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Last Updated on June 10, 2024 by Paul Clayton
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How to Waterproof Plywood?
Waterproofing plywood ensures its durability and longevity, especially in moist environments. Understanding how to waterproof plywood can help protect your investment and maintain the material’s structural integrity.
Key Takeaway
The plywood needs waterproofing to prevent moisture damage, which can cause rotting, warping, and mold growth. Different techniques are suitable for indoor and outdoor applications.
Summary
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- Plywood is susceptible to moisture damage due to its glued wood layers and veneer composition.
- Moisture exposure can lead to rotting, warping, and mold growth.
- To prevent this damage, waterproofing techniques are necessary, especially for outdoor plywood.
- Moisture Prevention Techniques
- Keep plywood covered during construction.
- Apply a varnish coating to the edges.
- Use latex for aesthetics and waterproofing.
- Types of Plywood Waterproofing Techniques
- Paint-on/Spray-on waterproofing (usually with latex for easy application)
- Penetrating oils (often with antifungal preservatives for indoor use)
- Sealers
- Plastic sheets (stapled or tacked)
- Waterproofing membranes
- Indoor vs. Outdoor Plywood Waterproofing
- Indoor plywood can use penetrating oils with antifungal properties.
- Outdoor plywood needs a protective paint coating or spray with a latex base.
- Choosing a Waterproofing Technique
- Paint-on waterproofing is applied before installation for raw plywood.
- Penetrating oils and preservatives are used on finished plywood to retain the wood look.
- Waterproofing Plastic Sheet
- Plastic sheets or membranes are stapled over the plywood for waterproofing.
Do you want to protect your boat’s plywood flooring from water?
You’ll find a detailed answer in this article if you are wondering how to waterproof plywood.
Owning a boat comes with a lot of responsibility, including water-sealing the plywood flooring. You want to maintain your boat and increase its durability by protecting it from moisture and humidity.
Most boats have plywood flooring due to its affordability and easy installation. Unfortunately, it isn’t waterproof like plastic, so it may rot and peel apart with time.
That’s why it’s essential to waterproof plywood using the sealing techniques discussed further.
Why Plywood Needs Waterproofing?
The answer lies in the plywood’s composition. It’s made of thin layers of softwood joined together by adhesive glue and then finished with several veneers.
These veneer layers are prone to damage by moisture, which is the main reason plywood disintegrates upon water exposure.
Next, the softwood flakes peel away and gradually rot. The thin separation between the layers is a perfect spot for mold growth.
By the way, it’s not just water that damages the plywood; humidity also causes it to warp and bow.
Now that I have established ground to emphasize waterproofing plywood, let’s learn about sealing techniques.
Moisture Prevention Techniques
First, discussing moisture prevention techniques to increase the longevity of plywood sheets is better.
- Keep the plywood covered during the construction process.
- Use a paintbrush to apply the waterproofing element.
- A varnish coating on the edges is a protective layer, preventing water from seeping.
- Latex not only adds to aesthetics but serves as a robust water seal.
Types of Plywood Waterproofing Techniques
The following are the most commonly used plywood waterproofing techniques:
- Paint-on/Spray-on waterproofing
- Penetrating oils
- Sealers
- Plastic sheet
- Waterproofing membranes
Indoor vs. Outdoor Plywood Waterproofing
These techniques differ depending on whether plywood is used indoors or outdoors. For indoor use, penetrating oils with antifungal preservatives suffice. However, outdoor plywood requires a protective coating of waterproofing paint or spray.
A liquid latex element is present in the waterproofing sprays or paints.
It’s very convenient to apply them to plywood without much effort. Remember that the surface should be wet before you spray or paint. Once dried, it hardens to form a plastic-like protective layer.
Alternatively, you can also apply sealers and penetrating oils with a sprayer or a paintbrush.
So, how do you choose between the two? Don’t worry; it’s pretty simple.
The paint-on waterproofing is done when the plywood is raw before installation. On the other hand, preservatives and penetrating oils are coated on the finished plywood to retain the original wooden look.
Waterproofing Plastic Sheet
It would help if you stapled the plastic sheets or waterproofing membranes over the plywood.
