How to Use Flex Seal On Rotted Wood

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Are you tired of dealing with rotted wood’s unsightly and potential hazards? Have you thought about using Flex Seal as a speedy and efficient remedy for decayed wood?

If so, our woodworkers will explore the possible uses of Flex Seal on rotted wood and if it can turn your deteriorated wood into a durable and long-lasting surface. Keep reading!

Can Rotten Wood Be Fixed Using Flex Seal?

Flex Seal is a coating made of liquid rubber sealant for do-it-yourself (DIY) indoor and outdoor projects. Moreover, this versatile product can be applied to a wide variety of surfaces such as wood,  fabric, rubber, metal, plastic, and many others. 

Certainly, Flex Seal can be used on rotted or decayed wood to seal it off and prevent moisture from penetrating the wood. Furthermore, it offers the advantage of withstanding high temperatures without drooping or dripping and low temperatures without cracking or peeling.

However, it is crucial to acknowledge that if moisture has already infiltrated the wood, simply applying a layer of flex seal to the wood surface will not solve the underlying moisture issue within the wood. 

rotting wood fence

Applying a flex seal can halt the evaporation of moisture and can potentially accelerate the decay process by trapping moisture inside the wood. Thus, it is recommended to mend the rotted or decayed wood beforehand and then use a Flex Seal to make it water-resistant.

Pros And Cons of Applying Flex Seal on Rotted Wood



How To Apply Flex Seal on Rotted Wood

Tools and Materials

Step #1: Allow the wood to fully dry

flex seal and painting tools

It is advisable to place the damaged wooden furniture or structure in a dry and well-ventilated place and allow it to dry thoroughly to eliminate the deteriorated parts of the wood effortlessly. 

In addition, this is very crucial because the rotted portions can be more readily removed when the wood is completely dried out.

See Also: How to Fix Water Damaged Swollen Wood Furniture

Step #2: Cut away any rotted sections

For this step, utilize the hammer you prepared to extract the deteriorated or rotted section by clawing it out. Position the hammer’s claw at the lower end of the rotted portion; exerting force, you must pull the claw towards yourself to eliminate the decayed surface.

Continue with the previously stated process utilizing the hammer until the entire decayed or rotted section is eliminated, as applying Flex Seal on deteriorated surfaces can be challenging. 

remove rotting section

Be cautious not to exert excessive pressure or force on the hammer to prevent any harm to the unaffected parts of the wood.

Step #3: Clean the wood thoroughly, removing any debris or dirt

For the next step, wipe the entire wood surface meticulously with a clean cloth or rag to remove all debris and dust, ensuring every area is thoroughly cleaned. 

However, we advise not to utilize cleaning solutions on the wood, as removing the rotted or decayed section, there is a risk that the wood may absorb water due to the open fibers of its interior.

Step #4: Sand the wood and remove any sawdust

For the optimal application of Flex Seal, it is highly advised to sand the wood surface beforehand utilizing your sandpaper (220-grit). Sanding in the wood grain’s direction is recommended to prevent any scratches on the wood.

sanding block

After sanding, use a damp rag or cloth to wipe the entire wood surface and remove any sawdust. This step will provide you with a clean, smooth wood surface that will be ideal for the application of Flex Seal without encountering any problems.

Step #5: Apply Flex Seal by either spraying or brushing it onto the surface

Flex Seal is effective in filling cracks and gaps in rotted wood. Moreover, it is essential to spray it slowly, ensuring that all cracks and gaps are filled. But be cautious not to notice all areas, as it can be challenging to identify them once the Flex Seal dries.

For the ideal application of Flex Seal, it is recommended to spray it in a sweeping motion while maintaining a distance of ten to twelve inches. To achieve the desired outcome, applying three coats of Flex Seal to the rotted wood is advisable.

Flex Seal works in two steps: the initial coat penetrates the fibers of the wood, and it seals the wood for its second coat. The application of the third coat will protect the wood from environmental factors, such as moisture and UV rays.

Step #6: Allow Flex Seal to dry and cure completely

It is essential to allow the rotted wood to dry for approximately twenty-four hours after applying all Flex Seal layers. To ensure the best results, it is further suggested to let the wood cure for about forty-eight hours prior to using it.

Flex Seal Used in Wood Posts

However, Flex Seal’s process for drying and curing can be affected by various factors such as the type of wood, humidity levels, and weather changes. Applying Flex Seal to healthy wood also takes longer to dry than to rotted wood due to its extended drying time.

It is crucial to avoid applying another layer of Flex Seal while the previous coat has not completely dried, as moisture trapped between layers of Flex Seal can penetrate through the fibers of the wood, ultimately leading to the rotting of the wood.

What is The Drying Time For Flex Seal On Rotted Wood?

As mentioned previously, the length of time it takes for Flex Seal to dry is influenced by various factors such as the coating’s thickness, humidity level, weather changes, and the type of wood.

However, the coating will typically be dry within two to three hours and completely cured after twenty-four hours, becoming more robust as time passes.

Signs of Rotting Wood

Although wood has many positive qualities, it is prone to deterioration. If it is not adequately maintained, wood can become a desirable food source for different types of fungi and pests. 

rotting wood due to water damage

Identifying rot is one of the most frequent problems to watch out for in wooden structures, and the earlier you detect it, the simpler it is to resolve. There are two primary categories of rot that may impact your wood, namely dry and wet rot.

Dry rot is a highly destructive form of fungal deterioration that consumes the structural components of wood and can spread even without external moisture, as it generates moisture by breaking down the wood.

Wet rot, conversely, is a fungus [1] that grows on wood and feeds on moisture and the wood’s nutrients. It spreads by consuming wood and releasing spores into the air to find new moist wood surfaces to feed on.

Nonetheless, decaying wood has various manifestations, such as reduced size, splintering, discoloration, and cracking. 

Inspecting the wood’s surface can reveal its state of decay. If there are areas that resemble mushrooms and produce spore dust, this is an indication that the wood is decaying.

deck water damage

As the decomposition process advances, the cellulose in the wood is broken down, resulting in its softness and darkening color. The wood’s size decreases as the cellulose is depleted.


What is the best sealant for rotten wood?

The best sealant for rotten wood is Epoxy. It is an effective solution for filling cracks and gaps in the wood, creating a durable and hard surface. It is also advantageous due to its high water resistance and compatibility with being painted and sanded.

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Utilizing Flex Seal on rotted wood can be a successful method for renewing its sturdiness and endurance. Adequate surface preparation is critical, including eliminating any weakened or broken wood and thoroughly cleaning the area. 

It is also advisable to apply several coats of Flex Seal, allowing each one to dry entirely before adding another. 

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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