How to Waterproof Plywood? 6 Methods

Written By Adam Paul - Waterproofing Expert

Plywood can be protected from the water by applying coatings and membranes on the surface. As well as some plywood has a built-in waterproofing capability. In order to protect plywood from water, you should follow these 6 methods.

6 Methods to Protect Plywood from Water

1. Apply Waterproof Sealant
2. Use Epoxy Resin
3. Use Waterproof Paint
4. Install a Waterproof Membrane
5. Use Pressure treated Plywood
6. Apply Wood Oils

Aqviz experts have prepared this method by considering several factors, such as where you can apply the waterproofing method, and how to apply the waterproofing method on the surface. And also what type of water protection it provides, its curing time, suitable products, cost per square feet, expertise to do the work, and the layer protection duration. So we recommend you to refer to this guide before applying water protections to the plywood.

1. Apply Waterproof Sealant

Applying a waterproof sealant is one of the most effective ways to create a water protective barrier on plywood. Sealants penetrate the plywood and form a hydrophobic layer that repels moisture, preventing absorption and degradation when it is open. You can use industrial-grade sealants such as polyurethane, silicone-based solutions, and penetrating epoxy, which provide superior resistance against water ingress. These coatings are widely used to seal plywood in construction, marine applications, and outdoor furniture.

Before applying waterproofing methods on plywood, you should know these important factors about the Plywood Waterproofing.

How to Apply Waterproof Sealant on the Plywood?

To apply a waterproof sealant on plywood, start by sanding the plywood surface with medium-grit sandpaper (120-150 grit) to remove imperfections and open up the pores for better adhesion. Clean the surface thoroughly with a dry cloth. You can use a brush or roller to apply the sealant evenly, ensuring full coverage. You should especially pay attention to the plywood edges, which are highly susceptible to moisture penetration. For best results, apply at least two coats on the plywood. First coat should be completely dry before applying second coat on the plywood. 

Suitable Water Conditions

Waterproof sealants protect plywood against moderate to heavy moisture exposure. Hence sealants are ideal for exterior plywood used in roofing, decks, and bathroom applications. They can resist rain, humidity, and minor water spills. But sealants are not designed for prolonged water submersion in plywood.

Curing Time of Waterproof Sealant on the Plywood

Most sealants take 12-24 hours to dry to the touch and fully cure within 48-72 hours. Environmental factors like humidity, temperature, and airflow can affect curing time. Lower temperatures and high humidity can extend the drying process, while warm, dry conditions accelerate it.

Suitable Waterproof Sealant Products for Plywood

1. Thompson’s WaterSeal Advanced Natural Wood Protector
2. Minwax Helmsman Spar Urethane
3. Rust-Oleum Marine Spar Varnish
4. Seal-Once Nano+Poly Premium Wood Sealer
5. DEFY Extreme Wood Stain & Sealer

Cost per Square Foot

The average cost of applying a waterproof sealant on the plywood ranges from $0.50 to $1.50 per square foot, depending on the type and brand of sealant used.

Level of Expertise for Applying Waterproof Sealant on the Plywood

Applying a waterproof sealant on the plywood is a beginner-friendly method, making it suitable for DIY enthusiasts. 

However, Aqviz, we recommend for large projects, hiring a professional can ensure a more uniform and durable application.

Durability of the Protection on the Plywood

A well-applied waterproof sealant can last 3-5 years on the plywood before requiring reapplication, but it depends on environmental exposure and maintenance.

2. Apply Epoxy Resin Coating

Epoxy resin is one of the most durable waterproofing solutions for plywood. Epoxy resin creates a thick, non-porous barrier on the plywood that completely seals the wood, preventing moisture penetration. Epoxy resin is widely used in plywood, where use for marine applications, construction, and outdoor furniture due to its exceptional resistance to water, chemicals, and abrasion. Unlike traditional sealants, epoxy not only protects but also strengthens plywood, making it a preferred choice for high-exposure areas.

Read more: Epoxy Waterproofing: What You Should Know?

How to Apply Epoxy Resin on the Plywood?

