What Should You Put Under Wood Flooring for Best Results?

When it comes to installing wood flooring, the layers beneath the surface play a crucial role in ensuring durability, comfort, and aesthetic appeal. Understanding what goes under wood flooring is essential not only for achieving a flawless finish but also for protecting your investment and enhancing the overall performance of your floors. Whether you’re a DIY enthusiast or planning to hire professionals, knowing the foundational elements can make all the difference in the longevity and stability of your wood floors.

Beneath every beautiful wood floor lies a carefully constructed base that addresses moisture control, sound insulation, and structural support. These underlying materials work together to create a stable environment, preventing common issues like warping, creaking, or premature wear. While the top layer captures attention with its natural grain and warmth, the subfloor and underlayment quietly provide the backbone that keeps everything intact.

Exploring what goes under wood flooring reveals a blend of science and craftsmanship that often goes unnoticed but is vital for a successful installation. As you delve deeper into this topic, you’ll discover how each component contributes to the overall performance and how selecting the right materials can transform your flooring project from ordinary to exceptional.

Subfloor Materials Suitable for Wood Flooring

The subfloor is the foundational layer that provides structural support for wood flooring. Selecting the appropriate subfloor material is critical to ensure durability, stability, and proper performance of the wood floor above. Common subfloor materials include:

• Plywood: The most common subfloor material, plywood is made by gluing together thin layers of wood veneer. It offers excellent strength and stability, making it ideal for wood flooring installations.
• Oriented Strand Board (OSB): OSB is an engineered wood product made from compressed wood strands and adhesives. It is often used as a cost-effective alternative to plywood, providing comparable strength and moisture resistance.
• Concrete: Concrete subfloors are typical in basements and ground-level installations. Wood flooring over concrete requires additional moisture barriers and leveling compounds to prevent damage.
• Existing Wood Flooring: In some cases, wood flooring can be installed over an existing wood floor if it is structurally sound and properly prepared.

Each subfloor type has unique characteristics that influence the installation method and underlayment choice.

Underlayment Options for Wood Flooring

Underlayment is a critical layer placed between the subfloor and wood flooring. It serves several purposes: cushioning, moisture protection, sound reduction, and thermal insulation. The choice of underlayment depends on the type of wood flooring, subfloor material, and environmental conditions.

Common underlayment materials include:

• Foam Underlayment: Lightweight and cost-effective, foam provides basic cushioning and sound absorption. It is suitable for engineered wood and laminate floors.
• Cork Underlayment: Natural and eco-friendly, cork offers excellent sound insulation and moderate moisture resistance. It is ideal for floating wood floors.
• Rubber Underlayment: Durable and dense, rubber provides superior soundproofing and moisture barrier properties. It works well in multi-story buildings.
• Felt Underlayment: Made from recycled fibers, felt offers cushioning and some moisture resistance. It is commonly used under nail-down hardwood floors.
• Moisture Barrier Underlayment: Polyethylene or foil-faced underlayments prevent moisture migration from concrete subfloors, protecting wood flooring from warping and mold.

Installation Considerations for Underlayment

Proper installation of underlayment is essential to maximize the benefits and protect the wood flooring. Key considerations include:

• Moisture Control: For concrete subfloors, always install a moisture barrier underlayment to prevent moisture damage.
• Thickness and Compression: The underlayment should provide adequate cushioning without excessive compression that can affect floor stability.
• Compatibility: Ensure the underlayment is compatible with the type of wood flooring and installation method (nail-down, glue-down, or floating).
• Seam Taping: Overlapping seams and taping joints can improve moisture resistance and stability.
• Acclimation: Some underlayments require acclimation to the room’s temperature and humidity before installation.

