Laminate underlayment is the layer that sits between the laminate planks and the substrate below, and it’s one of the more consequential installation choices in a laminate project. The right underlayment handles acoustic dampening, vapour management, and minor surface smoothing; the wrong underlayment leaves all those problems to the laminate above and produces installations that don’t perform as designed.
This guide walks through what underlayment actually does, which products are appropriate for which applications, and how to think about the underlayment investment in the context of a quality laminate installation.
Table of Contents
- The Short Answer
- What Underlayment Does
- Underlayment Is Not an Upgrade
- The Four Types, and What Each Is For
- Reading an Underlayment Spec Sheet
- When You Need a Vapour Barrier
- How Underlayment Affects Warranty
- What We Recommend, and Where We Talk People Out of It
- Related Guides
- Need Help Choosing the Right Underlayment?
- Frequently Asked Questions
The Short Answer
Basic foam over a plywood subfloor, a combination underlayment with a built-in vapour barrier over concrete, and cork or rubber where somebody lives underneath. That covers almost every laminate installation in an Ontario home. The only two decisions that carry real consequence are whether the substrate needs vapour protection and whether the room below needs quiet.
Underlayment is a small fraction of a laminate project’s cost and a large fraction of how the finished floor feels to live with, which is an awkward combination — it is exactly the line item that gets trimmed. It is also the one most likely to void a warranty when substituted casually. The laminate pillar sets out where underlayment sits in the wider specification.
What Underlayment Does
Four jobs, in a typical installation, and no single product does all four equally well.
- Acoustic dampening — reducing the hollow click laminate would otherwise produce underfoot.
- A modest thermal break between substrate and plank, which is most of the difference between a floor that feels cold and one that does not.
- Minor smoothing of small bumps and slight unevenness, so the planks sit flat and the click joints are not working against a hump.
- Vapour management over concrete, keeping slab moisture out of the HDF core above it.
Basic foam does the first three and none of the fourth. Combination products add the vapour barrier. Premium products do the first two better. Which of these you need is decided by the substrate and the room below. The laminate itself has almost no say in it.
Underlayment Is Not an Upgrade
Laminate manufacturers nearly universally require underlayment between the plank and the substrate. Laying laminate directly on a subfloor voids the warranty in essentially every case, and it performs poorly on every dimension underlayment exists to address. Underlayment is routinely presented as an optional extra in quotes. It is not one, and a quote that treats it that way is describing an installation that voids its own warranty.
Some premium laminates arrive with underlay already bonded to the back of each plank. These run a few dollars per square foot above the equivalent product without it, which is frequently less than buying separate underlayment and paying to lay it — good value when what is attached happens to match what the room needs. The catch is that it is not upgradeable: if the room turns out to want acoustic performance the attached layer does not provide, there is no adding it later.
The Four Types, and What Each Is For
| Type | Typical cost per sq ft | Acoustic performance | Vapour barrier | Where it belongs |
|---|---|---|---|---|
| Basic foam | $0.30–$0.50 | Modest | No | Above grade over plywood, no sound priority |
| Acoustic-enhanced foam | $0.50–$1 | Better | No | Same, where the room reads hollow |
| Cork | $1–$2 | Strong, especially footfall | No | Bedrooms over living space, upper floors |
| Rubber | $2–$4 | Best available | Usually included | Home theatres, music rooms, resolved noise complaints |
| Felt | Varies | Decent | No | Only where a manufacturer specifies it |
Foam, and Why It Is the Default
Foam is 2 to 3 mm of polyethylene or polyurethane, and it is the right answer for the majority of above-grade laminate installations over a wood subfloor. It is not appropriate over concrete on its own — there is no vapour function in it — and pairing basic foam with a separate poly sheet is a perfectly legitimate way to get there if the combination product is not available.
When the Upgrade to Cork or Rubber Is Worth It
Cork absorbs impact noise — footsteps specifically — better than foam does, and adds a small amount of R-value on top. It is also the option homeowners ask for on environmental grounds, which is a fair reason to choose between two products that both work.
Rubber is the maximum available in a residential laminate underlayment, dense enough to absorb both impact and airborne sound, and it usually carries vapour function as well. It is heavier to work with and it costs several times what foam costs. For a standard installation the premium does not justify itself. For a household that has already had the downstairs-noise conversation, it does — and upgrading the underlayment is a far cheaper fix than upgrading the floor. The audible difference between $0.40 foam and $1.50 cork is real in the room and larger again in the room below.
Felt is the outlier. It performs adequately and carries no vapour function, and most current manufacturers specify foam, cork or rubber instead. If felt is called for, it is almost always a product-compatibility requirement and not a performance choice, and that is reason enough to follow it.
Reading an Underlayment Spec Sheet
- STC and IIC — Sound Transmission Class and Impact Insulation Class. Higher is better; IIC is the one that matters for footsteps.
