How to Choose the Right Underlay for Your Flooring

Underlay is one of the most overlooked parts of a flooring purchase. Most people spend time choosing the perfect floor, then let the installer pick whatever underlay is on the truck. That's a mistake — the right underlay makes a real difference in how the floor feels, sounds, and performs over time.

What Underlay Actually Does

Underlay sits between your subfloor and your flooring and serves three main functions:

• Sound dampening: Reduces impact noise (footsteps, dropped objects) from transmitting through the floor. This matters a lot in multi-storey homes, condos, and apartments.
• Thermal insulation: Adds a layer of warmth, especially important for floors installed over concrete like basement floors.
• Subfloor smoothing: Helps bridge minor imperfections in the subfloor so the floor feels more stable and solid underfoot.

It does NOT make a floor significantly thicker in a meaningful way, and it does NOT compensate for a seriously uneven subfloor — those still need to be addressed before installation.

The Main Types of Underlay

Foam Underlay (Basic)

Standard polyethylene foam is the entry-level option — cheap, thin (2–3mm), and adequate for laminate and LVP in low-stakes applications like a bedroom. It provides minimal sound dampening and very little thermal insulation. It's the right choice when budget is the priority and the floor won't see heavy traffic.

IXPE (Cross-Linked Polyethylene Foam)

IXPE is a higher-quality foam with a closed-cell structure that gives it better acoustic performance, more consistent thickness, and better moisture resistance than standard foam. Many premium LVP products come with IXPE underlay pre-attached — this is a genuine selling point, not just marketing. IXPE is our most common recommendation for main floors and basements when the product doesn't already include it.

EVA Foam

Ethylene-vinyl acetate foam is similar to IXPE — denser than standard foam, better acoustic properties, more resilient over time. Used in many mid-range attached underlays. Both IXPE and EVA are good choices and the distinction between them matters less than the thickness and density.

Rubber Underlay

Rubber underlay provides superior sound dampening compared to foam — it's the choice for condos, apartments, and any space where impact noise transmission to the floor below is a concern. Many Ontario condo corporations require a specific STC (Sound Transmission Class) or IIC (Impact Insulation Class) rating for flooring installations, and rubber underlay is typically what gets you there. It's more expensive than foam but significantly better at its primary job.

Cork Underlay

Natural cork is an excellent thermal insulator and provides good acoustic performance. It's the warmest underfoot option and works well over concrete basement floors where the thermal benefit is felt most. Cork compresses over time more than rubber, which is worth considering for high-traffic areas.

Attached vs Separate Underlay

Many SPC vinyl and laminate products now come with underlay pre-attached to the back of the plank. If your product has attached underlay, do NOT add another layer underneath — you'll create too much movement in the floating floor and can cause clicking and instability. The product is engineered for the specific thickness and compression of its attached underlay.

Only add separate underlay if your flooring product has no attached underlay.

What We Recommend at Advanced Flooring

• Basement LVP over concrete: Product with attached IXPE, or add a cork underlay if the product has none. Cork adds thermal comfort that makes a basement feel warmer underfoot year-round.
• Main floor LVP or laminate in a house: Attached IXPE is sufficient for most applications. If sound dampening to the basement below matters, add 3mm rubber.
• Condo or multi-storey apartment: Check your condo corporation's requirements first. Rubber underlay with an appropriate IIC rating is almost always required. We can advise based on your building's specs.
• Engineered hardwood (floating): 2–3mm EVA or IXPE foam is standard. Never use cork under hardwood — cork is too compressible for nail-down or floating hardwood installations.

Questions?

When you get a free in-home estimate from Advanced Flooring, we'll assess your subfloor and recommend the right underlay for your specific situation — not just a generic option. Call 519-279-8456 or book at advancedflooring.net/pages/free-home-estimate.