Underlay for Laminate Flooring: Types, Thickness, and Best Options

Underlay is the thin layer of material that sits between your subfloor and your laminate flooring. It might seem like an afterthought — something the flooring store tries to upsell — but the right underlay has a measurable impact on how your floor sounds, feels, and lasts. The wrong underlay (or no underlay at all) leads to a floor that clicks hollow underfoot, transmits noise to the room below, wears unevenly, and potentially develops moisture damage.

What Does Underlay Do?

Underlay serves four main functions, each important in its own right:

Sound Reduction

Laminate flooring is a hard, thin material floating above a hard subfloor. Without underlay, every footstep creates a hollow tapping sound in the room and transmits impact noise to the floor below. Underlay absorbs that impact and reduces both in-room noise and sound transmission to lower levels.

Comfort

The thin cushion layer between the subfloor and laminate adds a slight give underfoot. It is not the same as walking on carpet, but it makes a significant difference compared to laminate laid directly on concrete or plywood.

Subfloor Smoothing

Minor subfloor imperfections — small bumps, texture variations, and slight unevenness — are absorbed by the underlay rather than telegraphing through to the laminate surface. This extends the flooring’s lifespan by reducing uneven stress on the click-lock joints.

Moisture Protection

When installing over concrete, moisture vapor can migrate upward through the slab and damage the laminate’s HDF core. Many underlay products include a built-in moisture barrier (a thin polyethylene film) that blocks this vapor.

Types of Underlay

Standard Foam (Polyethylene)

The most common and affordable option. Basic foam underlay provides adequate cushioning and some sound reduction.

• Thickness: 2mm to 3mm
• Sound reduction: Moderate
• Moisture protection: None (unless a film is included)
• Cost: $0.15 to $0.30 per square foot
• Best for: Budget installations, upper floors over plywood subfloors, bedrooms and low-traffic areas

Foam with Built-In Moisture Barrier

Standard foam with an attached polyethylene film on one side. This is the minimum underlay for any laminate installation over concrete.

• Thickness: 2mm to 3mm
• Sound reduction: Moderate
• Moisture protection: Good — blocks moisture vapor from concrete
• Cost: $0.20 to $0.40 per square foot
• Best for: Concrete subfloors, basements, ground-floor installations

Cork Underlay

Cork is a natural material with excellent sound-dampening properties. It is the preferred choice when minimizing noise transmission is a priority, such as in apartments and upper-story rooms.

• Thickness: 3mm to 6mm
• Sound reduction: Excellent — the best performer for both impact sound and airborne sound
• Moisture protection: Moderate — cork is naturally moisture-resistant but not a vapor barrier. Pair with a separate poly film over concrete.
• Cost: $0.50 to $1.00 per square foot
• Best for: Apartments, condos, upper floors, home offices, bedrooms, anywhere noise is a concern

Rubber Underlay

Dense rubber underlay offers superior sound reduction and durability. It compresses less over time than foam, maintaining its performance for the life of the floor.

• Thickness: 2mm to 5mm
• Sound reduction: Very good
• Moisture protection: Good natural resistance, but add a vapor barrier over concrete
• Cost: $0.60 to $1.50 per square foot
• Best for: High-traffic areas, commercial spaces, multi-story buildings with strict sound requirements

Combination (Film + Foam + Moisture Barrier)

Multi-layer underlay products combine a foam or fiber cushion layer with an integrated moisture barrier and sometimes an additional sound-dampening layer. These all-in-one solutions simplify installation.

• Thickness: 3mm to 5mm
• Sound reduction: Good to excellent (varies by product)
• Moisture protection: Yes — integrated
• Cost: $0.30 to $0.75 per square foot
• Best for: Most residential installations — a good balance of performance and value

Fiber (Felt) Underlay

Made from recycled fibers compressed into a dense sheet. Fiber underlay is denser than foam, providing better sound reduction and more cushion. It also performs well over slight subfloor imperfections.

• Thickness: 3mm to 4mm
• Sound reduction: Good to very good
• Moisture protection: Some products include a film; otherwise, add separately over concrete
• Cost: $0.40 to $0.80 per square foot
• Best for: Living areas, hallways, anywhere you want solid sound reduction at a mid-range price

How Thick Should Your Underlay Be?

Thicker is not automatically better. Too much cushion under a floating floor causes the surface to flex when you walk on it, which stresses the click-lock joints and can lead to joint failure and gaps over time.

General guidelines:

• Minimum: 2mm — provides basic cushioning and smoothing
• Recommended: 3mm — the sweet spot for most residential laminate installations
• Maximum: 6mm — only with manufacturer approval. Some premium laminate products are rated for thicker underlay.

Critical: If your laminate has an attached pad, do not add additional underlay. Doubling up creates too much cushion and will void most warranties.

Choosing Underlay by Subfloor Type

Over Concrete

Concrete releases moisture vapor, which can damage laminate’s HDF core. Always use underlay with a built-in moisture barrier, or lay a separate 6-mil polyethylene sheet with taped seams before installing the underlay.

Over Plywood or OSB

Moisture barriers are not required over plywood in most cases (unless the subfloor is over an unheated crawl space). A standard foam or combination underlay works well.

Over Existing Hard Flooring

When installing laminate over tile, vinyl, or hardwood, a thinner underlay (2mm foam) is usually sufficient since the existing floor provides some cushion and smoothness. Thicker underlays may raise the floor too high for door clearances.

Over Radiant Heating

Underlay acts as insulation, which can reduce the effectiveness of radiant heating. For floors with underfloor heating, choose the thinnest underlay that meets your sound and comfort requirements. Some manufacturers offer specific underlay products rated for radiant heat with low thermal resistance (R-value).

Installation Tips

1. Roll it out in the same direction you plan to install the laminate planks.
2. Butt edges together — do not overlap (unless the manufacturer specifies overlap).
3. Tape all seams with the provided tape or painter’s tape to prevent shifting during installation.
4. Run the underlay up the wall about an inch. Trim after the laminate is installed.
5. Only lay one to two rows of underlay ahead of your laminate installation. Laying out the entire room at once means walking on the underlay and potentially shifting it before the laminate is in place.

How Much Does Underlay Add to the Project Cost?

For a 500-square-foot room:

Even premium cork underlay at $1 per square foot adds only $500 to a 500-square-foot project. Given that it meaningfully improves sound, comfort, and flooring longevity, underlay is one of the most cost-effective upgrades you can make to a laminate flooring installation.

Does Vinyl Flooring Need Underlay?

For comparison, vinyl flooring with an attached pad typically does not need additional underlay. Products without an attached pad may benefit from a thin (1.5mm to 2mm) vinyl-compatible underlay. Never use standard laminate underlay under vinyl unless the manufacturer specifically approves it — the wrong underlay can interfere with click-lock performance and void the warranty.

Final Thoughts

Underlay for laminate flooring is a small investment that makes a noticeable difference in how your floor sounds, feels, and holds up over time. For most homes, a 3mm combination underlay with a built-in moisture barrier covers all the bases at a reasonable cost. If noise reduction is a priority (apartments, upper floors), upgrade to cork. Match the underlay to your subfloor type, follow the manufacturer’s thickness limits, and never double up. It is the kind of behind-the-scenes detail that separates a floor you enjoy from one that disappoints.