- R-value — thermal insulation, relevant when cold transmits up from below.
- Vapour rating — non-negotiable over concrete, irrelevant over a dry second-storey subfloor.
- Thickness — affects all of the above, and is also constrained by the laminate’s click system.
- Named product compatibility — the line most people skip, and the one that decides whether a warranty claim gets paid.
Read them against what the room actually needs. Hunting for the highest number in every column is how people buy acoustic performance for a slab. A second-storey bedroom over a garage wants R-value and IIC. A basement slab wants vapour rating and nothing else particularly. Buying the most expensive underlayment without knowing which column mattered is the same mistake as buying the cheapest.
Nobody ever sees the underlayment and everybody hears it. Book an in-store appointment and bring the laminate you are considering — matching the two takes five minutes and it is what keeps the warranty intact.
When You Need a Vapour Barrier
Any laminate over a concrete substrate needs one. A slab releases moisture vapour year-round. That is what concrete does, and it is not a sign that anything is wrong. Without a barrier that vapour migrates into the HDF core above and delaminates it from underneath, where nobody sees it happening. The same applies over a crawl space and anywhere else the substrate has moisture exposure. In a basement, this is the decision the whole installation turns on.
You can get the barrier three ways: a combination underlayment with vapour function built in, a separate 6-mil polyethylene sheet beneath standard underlayment, or an integrated underlay on a plank that includes it. All three work. What matters in every case is that the barrier is continuous and the seams are sealed — a barrier with gaps is not a partial barrier, it is a barrier that lets moisture through the gaps.
How Underlayment Affects Warranty
Laminate warranties specify acceptable underlayment products, and using something off-list can void the laminate warranty even when the substitute looks entirely appropriate. The compatibility is documented in the laminate’s installation guide, and reading it before the underlayment is bought saves the argument afterwards.
Most manufacturers approve several products, including their own branded option and third-party alternatives. Staying on that list is the safe path. Where a product is not listed but meets every published specification, send the manufacturer an email and get the confirmation in writing. A warranty dispute two years later turns entirely on whether that email exists.
What We Recommend, and Where We Talk People Out of It
Match the substrate first and the room second. Above grade over plywood with no particular sound concern, basic foam is the correct choice and spending more on it is spending for nothing. Over concrete, a combination underlayment with vapour barrier, every time. Where a bedroom sits over a living room, cork. Where noise has already been a complaint, rubber.
The upgrade we most often steer people away from is buying premium acoustic underlayment for a ground-floor room with nothing beneath it. It performs exactly as advertised and there is nobody down there to benefit. The upgrade we most often steer people towards is the opposite case, and it costs less than a dollar a square foot: whatever the plank costs, if there is a bedroom underneath, the underlayment is where the money works hardest. Laminate Installation covers how it goes down, and the thickness guide explains why underlay and plank thickness have to be specified together.
Related Guides
A few other guides connected to this topic:
- Laminate Flooring Guide for Ontario Homes (AC Ratings, Cores, Finishes & Where It Works) — The complete laminate flooring pillar.
- Laminate vs Vinyl Plank vs Engineered Hardwood: Which Should You Choose? — Direct comparison with related materials.
- Water-Resistant vs Waterproof Laminate: What Is the Real Difference? — Direct comparison with related materials.
- Vinyl vs Laminate Flooring: What’s the Difference and Which Should You Choose? — Direct comparison with related materials.
- Vinyl & Laminate Floor Cleaning Guide: How to Clean Floors Without Causing Damage — Closely related topic in this category.
- How to Choose the Right Flooring for Your Home in Ontario (Complete Guide) — The complete flooring decision pillar.
- Flooring Installation Services — Our sell-and-install service — measuring, an itemized quote, and certified installation handled as part of your purchase.
- Why Work With Alexanian — A century of flooring and rug expertise, sell-and-install accountability, and full-service care.
Need Help Choosing the Right Underlayment?
The best way to choose what’s right for your home is to see the options side by side. Book an in-store appointment at one of our 17 Ontario showrooms and one of our consultants will walk you through what fits your space, your needs, and your budget – or request an in-home visit if that’s easier.
Frequently Asked Questions
Do I need underlayment for laminate flooring?
Yes, unless the laminate has attached underlay. Most laminate requires separate underlayment, and skipping it voids most warranties.
What is the best underlayment for laminate?
Foam is standard for most residential applications. Cork and rubber provide better sound dampening for condos and sound-sensitive areas.
Do I need a vapour barrier under laminate in a basement?
Yes—any laminate installation over concrete requires a vapour barrier, either as part of the underlayment or as a separate poly sheet.
Can I use thicker underlayment to make laminate feel softer?
No—using thicker underlayment than specified can interfere with click-lock and void warranties. Use the underlayment thickness specified by the laminate manufacturer.
