Is plywood or OSB better for a bathroom floor?

Author: Dr. Orion Green  |  Last update: Thursday, July 10, 2025

Both OSB and plywood are great materials for a subfloor, but in our books, there's one winner. Plywood is simply a much better product from different perspectives, from water-resistance to durability.

Should I use OSB or plywood for bathroom subfloor?

Plywood is the correct substrate for a bathroom floor really - it has the best moisture resistance. While, ideally, your subfloor shouldn't actually get wet, there is always a puddle that seeps past a compromised mastic joint or something somewhere that gets it wet eventually.

What is the best board for a bathroom floor?

Plywood is the correct substrate for a bathroom floor really - it has the best moisture resistance. While, ideally, your subfloor shouldn't actually get wet, there is always a puddle that seeps past a compromised mastic joint or something somewhere that gets it wet eventually.

What is the best subfloor to use in a bathroom?

Cement board is best suited for: Ceramic and Porcelain Tile: Cement board is specifically designed to be a moisture-resistant substrate for tile in high-moisture areas like bathrooms and kitchens.

What plywood should I use for a bathroom floor?

Many bathroom flooring projects have traditionally employed external grade plywood as the subfloor, with CDX plywood (34" in particular) being popular due to its strong moisture and humidity resistance.

Which is better, OSB or Plywood?

What is the best base for a bathroom floor?

The best flooring options for bathrooms are floors that can withstand moisture and humidity, aren't slippery when wet, are easy to clean, and comfortable underfoot. In terms of withstanding moisture and humidity, luxury vinyl tiles (LVT), vinyl roll, and porcelain or ceramic tile are the best bathroom flooring options.

What wood should I use for a bathroom floor?

Teak, ipe, and white oak rank as three of the best bathroom floor wood options due to their water-resistance. Look for wood floors with a hardness rating of at least 1,200 on the Janka scale to stand up to bathroom foot traffic. Choose wide-plank wood floors over thin strips to minimize seams and moisture issues.

Is plywood or OSB better for showers?

Humid conditions - Plywood is the safer choice in damp basements, bathrooms and other humid indoor areas where moisture damage is a concern.

How to waterproof a plywood bathroom floor?

Methods for Waterproofing Plywood
  1. Mix the epoxy according to the manufacturer's instructions.
  2. Apply a thin, even coat using a paintbrush or roller.
  3. Allow the first coat to dry completely before applying additional coats.
  4. Sand lightly between coats for better adhesion.

What is the best thing to put on the bathroom floor?

Ceramic tiles

Perfect for muddy footprints, rainy days, and accidental spillages. Water-resistant ceramic tiles are a great choice for your bathroom floor. They are glazed, resistant against stains, and water damage.

What thickness of plywood for bathroom floor?

Flooring grade, 15-18mm plywood should be fixed to the existing subfloor in a brick bond or staggered fashion so the joints are not uniform, screwed down at 300mm centres, ensuring the screw heads are flush with the boards surface.

Is plywood waterproof for a bathroom?

Unlike other wood-based materials, plywood isn't fully waterproof. Still, the good news is that you can produce waterproof plywood, thereby giving your furniture a longer life. You must seal your plywood, mainly if used in high-moisture areas such as bathrooms, kitchens, or outdoors.

Is plywood or cement board better for bathroom floor?

Plywood may be the more budget-friendly option, but it is less moisture-resistant and stable than cement board. Cement board is better for areas with movement, water exposure, and subfloor imperfections, like kitchens, bathrooms, and laundry rooms. But plywood is an acceptable choice if your subfloor is dry and stable.

Why use OSB instead of plywood?

OSB is generally less expensive than plywood. OSB is more uniform, with fewer voids, soft spots, or gaps. OSB is considered by many to be a more environmentally friendly product since it can be made from scrap and smaller trees, rather than old-growth trees. OSB does not delaminate, as plywood can.

Is OSB or plywood better for moisture?

Plywood absorbs water faster than OSB but it dries faster compared to OSB. This could be a major issue, especially when used as material for new roof installations. OSB tends to puff up like a sponge when wet, especially around the edges.

What board to use for a bathroom floor?

Backer boards serve as a stable and moisture-resistant surface to support and protect tiles from damage and moisture-related issues. As a result, they are commonly used in wet areas like bathrooms, kitchens, and showers, as well as for exterior applications.

What is the best plywood for bathroom floor?

Moisture Resistance: For areas prone to moisture, such as bathrooms or basements, it is crucial to use plywood with higher moisture resistance. Marine-grade plywood or pressure-treated plywood can be excellent choices in these scenarios.

Do you need a vapor barrier on a plywood subfloor?

Yes. Hardwood flooring is quite sensitive to moisture and it's always worth adding a moisture barrier during installation. It is a necessity with concrete subfloors and damp areas, but water-resistive underlayments should be considered with other subfloors as well.

What is the best waterproof flooring for a bathroom?

Specifically, ceramic and porcelain tiles are great options for bathrooms. Tile flooring is resilient, waterproof, available in a variety of colors and designs, and generally less expensive than other hard surface options. Porcelain tiles absorb less water than any other ceramic product.

Is plywood or OSB better for bathroom subfloor?

Both plywood and OSB are effective choices for your subfloor needs. Plywood is a better option for projects that require a lot of cutting and molding, while OSB is a good option for those who need to cover areas where moisture exposure may be an issue.

What is the disadvantage of OSB?

“The major disadvantage of OSB is that if it gets exposed to significant amounts of water or moisture, the edges expand by up to 15% ... especially if they are cut edges. This swell will then telegraph onto the shingles or some flooring," according to PATH.

Which side of OSB is more waterproof?

Using OSB Safely

When installing in vertical applications such as wall sheathing, you'll want to orient the smooth or stamped side facing out. The smooth side has a better moisture resistance and will ultimately provide better performance against weather.

What is the best waterproof wood for bathrooms?

Oak: Oak is a robust wood with water-resistant qualities. It is also well known for its durability and can cope well with moisture if it is sealed correctly. Larch: Due to its natural resin content, larch wood is particularly durable against moisture and putrefaction.

What is the best flooring for a small bathroom?

Luxury Vinyl Tile (LVT) is a superstar when it comes to small bathroom remodels. Why? Because it offers the look of natural stone or wood, without the high maintenance or cost. LVT can be waterproof, durable, and incredibly easy to clean—a must for any bathroom.

Do I need marine plywood for a bathroom floor?

Using marine grade plywood can offer a different aesthetic than the standard materials used in bathrooms. It will also withstand the high moisture environment that comes from the shower and sink. Using it for flooring or a sink backsplash means you won't be taking any chances with rot or mold in your bathroom.

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