Can You Use Flex Seal On Wood?

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If you’ve had trouble sealing cracks and leaks on wood, you might have heard of Flex Seal. But is it an ideal product for wood or will it damage your wood even more?

If you want to know if you can use Flex Seal on wood safely, I’ll provide you with all the information you need in this guide.

Does Flex Seal Work on Wood?

Flex Seal can work on wood surfaces and is an effective solution for wood protection. It’s designed to seal out air, water, and moisture to prevent damage and leaks. 

It creates a rubberized, waterproof coating that guards against moisture, scratches, UV light, fungi attacks, moldings, decay, and sunlight damage. It’s also easy to use and provides better results than other wood finishing products, including epoxy.  

However, it’s important to note that the effectiveness of Flex Seal on wood will depend on various factors, such as the severity of the damage and the type of wood surface. 

applying flex seal on wood

For best results, apply Flex Seal to dry wood in 2-3 coats, but avoid using it on rotten wood. Each coat will treat the wood differently, so multiple applications may be necessary.

Flex Seal Used in Wood Decks

Flex Seal can be used to protect any type of wood deck by filling in cracks and splits, making it water-resistant and preventing rotting. 

Before applying Flex Seal to your wood deck, it’s important to clean the surface thoroughly to ensure it’s free of dirt, debris, and other contaminants. Once the surface is clean and dry, you can apply Flex Seal using a brush or spray. 

holding a Deck BOSS brush by Perdura

But be patient. The stuff takes about 2 to 3 hours to dry and about 24 hours to really cure, especially if you’re dealing with humidity.

Now, a word of caution: Flex Seal isn’t cheap, and you’ll likely need to lay down three coats for full coverage. Plus, those gallons don’t stretch as far as you might think. So, if you’ve got a larger deck, you might find that replacing the boards is more cost-effective in the long run.

Flex Seal Used in Wood Posts

Flex Seal is a great option to protect outdoor wood posts from water and sunlight damage. It creates a coating that makes the posts resistant to water and rot. 

Sunlight can also harm the posts by darkening them, but Flex Seal contains UV stabilizers to protect them. 

Flex Seal Used in Wood Posts

Whether you have fence posts, mailbox posts, or other types of wood posts, Flex Seal can help provide a protective barrier.

Also, if you’re concerned about fungus or mold—trust me, I’ve seen some posts go from great to gross—some Flex Seal products contain inhibitors that keep those nasties away. Using Flex Seal can help extend the lifetime of wood posts by protecting them from various outdoor environmental elements.

Flex Seal Used in Wood Floors

You know, Flex Seal gets a lot of love for being this versatile, do-it-all kind of product. But when it comes to wood floors, I’d steer clear. Flex Seal may create a slippery surface that can be dangerous, especially if applied to a high-traffic area.

Moreover, it should be noted that Flex Seal may not be the most optimal long-term solution for sealing and safeguarding wood floors. 

Given the high amount of foot traffic and general wear and tear that floors experience, there is a possibility that the Flex Seal coating may eventually peel off or deteriorate over time.

Thus, this can leave your floors vulnerable to damage and require costly repairs or replacements. If you need to seal or protect your wood floors, it’s recommended to use a product that is specifically designed for use on floors, like Epoxy. 

Flex Seal Used in Wood Fence

Yes, Flex Seal can be used on wood fences to help protect them from water and moisture damage. 

wooden fence

Wood fences are subject to a lot of moisture exposure, especially in areas with high humidity or frequent rain. This can cause the wood to rot or warp over time, which can compromise the structural integrity of the fence.

So, here’s my advice: give that fence a good Flex Seal treatment. The product contains both fungi and UV inhibitors, addressing the major culprits you have to worry about with outdoor wood.

Flex Seal Used in Wood Siding

You can use Flex Seal on wood siding. However, it can be costly due to its extensive coverage area and the need for a substantial amount of it.

So, it’s important to apply Flex Seal properly on the wood siding in one go to avoid wasting time and money. If you want a cheaper and better alternative for finishing wood sliding, I recommend using epoxy paint [1].

How To Apply Flex Seal on Wood: 5 Steps

Materials required

Step #1: Choose and prepare the area

flex seal and painting tools

Before applying Flex Seal, it is essential to prepare the area properly. This means finding a space that has sufficient airflow and ventilation, as Flex Seal is a highly chemical compound that can cause breathing issues. 

To prevent spraying Flex Seal on unwanted areas, cover them with a cloth if you want to spray only a specific area. Additionally, ensure that you have enough space to achieve the best results.

Step #2: Clean the wood

Ensuring that the wood surface is clean is an important step because it can affect the performance of the Flex Seal coat. 

To clean the wood, start by removing any dirt, debris, or loose particles from the surface of the wood using a brush or broom. 

removing dust with Eshazu Tack Cloth

You can also use mild detergent and water to clean the area if necessary. Make sure to rinse the area thoroughly with clean water and allow it to dry completely before applying Flex Seal.

Cleaning the wood is important because any debris or dirt on the surface can prevent the Flex Seal from adhering properly, which can compromise its effectiveness. 

Additionally, cleaning the wood helps ensure the surface is free from any potential contaminants that could interfere with the seal.

Step #3: Sand and clean the dust

While sanding and cleaning the dust off the wood is not always necessary when using Flex Seal, it can be a helpful step to take for certain wood surfaces. 

