One of the tricks to keeping your painted wood in fantastic shape for an extended duration is knowing how to waterproof painted wood. It involves applying a clear topcoat over the paint to ward off water and other damaging elements that make paint deteriorate quickly.

Waterproofing painted wood is a simple practice, but some aspects confuse the DIY community, especially beginner painters. Some don’t know what products to use or the proper application techniques of the products. Therefore, I’m here to guide you on how to waterproof painted wood.

We waterproof painted wood by applying polyurethane, polycrylic, or wax over the paint after it cures. Wait for the last coat of paint to dry, clean it, then use 220-grit sandpaper to flatten the paint sheen. The sandpaper will also make the paint coat rough to improve the adhesion of the sealing top coat.

Apply the first layer of the topcoat, making sure it is thin to fasten drying and prevent peeling. Let it dry for the time recommended on the product label, then sand it before applying the second layer.

You can use more than two coats of the sealer but ensure that you sand between each coat to achieve the best finish results.

With the right approaches, you will not have to worry about your paint and more, your wooden structure as the waterproofing aspect help protect the surface against water for a foreseeable future.

This post aims to offer elaborate information about the waterproofing of painted wood. Keep reading for more insight and tips regarding the subject.

What Is Wood Paint?

Wood paint is a colored product that you apply on wooden surfaces such as furniture, small crafts, and home sidings. Its primary purpose is to keep moisture from penetrating wood fibers, causing the wood to swell, rot or grow mold over time.

On top of that, wood paint allows you to give your pieces a beautiful look with any color and sheen level you prefer.

Wood paint contains four essential ingredients in its formula – pigments, resin/binder, a solvent, and an additive. The pigment, binder, and additives are solids, while the solvent is the liquid ingredient that carries them.

• Pigments are finely ground particles that provide color to wood paint. They are insoluble, and they determine the thickness of paint depending on how much the manufacturers used in the formula. Moreover, pigments determine how well the product will perform when it comes to hiding imperfections on the surface – you will achieve better coverage if you use wood coatings with higher pigment percentages.
• The binder, aka resin, is the ingredient that holds the pigment particles together on the surface. It determines how well the paint will adhere to the wood and the sturdiness of the paint film. Resin also determines how well the paint product will retain gloss over time.
• Additives are the ingredients that add specialized functions to some wood paints. You can find some products equipped to resist UV rays better, while others will be more waterproof than others. 

Even though additives make up the smallest percentage of paint ingredients, all wood paints that have them are a bit more expensive than standard paints.

• The solvent is the liquid medium that carries all the other ingredients making them easy to move from the paint container to the surface. However, this ingredient evaporates over time; therefore, it plays no crucial role in the durability or beauty of wood paint.

You can use either a brush, a sprayer, or a roller to apply wood paint. Brushes work well when painting small wooden structures with intricate designs, while rollers are best for larger projects.

You can use spray wood paint for small or large projects, but the method wastes too much product, especially if you have never used it before.

What Is Wood Painting?

Wood painting refers to applying paint on wood to improve its lifespan and visual appeal. The paint coating you use will prevent moisture from reaching the wood, thus preventing moisture damage and mold growth.

Furthermore, there are several colors and sheen levels to choose from, allowing you to customize your wood pieces as you like.

The kind of paint you choose for wood painting depends on the location of your pieces, how much you use them, and the type of wood used to make them. For instance, you can use interior-grade wood paint on kitchen and bathroom cabinets.

However, bathroom cabinets will require indoor coatings with extra waterproofing abilities because they are constantly humid.

You can use water-based paints on most types of wood, but they won’t perform well on MDF. Furthermore, you cannot use interior wood paint on outdoor pieces because they will not stand up well to the harsh outdoor environment.

How to Waterproof Painted Wood 

Before we jump into the waterproofing procedure, it is essential to know that there are several products you can use to add moisture protection to painted wood. Manufacturers did not formulate these products equally; therefore, you need to understand how they work to achieve the best results.

There are three primary sealants perfect for use on painted wood – polyurethane, polycrylic, and paste wax. Below is a breakdown of each of them to help you choose one that will work best for your painted surface.

Polyurethane

Polyurethane is a synthetic oil-based product used widely to protect bare, stained, and painted wood from moisture damage. It also dries into a very sturdy protective coating that prevents the paint from developing scratches and dents that cause you to repaint often.

Polyurethane comes in liquid form, and you can use either a paintbrush or sprayer to apply it on painted wood. You can also use a roller to apply poly, but I do not recommend it because rollers tend to leave bubbles on the surface.

If you must use a roller, I recommend using a foam roller to reduce the chances of leaving bubbles on the wood.

