Best Subfloor for Bathroom – Comparison, Benefits, and Guide

When it comes to bathroom renovations or new construction, choosing the right subfloor is essential for ensuring a solid foundation and long-lasting flooring.

But with so many options out there, it is hard to pick the right material that matches your project requirements, right? Well, not anymore!

Plywood is the best choice for a bathroom subfloor due to its versatility, affordability, and high moisture resistance. With a smooth and level surface, plywood can accommodate various flooring types, making it a flexible option for any bathroom design.

In this blog, we will explore the top five options for determining the best subfloor for bathroom that excel in moisture resistance, durability, and suitability for bathroom environments.

5 Best Subfloors for Bathrooms

In this section, I will provide you with a complete overview of the best subflooring options that will give your bathroom a complete overlook!

Subflooring OptionKey FeaturesMoisture ResistanceInstallation StabilitySound InsulationCompatibility
PlywoodVersatile, smooth surface, affordableHigh resistanceRelatively easyMore flexible and may require additional support for heavier flooringProvides some noise reductionSuitable for various flooring types
Cement BoardDurable, moisture-resistant, stable surfaceResistant to water damage, prevents mold and mildew growthMore complexRigid and stable, suitable for tilesProvides limited noise reductionExcellent for tile installations
Oriented Strand Board (OSB)Cost-effective, good structural stabilityRequires moisture barrier, less moisture-resistant compared to other optionsModerate complexityStrong and durableOffers some noise reductionCompatible with various flooring types
AdvanTech SubflooringExceptional moisture resistance, dimensional stabilityHighly resistant to moisture and swellingEasy installationProvides exceptional stability and prevents floor squeaksProvides some noise reductionSuitable for various flooring materials
DITRA or Schluter SystemsAdvanced waterproofing, uncoupling propertiesEffective waterproofing, prevents subfloor damage and tile failureModerate complexityMinimizes the risk of tile cracks caused by subfloor movement or expansionLimited noise reductionCompatible with cement board or plywood subfloors


Plywood is a versatile and most commonly utilized material for bathroom subfloors. It offers a smooth and level surface that can accommodate various types of flooring.

When selecting plywood for a bathroom subfloor, it is crucial to choose exterior-grade plywood that is specifically designed for wet areas to ensure its durability and moisture resistance.

One of the key advantages of using plywood is its affordability. Compared to other subfloor options, plywood is relatively cost-effective, making it a popular choice for many homeowners.

Additionally, plywood is widely available and easy to work with, allowing for straightforward installation.

To enhance the moisture resistance of plywood in a bathroom setting, applying a waterproofing membrane or sealer is essential.

This additional layer acts as a barrier, protecting the plywood from water damage and preventing moisture from seeping through to the subfloor.

Proper waterproofing measures are crucial to ensure the longevity and performance of the subfloor.

However, there are a few considerations to remember when using plywood as a bathroom subfloor.

First, plywood is highly water resistant but still susceptible to water damage if not adequately sealed or protected. Any moisture infiltration can cause the plywood to swell, warp, or rot over time.

Therefore, it is crucial to address any leaks or moisture issues promptly to prevent damage to the subfloor.

Another factor to consider is the potential for plywood to expand or contract with changes in humidity and temperature.

Proper spacing and installation techniques, such as leaving small gaps between plywood sheets, can help accommodate these fluctuations and prevent buckling or warping.

While plywood provides a suitable base for various flooring types, it may be more flexible and stable than other options like cement board.

This can be a concern when installing heavier or more delicate flooring materials, such as tiles.

Additional measures, such as adding an underlayment or reinforcing the plywood with additional support, may be necessary to ensure adequate stability.

In terms of sound insulation, plywood offers some degree of noise reduction, but it may provide less soundproofing than other materials.

When choosing plywood, it is important to select exterior-grade plywood designed for wet areas and apply proper waterproofing measures.

While plywood offers a smooth surface for various flooring types, it may require additional moisture resistance and stability precautions.

Cement Board

A cement board is a popular choice for bathroom subfloors due to its durability and moisture-resistant properties.

It is composed of a combination of cement and reinforcing fibers, creating a strong and stable surface that can withstand the demands of a bathroom environment.

The primary advantage of using cement board is its resistance to water damage.

Bathrooms are prone to moisture and water exposure, making it crucial to have a subfloor to withstand these conditions.

Cement board effectively prevents water penetration, minimizing the risk of subfloor damage and potential issues such as warping, rotting, mold, and mildew growth.

In terms of installation, a cement board is typically placed over a plywood or OSB subfloor. This adds an extra layer of stability and ensures a solid base for the finished flooring.

The cement board is secured to the subfloor using screws or mortar, providing a secure and immovable surface.

One of the key advantages of cement board is its compatibility with tile installation.

