What Goes Under Laminate Flooring: Pros, Cons, and Buying Guide

The wrong underlayment causes 70 percent of failed laminate installations — popping joints, hollow sounds, and edges that lift within a year. Knowing what goes under laminate flooring matters more than the laminate brand itself in many cases. After installing laminate over plywood, OSB, concrete, tile, and existing vinyl in dozens of homes, I have a clear hierarchy of which underlayments solve which problems and which products waste money. This guide covers every layer between your subfloor and your laminate planks.

The Three Layers Beneath Laminate

A complete laminate floor system includes three distinct layers below the planks:

• Subfloor — structural plywood, OSB, or concrete that supports the floor
• Vapor barrier — moisture-blocking layer (mandatory over concrete, optional over wood)
• Underlayment — sound and impact-absorbing pad between vapor barrier and laminate

Some premium laminates include attached underlayment on the back of each plank, eliminating the need for a separate underlayment layer. Always check the manufacturer spec.

Subfloor Requirements

The subfloor must be flat, dry, clean, and structurally sound before any underlayment goes down. Specific requirements:

• Flatness — 3/16 inch deviation over 10 feet maximum
• Moisture (concrete) — under 3 lbs per 1,000 sq ft per 24 hours via calcium chloride test
• Moisture (wood) — under 12 percent moisture content
• Cleanliness — vacuumed of all debris, no protruding nails or staples
• Structural integrity — no soft spots, sagging, or rot

Skip the prep and you guarantee future problems. Sand high spots on plywood with a belt sander; fill low spots with a self-leveling compound like Henry 555 ($40 per 40-pound bag).

Vapor Barriers Over Concrete

Concrete subfloors continuously wick moisture upward, especially below grade. A vapor barrier prevents that moisture from reaching the laminate’s HDF core, where it causes swelling and joint failure.

Standard 6-mil polyethylene sheeting (sold in rolls at any home improvement store, $20 for 100 sq ft) is the most common choice. Overlap seams by 8 inches and tape with vapor-barrier tape. Run the barrier 4 inches up the wall and trim flush after the floor is installed.

Some underlayments include a built-in vapor barrier — these are sold as “2-in-1” or “3-in-1” products. They simplify installation but cost more upfront.

Foam Underlayment (Most Common)

Standard foam underlayment is closed-cell polyethylene, usually 2mm or 3mm thick. It costs $0.20 to $0.50 per square foot and provides basic sound dampening and minor cushioning.

Foam works for typical residential installs over plywood subfloors with no moisture concerns. Roll it perpendicular to the planks, butt seams together (do not overlap), and tape seams with the manufacturer’s tape.

The downsides: foam compresses over time, transmits more impact noise than premium underlayments, and lacks moisture protection. For basements and high-traffic areas, upgrade to felt or cork.

Felt Underlayment (Best for Sound)

Felt or fiber-based underlayments (QuietWalk Plus, FloorMuffler, Pergo Gold) cost $0.40 to $1.00 per square foot. They are denser than foam, dampen sound significantly better, and resist compression over time.

Felt underlayment is the right choice for:

• Multi-story homes where downstairs noise matters
• Condos and apartments with HOA noise requirements
• High-traffic areas where foam would compress
• Homes with hard ceilings (no carpet) below the laminate

QuietWalk Plus also includes a built-in vapor barrier, making it a complete solution for concrete subfloors.

Cork Underlayment (Premium Sound)

Cork underlayment runs $0.80 to $1.50 per square foot. It is the gold standard for sound absorption and impact reduction — typically rated 65 to 70 IIC (Impact Insulation Class) compared to 50 to 55 for foam.

Cork is the right choice for:

• Upper-floor installations in multi-family buildings
• Home theaters and music rooms
• Spaces above home offices or bedrooms
• Premium installations where sound quality matters

The downsides: higher cost and reduced moisture resistance. Pair with a separate vapor barrier on concrete.

Combination “2-in-1” and “3-in-1” Underlayments

Multi-function underlayments combine cushioning, sound dampening, and vapor barrier into a single roll. Roberts Quiet Walk, Pergo Gold, and QuietWalk Plus are popular 3-in-1 options at $0.60 to $1.20 per square foot.

These simplify installation by eliminating a separate vapor barrier layer. They are ideal for concrete subfloors where you would otherwise need both underlayment and 6-mil poly.

What NOT to Put Under Laminate

Several common mistakes cause failures:

• Carpet padding — too soft, causes laminate to flex and pop joints
• Multiple layers of underlayment — voids most warranties and exceeds spec compression
• Existing carpet — laminate is not rated for installation over carpet
• Plywood on top of underlayment — defeats the purpose of cushioning
• Tar paper or roofing felt — outdated, off-gases chemicals, can stain through
• Foam meant for under hardwood — different compression rating

Always use underlayment specifically rated for laminate flooring. The manufacturer’s spec sheet lists approved options.

Existing Floors as a Substrate

You can install laminate directly over many existing hard surfaces if they meet flatness and moisture specs:

• Vinyl sheet or tile — yes, if well-bonded and flat
• Ceramic tile — yes, with thin underlayment to bridge grout lines
• Hardwood — yes, with standard underlayment
• Engineered wood — yes, but check stability first
• Carpet — never, regardless of underlayment
• Cushion vinyl — never, too soft

If existing flooring is loose, damaged, or thicker than 1/4 inch, remove it before installing laminate.

Installation Sequence

Once you know what goes where:

1. Verify subfloor flatness, moisture, and structural integrity
2. Install vapor barrier on concrete (skip on dry wood subfloors)
3. Roll out underlayment perpendicular to planned plank direction
4. Tape underlayment seams with manufacturer’s tape
5. Trim underlayment flush with walls (no overlap onto walls)
6. Install laminate planks with proper expansion gap

The whole underlayment install for a 200 sq ft room takes 30 to 60 minutes.

Cost Summary

Underlayment cost per square foot:

• Standard foam — $0.20 to $0.50
• Felt or fiber underlayment — $0.40 to $1.00
• Cork underlayment — $0.80 to $1.50
• 3-in-1 with vapor barrier — $0.60 to $1.20
• Plus 6-mil poly vapor barrier (separate) — $0.20 per sq ft

For a typical 1,000 sq ft install, budget $300 to $1,200 for underlayment depending on tier.