Before applying epoxy, the plywood must be properly prepared. So you should start by sanding the surface with 120-150 grit sandpaper to ensure better adhesion. Wipe away dust using a clean, dry cloth. Mix the epoxy resin and hardener according to the manufacturer’s instructions. Using a brush or roller, apply a thin coat evenly across the surface, ensuring full coverage, including edges and corners. Allow it to cure before applying a second coat for added protection. For better results, use a fiberglass cloth reinforcement over the plywood before applying epoxy to enhance its durability.

Suitable Water Conditions

Epoxy resin provides full waterproofing to the plywood and is suitable for high-moisture environments, including direct exposure to rain, standing water, and even full submersion in water (such as in boat-building applications). Applying epoxy resin on plywood is ideal for outdoor structures, marine plywood, and heavy-duty waterproofing projects.

Curing Time of Epoxy Resin on Plywood

Epoxy generally cures on the plywood within 24-48 hours, but full strength is achieved after 7 days. When you apply epoxy on plywood, lower temperatures slow the curing process, while warm, dry conditions speed it up. Some fast-curing epoxies set within 12 hours but require additional curing time before exposure to moisture.

Suitable Epoxy Resin Products for Plywood

1. West System 105 Epoxy Resin with 205 Hardener
2. TotalBoat Epoxy Resin
3. MAS Epoxies Penetrating Epoxy Sealer
4. System Three Clear Coat Epoxy Sealer
5. Pro Marine Tabletop Epoxy Resin

Cost per Square Foot

The cost of applying epoxy resin is  $2.00 to $5.00 per square foot. But it depends on the quality and the thickness of the epoxy.

Level of Expertise for Epoxy Resin Applying on Plywood

Applying epoxy resin on plywood requires intermediate to advanced skills, as it involves precise mixing, application, and curing process. As the first-time you should practice on a small section before tackling a full project, or consider hiring a professional for large-scale plywood applications.

Durability of the Protection of Epoxy Resin on Plywood

A properly applied epoxy coating can last 10+ years on plywood with minimal maintenance. It is one of the most durable waterproofing methods for plywood that offers excellent resistance to moisture, UV damage, and wear.

3. Use Waterproof Paint

Waterproof paint is a practical and cost-effective solution for protecting plywood from water damage. It forms a protective film over the plywood surface, preventing moisture penetration while adding an aesthetic appeal. You can use specially formulated waterproof paints, such as acrylic, latex, and oil-based exterior paints, on the plywood. They offer excellent water resistance, making them ideal for outdoor furniture, fences, sheds, and structural elements. 

How to Apply Waterproof Paint on the Plywood?

Start by sanding the plywood with 120-grit sandpaper to create a smooth, even surface. Wipe off dust using a dry cloth or tack cloth. Apply a waterproof primer to enhance adhesion and improve the paint’s durability. Once dry, use a paintbrush, roller, or spray gun to apply the first coat of waterproof paint evenly. Allow it to dry completely (as per manufacturer’s instructions) before applying a second or third coat on the plywood for maximum protection. 

Suitable Water Conditions

Waterproof paint protects plywood from moderate water exposure, humidity, and rain, making it suitable for outdoor projects, sheds, fences, and furniture. However, it is not ideal for prolonged plywood water submersion or high-moisture environments like bathrooms or marine applications.

Curing Time of Waterproof Paint on Plywood

Waterproof paint typically dries to the touch within 2-4 hours, but full curing takes 24-48 hours. 

Suitable Waterproof Paint Products for Plywoods

1. KILZ Interior/Exterior Waterproofing Paint
2. BEHR Premium Elastomeric Masonry, Stucco & Brick Paint
3. Rust-Oleum Painter’s Touch 2X Ultra Cover
4. Zinsser Watertite Mold & Mildew-Proof Waterproofing Paint
5. INSL-X Tough Shield Floor and Patio Paint

Waterproof Paint Cost for Plywood

Waterproof paint is an affordable solution, costing between $0.75 and $2.50 per square foot, depending on the brand, quality, and number of coats required.

Level of Expertise for Waterproof Paint on Plywood

Applying waterproof paint on plywood is beginner-friendly. Hence they are suitable for DIY homeowners. 