Its rigid and level surface is particularly well-suited for tiles, offering a sturdy foundation that helps prevent cracking or shifting over time.

This makes cement board an excellent choice for bathrooms where tiles are the desired flooring material.

However, there are a few considerations when using cement board as a bathroom subfloor.

Firstly, the installation process can be more complex than other options, as it requires properly cutting, fitting, and securing the boards.

It may involve specialized tools and techniques, and professional assistance may be beneficial for ensuring accurate installation.

Cement boards are heavier compared to alternative subfloor materials, which may require additional structural support or reinforcement, particularly in older homes or when replacing an existing subfloor.

Cost is another factor to take into account. Cement board is generally more expensive than plywood or OSB, which can impact the overall budget for the bathroom flooring project.

Additionally, cement boards can feel cold underfoot, especially in colder climates or without proper insulation or heating systems.

This may affect the comfort level in the bathroom, and using rugs or installing floor heating can help mitigate this issue.

Lastly, while cement board offers some degree of sound insulation, it may provide little noise reduction on its own.

Additional measures, such as incorporating acoustic underlayment, may be necessary if soundproofing is a priority.

Oriented Strand Board (OSB)

Oriented Strand Board (OSB) is an engineered wood product commonly used as a bathroom subfloor.

It is created by compressing and bonding wood strands together with resin, resulting in a strong and durable material.

One of the main advantages of OSB is its cost-effectiveness, making it a popular alternative to plywood.

In terms of structural stability, OSB performs well and provides a solid base for various flooring types.

It offers good load-bearing capacity, allowing it to support heavy fixtures and furniture in the bathroom.

The composition of OSB, with its oriented strands and resin bonding, contributes to its strength and resilience.

However, it is important to note that OSB is less moisture-resistant than some other subfloor options.

When exposed to excessive moisture or water, OSB can swell, warp, and deteriorate over time.

To mitigate this risk, it is crucial to use a moisture barrier, such as a waterproofing membrane, over the OSB subfloor in wet areas like bathrooms.

This barrier acts as a protective layer, preventing moisture from seeping into the OSB and causing damage.

It is important to leave small gaps between the OSB sheets to allow for natural expansion and contraction with changes in humidity.

This helps minimize the risk of buckling or warping.

Compared to other subfloor options, such as cement board, OSB may require extra precautions to ensure its moisture resistance.

However, with the appropriate measures in place, such as proper sealing and waterproofing, OSB can provide a reliable and functional subfloor in bathroom settings.

OSB offers some degree of sound reduction, helping to minimize noise transmission between floors.

OSB can accommodate various types of flooring, including tiles, vinyl, and laminate.

AdvanTech Subflooring

AdvanTech Subflooring is a premium option specifically engineered for high-performance bathroom subfloors.

It is renowned for its exceptional moisture resistance and dimensional stability, making it an ideal choice for wet environments.

The key feature of AdvanTech subflooring lies in its construction. It is made with a resin-saturated overlay and high wood density, resulting in a product that offers superior protection against moisture and swelling.

This moisture resistance is crucial in bathroom applications, where exposure to water and humidity is common.

With AdvanTech, you can have peace of mind knowing that your subfloor is well-protected against moisture-related issues.

In addition to its moisture resistance, AdvanTech subflooring provides a solid and stable base for various flooring materials.

It minimizes floor squeaks and enhances the overall structural integrity of the bathroom floor.

This stability is particularly important when installing heavier fixtures, such as bathtubs or cabinets, ensuring that the subfloor can adequately support the load.

AdvanTech subflooring is specifically designed to withstand high humidity levels and wet environments. It is engineered to resist swelling, warping, and delamination, even when exposed to prolonged moisture.

This durability and resilience make it an excellent choice for bathroom subfloors, where moisture is a constant factor.

Furthermore, the superior dimensional stability of AdvanTech subflooring ensures that it maintains its shape and integrity over time.

This reduces the risk of uneven floors or gaps developing between floorboards, providing a smoother and more aesthetically pleasing surface for the final flooring material.

When it comes to installation, AdvanTech subflooring is easy to work with. It can be fastened securely using nails or screws, providing a reliable and secure base for the flooring.

Its consistent thickness and flatness make it a convenient choice for installation, saving time and effort during construction.

DITRA or Schluter Systems

DITRA and Schluter Systems are innovative and widely used membrane systems specifically designed to enhance the performance of tile installations in bathrooms.

These systems offer advanced waterproofing and uncoupling properties, ensuring the longevity and durability of the tile surface.

Both DITRA and Schluter Systems consist of a polyethylene membrane with a unique grid structure.

This grid creates an airspace between the subfloor and the tile, providing effective waterproofing by preventing moisture from penetrating the subfloor.

This feature is especially crucial in bathrooms, where water exposure is common and can lead to subfloor damage, mold growth, and tile failure.

