Do you want to protect your boat’s plywood flooring from water?
If you are wondering how to waterproof plywood, you’ll find a detailed answer in this article.
Owning a boat comes with a lot of responsibility to water seal the plywood flooring. You surely want to maintain your boat and increase its durability by protecting it from moisture and humidity.
Due to the affordability and easy installation, most of the boats have plywood flooring. 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 composition of the plywood. It’s made of thin layers of softwood joined together by adhesive glue and then finished off by several layers of veneers.
These veneer layers are prone to damage by moisture. That’s the main reason behind the disintegration of plywood upon water exposure.
Next, the softwood flakes peel away and gradually rot. The thin separation between the layers is a perfect spot for the molds to grow.
By the way, it’s not just water that damages the plywood; it’s the humidity as well that causes it to warp and bow.
Now that I have established firm ground to emphasize waterproofing plywood, let’s learn about the sealing techniques.
Moisture Prevention Techniques
First, it’s better to discuss moisture prevention techniques to increase the plywood sheets’ longevity.
- Keep the plywood covered during the construction process.
- Use a paintbrush to apply the waterproofing element.
- A varnish coating on the edges acts as 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 based on plywood’s indoor or outdoor use. In the case of indoor use, penetrating oils with antifungal preservatives suffice the purpose. 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. Just keep in mind 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 quite simple.
The paint-on waterproofing is done when the plywood is in its raw form 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
You need to staple 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 sheets once worn out.
The sheets don’t stick directly on the plywood floor; thus, it retains the original wood appearance. The waterproofing paint coating modifies the plywood 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 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
You need to apply the polyurethane varnish to the edges of the plywood to seal them. It’s better to apply multiple coats to seal the edges correctly.
Please be careful not to apply the varnish on the surface of the plywood. You can use masking tape to cover it.
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, it would be best if you left the plywood to dry completely for 24 hours.
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 an oil-based paint/stain. Please don’t paint the plywood earlier.
Waterproofing Process Repetition
By the way, it’s not a one-time process because you have to reapply all the layers after two years. The water sealing wears off with time, depending upon its exposure to water. For instance, if you frequently fish in salt waters, you may have to re-apply the sealer earlier.
How to Waterproof Plywood with PVA
Besides the regular waterproof paint, you can opt for PVA (polyvinyl alcohol, polyvinyl acetate). It easily adheres to the plywood surface, forming an effective 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?
In terms of quality, both are equally efficient. However, it’s recommended to apply PVA to indoor plywood as it can easily get washed away with water or rain.
Unlike the 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
You can use sealers or penetration oils to waterproof plywood sheets. Firstly, you need to moisten the plywood’s surface so that it can rise slightly. Once the surface dries, you can scrape off the surface 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 as it requires you to be extra careful about the boat corners and sides.
Deep Cleaning
Before starting the waterproofing process, you must 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 the insufficient coating. It won’t matter how many coats you apply because they won’t 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 coating 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, you’ll apply the waterproofing polish all over the boat, including the bottom side. You need to apply two coats at one time. Then, leave the boat for six to eight hours allowing the coats to dry out completely.
Lastly, again apply the third and fourth coat simultaneously. It completes the process of waterproofing a plywood boat.
Sandpaper
Waterproofing Deck
The deck is the most important of the boat, fully exposed to water spatters. You should use a unique liquid rubber waterproofing system to seal it.
The process of sealing the deck is more or less similar to the rest of the boat. All you need is to clean the surface with a dry cloth before applying the coat.
One more thing, a rubber liquid takes at least 24 hours to settle down and dry out. You should apply two to four layers for precise waterproofing.
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; however, marine plywood contains ten or even more layers.
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 use an 80 grit sandpaper for sanding the plywood surface thoroughly. The sandpaper not only evens the texture but also removes the previous sealing layer.
There are two types of sandpaper available in the market – rough and fine sandpapers. You can use both the sandpapers simultaneously.
Rough sandpaper reaches into the crevices to the wood to scrape off any previous sealing layer. When used on top of it, a fine paper gives it a uniform finishing.
After that, you need to wipe the surface with a clean cloth to remove all the unwanted particles or debris. If required, you can also wash it with water.
Now you can apply a thin layer of sealant using a paintbrush. Leave no edge or corner uncoated. It usually takes four to ten hours for one seal layer to dry out completely.
Repeat the coating process three to four times to ensure proper water sealing.
Marine Grade Wood Sealers
The market is full of waterproofing sealers; however, it’s better to do proper research before buying one.
The latest sealers not only protect against water but also from UV rays. Moreover, 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 you need to apply only two coats instead of the usual 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. It contains low VOC content ensuring low or minimal harmful odors. Moreover, it prevents the harmful UV rays from damaging the paint.
You can use TotalBoat Danish Teak Wood Sealer, which penetrates the wood cracks to ensure long-term sealing. It’s an excellent water-repellant which doesn’t make the floor slippery. This diverse sealer is best for both hard and softwoods.
Conclusion
Plywood is made with softwood layers joined together with glue. You must protect it with a durable waterproofing latex, preventing moisture or mold from getting trapped within the layers.
Waterproofing the plywood serves as a life-saver for your boat. It increases the durability and keeps it in a well-maintained condition.
All you need is to identify the use of plywood, either indoors or outdoors, and select the most suitable waterproofing techniques discussed above.
You can waterproof your plywood boat today and thank me later.
