To make plywood moisture-resistant, start by sealing all six sides—especially the edges, where end grain absorbs moisture fastest. Apply multiple coats of Marine Epoxy, polyurethane, or exterior-grade Wood Sealer, allowing proper dry times between coats to build a protective moisture barrier.
To waterproof plywood, start by selecting exterior-grade or marine-grade wood. Sand the surface smooth, thoroughly seal all exposed end-grain with exterior caulk, and coat the entire sheet with a heavy-duty waterproofing membrane, epoxy resin, or multiple layers of exterior spar urethane.
Epoxy Resin
Epoxy is a two-part system: resin and hardener. When you combine them, a chemical reaction will change the liquid into a tough, totally waterproof finish. It completely seals the wood, filling every pore and creating a surface that water literally can't penetrate.
No, standard wood stain does not make plywood waterproof.
Waterproofing plywood generally requires penetrating sealers or thick elastomeric coatings rather than standard aerosol sprays. For best results, choose a high-quality product that penetrates the grain or forms a heavy-duty, protective membrane.
The most affordable way to waterproof wood is by starting with a natural wood oil and following with a coat or two of outdoor paint. Though more budget friendly in the short term, you will need to redo this method more frequently, as it is not as long lasting as, say, a pricier, high-quality sealant.
Another way on how to waterproof plywood would be to use Polyurethane as a finish. Polyurethane is a polymer compound that is applied as a protective finish over wood surfaces across multiple applications. This plywood treatment is particularly renowned for its tough, water-resistant properties.
Painting does not make plywood completely waterproof, but it does make it highly water-resistant. A proper paint job creates a protective film that prevents moisture from soaking in, provided the film remains intact. However, exposed edges, deep scratches, or standing water can eventually cause the wood to rot or swell.
Yes, absolutely. Many exterior and specialty wood finishes are "stain and sealer in one," which add color while providing a water-resistant or waterproof barrier.
Latex-based or polyurethane-based paint is one of the most accessible forms of waterproofing plywood. There are plenty of colours to choose from, which can be applied using a spray gun or painted with a roller. You must apply two to three coats of paint for maximum effectiveness.
To DIY waterproof wood, prepare the surface by sanding and cleaning thoroughly, then apply a penetrating natural oil or a dedicated water seal. Popular options range from food-safe beeswax-and-oil rubs for bowls to heavy-duty commercial finishes like BEHR Premium Waterproofing Finish.
Homemade sealer (Mod Podge)
Mod Podge does not make wood waterproof. It is a water-based acrylic sealer and glue, meaning it is only water-resistant. While it will protect decoupaged wood from minor splashes or a damp cloth, it will soften or peel if submerged or heavily exposed to the elements.
The 30-Second Answer: To waterproof standard plywood, sand the surface, apply a wood sealer or epoxy resin to all six sides, and finish with an exterior-grade paint or varnish.
Epoxy. Epoxy sealers are usually the preferred method of sealing and waterproofing plywood. Epoxy doubles as an adhesive, which gives an additional layer of strength plus protection for the wood, helping it to last even longer. It can double as a primer too, if the wood is to be painted after sealing.
Using Liquid Rubber on Flat Plywood Decks
You'll be able to achieve a perfect, seamless finish with this product, and it can be applied to any type of wood surface, including flat plywood. The amount of Liquid Rubber Deck Coating you will need depends on the size of your deck and the desired thickness of the coating.
The cheapest way to effectively waterproof plywood is by sealing the vulnerable end grains with exterior caulk or waterproof wood glue, then applying 2-3 coats of exterior oil-based primer and high-quality exterior latex paint. This method costs approximately $15−$35 per gallon and utilizes basic supplies.
Sherwin-Williams Protective & Marine offers an extensive range of high-performance coatings and linings engineered to fight corrosion, safeguard valuable assets, enhance safety, and elevate the appearance of your marine investments.
To make wood waterproof, your best approach depends on whether you want to preserve the natural grain or use a colored paint. The most durable, highly protective waterproofing solutions include:
The cheapest way to waterproof wood is by using repurposed natural oils (like mineral oil) or repurposed used motor oil. For a natural, food-safe option, a mix of beeswax and mineral oil is highly affordable. These methods cost just pennies on the dollar compared to store-bought sealers.
Yes, Kilz manufactures specific products designed to waterproof and protect wood. However, standard Kilz primers are not waterproofing sealers and are only meant to block stains and prepare surfaces for paint.
No, standard wood stain does not make plywood waterproof.
Interior plywood uses non-waterproof glue that delaminates when exposed to moisture. Even painted or sealed, interior plywood will fail outdoors because water penetrates through cut edges and fastener holes, causing layers to separate. Always use exterior-grade (X-marked) plywood for outdoor applications.
You can paint directly on plywood, but it is highly recommended to prep the surface first. Applying a wood primer prevents the porous wood from soaking up too much paint, stops underlying knots or tannins from bleeding through, and ensures an even, lasting finish.
Yes, you can stain plywood for outdoor use, but it requires the right materials to prevent peeling, warping, or rot. Because exterior weather can be harsh on wood, your success depends on choosing the correct type of plywood, properly sealing the edges, and applying a high-quality protective finish.