Thick vs. Thin Underlayment: Which Should You Choose?

Many assume that thicker underlayment is the superior option for flooring projects, but this is not always the case. While thicker underlayment is ideal for certain applications and flooring types, other flooring projects require thinner options. Matching the right underlayment thickness to your precise project requirements is vital for a new floor’s durability, sound insulation, and moisture protection.

Understanding Underlayment Basics

Underlayment is a crucial foundational layer between a subfloor and a finished flooring material. It comes in a wide spectrum of materials and thicknesses, ranging from 1 mm to 12 mm. Each thickness is intended for specific applications and flooring types.

Common underlayment materials are cork, rubber, foam, and felt. Each of these materials offers distinct properties, such as compression and thermal regulation. For example, foam is a lightweight option that offers basic cushioning, while cork provides excellent thermal properties. Some premium underlayments, such as floorMuffler®’s cross-linked closed-cell polypropylene foam, provide moisture resistance, excellent durability, and various levels of sound absorption. floorMuffler® carries a range of advanced underlayment solutions engineered from high-quality materials.

Thick vs. Thin Underlayment: Key Differences

Thick and thin underlayment serve distinct purposes and excel in different scenarios:

Thin Underlayment (1-2 mm)

Thin underlayment is typically 1-2 mm thick and ideal for glue-down installations or when minimal height addition is desired. They are highly compatible with flooring types that require firm, stable support directly against the subfloor.

A thin underlayment’s excellent dimensional stability helps prevent movement in click-together flooring. It also offers sufficient thermal properties for many standard applications without impeding radiant heating systems.

Despite its low profile, a well-engineered thin underlayment can deliver strong acoustic and thermal performance. Material composition and density—rather than thickness alone—play a key role in how effectively sound is absorbed and heat is retained or transferred.

Thick Underlayment (4mm+)

Thick underlayment is generally 4 mm or more and is often selected for its structural and installation-related advantages rather than performance alone. One of its primary benefits is the ability to increase overall floor height, if needed,for transitions between rooms or aligning with adjacent flooring surfaces.

Its added density and cushioning also help absorb impact from heavy foot traffic and dropped objects, offering an extra layer of protection for the finished floor. This can be especially valuable in high-use areas or spaces where durability is a priority.

Additionally, thicker underlayment can help smooth out minor subfloor irregularities, however subfloor preparation is still needed. This makes it a practical choice for renovation projects where achieving a perfectly level surface may be challenging.

When Thicker Isn’t Always Better

While some floors require thick underlayment, exceeding the necessary thickness for an application can introduce complications. Thin underlayment is the better option in situations where excessive thickness could cause:

• Floating floor instability: Floating floor instability occurs when excessive cushioning allows too much movement. This can lead to gaps, joint separation, and premature wear in applications such as click-together flooring.
• Height transition problems: Overly thick underlayment can create undesirable height differences between rooms or make it difficult for doors to clear the new floor level. It’s important to consider the desired height for each room before deciding on underlayment thickness.
• Radiant heat inefficiency: Excessive thickness can hinder radiant heat efficiency by creating an additional barrier that prevents heat from effectively reaching the finished floor surface. A thinner underlayment is ideal for projects involving radiant heating systems.

floorMuffler®’s engineered solutions are designed to precisely address these concerns with optimized thicknesses and material compositions for your needs. For example, floorMuffler® is an excellent option for floating floor installations and protects interlocking systems.

Best Underlayment Thickness for Various Flooring Types

Matching the right thickness to your floor type is vital for your floor’s performance. The ideal option depends on the flooring material, its installation method and the desired characteristics.

Hardwood Flooring

A thin vapor barrier of 1-2 mm, such as floorMuffler®’s ultraSeal or ultraSeal HD, is typically sufficient for traditional nail-down hardwood, as the wood itself offers excellent stability. If you plan to float an engineered hardwood floor, a premium 2-3 mm dense foam or cork underlayment can provide sound dampening and moisture protection.

Laminate Flooring

floorMuffler®’s ultraSeal is also a fantastic option for laminate floors. This 2mm high-performance acoustic underlayment doubles as a moisture barrier and features a patented lip and tape system for simple installation. floorMuffler ultraSeal helps reduce impact sound, preventing the hollow sound often associated with laminate. 

Luxury Vinyl (LVP/LVT)

Luxury vinyl plank (LVP) and luxury vinyl tile (LVT) require a thin, dense underlayment between 1 mm and 1.5 mm. This prevents excessive movement that could stress the locking mechanisms and gradually cause separation or damage. You can depend on floorMuffler® LVT ultraSeal or floorMuffler® Encore, for flooring with a pre-attached pad, as high-performance moisture barriers and acoustic underlayments.

Engineered Wood

Engineered wood flooring pairs well with a range of underlayment thicknesses. A 2-3 mm underlayment made of cork or high-density foam is ideal for floating installations. The 2-3 mm thickness typically delivers excellent sound reduction and comfort in floating engineered wood applications. For glue-down installations, a thin moisture barrier is often sufficient. Consider high-performance solutions such as floorMuffler® quietCure™, comboFoam® or Natura™ for your engineered wood floor.

What to Consider When Selecting an Underlayment

Aside from flooring type, the following qualities determine which underlayment option is best suited for your project:

Subfloor Type

While wood and concrete subfloors have different characteristics, selecting the right underlayment is less about thickness and more about choosing the appropriate material and construction for the application.

Concrete subfloors, for example, are dense and can emit moisture, making moisture protection a critical factor. In these cases, underlayments with built-in vapor barriers or moisture-resistant materials are often required—regardless of thickness.

Wood subfloors, on the other hand, are typically drier and more forgiving, so the focus is often on sound control and floor stability, especially in multi-level environments.

Existing Flooring

When installing new flooring over existing flooring, such as vinyl over linoleum, the underlayment decision is especially vital. A thin, dense underlayment of 1-2mm is typically the best option for avoiding excessive buildup, maintaining proper transitions, and ensuring the new floor’s stability.

Acoustic Performance

Premium underlayments offer better sound reduction, particularly for impact noise, by absorbing more vibrational energy. However, it’s important to have realistic expectations. Underlayment alone cannot eliminate all sound, but it can significantly dampen it.

When noise is a primary concern, such as in apartments or multi-story dwellings, it’s best to invest in a thicker, premium acoustic underlayment. A thinner underlayment focused on stability or moisture prevention is best if sound reduction is a minor concern.

floorMuffler® is dedicated to acoustic excellence. Our underlayments, such as floorMuffler® quietCure™, undergo rigorous testing to ensure they demonstrate superior sound transmission reduction. 

Find High-Quality Underlayment for your Next Flooring Installation

Before choosing underlayment thickness, consider your project’s unique requirements and priorities. Finding the right balance between thickness and required characteristics helps ensure stability and comfort in every room.

floorMuffler® offers high-quality flooring solutions for all types of projects, ensuring optimal performance. Our underlayment solutions are engineered with advanced technology to optimize every flooring installation. Explore our comprehensive range of premium underlayment products, or contact our team for help choosing the right option for your project.