Can You Put Polyurethane Over Latex Paint?

After painting your outdoor furniture or fence, you may notice the effects of the elements setting it. When that happens, how do you curb such natural effects? You give it a protective coating, such as adding a sealant or varnish. 

These are the two most popular finishes for protecting outdoor painting projects. But there are similar options, like Polyurethane. So, can you apply a polyurethane finish over latex paint? 

Absolutely. And we will show you how to achieve that in today’s post. If you don’t know what Polyurethane is, we will give you a detailed definition, the types of poly you can paint over latex, and pro tips to ensure an excellent job. Keep reading.

What Is Polyurethane, And How Does It Work?

Polyurethane is a plastic polymer used to make different objects, such as foam sponges, gaskets, spandex, and finishing formulas. Polyurethane finishes are clear sealants or coats used to seal or protect a painted surface and enhance its overall look. 

You can apply polyurethane on your furniture, fence, staircase, or any surface and material. For outdoor items like furniture and fences, poly helps protect against corrosion and weather effects. 

In addition, sanding your polyurethane between coats during application ensures the surface is water-resistant, and the paint lasts longer. Adding a poly finish to your painting job ensures the surface does not retain mud, fungus, mold, and mildew. 

What Types of Polyurethane for latex paint?

There are several different types of polyurethane, but the most commonly used on latex paint include: 

Water-based Polyurethane 

Water-based polyurethane is the most popular choice of poly sealant and the most preferred by artists and professionals. It is an easy-to-use sealant with zero odor, limited toxicity, and fast-drying properties. You can easily clean it up with water, which is eco-friendly. 

Solvent-based Polyurethane

Solvent-based polyurethane also dries faster and provides long-lasting finishes. However, it is not as eco-friendly as water-based polyurethane, and due to its high toxicity levels, it’s not as popular though you can use it on latex. 

Oil-based Polyurethane 

Our third option for poly finishes on latex paint is oil-based polyurethane. This is the oldest type of poly sealant ever invented and the most durable. 

It creates thicker protective coats, which ensure superior protection and longevity. It also gives the surface an attractive amber tint, unlike other types of finishes. 

Why Use Polyurethane Over Latex Paint?

Applying polyurethane over latex paint or any other type of paint comes with a few advantages. Some of them include: 

• Enhanced protection: A few layers of water-based polyurethane over latex paint will give your paint job additional protection than if you added no sealant to the top coat. This is advantageous if you wish to retain the surface aesthetics in high-traffic areas, which easily get worn out. 

• Improve the hue of your colors: Poly finishes, especially oil-based polyurethane, tend to create a unique amber tint. If painting darker colors, using oil polyurethane over your latex paint will make the colors stand out boldly and improve your furniture’s aesthetics. 

• Shield against the elements: Did you know that adding a few layers of clear coats on your outdoor painting project can protect your items from extreme natural elements for up to 10 years? And which better sealant to use than polyurethane which can last for as long as 20 years? 

When to Paint Polyurethane Over Latex Paint?

As mentioned above, you can add a polyurethane finish over latex paint if the paint has been left to cure for at least 24 hours. 

The reason you should wait for this long is to ensure that the paint looks professional and that it creates an effective, protective coating. This is not possible with uncured or wet paint. 

Once the paint has dried and cured within the recommended time, it’s imperative that you seal it with polyurethane before using the model to protect it from dings, scratches, and other surface damages.

If you don’t apply poly on the top coat and it develops some defects, ensure you fix them before applying the sealant. 

The bottom line is, if you want your latex-painted surface to retain its beautiful look and serve you longer, let it cure, then seal it up with a high-quality polyurethane. 

How Long Should Paint Dry Before Applying Polyurethane?

It’s always a good idea to follow the instructions on the product label. Different types of polyurethane contain different ingredients, and the manufacturer will have specific instructions on using the product. 

Let the latex paint dry fully for up to four hours, even if it’s a fast-drying brand. Note that this is just the recommended time for the paint to dry to touch. 

After 24 hours, you can add a poly sealant to the latex with a sprayer. But if using a paintbrush, give it 48 hours to cure before using a natural bristle brush to paint. Otherwise, you may create uneven brush marks on the surface if it’s half-dry. 

However, it’s best to spray polyurethane over latex paint. When spraying, you’re not touching the surface and will not cause any damage. 

We recommend letting the item cure fully for 2-3 days. This is especially recommended for water-based polyurethane, but oil-based options could take longer. 

Remember that the temperature levels influence the drying process, so your paint may dry faster than the recommended time or take longer than normal. 