Tacking up the sheets is a tedious and time-consuming task; however, you can replace them with new ones once they are worn out.
The sheets don’t stick directly on the plywood floor, retaining the original wood appearance. The waterproofing paint coating modifies the plywood’s original surface texture, giving it a plastic-like outlook.
How to Waterproof Outdoor Plywood
Sealing prevents the water from penetrating the wooden layers. So, the first thing to do is to apply an epoxy seal on the plywood’s surface. The following are the pre-requisite items to waterproof the outdoor plywood:
- Water sealer
- Polyurethane varnish
- Stain brush (small)
- Water-based pigment stain
- Pump-up garden sprayer
Polyurethane Varnish
To seal the plywood edges, you need to apply polyurethane varnish. It’s better to apply multiple coats.
Please be careful not to apply varnish to the surface of the plywood. You can cover it with masking tape.
Water-Based Pigment Stain
The next step is to apply an exterior water-based pigment stain to coat the surface. You can use garden spray for this purpose. It not only tints but also prevents UV damage.
Afterward, leaving the plywood to dry completely for 24 hours would be best.
Once the varnish is completely dried out, you can apply the water sealer with the help of a pump-up garden sprayer. Not just once, you have to use multiple coats to ensure excellent water sealing.
One thing to keep in mind is that the epoxy seal doesn’t stick to oil-based paint or stain. Please don’t paint the plywood earlier.
Waterproofing Process Repetition
It’s not a one-time process because you must reapply all the layers after two years. The water sealing wears off with time, depending on its water exposure.
For instance, if you frequently fish in salt waters, you may have to re-apply the sealer earlier.
How to Waterproof Plywood with PVA
In addition to regular waterproof paint, you can opt for PVA (polyvinyl alcohol, polyvinyl acetate). It easily adheres to the plywood surface, forming a compelling waterproof film.
As already discussed above, waterproof paint is made with a latex element. On the other hand, PVA is a water-soluble synthetic polymer. So, what’s the difference?
Both are equally efficient in terms of quality. However, it’s recommended to apply PVA to indoor plywood as it can easily be washed away by water or rain.
Unlike regular waterproof paint, you only need to apply three coats of undiluted PVA. Just ensure the previous coat dries up completely before applying the next one.
How to Waterproof Plywood Sheets
To waterproof plywood sheets, you can use sealers or penetration oils. First, moisten the plywood’s surface so that it rises slightly. Once the surface dries, scrape it off with sandpaper to further smoothen it.
You can apply the waterproofing paint with a brush or a spray all over the sheets, especially around the edges. To achieve better results, you should apply three or more coats.
Once the latex dries up, it forms a thin layer of plastic around the sheet. This additional plastic layer serves as a protective layer from water and humidity.
How to Waterproof Plywood Boats
It’s a more daunting task because it requires extra care when navigating the boat’s corners and sides.
Deep Cleaning
Before starting the waterproofing process, clean all the veneered boat’s sides with a clean cloth. You don’t want any dust or dirt particles entrapped in the coating.
You must be wondering why it’s essential to deep clean the boat and deck before applying the waterproofing coat.
The presence of dust may decrease the adhesion, resulting in insufficient coating. How many coats you apply will not matter because they will not last long enough on the plywood surface.
Epoxy Coating
Once you are done with deep cleaning the boat, combine epoxy and glue in equal proportion to fill the holes and joints. You can use a small paintbrush for that purpose.
It requires a total of four to five epoxy coatings after every three to five hours. It would help if you let the previous coat dry out completely before applying the next one. The entire process may take five to six days.
Waterproofing Polish
In the next step, apply the waterproofing polish all over the boat, including the bottom side. You need to use two coats at one time. Then, leave the boat for six to eight hours, allowing the coats to dry out completely.
Lastly, apply the third and fourth coats simultaneously again. This completes the process of waterproofing a plywood boat.
Waterproofing Deck
The deck is the most essential part of the boat, fully exposed to water spatters. It would help if you sealed it with a unique liquid rubber waterproofing system.
Sealing the deck is similar to sealing the rest of the boat. Before applying the coat, you need to clean the surface with a dry cloth.
Another thing: a rubber liquid takes at least 24 hours to settle down and dry out. For precise waterproofing, you should apply two to four layers.
