Choosing the Right Underlayment for Laminate and LVP Flooring
A comprehensive guide on selecting underlayment padding for floating floors. Moisture barriers, sound dampening (IIC/STC), and comfort.
Underlayment is the thin layer of material installed between your subfloor and your finished flooring. For floating floors like laminate and luxury vinyl plank (LVP), selecting the correct underlayment is essential for noise control, warmth, and moisture protection.
Do You Need Underlayment?
Before buying separate rolls of underlayment, inspect your flooring choice:
- Pre-attached Pad: Many LVP and laminate planks come with a foam or cork underlayment pre-attached to the back. Do not install a secondary underlayment unless explicitly allowed by the manufacturer—doing so can make the floor too soft, causing joints to break.
- Bare Backing: If your flooring has a hard plastic backing, a separate underlayment is required.
Underlayment Materials Comparison
| Material | Best For | Sound Dampening | Moisture Resistance | Thickness |
|---|---|---|---|---|
| Standard Foam | Budget laminate | Low | Moderate | 2mm |
| Felt Underlayment | Heavy laminates | High (absorbs footfalls) | Low (needs plastic vapor barrier) | 3mm |
| Cork | Condos & apartments | Very High (impact sound) | Moderate | 2mm - 6mm |
| Rubber | Engineered wood | High | High | 2mm - 3mm |
Key Performance Ratings
When comparing underlayment options (especially for multi-family residential projects), check these two ratings:
- IIC (Impact Insulation Class): Measures how well the underlayment dampens impact sounds (e.g. footsteps, dropping objects). A rating of 50 or higher is typical for building code compliance.
- STC (Sound Transmission Class): Measures how well the material blocks airborne noises (e.g. voices, music).
Concrete Subfloors and Moisture Barriers
Concrete slabs constantly release moisture vapor. If you are laying flooring over concrete, you must install a 6-mil plastic polyethylene vapor barrier (often called a 2-in-1 or 3-in-1 underlayment if it includes foam padding) to prevent water vapor from warping your floorboards or promoting mold growth.