Finally, some paints can take as long as 30 days to cure and the same is true with other specific types of polyurethane. 

How to Apply Polyurethane Over Latex Paint 

To apply polyurethane over latex paint, you’ll need to get all the tools and supplies in one place. Some of the items you’ll need include: 

• Safety goggles.
• Rubber gloves.
• Water.
• Sponge.
• Water-based polyurethane.
• Oil-based polyurethane.
• Trisodium phosphate (TSP).
• Tack cloth and lint-free cloth.
• 120-grit sandpaper.
• 220-grit sandpaper and palm sander.
• The poly applicator of your choice.

Step 1: Let the paint dry

Remember we mentioned that you can’t add polyurethane over wet latex paint as that would create a mess and ruin everything. It’s best to wait for the paint to dry and cure; then, you can seal it. 

Step 2: Clean the surface

Once the surface dries, clean it thoroughly to ensure no surface pollutants. Use a mild detergent or trisodium phosphate to clean it. We recommend TSP for older coats of latex paint and mild detergent for new applications. 

Step 3: Sanding 

When you get to this step, you should protect yourself by wearing safety goggles and rubber gloves. If the surface has scratches or bumps, lightly sand them with 120-grit sandpaper. If this doesn’t achieve the desired finish, use a palm sander.

Further read on sanding: Can you sand Latex paint?

Step 4: More cleaning 

Sanding generates dust, and using a shop vac can help by sucking it up. With that done, finish it with a new round of cleaning, but for this step, wipe the surface with a clean damp tack cloth, then let it dry. 

Step 5: Choose a suitable polyurethane coating

With the surface well prepared, it’s best to choose the most suitable Polyurethane that will work best on your project. 

For exterior surfaces, use oil-based polyurethane to ensure better protection against weather, temperature fluctuations, and other elements of wear and tear. 

Again, the light amber tint synonymous with oil-based polyurethane will accentuate the surface color hues, creating an overall glossy finish. 

That means oil poly isn’t the best choice for white latex paint, as it will leave a yellow tinge. Instead, use this type of poly on darker or natural colors. 

If it’s an outdoor project, use water-based polyurethane, which is less resilient to the elements than oil-based options. 

Water-based poly is also translucent and light colors will respond to it more positively without annoying yellow tints. It’s the best choice for preserving the natural grain in wood substrates and it also dries faster. 

Step 6: Apply Polyurethane

We recommend using a paint sprayer, preferably a gun or aerosol can. Apply 2-4 coats of polyurethane, and if you deem it necessary, sand between each coat with a 300-grit sanding sponge to create a smooth, shiny finish.  

Step 7: Apply a second coat

A single polyurethane sealant coat is insufficient to provide the necessary protective coating. Once the first coat dries, spray the subsequent coats until you achieve the best level of smoothness. A maximum of five coats of poly is advisable, especially if using a water-based option. 

Step 8: Leave to dry 

After applying the desired number of coats, let the poly dry overnight, then check it out in the morning. Letting the coats dry overnight is recommended to ensure it fully hardens since poly can take several weeks to cure.

How Many Coats of Polyurethane for Latex Paint?

Regarding the number of polyurethane coats, you can add over latex paint, you’ll need to use your best judgment depending on the paint you use. 

For oil-based poly, 2-3 coats are enough since this option tends to be thicker and more robust. For water-based options, 4-5 coats are ideal. 

However, if you believe the surface will be prone to dents and scratches, consider adding several coats of poly, whether oil- or water-based. 

Can You Put Water-based Polyurethane Over Latex Paint?

Traditionally, oil-based polyurethane was more durable and robust than water-based polyurethane. 

However, there has been significant improvement in the development of water-based polyurethane sealants, and some brands have higher quality than others. 

Using water-based flooring polyurethane on hardwood floors painted with latex is possible, and you’ll have the same durability as oil poly. 

Water-based polyurethane also dries faster within two hours, so you can recoat within the shortest time possible. 

In addition, some brands are known to partially cure in 2-3 days, meaning you can expect to lightly use your items within four days after painting and sealing. 

Finally, water-based polyurethane over latex is preferable since it’s easy to clean with water and soap.  

Can you put oil-based Polyurethane over latex paint?

Yes, you can use oil or water poly on latex paint; it depends on your preferences and end goals. If painting natural or stained wood, use oil poly since the amber hue will highlight its tint, retaining its original wood grain stain. 

The poly will take 6-24 hours to dry but can take up to 21 days to cure. Since this product is usually thick, you can lightly thin it with a paint thinner, but once it cures, it provides superior protection. 

Can you mix Polyurethane with latex paint?

