underlayment plywood

Plywood underlayment is a thin plywood sheet mainly used under resilient flooring such as vinyl and linoleum sheets and tiles. Though it can also be placed under hardwood, laminate, and carpet, this is now less frequent as subflooring is usually smooth enough for these materials. Many of these materials come with their own underlayment or padding. Plywood underlayment provides a flat, smooth surface, eliminating the voids, knots, and surface flaws often found in subflooring.
> Read more: plywood sizes, 3/4 plywood, 4×8 plywood, 1/2 plywood, 5/8 plywood, 1/4 plywood

What plywood is used for underlayment?

For underlayment, you typically use plywood that is specifically designed for this purpose. Underlayment-grade plywood is smoother and more uniform than standard construction plywood, providing a stable base for various flooring types such as vinyl, laminate, and carpet. Common types include:

  • BC Plywood: One side is sanded smooth, ideal for a uniform underlayment surface.
  • AC Plywood: AC plywood is frequently used, where “A” denotes a smooth, sanded face that is free of defects, and “C” indicates the back side, which may have minor imperfections.
What plywood is used for underlayment?
What plywood is used for underlayment?

Do I need underlayment over the subfloor?

Yes, underlayment is generally recommended over the subfloor for several reasons:

  • Smooth Surface: It provides a smooth and level surface for the final flooring, preventing imperfections from showing through.
  • Moisture Barrier: Some underlayment options offer additional moisture protection.
  • Sound Reduction: It can help reduce noise, making the floor quieter underfoot.

However, the specific need and type of underlayment will vary based on the flooring material and subfloor condition. Here are some considerations:

  1. Type of Flooring:
    • Laminate Flooring: Typically requires underlayment to provide cushioning, sound absorption, and moisture protection.
    • Engineered Hardwood: Often benefits from underlayment for added stability and moisture control.
    • Vinyl Plank Flooring: Some types come with built-in underlayment, but if not, a separate underlayment can help with cushioning and noise reduction.
    • Carpet: Usually has a separate underlayment or padding to enhance comfort and extend the carpet’s life.
    • Tile: Requires a very smooth and stable surface, so a cement board or similar hard underlayment is often necessary to prevent cracks.
  2. Condition of the Subfloor:
    • Uneven Subfloor: If your subfloor has imperfections, underlayment can help create a smooth surface.
    • Moisture Concerns: In areas prone to moisture, such as basements or bathrooms, underlayment with moisture barriers is crucial.
    • Sound Insulation: In multi-story buildings, underlayment can provide sound insulation, reducing noise transmission between floors.
  3. Manufacturer’s Recommendations:
    • Always follow the flooring manufacturer’s guidelines. Some flooring products have specific underlayment requirements to maintain warranties and ensure optimal performance.
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Do I need underlayment over the subfloor?

Which is stronger plywood or underlayment?

In terms of subfloor materials, plywood is generally considered stronger and more durable compared to underlayment. This strength and durability are factors that very discerning home buyers might consider when evaluating properties, potentially placing a slight premium on homes with plywood subfloors.

Is underlayment plywood waterproof?

Underlayment plywood can be water-resistant but not entirely waterproof. It’s designed to handle minor spills and moisture exposure, but prolonged contact with water can still cause damage. For areas prone to moisture, consider using moisture-resistant or waterproof underlayment products.
> Read more: laminate flooring, hardwood flooring, baltic birch plywood, maple plywood, ACX plywood, BBOES plywood

What is the best material to use for underlayment?