Durability of the Protection on Plywood

A high-quality waterproof paint job can last 3-7 years on the plywood. But it depends on environmental conditions, surface preparation, and maintenance.

4. Install a Waterproof Membrane

A waterproof membrane is one of the most effective long-term solutions for protecting plywood from water damage. Unlike plywood surface coatings, a waterproof membrane provides a fully impermeable layer, preventing moisture from penetrating the plywood. This method is commonly used in roofing, flooring, outdoor decking, and high-moisture environments such as bathrooms and basements. Waterproof membranes come in various forms to protect the plywood, including bituminous sheets, rubberized coatings, PVC membranes, and liquid-applied membranes, each offering superior water resistance and durability.

How to Apply Waterproof Membrane on the Plywood?

Waterproof membranes are mainly 3 types. Each type can be applied on the plywood as follow.

• Self-Adhesive Membranes (Bituminous, PVC, or Rubberized Sheets): Peel off the backing and firmly press the sheet onto the plywood. Measure whether it is fully adhered, overlap seams by at least 2 inches to prevent leaks.
• Liquid-Applied Membranes: Use a brush, roller, or spray gun to apply an even layer over the plywood. Apply multiple coats on the plywood if required, allowing each layer to dry before reapplying.
• Torch-On Membranes: Heat the underside of the membrane with a propane torch to activate the adhesive and bond it to the plywood. We recommend to use this method for experts.

Suitable Water Conditions

Waterproof membranes provide superior protection against heavy rain, standing water, and extreme humidity. They are suitable for roofing, wet rooms, exterior plywood structures, and even below-grade applications like basements.

Curing Time of Waterproof Membrane on Plywood

• Self-adhesive and torch-on membranes: Ready for use immediately after installation.
• Liquid-applied membranes: Take 24-72 hours to fully cure, depending on thickness and environmental conditions.

Suitable Waterproof Membranes Products for Plywood

1. Grace Ice & Water Shield Roofing Underlayment (Self-Adhesive Bituminous Membrane)
2. RedGard Waterproofing and Crack Prevention Membrane (Liquid-Applied)
3. Schluter Kerdi Waterproofing Membrane (Sheet Membrane for Bathrooms and Flooring)
4. Polyguard 650 Waterproofing Membrane (Bituminous Peel-and-Stick)
5. Henry Blueskin VP100 (Self-Adhering Air & Water Barrier)

Waterproof Membranes Cost per Square Foot

The cost varies depending on the type of membrane used:

• Self-Adhesive or Bituminous Membranes: $1.50 – $4.00 per square foot on plywood
• Liquid-Applied Membranes: $1.00 – $3.50 per square foot on plywood
• Torch-On Membranes: $3.00 – $5.00 per square foot on plywood (including labor)

Level of Expertise for Applying Waterproof Membranes

• Self adhesive membranes: Intermediate expert level
• Liquid applied membranes: Beginner to Intermediate expert level
• Torch on membranes: Advanced/Professional expert level

Durability of the Protection on Plywood

A properly installed waterproof membrane can last 15-25 years, depending on environmental exposure, material quality, and maintenance. It is one of the most durable solutions for protecting plywood from water damage.

5. Apply Wood Oils

Applying wood oil is a natural and effective way to protect plywood from moisture while enhancing its appearance and durability. Unlike synthetic waterproofing methods, wood oils penetrate deep into the plywood, strengthening the fibers and creating a water-resistant surface. This method is widely used for furniture, indoor flooring, wooden countertops, and decorative plywood applications. Popular wood oils include linseed oil, tung oil, teak oil, and Danish oil.

How to Apply Wood Oil on the Plywood?

Start by sanding the plywood with 120-150 grit sandpaper to remove any imperfections and open up the pores for better absorption. Wipe off the dust with a tack cloth. Using a lint-free cloth or a brush, apply a generous coat of wood oil, rubbing it into the plywood surface in the direction of the grain. Allow the oil to soak in for 30-60 minutes, then wipe off excess oil with a clean cloth. Apply at least 2-3 coats, allowing each coat to dry for 12-24 hours before reapplying on plywood.

Suitable Water Conditions 

Wood oils provide protection against light moisture, humidity, and minor water spills. They are best for indoor applications, covered outdoor furniture, and decorative plywood projects. 