Yes, mixing latex with polyurethane is possible and highly recommended. We’re talking of adding just a few drops of poly into the paint, nothing more than that. 

It’s a trick you can employ to prevent a cloudy finish in the outcome, especially if working with darker paint. 

Again we recommend water-based Polyurethane because it has a common solvent with latex: water. This means compatibility is not an issue. 

As a clear coat with little to no tint, water-based polyurethane helps bring out the color tint of latex paint. The outcome will have the durability of polyurethane and the color hue of latex paint. 

To get the best of both worlds, mix a few drops of poly and latex paint, then, after painting, add several more layers of the sealant. 

However, avoid mixing exterior polyurethane with latex paint. The oil and water solvents in the two products do not mix, so the finish will not adhere properly or dry optimally. 

Tips for applying Polyurethane over latex paint

Now that the concept of spray painting polyurethane over latex painted surface is more straightforward, here are a few more tips to ensure you get the best results with each project you undertake: 

1. Ensure the latex paint is thoroughly cured before coating it with poly. Three to four weeks is enough time for the paint to be coated. 

2. Apply as many coats of polyurethane as possible. More coats mean better protection and durability. 2-4 coats are recommended for oil poly, while 4-5 coats are best for water-based polyurethane. 

3. Let each coat dry adequately before recoating

4. Only spray paint polyurethane in optimal weather. Low humidity levels will compromise the drying process.

5. Working with clear polyurethane options prevents discoloration of the base latex coat.  

6. Handle with care. Polyurethane is a high gloss paint formula that makes surfaces slippery. Avoid using it in sensitive areas where it could pose a safety risk especially to children.  

FAQS: Painting Polyurethane over paint

Can I put a clear coat over latex paint?

A clear coat over latex paint is recommended to make the colors stand out. It’s also a great way to ensure your painted surface retains a glossy finish that’s both smooth and appealing. The common clear coats you can add to your latex include vanish, lacquer, and polyurethane. Since latex is water-based paint, use a water-based clear coat for better compatibility. 

What happens if you put polyurethane on paint?

Putting water-based polyurethane on latex paint will highlight the colors. But it depends on the type of poly used. Oil-based poly will leave an amber tint on lighter colors causing yellowing, so it’s best used on darker shades. However, water-based paint is clearer and accentuates the paint, so you should use it on light or white colors. 

Can you put urethane over paint?

Yes. Urethane is a great sealing product perfect for protecting outdoor furniture and woodwork. To use this sealant, ensure the paint is dry and cured to enable the urethane protect both the substrate and the paint from U.V. lights. This sealant also helps prevent the paint finish from developing a cloudy appearance. For best results, apply thin coats of urethane. 

Can you use water-based Polyurethane over oil-based paint?

Yes, it’s possible to coat oil-based paints with water-based polyurethane. However, the oil paint must be dry. Since oil-based paints have different drying times, it should be at least two months before you can seal it with poly. If you apply poly on uncured oil paint, it will not dry adequately, affecting the outcome. 

What kind of Polyurethane to use over latex paint?

You can use either water-based polyurethane or oil-based polyurethane. Both options are compatible with latex paint and will adhere perfectly. In addition, both have durable, high-quality properties that will create beautiful color outcomes depending on your design goals. Use oil-based polyurethane on darker latex paint to prevent yellowing and water-based poly on whiter colors to retain the natural look of your material. 

Can I put Polyurethane over water-based paint?

Absolutely. Polyurethane is flexible and versatile, so you can use it on any substrate, especially if it’s painted with water-based paint. Paints like latex and acrylic look better with a clear coat finish or sealant, and polyurethane is one of the best options. Whether you choose oil-based or water-based poly, both are compatible with water-based paint like latex, so you can paint without issues. 

Can you use a roller to apply Polyurethane?

Yes, although it’s not recommended. When applying a clear coat like polyurethane on a top coat, you want to ensure a perfectly smooth finish without dents or nicks. Spraying will give you better results than applying with a roller or brush. However, rolling is best suited for larger surfaces like walls and ceilings, but spraying is more efficient and effective for small furniture pieces and models. 

Final Thoughts? Can I use Polyurethane on Latex Paint?

At the beginning of this article, we promised to answer your question: can you add polyurethane to latex paint? Now you know you can use this unique sealant on your painted surface. 

You also know which specific polyurethanes work best with latex paint, so you can confidently use it on your art projects or DIY home renovations to make your work aesthetically appealing and durable. 

In addition, you can add polyurethane to countertops and even raw, unpainted surfaces to make them more attractive. Working with polyurethane will give you a broader perspective on how clear sealants work and which materials to use.