Even though polyurethane is a robust paint sealer, it is highly flammable and emits toxic Volatile Organic Compounds while still wet.

You always have to wear protective gear such as goggles, a gas mask, and rubber gloves whenever you use polyurethane. Additionally, it is best to use them outdoors or in a well-ventilated indoor space.

Polyurethane takes the longest time to dry – it dries to the touch in 24 hours and needs up to a month to cure fully. Furthermore, cleaning painting tools after poly is quite challenging – you will need to use paint thinner or mineral spirits to make the task easier.

Note: Polyurethane yellows over time, so it is best to use it over dark paint colors instead of lighter ones.

How to Waterproof Painted Wood With Polyurethane

Here are the steps involved in waterproofing painted wood using polyurethane:

Step 1: Clean the Surface

Polyurethane will not adhere properly to dirty and greasy surfaces; therefore, you must clean the painted wood thoroughly before application.

If you’re waterproofing old paint, I recommend making a cleaning solution with ½ cup TSP and a bucket of warm water. If you applied the paint recently, use a mild surface cleaner and water to wash the paint film.

Step 2: Sand the Paint Surface

Use 220 grit sandpaper to knock down any high points on the film and flatten the sheen of the paint. Before applying polyurethane, you must perform this step to improve adhesion and reduce the chances of future peeling and bubbling.

Step 3: Remove the Paint Dust

Start by removing the sanding residue using a vacuum cleaner, then wipe the surface with a damp cloth for better cleaning. Ensure that you don’t leave any speck of paint dust on the surface, or it will ruin your polyurethane finish.

Allow the surface to dry after cleaning before moving on.

Step 4: Apply the Polyurethane

• Before applying polyurethane, ensure that you stir the product first. Stirring is essential because it will reduce the bubbles in the poly container to reduce the chances of transferring them to your painted surface. Make sure that you stir gently, or else you will re-introduce bubbles into the product.
• After stirring, dip a clean brush into the poly, then apply a thin coat on the wood. Ensure that you apply the sealant in one direction, overlapping each stroke to avoid leaving brush strokes in the finish.
• Next, allow the first coat to dry according to the manufacturer’s recommendation, then sand it. Use 220-grit sandpaper to make the surface a bit rough for the next coat to grip correctly. Sanding also eliminates dust nibs, scratches, and brush marks to make the finish uniform.
• Clean the sanding residue like before, allow the surface to dry, then apply the final coat of polyurethane.

Polycrylic

Polycrylic is a water-based finish coat that holds up well to abuse but is not as durable as polyurethane. You can quickly apply it with a paint sprayer or a paintbrush, and tool clean-up is also simple because you only require water to do it.

Polycrylic products emit low odors and VOCs when wet, and they do not cause paint to yellow over time. They are cheaper than polyurethane, and they dry faster, needing as little as 2 hours to dry to the touch.

On the downside, polycrylic sometimes leaves a milky appearance on dark paints and will appear yellow if you apply thick coats over the paint.

How to Waterproof Painted Wood With Polycrylic

• Start by cleaning your painted wood with TSP following the manufacturer’s cleaning directions on the product label. You can also clean with a mild detergent and some warm water if you don’t have TSP on hand.
• Allow the surface to dry properly, then sand it with 220-grit sandpaper or higher. I recommend using high-grit sanders to level the paint surface without leaving deep scratches that would show after sealing. Also, ensure that you sand in one direction following the wood grain to keep the surface uniform.
• After sanding, wipe the painted wood with a damp tack cloth to remove the sanding dust. You can vacuum the dust before wiping the wood with a cloth for better results.
• Next, use a wooden or plastic rod to stir the polycrylic. Stirring will remove any bubbles formed in the product during transportation; therefore, you won’t transfer them onto the painted wood.
• Apply the polycrylic using a synthetic brush to achieve the best results. Natural bristle brushes will soak up a lot of product and lose shape because polycrylic is water-based. Consequently, the finished coat will not look uniform. Allow the first layer to dry for 2 hours or as specified by the manufacturer before proceeding.
• Scuff the first coat with fine-grit sandpaper to give the second coat some tooth to grip. Clean the surface again with a damp tack cloth, let it dry, then apply the second coat of finish.
• As with polyurethane, you can apply up to three coats of polycrylic – just ensure that you sand between coats for best results.

Here’s How to Waterproof Using Polycrylic:

Paste Wax

Paste wax is any wax dissolved in a bit of solvent for easy application. You can apply it with a special wax brush or a rag to achieve great finish results on painted wood. Wax dries into a matte finish, but you can buff it until you reach your desired sheen level after it dries.