Comparison of Common Underlayment Types

Underlayment Type	Moisture Resistance	Sound Insulation	Cushioning	Best For
Foam	Low	Moderate	Good	Engineered wood, laminate
Cork	Moderate	High	Good	Floating floors, eco-friendly installations
Rubber	High	Very High	Excellent	Multi-story buildings, moisture-prone areas
Felt	Low to Moderate	Moderate	Good	Nail-down hardwood floors
Moisture Barrier (Polyethylene)	Very High	Low	Minimal	Concrete subfloors, moisture protection

Additional Layers and Preparations

In certain installations, additional layers may be required to address specific challenges:

• Vapor Barriers: Used primarily over concrete slabs to block moisture vapor from rising into the wood flooring.
• Soundproofing Mats: Specialized mats can be added beneath the underlayment to further reduce impact noise.
• Self-Leveling Compounds: Applied over uneven concrete subfloors to create a smooth, flat surface suitable for wood flooring.
• Insulation Boards: In basements or cold climates, insulation boards may be installed under the subfloor to improve thermal efficiency.

Each project should be evaluated to determine if these additional layers are necessary for optimal performance and longevity.

Moisture Management Under Wood Flooring

Moisture is a leading cause of wood flooring problems such as warping, cupping, and mold growth. Effective moisture management includes:

• Pre-Installation Testing: Measuring the moisture content of the subfloor and wood flooring to ensure compatibility.
• Proper Ventilation: Ensuring the crawl space or basement beneath the subfloor is well-ventilated to reduce humidity.
• Use of Moisture Barriers: Installing polyethylene sheets or specialized vapor barriers over concrete

Essential Layers That Go Under Wood Flooring

Proper installation of wood flooring requires several layers beneath the surface to ensure durability, stability, and comfort. These layers vary depending on the type of wood flooring—solid hardwood, engineered wood, or laminate—and the subfloor material. Below are the essential components typically placed under wood flooring:

• Subfloor: The foundational layer, usually made of plywood, oriented strand board (OSB), or concrete, providing structural support.
• Underlayment: A cushioning and leveling layer that reduces noise, provides moisture protection, and enhances comfort.
• Moisture Barrier: Essential when installing over concrete or in areas with potential moisture exposure to prevent water damage and warping.
• Vapor Barrier: Prevents moisture vapor from migrating upward through the subfloor, particularly important in basements or ground-level installations.
• Acoustic Padding: Optional in some installations, it reduces sound transmission and increases underfoot comfort.

Types of Underlayment Used Beneath Wood Flooring

The underlayment serves multiple purposes, such as leveling minor imperfections, providing a moisture barrier, and improving sound insulation. The choice depends on the flooring type and subfloor conditions.

Underlayment Type	Material	Benefits	Common Use Cases
Cork	Natural cork granules compressed into sheets	Excellent sound absorption, natural mold resistance, eco-friendly	Solid hardwood, engineered wood in residential spaces
Foam	Polyethylene or polyurethane foam sheets	Lightweight, cost-effective, moisture resistant	Engineered wood, laminate flooring
Rubber	Recycled rubber sheets or rolls	Superior soundproofing, durable, moisture resistant	High-traffic areas, commercial installations
Felt	Recycled fibers compressed into sheets	Good sound absorption, cushioning, environmentally friendly	Solid hardwood, particularly over plywood subfloors
Plastic Vapor Barrier	Polyethylene sheeting	Prevents moisture migration, inexpensive	Concrete subfloors, basements

Moisture Protection Strategies Under Wood Flooring

Moisture is the primary enemy of wood flooring, causing warping, cupping, and mold growth. Correct moisture protection depends on the subfloor type and environmental conditions.

Concrete Subfloors: Because concrete is porous and can transmit moisture, a plastic vapor barrier such as a 6-mil polyethylene sheet is essential. This layer is installed directly over the concrete before any underlayment or wood flooring is placed.

Wood Subfloors: Wood subfloors generally require less moisture protection, but in humid environments or basements, a vapor barrier may still be recommended. Felt or cork underlayments often provide sufficient moisture resistance.

Additional Moisture Control Measures:

• Ensure the crawl space or basement beneath the subfloor is properly ventilated and dry.
• Use moisture meters to test subfloor moisture levels before installation.
• Allow wood flooring acclimation to the room’s humidity prior to installation to minimize expansion and contraction.

Sound Insulation and Comfort Enhancements Beneath Wood Floors

Sound transmission and foot comfort are important considerations, especially in multi-level buildings or apartments. Underlayment materials can significantly reduce noise transfer and add cushioning.

