Is Plywood Waterproof? Not at All
Plywood is a popular material used in construction, interior design, and woodworking projects. It’s made by stacking thin layers of wood veneers and sticking them together, which gives it strength and stability.
But when it comes to whether plywood can withstand moisture and water exposure, things can get confusing. Many people are unsure about its waterproofing abilities and have questions.
Is Plywood Waterproof?
Plywood is not naturally waterproof, but it does have some built-in resistance to water. The glue used to stick the layers of wood together in plywood has properties that make it resistant to moisture. This means that plywood can handle occasional exposure to water or high humidity.
However, if plywood is exposed to moisture and water for a long time, it can swell, warp, or come apart.
The edges and untreated surfaces of plywood are especially prone to water getting in.
Is Plywood Waterproof if Painted?
Painted plywood offers better resistance to water exposure compared to untreated plywood but it’s not completely waterproof. The paint creates a protective layer on the plywood’s surface that prevents immediate water penetration.
This protection is temporary and works better if you use paint made for outdoor or waterproofing purposes.
Plywood can still get damaged by water if it’s exposed to it for a long time. The paint can crack, chip, or wear off over time, allowing water to reach the wood underneath.
To make plywood more waterproof, apply waterproofing sealants or special waterproofing treatments for wood.
How Can I Waterproof Plywood?
To make plywood more water resistant, you can apply special waterproofing sealants, paints, or varnishes. These solutions seal the wood and prevent water from getting inside.
Step 1: Prepare the Surface
Make sure the plywood is clean, dry, and free from dust or dirt. Lightly sand the surface to make it smooth for the waterproofing treatment.
Step 2: Apply the Waterproofing Solution
There are different ways to waterproof plywood, depending on your preferences and project needs. You can use waterproof sealants, paint, varnish, or epoxy resin.
Sealants
Use a waterproof sealant or wood preservative and apply it all over the plywood using a brush or roller. Make sure to cover the entire surface evenly.
The sealant forms a protective layer that stops water from getting in. Follow the drying time recommended by the manufacturer.
Paints and varnishes
Look for waterproof paints and varnishes designed for outdoor or marine use. Polyurethane varnish is an excellent choice.
Apply multiple coats following the instructions, including the recommended drying time between each coat.
Epoxy resin
Epoxy resin is a strong and durable option to make plywood more water-resistant. Mix the resin and hardener as instructed and apply it to the plywood with a brush or roller.
Make sure to coat the surface evenly. Allow the epoxy to fully cure.
Pay attention to edges and joints. The edges and joints of plywood are more vulnerable to water. Apply the waterproofing treatment carefully to these areas to create a strong seal.
Remember, even with waterproofing, plywood is not completely resistant to water damage. Avoid prolonged exposure to water.
What Is the Cheapest Way to Waterproof Plywood?
The cheapest way to waterproof plywood is by using a waterproof sealant. A tub of polyurethane sealant is around $40.
Waterproof sealants are cost-effective and widely available at hardware stores or online.
What Happens if Plywood Gets Wet?
When plywood gets wet, it can swell, warp, delaminate, decay, and mold.
Plywood has a natural tendency to absorb water, especially along the edges and untreated surfaces. When exposed to water, the wood fibers absorb moisture, causing the plywood to swell.
Prolonged exposure to water can cause plywood to warp or distort. As the moisture content changes, the different layers of the plywood may expand or contract unevenly, resulting in a curved or twisted shape.
The layers of wood veneers in plywood are held together with adhesive. Excessive moisture can weaken the adhesive bonds, leading to delamination, where the layers start to separate from each other.
Moisture creates a favorable environment for decay-causing fungi and mold growth. If the plywood remains wet or damp for extended periods, it can start to rot or develop mold.
How Long Will Plywood Last in the Rain?
When plywood is left untreated and exposed to rain, it usually lasts around 1 to 3 years outdoors.
Water absorption can cause swelling, warping, and delamination, leading to decreased lifespan.
To make plywood last longer in rainy conditions, apply waterproofing treatments and ensure your plywood items are adequately protected from the rain.