This topcoat works best on chalk and milk paints or other low gloss paints. You can also use it over polyurethane or polycrylic to give the finish a more silky feel.

Unlike the other topcoats, paste wax is less durable; therefore, you must reapply every 1 or 2 years to keep your surface looking good. Furthermore, waxed surfaces do not fare well near high heat or in places with direct sunlight.

When the wax gets exposed to such conditions, it will soften and become sticky. Therefore I do not recommend using this finish on outdoor painted wood.

Additionally, the wax dries the quickest among all the finishes I’ve mentioned. It requires only 6 hours to dry to the touch and 24-48 hours to cure completely. 

How to Waterproof Painted Wood With Wax

Step 1: Clean the Surface

Ensure that the painted wood is free from dust and other debris for the wax to take on well. Use a damp rag to clean your piece thoroughly, then let it dry for a few minutes before proceeding.

Ensure that you build a shed to prevent wind from blowing contaminants onto your freshly cleaned surface while working outside.

Step 2: Apply the Wax

You can use brushes made explicitly for waxing furniture or a cloth to apply the wax. If you go the cloth route, choose a lint-free cloth for the best results. If you use a fabric with many fibers, the loose ones will come off and stick to the wax, leaving you with a messy finish.

Ensure that you apply thin wax coats for best results. Thicker layers will take too long to dry, and they increase the chances of having a streaky or a blotchy wax job.

Step 3: Allow the Wax to Dry, then buff

Wax takes about 40 minutes to dry to the touch; however, at that point, it is not ready to buff. The reason is that, even though the wax surface is dry, it is still wet underneath. Therefore, any attempts to buff will move the wax around the surface, leaving streaks behind. 

I recommend waiting 24 hours before waxing because the finish will be hard enough to add shine without problems. Do not leave the wax on for more than 24 hours either. At that point, the finish will have hardened too much, and it will take more effort to buff it.

Pros and Cons of Waterproofing Painted Wood?

Even though waterproofing painted wood has many advantages, it also comes with disadvantages. You must understand both ends of the spectrum to make informed choices whenever you seal your painted works. Here are the pros and cons of waterproofing painted wood.

Pros

• Extra Protection for the Wood

Waterproofing painted wood is essentially adding an extra shield for defending wood against the elements. The additional protection will keep the paint looking great for longer, thus saving you the extra costs that come with a new paint job.

When you compare the cost of waterproofing to the price of a fresh paint job, the former costs much less. Therefore it is better to seal painted wood regularly than leaving the paint bare and repainting every five years.

• It Makes the Surface Easier to Clean.

Paint sealants prevent dust and other contaminants from embedding into your wood paint. Most of these contaminants are super small in size, making them tough to notice at first. However, after some time, more of them accumulate on the paint surface, thus ruining your paint job.

The sealant keeps the dust from bonding with the paint; therefore, it is easier to clean your painted wood. You will not have a fear of scratching the paint coat as you remove the dirt.

• Enhances Paint Color

After painting the wood, the piece looks fantastic. However, the color increases in depth upon applying the paint sealer, making your wood pieces stand out even more.

• Help You Sell Your Pieces Faster.

If your main priority is to sell your wood products after paining them, you should consider waterproofing them to boost your sales. Wood pieces painted and sealed using proper products and techniques stand out, thus attracting more customers.

Furthermore, they will bring more people to your workshop because they know the kind of value that comes with your products.

Cons

• Sealants Amplify Imperfections

Paint sealants amplify paint color; however, they also make any imperfections in the paint coat stand out more. Minor scratches or brush and swirl marks on the paint film will look exaggerated, thus ruining your whole finish.

The only way to avoid such an effect is by applying the wood paint carefully, to begin with. Make sure that you clean the wood, prime it then apply the appropriate wood paint.

Also, ensure that you sand the final coat with fine-grit sandpaper to level the surface and remove imperfections for your finish to look uniform.

• Waterproofing Requires a Lot of Prep Work

Cleaning the painted wood is only one of the several requirements for preparing it for a sealant. Since blemishes and other contaminants will be more noticeable after waterproofing, it is mandatory to make surface corrections before application.

If you follow proper procedures when applying paint, you’re on the safe side. Otherwise, you must ensure no bubbles, cracks, or dirt remain on the paint coat before applying the sealer.

Some minor surface imperfections, like brush marks, are easy to rectify with a bit of sanding. However, if there are cracks on the surface, you will have to strip the paint back to bare wood and repaint it before waterproofing.

All of these extra preps can cause your project to last for upwards of 8 hours, which is a major inconvenience for most painters.

• Removing the Paint Sealer is Hard.