The best material to use for underlayment plywood depends on the type of flooring and specific requirements of your project. For carpet underlayment, foam or rubber carpet padding is commonly used, especially when the subfloor (whether wood or concrete) is in good condition. Here are some popular types of carpet padding:

  1. Rebond Padding: Made from recycled pieces of high-density foam, rebond padding is one of the most popular types. It provides good cushioning and durability.
  2. Memory Foam Padding: This type of padding contours to the shape of your foot and provides excellent comfort underfoot.
  3. Waffle Rubber Padding: Waffle rubber padding offers good support and resilience, making it suitable for high-traffic areas.
  4. Fiber Cushion Padding: Fiber cushion padding is made from natural or synthetic fibers and provides a firm support for the carpet.
  5. Rubber Padding: Rubber padding is durable and resistant to moisture, making it suitable for areas prone to moisture.

When choosing carpet underlayment, consider factors such as the carpet type, traffic levels, moisture resistance, and comfort requirements. It’s also important to follow the carpet manufacturer’s recommendations for underlayment to ensure proper installation and performance of the carpet.

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What is the best material to use for underlayment?

How thick should plywood underlayment be?

The thickness of plywood underlayment typically depends on the type of flooring being installed and the condition of the subfloor. Here are some general guidelines:

  1. Laminate Flooring: For laminate flooring, a plywood underlayment thickness of 1/4 inch to 3/8 inch is usually sufficient. It provides a smooth surface and helps to cushion the flooring.
  2. Vinyl Flooring: For vinyl sheet or vinyl tile flooring, a 1/4 inch thick plywood underlayment is common. This helps to ensure a smooth, defect-free surface that won’t telegraph imperfections from the subfloor.
  3. Hardwood and Engineered Wood Flooring: For hardwood or engineered wood flooring, the plywood underlayment might range from 3/8 inch to 1/2 inch thick. This provides a solid and stable base that can support the weight of the wood flooring.
  4. Tile Flooring: When installing tile, a thicker underlayment is needed to provide stability and prevent cracking. Cement board or a similar underlayment is typically used, but if plywood is used as an additional layer, it should generally be at least 1/2 inch thick.
  5. Condition of Subfloor: If the subfloor has significant imperfections or is not level, a thicker underlayment might be necessary to create a smooth surface.
Underlayment in the corner
Underlayment in the corner

Can I use regular plywood for underlayment?

Using regular plywood for underlayment is possible, but it may not provide the best results compared to specially designed underlayment plywood. Here are some considerations:

  1. Smoothness: Underlayment plywood is typically sanded to be smooth and free of voids or imperfections. Regular plywood may have surface defects that could telegraph through thinner flooring materials like vinyl or laminate.
  2. Moisture Resistance: Underlayment plywood often has better moisture resistance properties compared to regular plywood, which helps prevent warping or swelling when exposed to moisture.
  3. Thickness and Stability: Underlayment plywood is manufactured to provide a stable and even base. Regular plywood might not offer the same level of stability, particularly in thinner sheets.
  4. Adhesive Compatibility: Some flooring types require adhesive for installation, and underlayment plywood is designed to work well with these adhesives. Regular plywood might not adhere as effectively.

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Should you nail or screw plywood underlayment?

For securing plywood underlayment, both nails and screws can be used, but screws are generally preferred:

  • Screws: Provide a more secure and stable hold, reducing the risk of movement over time.
  • Nails: Can be used, but may not offer the same level of security and might lead to squeaking floors.

Does plywood underlayment need to be glued down?

Gluing down plywood underlayment is not always necessary, but it can add stability and reduce movement:

  • With Glue: Provides a stronger bond, ideal for high-traffic areas.
  • Without Glue: Still effective, especially when using screws or nails properly.

Does plywood underlayment need gaps?

Yes, plywood underlayment should have small gaps, typically 1/8 inch, between sheets to allow for expansion and contraction due to changes in humidity and temperature. This prevents buckling and other issues over time.


Selecting the right plywood underlayment and installing it correctly is essential for achieving a high-quality, long-lasting floor. Consider the type of plywood, the necessity of underlayment, its water resistance, appropriate thickness, and proper installation techniques to ensure the best results for your flooring project. By following this comprehensive guide, you’ll be well-equipped to make the right choices for your home or commercial space.
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