How to Waterproof Marine Plywood?
Marine plywood isn’t like any ordinary plywood. The significant difference lies in the total number of layers. Standard plywood usually has three to five layers; marine plywood contains ten or even more.
The best way to seal marine plywood is to use a wooden sealant. You require the following essentials for the process:
- Sandpaper
- Cloth
- Sealant
- Paintbrush
First, you can thoroughly sand the plywood surface with 80-grit sandpaper. The sandpaper evens the texture and removes the previous sealing layer.
Two types of sandpaper are available in the market: rough and fine. You can use both sandpapers simultaneously.
Rough sandpaper reaches into the wood’s crevices to scrape off any previous sealing layer. Fine paper gives it a uniform finish when used on top of it.
After that, you must wipe the surface with a clean cloth to remove all the unwanted particles or debris. If required, you can also wash it with water.
You can apply a thin sealant layer using a paintbrush, leaving no edge or corner uncoated. One seal layer usually takes four to ten hours to dry completely.
Repeat the coating process three to four times to ensure proper water sealing.
Marine Grade Wood Sealers
The market is entire of waterproofing sealers; however, it’s better to research before buying one.
The latest sealers protect against water and UV rays. They require less coating and prevent warping and wood rotting.
You can select SEAL-ONCE Exotic Premium Wood Sealer, which is eco-friendly and doesn’t harm your pets or marine life. It protects against decay, mold, and water. The best part is that you need to apply only two coats instead of three or five.
Or, you may opt for the DeckWise WiseCoat Hardwood Deck, which prevents water build-up on the deck for around six years. Its low VOC content ensures low or minimal harmful odors. Moreover, it prevents harmful UV rays from damaging the paint.
You can use TotalBoat Danish Teak Wood Sealer, penetrating the wood cracks to ensure long-term sealing. It’s an excellent water repellant that doesn’t make the floor slippery. This diverse sealer is best for both hard and softwoods.
Most Common Questions
How do you keep moisture out of plywood?
Sealing the edges with an appropriate sealant or edge banding can help protect the plywood from moisture-related issues. Applying a high-quality wood sealant designed explicitly for plywood creates a barrier that impedes water infiltration.
How to dry out plywood fast?
Placing the plywood outdoors with direct sunlight can significantly expedite the drying process. Sunlight provides heat and promotes air circulation, which helps evaporate moisture more quickly.
Additionally, ensure that the plywood is elevated from the ground to allow air to flow underneath, further enhancing the drying efficiency.
What is the cheapest way to waterproof plywood?
One practical and economical method is using PVA glue (polyvinyl acetate). Not only is PVA glue widely available and easy to apply, but it also offers robust waterproofing capabilities.
When appropriately applied, PVA glue forms a protective barrier that prevents moisture from penetrating the plywood, extending its lifespan.
This makes it a good value option for DIY enthusiasts and professionals who want to protect their plywood investments without incurring substantial costs.
How to fix water-swollen wood?
To understand how to fix water-swollen wood, remove all swollen wood, bulging paint, and water stains using sandpaper or a putty knife.
Next, clean the surface with a brush to ensure it is debris-free. Apply wood filler to the affected area and allow it to cure fully. Once cured, sand the new surface until it is even and smooth.
Finally, furniture oil is applied to complete the restoration process.
Summary
A comprehensive waterproofing process is essential to ensuring the longevity and durability of plywood in outdoor conditions.
The first step in understanding how to waterproof plywood is selecting exterior-grade plywood designed to withstand moisture and environmental stress.
After this, thoroughly sand and clean the plywood surface to remove debris and enhance subsequent treatments’ adhesion. A high-quality wood sealant is crucial as it penetrates the wood fibers, providing an initial layer of waterproofing.
For additional protection, use waterproofing paint; this not only seals the surface but also adds a layer of defense against UV rays and other elements.
Coating the plywood with epoxy resin, which forms a robust barrier against moisture infiltration, further enhances durability.
Lastly, ensure that edges and joints are meticulously sealed with waterproof caulk to prevent water ingress at these vulnerable points. Adhering to these steps will significantly extend the lifespan of plywood used in outdoor applications.
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