For a bathroom floor, you should use Exterior-grade or Marine-grade plywood (like CDX or Advantech) with a minimum thickness of 34 34-inch for the subfloor. If you are installing tile, you will also need a cement backer board on top of the plywood.
For a bathroom floor, the best option is 3/4-inch exterior-grade, tongue-and-groove plywood (such as Advantech or a Sturd-I-Floor rated panel). Because bathrooms have high humidity and water exposure, you need moisture-resistant panels. Marine-grade plywood is also an excellent waterproof choice, though it is often more expensive.
For a bathroom floor, you should use Exterior-Grade or Marine-Grade Plywood. Marine-grade is the most durable, utilizing waterproof glue and zero-void veneers, but it still requires a secondary waterproof membrane—like liquid coatings or uncoupling mats—before installing tile or vinyl to prevent moisture damage.
For a highly rigid bathroom subfloor, use a minimum of 𝟑/𝟒-inch (23/32") exterior-grade tongue-and-groove plywood. If installing heavy tile, you will need a total combined thickness of at least 𝟏--𝟏/𝟖 inches, which requires adding a 1/2-inch cement backer board or uncoupling membrane on top of your 3/4-inch subfloor.
The truth is, you can use plywood in wet rooms — but only if you pick the right grade and protect it properly. Here's how to choose plywood that survives bathrooms, and where each grade actually works.
To waterproof plywood, an epoxy, waterproof paint, oil, varnish, latex or PVA can seal the wood for both indoor and outdoor use. These can come in either a paint-on or spray form, and they all bond easily to the wood to seal it and protect it from moisture.
When looking for the "best" waterproof plywood, there is technically no such thing as 100% waterproof wood. Instead, you need Marine Grade Plywood (the industry standard for water and rot resistance) or high-performance marine-grade alternatives.
Pressure-treated plywood is commonly used in subflooring and single-layer flooring for its ability to withstand potentially damp conditions. This makes it an ideal choice for areas below kitchens and bathrooms.
Particle Board (Chipboard)
Particleboard is widely used to make furniture, as well as the construction industry as a cheaper alternative to plywood. It's commonly used for shelves, cabinets, and tabletops, as well as subfloors and wall panels.
Yes, you can lay floor tiles on plywood, but you should never tile directly onto a raw plywood subfloor. Plywood is susceptible to moisture and expands or contracts with temperature changes. Tiling directly onto it will cause the wood to absorb moisture from the adhesive, resulting in cracked tiles and popping grout.
Subfloor Options
The best plywood for a bathroom depends on your application. For vanities and cabinets, use BWP (Boiling Water Proof) or Marine-grade plywood. For subfloors, exterior-grade plywood (like ACX or CDX) or specialty engineered subfloor panels are ideal.
1/2" plywood is too thin for most subfloor applications and will flex or sag, especially if joist spacing is 16 inches or more. This can lead to squeaky floors and structural issues. -> The minimum recommended is 5/8" plywood, but 3/4" is preferred for strength and long-term durability.
For bathroom applications, use Marine-grade or BWP (Boiling Water Proof) plywood. Bonded with waterproof adhesives, these materials resist delamination and swelling caused by high humidity and moisture. Standard plywood will warp and rot. Always seal exposed edges and surfaces for maximum longevity.
Paged MouldGuard plywood is a thick-layered softwood plywood, specially designed to withstand harsh weather conditions and protect against microorganisms Thanks to its advanced surface protection, this plywood is resistant to moisture absorption (in accordance with PN-EN 927-5), mold (in accordance with PN-EN 927-3), ...
Plywood is the superior choice for a bathroom subfloor. While OSB is cheaper, OSB swells, flakes, and loses structural integrity if exposed to standing water. Plywood is stiffer, has superior fastener-holding power, and dries out much faster than OSB if a plumbing leak occurs.
A mixture of wood fibers and thermoplastics, WPC is an excellent waterproof plywood alternatives. Features: Durable and moisture-resistant. Perfect for outdoor decks, fences, and bathroom furniture.
Reject Plywood, is the most economical grade at the lowest price point. Reject grade means it did not pass inspection to be first quality plywood but is often sufficient for small projects. If saving money is your priority, you will find our Reject plywood as a suitable option for you.
Oriented strand-board
Also known as OSB, oriented strand board is a popular subflooring material. OSB is similar to plywood subflooring, it has the same installation process, and it offers similar performance. However, OSB can often achieve lower costs than plywood.
In 2026, bathroom flooring trends prioritize a blend of organic warmth and dramatic, personalized style, with popular choices including travertine, limestone, large-format porcelain tiles, and intricate patterned tiles. Top trends for the year include herringbone patterns, "tile drenching" (running the same tile on floor and wall), and high-contrast, artistic patterns that turn floors into a focal point.
Exterior Plywood
This is the best general choice for bathroom subfloors because it is designed for moisture exposure. It performs well under tile, vinyl, or laminate flooring.
You need exactly 4 sheets of 4×8 plywood for a 10×12 floor, as this size totals exactly 120120120 square feet and each sheet covers 323232 square feet.
To effectively waterproof plywood, coat the edges with caulk, then apply an epoxy resin for heavy-duty sealing, or use liquid rubber or marine-grade polyurethane for flexible exterior surfaces. Always seal edges—the most vulnerable area—with epoxy or hardwood glue.
Plywood can typically withstand rain exposure for a day or two without significant damage, depending on the type of layered wood and the severity of the rain. However, long-term exposure can lead to serious damage such as warping, cracking, or rotting.
Boiling Water Test
In this test, a small sample of plywood is boiled in water for several hours. High-quality sheets will remain intact without surface bubbles, cracks, or layer separation. If the plies stay firmly bonded after boiling, it indicates strong waterproof properties and reliable adhesive quality.