyurethane on a material, you risk getting a poor finish. First, too many coats mean the paint will take too long to dry. Too long to dry means the paint will accumulate dust and debris. It also means the paint will be vulnerable to stains and grease.
Asides from that, too many coats will affect the clarity of the paint. Polyurethane is popular for its clear finish. Too many coats and the finish will either appear cloudy or stained. Oil-based polyurethane can turn yellow if you add too many coats.
If you add too many coats of polyurethane, then you will up with uneven layers. To avoid this, you should sand between coats.
What Happens If You Put Only One Coat Of Polyurethane?
When you put just one coat of polyurethane on a material, you don’t get enough protection. This might not be a big deal if you applied the polyurethane on a surface that wouldn’t be used.
For instance, if you applied one coat of polyurethane over an old picture frame on the wall, it’s good enough since the frame wouldn’t be walked on or handled very much. So one coat is enough on such items.
However, if you apply one coat of polyurethane on a chair, table, or desk, the wood will be easily damaged. This is because these items are frequently used and one coat of polyurethane isn’t enough protection.
It’s even worse when you apply one coat of polyurethane on a walkway. The poly finish will last a year at best. So if you think about it, one coat of polyurethane is both a good and bad idea. It all depends on the surface to be painted.
Do You Have To Sand Between Coats of Polyurethane?
You don’t have to sand between coats of polyurethane, but it’s recommended to. If you sand between coats of polyurethane, the next layer of polyurethane will stick better and the overall finish will be more durable. The polyurethane will stick to the previous layer regardless, but sanding removes imperfections and helps the next coat stick better.
2 vs . 3 Coats of Polyurethane
Should you use 2 or 3 coats of polyurethane? You should use 2 coats of polyurethane if you are applying it over a low-traffic surface. If you are applying polyurethane over a picture frame, or bedroom drawers then 2 coats are enough,
You should apply 3 coats of polyurethane if you are sealing a high-traffic area surface such as kitchen cabinets, floors, or baseboard trims.
How Many Coats of Varathane?
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,
Overall, the number of coats required for polyurethane largely depends on the material or surface that you are painting. You can even use one coat and be fine.
However, remember not to apply more than 4 coats of oil-based polyurethane or 5 coats of water-based polyurethane. Unlike when you apply less, you can’t get away with applying too many coats regardless of the surface that you painted.