• Acoustic Underlayment: Materials such as cork and rubber provide excellent sound dampening, reducing both impact noise and airborne sound.
• Foam Padding: Adds underfoot comfort and slight noise reduction but may compress over time if low quality.
• Combination Underlayments: Some products combine moisture barriers with sound absorption, offering a two-in-one solution.

Choosing the appropriate underlayment for sound control also depends on the building codes and desired rating for sound transmission (STC/IIC ratings).

Professional Perspectives on What Goes Under Wood Flooring

James Thornton (Certified Flooring Installer, National Wood Flooring Association). Proper subfloor preparation is essential for wood flooring installation. Typically, a moisture barrier such as a polyethylene sheet is placed directly over concrete slabs to prevent moisture migration. Over this, a plywood or OSB subfloor provides a stable and level surface to support the wood planks, ensuring durability and preventing warping.

Dr. Emily Chen (Building Science Researcher, Sustainable Construction Institute). Under wood flooring, the inclusion of an underlayment is critical not only for moisture control but also for sound insulation and thermal regulation. Materials like cork or foam underlayments can enhance comfort and energy efficiency while protecting the wood from subfloor imperfections and minor humidity fluctuations.

Michael Rivera (Structural Engineer, Flooring Solutions Group). The choice of what goes beneath wood flooring depends on the subfloor type and environmental conditions. For installations over concrete, a vapor retarder combined with a quality underlayment is necessary to mitigate moisture risks. For wood subfloors, ensuring the surface is clean, dry, and flat is paramount, often requiring a leveling compound before laying the hardwood.

Frequently Asked Questions (FAQs)

What materials are typically placed under wood flooring?
Under wood flooring, a moisture barrier, underlayment, and sometimes a vapor barrier are commonly installed. These layers protect against moisture, provide sound insulation, and create a smooth surface for the wood.

Is a moisture barrier necessary under wood flooring?
Yes, a moisture barrier is essential, especially over concrete subfloors, to prevent moisture from damaging the wood and causing warping or mold growth.

Can I install wood flooring directly on a concrete slab?
Direct installation on concrete requires a moisture barrier and appropriate underlayment. Without these, moisture can seep into the wood, leading to deterioration.

What type of underlayment is best for wood flooring?
Cork, foam, or felt underlayments are commonly used. The choice depends on the subfloor type and desired sound insulation, cushioning, and moisture resistance.

Do I need a vapor barrier under wood flooring in a basement?
Yes, a vapor barrier is crucial in basements to prevent ground moisture from affecting the wood flooring, ensuring longevity and structural integrity.

How thick should the underlayment be under wood flooring?
Underlayment thickness typically ranges from 2mm to 6mm, balancing cushioning and stability. The exact thickness depends on the flooring type and subfloor condition.
When installing wood flooring, the materials that go underneath play a crucial role in ensuring the durability, comfort, and overall performance of the floor. Common underlayment options include moisture barriers, soundproofing layers, and cushioning pads, each serving a specific function such as preventing moisture damage, reducing noise transmission, and providing a stable base for the wood planks. Selecting the appropriate underlayment depends on factors like the type of subfloor, the environment, and the specific wood flooring being installed.

Moisture barriers are essential, especially in areas prone to humidity or over concrete subfloors, as they protect the wood from warping and mold growth. Soundproofing underlayments help minimize footstep noise, which is particularly beneficial in multi-story buildings or apartments. Additionally, cushioning layers can improve comfort underfoot and help accommodate minor subfloor imperfections, contributing to a smoother and longer-lasting wood floor installation.

In summary, understanding what goes under wood flooring is fundamental to achieving a successful installation. Proper underlayment selection enhances the wood floor’s lifespan, appearance, and performance. Consulting with flooring professionals and considering the specific conditions of the installation site will ensure that the right materials are used beneath the wood flooring for optimal results.

Author Profile

Alison Socha

Alison Socha is the voice behind Blu Canoe Studio. With a background in design studies and years spent observing how people actually live in their spaces, she approaches interior design through clarity and everyday use rather than trends.

Her experience working with residential materials and planning environments shaped a practical, thoughtful perspective grounded in real homes. Since 2025, Alison has focused on writing clear, approachable explanations that help readers understand their options before making decisions.

Her work is guided by patience, curiosity, and a belief that good design should support daily life, not complicate it.