Sanding the wood can help to smooth out rough areas and create a more even surface for the Flex Seal to adhere to. 

person holding sanding block

Additionally, cleaning off any dust after sanding can ensure the surface is free from any potential contaminants that could interfere with the seal.

To sand the wood, use fine-grit sandpaper and sand in the direction of the wood grain. Be careful not to sand too aggressively, as this can damage the wood. 

After sanding, use a clean, dry cloth or vacuum to remove any dust or debris from the surface.

Step #4: Spray Flex Seal into the wood

Before spraying Flex Seal, it is important to shake the can vigorously for approximately one minute to ensure proper mixing of the contents. It’s important to note that you should never spray Flex Seal directly into the wood. 

If using a spray can, hold the can about 10-12 inches away from the surface of the wood and spray in a sweeping motion, overlapping each pass slightly to ensure even coverage.  

spraying flex seal on woodworking project

Take care not to spray too quickly and pay particular attention to cracks and gaps in the wood surface, spraying them slowly and evenly.

Be sure to apply several thin coats rather than one thick coat to ensure a strong and durable seal. It’s essential to ensure that no areas are missed during the spraying process, as it can be challenging to identify them once the Flex Seal has fully dried.

To achieve optimal results, I recommend applying three coats of Flex Seal to the wood surface. 

Step #5: Let it cure and dry

After applying Flex Seal to the wood, the final step is to allow it to cure and dry completely before using the surface. 

The amount of time it takes for Flex Seal to cure and dry can vary depending on the temperature, wood type, and humidity of the environment.

wood art on work with Flex seal

In general, allow each coat to dry for approximately 24 hours before applying the next coat, and once all coats have been applied, let the wood dry for 24 hours and cure for 48 hours.

During this time, it’s important to keep the area clean and free from any potential contaminants that could interfere with the seal. Avoid touching or disturbing the surface during the curing process.

It is crucial to avoid applying a new coat while the previous one is still wet, as this could negatively affect the appearance of the wood and result in a wasted Flex Seal. So I advise using Flex Seal correctly on the first attempt since it can be expensive.

Which Works Better, Flex Seal Spray Or Liquid?

The choice between Flex Seal Spray and Flex Seal Liquid depends on the specific project and application you have in mind. I’ve tried both, and honestly, each has its own merits. It really boils down to what you’re trying to accomplish.

Flex Seal Spray is my go-to for larger surface areas and can be applied quickly. Let’s say you’ve got a roof or some gutters to seal, or perhaps a piece of outdoor furniture that’s seen better days. A few quick passes with the spray can and you’re golden. Also, you can use Flex Seal on rotted wood

brushing tabletop with flex seal

You may need to apply it twice or thrice until the area is adequately sealed. Once applied, it is essential to let it sit for at least 24 hours to see maximum results. 

Flex Seal Liquid is thicker and more viscous than the spray, making it better suited for more precise applications and larger projects such as asphalt and concrete repairs.

It can be applied using a brush or roller, making it ideal for projects such as sealing cracks or leaks in pipes, tanks, or other small areas. 

By using a paint tray, you can efficiently save the leftover liquid by replacing the lid, which allows for the reuse of the product for up to 24 months. The curing time for the liquid is also up to 24 hours. 

tabletop with flex seal finish

In general, both the spray and liquid versions of Flex Seal are effective at creating a strong and durable seal on various surfaces, including wood. The choice between the two ultimately comes down to the specific project and your personal preferences.

What is the longevity of Flex Seal on wood?

The longevity of Flex Seal on wood, whether treated or untreated, can vary depending on various factors, including the quality of the initial application, the environment in which the wood is located, and the level of wear and tear the wood surface experiences over time.

When applied correctly, Flex Seal can create a strong and durable seal on wood that lasts several years. 

However, if the application is not done properly or the surface is exposed to extreme conditions, such as harsh weather or high traffic, the seal may deteriorate more quickly.

Does Flex Seal Last Longer Than Gorilla Glue?

Comparing the strength of Flex Seal and Gorilla Glue is subjective, as people may have different opinions. So, I did a comparison test of the two products.

Flex seal products

In my test run, Flex Seal Glue can hold up to 1,000 lbs, but it requires seven days to reach its maximum strength. Gorilla Glue, on the other hand, can stick to most surfaces and hold up to 30 lbs, with a drying time of 1 to 2 hours.


What is the drying time of Flex Seal on wood?

The drying time of Flex Seal on the wood typically takes around 2 to 3 hours, but it requires a full 24 hours to cure fully.

Can Flex Seal be used on plywood?

Flex Seal cannot be used on plywood because it is a porous surface, and it may not adhere properly or provide a strong enough seal.

Is Flex Seal effective on treated wood?

Flex Seal can be effective on treated wood, but to achieve the best results, it is recommended to apply three coats of Flex Seal on treated wood as it works effectively on this type of wood.

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Flex Seal can be a useful product for sealing and protecting wood surfaces. However, it’s crucial to properly prepare the surface, use the appropriate type of Flex Seal, and follow the manufacturer’s instructions carefully. 

Overall, you can use Flex Seal on wood to provide a strong and durable seal helping to extend the life and beauty of your wooden surfaces.

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Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

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