One of the key benefits of DITRA and Schluter Systems is their ability to uncouple the tile from the subfloor.

This means that any movement or expansion in the subfloor does not transfer directly to the tile, minimizing the risk of cracks and damage.

The uncoupling effect is particularly important in areas prone to temperature fluctuations or structural movement.

DITRA and Schluter Systems are often used in conjunction with cement boards or plywood subfloors.

The membrane is applied over the subfloor, and the tile is installed on top of it using appropriate tile adhesives.

This combination provides a solid and stable surface for the tile, ensuring proper adhesion and reducing the likelihood of tile breakage.

In terms of installation, DITRA and Schluter Systems are relatively straightforward to work with.

The membrane rolls are easy to handle and can be cut to fit the specific dimensions of the bathroom floor.

The grid structure allows for proper bonding with the tile adhesive, ensuring a secure installation.

Bathroom Subfloor Replacement – DIY Guide

Replacing a bathroom subfloor is a significant undertaking that requires careful planning and execution.

A sturdy and moisture-resistant subfloor is crucial for your bathroom’s long-term stability and performance.

Whether you’re dealing with water damage, rot, or simply upgrading your subflooring, this comprehensive guide will walk you through the process of replacing your bathroom subfloor.

Step 1: Assessment and Planning

  • Carefully examine the current subfloor for any visible damage, such as rot, water stains, or soft spots.
  • Look for signs of mold or mildew, which indicate moisture issues.
  • If the damage is localized to a specific area, you may only need to replace a portion of the subfloor.
  • However, a full subfloor replacement may be required if the damage is extensive or the subfloor is generally compromised.
  • Use a measuring tape to determine the length and width of the bathroom floor.
  • Multiply the length by the width to calculate the total square footage of the floor.
  • Take note of any irregularities or obstructions, such as alcoves or corners that may require additional measurements and adjustments.
  • Determine if any plumbing pipes, drain lines, or electrical wiring need to be relocated or adjusted to accommodate the new subfloor.
  • Consider the installation of floor drains, if needed, and plan for their proper positioning in relation to the subfloor.

Required Tools

  • Measuring tape
  • Paper and pencil

Step 2: Safety Precautions

  • Wear safety goggles to protect your eyes from debris or dust particles that may be released during the subfloor replacement process.
  • Put on gloves to safeguard your hands from sharp edges, splinters, or any potential hazards.
  • Wear a dust mask to prevent inhaling dust or harmful particles that may be generated during the removal of the old subfloor.
  • Before starting the subfloor replacement, locate the bathroom’s water supply shut-off valve and turn it off.
  • Disconnect any electrical connections, such as lighting fixtures, outlets, or switches, to ensure your safety while working on the subfloor.
  • Open windows and doors to allow fresh air to circulate in the workspace. This helps dissipate any dust, odors, or fumes that may arise during the subfloor replacement.

Required Tools

  • Safety goggles
  • Gloves
  • Dust mask
  • Flashlight
  • Window or fan

Step 3: Removing the Old Subfloor

  • Start by disconnecting the water supply and draining the toilet tank and bowl.
  • Remove the toilet by unscrewing the bolts and securing it to the floor. Set the toilet aside in a safe area.
  • Disconnect the sink and remove it from its mounting.
  • If any cabinets or furniture are attached to the subfloor, remove them as well.
  • Depending on the type of flooring, use appropriate tools such as a pry bar, hammer, or floor scraper to carefully remove the tiles, vinyl, or any other flooring material.
  • Work systematically, starting from one corner and gradually moving across the entire bathroom floor.
  • Use a pry bar and hammer to detach the old subfloor from the floor joists carefully.
  • Start at one edge of the subfloor and work your way towards the center, gradually separating it from the floor joists.
  • Take caution not to damage the joists or any plumbing or electrical lines running through the subfloor.

Required Tools

  • Pry bar
  • Hammer
  • Floor scraper
  • Screwdriver or wrench
  • Utility knife

Step 4: Repairing Joists and Framing

  • Use a flashlight to thoroughly inspect the entire length of each joist, paying close attention to areas near plumbing fixtures or where moisture may have been present.
  • If you encounter any damaged or weakened floor joists, it is crucial to reinforce or replace them to ensure a solid and level foundation.
  • Reinforcing a joist can involve sistering, which is attaching a new piece of lumber alongside the existing joist or using steel plates or brackets for added support.
  • If a joist is beyond repair, it may need to be replaced entirely. Measure and cut a new joist to fit the exact length and dimensions needed.
  • Inspect the framing around the bathroom area, including walls, beams, and other structural elements.
  • Look for any signs of damage, such as cracks, warping, or shifting.
  • Make any necessary repairs like reinforcing weak areas, replacing damaged components, or consulting a professional for guidance.