If you make a mistake when applying paint sealant, you will need time and the right gear to rectify the problem. It may be easy to fix issues that you identify immediately, but once the sealant cures, it’s a whole other problem.

Removing a cured coat of sealant from painted wood without harming the paint film is challenging. You will have to be careful when sanding off the coat or when using chemicals to maintain the pristine condition of the paint below.

If you have never tackled a clear-coat removal task alone, it is best to enlist the services of a professional painter – which will add to the cost of your whole project. 

How to Waterproof Painted Wood for Outdoor Use

Painted wood meant for outdoor use require lots of protection; therefore, the best products to use are polyurethane and polycrylic. These two paint sealers can withstand the harsh weather conditions outside for years keeping your wood and the paint protected for longer.

Polyurethane is more durable than polycrylic; therefore, it offers the best protection for outdoor surfaces. However, it yellows over time, so if you don’t want your paint to develop an amber hue slowly, polycrylic will do the trick.

Polyurethane emits high VOC emissions even after it dries – the emissions stop after the finish cures. Therefore it is safer to use polyurethane on outdoor pieces so that the fumes and odors do not affect you.

Here’s a Video On Sealing Your Outdoor Painted Wood Furniture:

How to Waterproof Painted Wood for Interior Use

Wax and polycrylic are the best products for waterproofing interior wood pieces. Indoor pieces stay sheltered from the harmful UV rays and direct sunlight; therefore, they only require little protection.

Both wax and polycrylic have low VOCs; hence they do not emit fumes and odors as they dry. Your furniture finish can cure inside the house without disturbing your comfort.

The low VOCs also make wax and polycrylic safe to use on furniture and other pieces accessible to children, 

Polycrylic is the most durable interior sealer and does not cause paint to yellow over time. On the other hand, the wax will provide ample protection to indoor surfaces, but you will have to reapply yearly to keep the paint in good condition.

Always purchase “food safe” finishing products for your indoor painted wood – they are safest to use on children’s toys, kitchen cabinets, and tabletops.

When You Should Not Seal Painted Wood

Sealing painted wood has many advantages; however, you can skip this step in some situations without significant repercussions. For instance, you do not need to seal wood coated with quality exterior-grade paint.

Two or three coats of exterior wood paint will provide sufficient protection outdoors, provided you clean and prime the wood properly before application.

Indoor wood pieces such as picture frames and furniture pieces that you don’t use often don’t require sealing. There are lesser chances of scratching or denting their paint; therefore, they do not need the extra protection.

Also, ensure that you use quality interior wood paint on such pieces for the finish to last long. You can also skip the sealer when painting furniture pieces that you don’t use so much.

When to Seal Painted Wood

You must always seal wood colored with chalk or milk paint. These two products are delicate; hence they deteriorate faster than other types of wood paint. Sealing these paints provides extra protection and adds some sheen to their naturally matte appearance.

Always seal any exterior wood pieces colored with interior wood paint. Even the highest quality interior paints will degrade faster when exposed to extreme outdoor conditions. Therefore, you must always apply a protective clear coat on them for added protection.

Always seal paint on high traffic surfaces such as shelves, tabletops, and kitchen cabinets. These areas get used a lot; hence it is easy for the paint film to develop cracks and start fading quickly. Adding a layer of clear coat on the paint will increase the lifespan of the finish.

Conclusion

Waterproofing painted wood is an excellent way of preventing moisture damage and protecting the paint from harsh weather. It is simple for painters who have done it before, but beginners find it hard to execute the task.

Most beginners don’t know which products to use, where to use them and how to apply them properly. I believe this guide has offered so much to help your bid of waterproofing your painted wood. Here’s a recap on…

How to Waterproof Painted Wood.

Waterproofing involves applying polyurethane, polycrylic, or wax over painted wood to prevent moisture damage. These sealers also dry into a film harder than ordinary paint; therefore, they also protect the paint from mechanical forces that cause cracks and dents.

You can apply polyurethane and polycrylic on painted wood with a paintbrush or a sprayer. The paintbrush will give you full coverage in as little as two coats, but there are risks of leaving brush marks in the finish.

On the other hand, spraying produces smooth finishes, but you need to learn proper techniques to succeed. Spraying also produces thin coats, so you must apply several layers to achieve full overage.

Apart from protection, the sealants also intensify the color of the paint, making your wood pieces stand out. They also increase the wood’s value because they show you take extra steps to protect your work.

On the downside, paint sealants also amplify minor imperfections on the paint surface. Furthermore, if you make errors during the application, you may have to strip the sealer and paint then begin coating afresh.

I hope this article clears up everything about waterproofing painted wood. If you have any questions or more tips to share, feel free to reach out in the comments.