Curing Time of Wood Oil in Plywood

Wood oils take 24-48 hours to dry to the touch and 7-10 days to fully cure. Drying time depends on the type of oil used, temperature, and humidity levels. 

Suitable Wood Oil Products for Plywood

1. Watco Danish Oil (Fast-drying & water-resistant)
2. Minwax Tung Oil Finish (Deep penetrating & durable)
3. Howard Feed-N-Wax Wood Polish & Conditioner (For furniture & decorative plywood)
4. Star Brite Teak Oil (Great for outdoor plywood & marine applications)
5. Boiled Linseed Oil (BLO) (Affordable & deep-penetrating).

Wood Oil Cost per Square Foot on Plywood

Wood oil treatment costs between $0.75 – $2.50 per square foot, making it a budget-friendly waterproofing option for plywood..

Level of Expertise for Applying Wood Oil on Plywood

Applying wood oils is beginner-friendly and ideal for DIY homeowners. However, achieving a smooth, even finish requires patience, proper sanding, and careful application.

Durability of the Protection on Plywood

Wood oils provide moderate waterproofing for 1-3 years, depending on usage and exposure conditions. To maintain protection, reapply oil every 6-12 months for high-use areas like tables and flooring.

6. Use Pressure Treated Plywood

Pressure-treated plywood is one of the most durable and water-resistant options for preventing moisture damage. This plywood is infused with chemical preservatives under high pressure, making it resistant to rot, fungal growth, and insect infestations. Unlike standard plywood, which is prone to water absorption, pressure-treated plywood is ideal for outdoor structures, decking, and high-moisture environments. At Aqviz, we highly recommend this method for homeowners who need a long-term, low-maintenance waterproofing solution.

Should You Waterproof Pressure Treated Plywood?

Pressure-treated plywood is factory-treated, so no additional waterproofing is required upon purchase. However, for added protection, especially in extreme weather conditions, you can apply a waterproof sealer or wood stain. When cutting pressure-treated plywood, always seal the cut edges with a wood preservative to maintain its protective barrier..

Suitable Water Conditions

Pressure-treated plywood provides excellent resistance to high humidity, rain exposure, and ground contact moisture. It is commonly used for decks, exterior walls, fences, and subflooring. However, it is not recommended for full water submersion, such as in marine applications or prolonged standing water.

Suitable Pressure Treated Plywoods for your Project

1. Yellawood pressure-treated plywood (outdoor & decking use)
2. Acq treated plywood (alkaline copper quaternary for rot resistance)
3. CCA treated plywood (chromated copper arsenate for extreme conditions – limited use)
4. Wolmanized outdoor plywood (ideal for fences & landscaping)
5. Green-treated plywood (eco-friendly, low-toxicity option)

 Pressure Treated Plywood Cost per Square Foot

The cost of pressure-treated plywood varies based on thickness and treatment type:

• Standard pressure treated plywood: $2.00 – $4.00 per square foot
• Marine grade Pressure treated plywood: $4.50 – $8.00 per square foot

Durability of the  Pressure Treated Plywood

Pressure-treated plywood can last 15-40 years, depending on exposure conditions, proper sealing, and maintenance. When used for decking or exterior walls, re-sealing every 5-7 years can further extend its lifespan.

Is There Waterproof Plywood?

Yes, marine-grade plywood is the most water-resistant plywood available. It is made with waterproof glue and has no internal voids, making it highly durable against moisture. Additionally, pressure-treated plywood and exterior-grade plywood offer water resistance but may require additional sealing.

Is Pressure Treated Plywood Waterproof?

No, pressure-treated plywood is not fully waterproof. While it is treated with preservatives to resist rot, insects, and decay, it still absorbs moisture over time. To enhance its waterproofing, sealing the surface with a waterproof coating is recommended.

Is BC Plywood Waterproof?

No, BC plywood is not naturally waterproof. It is an exterior-grade plywood with a B-grade face (smooth with minor imperfections) and a C-grade back (rougher with visible defects). While it is made with water-resistant glue, the wood itself is not waterproof and needs a sealant or waterproof coating to withstand prolonged moisture exposure.