Required Tools

  • Flashlight
  • Measuring tape
  • Circular saw or reciprocating saw
  • Lumber
  • Steel plates or brackets
  • Nails or screws
  • Level

Step 5: Installing the New Subfloor

  • Measure and mark the bathroom dimensions on the new subfloor material, accounting for any necessary adjustments or cutouts for fixtures and pipes.
  • Use a circular saw or a jigsaw to cut the subfloor panels to the appropriate size carefully.
  • Remember to leave a 1/8-inch gap around the edges to allow for expansion.
  • Apply a generous amount of construction adhesive to the top of the floor joists. This adhesive helps enhance stability and prevents squeaks in the subfloor.
  • Begin laying the subfloor panels, starting from one corner of the bathroom.
  • Stagger the seams between the panels to improve strength and stability.
  • Ensure that the panels fit snugly against each other without any gaps or overlaps.
  • Use a rubber mallet or a hammer and a scrap piece of wood to tap the panels into place.
  • Secure the subfloor panels to the floor joists using flooring screws. It’s generally recommended to use screws for better holding power.
  • Drive the fasteners through the subfloor and into the joists 6 to 8 inches apart along the edges and 12 to 16 inches apart in the field of the panel.
  • Make sure the fasteners are countersunk slightly below the subfloor’s surface to avoid any interference with the subsequent flooring installation.
  • To prevent squeaks and improve stability, install blocking or bridging between the floor joists by adding additional pieces of lumber perpendicular to the joists.
  • Cut the blocking or bridging material to fit between the joists and secure it in place using nails or screws.
  • This helps distribute the load evenly and minimizes any potential flexing or movement.

Required Tools

  • Circular saw or jigsaw
  • Measuring tape
  • Construction adhesive
  • Rubber mallet or hammer
  • Scrap piece of wood
  • Flooring screws
  • Drill or screwdriver
  • Nail gun
  • Carpenter’s square
  • Chalk line

Step 6: Waterproofing and Moisture Protection

  • Select a high-quality waterproofing membrane or sealer specifically designed for subfloors in wet areas like bathrooms.
  • Start by applying the waterproofing material to the subfloor surface using a brush, roller, or trowel.
  • Focus on sealing the seams between subfloor panels and any corners or areas where water is likely to accumulate, such as near showers or bathtubs.
  • Apply an additional waterproofing membrane or sealer layer to these critical areas for added protection against moisture intrusion.
  • After applying the waterproofing material, allow it to cure and dry completely according to the manufacturer’s instructions.

Required Tools

  • Waterproofing membrane or sealer
  • Brush, roller, or trowel

Step 7: Reinstalling Fixtures and Finishing Touch

  • Start by reattaching the toilet, sink, and any other fixtures removed during the subfloor replacement process.
  • Ensure proper alignment and secure them tightly to prevent any movement or leaks.
  • Ensure the subfloor is clean, dry, and free of debris or imperfections before laying the new flooring.
  • Install the trim or molding securely, ensuring it aligns with the flooring and provides a clean transition between the floor and walls.
  • Check for any signs of unevenness, squeaks, or movement in the subfloor.
  • Verify that the bathroom floor feels solid, stable, and level when walked upon.
  • Look for any gaps or areas that may require additional sealing or finishing touches.

Required Tools

  • Screwdriver or wrench
  • Trim or molding materials
  • Miter saw or coping saw
  • Nails, screws, or adhesive
  • Caulk or sealant
  • Level

By following this step-by-step guide, you can successfully replace your bathroom subfloor, ensuring a stable and moisture-resistant foundation for years to come.

Bottom Line

In conclusion, selecting the best subfloor for your bathroom is crucial for ensuring a durable and moisture-resistant foundation.

In this blog, we have explored the different types of subfloors available and discussed their benefits and considerations.

Throughout the guide, I have provided a detailed step-by-step process for replacing a bathroom subfloor, emphasizing safety precautions and necessary tools for each stage.

So, what’s holding you back? Get your toolbox and start renovating your bathroom today!


What is the best bathroom subfloor thickness?

The best bathroom subfloor thickness is at least 1 ⅛ inches. By ensuring a minimum thickness of 1 ⅛ inches, you can create a solid foundation that will effectively support your chosen bathroom flooring.

What is the best material for a subfloor?

The best material for a subfloor is plywood. While standard plywood is suitable for subflooring, the best option is ¾” tongue-and-groove plywood subflooring.

This type of plywood offers enhanced stability and strength due to its interlocking design, providing a solid base for various types of flooring materials.

Which plywood is best for bathroom?

The best plywood for bathroom use is Boiling Waterproof or BWP-grade plywood. This type of plywood is specifically designed to withstand high moisture levels and prolonged exposure to water.

It is highly resistant to water damage, making it an ideal choice for areas such as bathrooms where moisture is a constant concern.

BWP-grade plywood offers excellent durability and can withstand the humid and wet conditions typically found in bathrooms.