Laminate Underlayment Guide

Laminate Underlayment Guide

Behind the scenes, underlayment plays a big role in laminate’s performance. The underlayment you choose will affect how your laminate sounds, feels, and its life expectancy. It’s definitely not “out of sight, out of mind.”

So how do you make sure you get the best underlayment for your room?

If you don’t work in the flooring or construction industry, weeding out what’s important and what you can ignore isn’t easy. Fortunately, you can learn everything you need to know from materials to density by reading this article. It shouldn’t take much more than 10 minutes.

Before I dive into picking the best underlayment, let’s start by going over the benefits of it. This will help you decide if you even need to buy underlayment in the first place.

Benefits and purpose of laminate underlayment

Underlayment’s primary purpose is to support the laminate installation. Laminate planks will break apart over time with even mild imperfections in the sub-floor. The underlayment is the buffer that smooths out these imperfections. Here are more underlayment benefits:

  • prevents moisture
  • reduces sound echoing and footstep noise
  • insulates your home reducing energy bills

The first two benefits (support and moisture prevention) are essential to laminate installation. Your laminate installation will fail without them. The last two benefits are “nice to have’s.” You can technically do without them, but especially with noise echoing, your laminate might drive you crazy.

Decision 1: Do I need underlayment for laminate flooring?

In 95% of cases, you need underlayment for your laminate flooring. Without it, you risk prematurely damaging your laminate from an uneven sub-floor or moisture. Therefore, the only time you don’t need laminate is when you are certain that your floor is perfectly level with no hint of moisture–the combo is extremely rare.

If you’re really pinching pennies, you might be able to do without underlayment over vinyl flooring or a newly installed sub-floor. Both can be smooth, dry surfaces.

Do I need underlayment if my laminate flooring has attached pad?

The purpose of attached pad is to eliminate the need for underlayment. So no, you don’t need underlayment for laminate with attached pad. In fact, combining attached pad and underlayment is not just a waste of money, there’s a good chance it will damage your laminate installation. However, make sure your attached pad comes with a moisture barrier. If it doesn’t, you need to look into buying a moisture barrier to go under your laminate–more on this later.

Decision 2: Should I buy laminate with attached pad or the underlayment separate?

You know you shouldn’t buy both laminate with pad and a separate underlayment. But which of the two options is better?

This is a boring fight because there’s no winner. Both attached pad and separate underlayment can be effective. But there are still a few things to keep in mind and ways you can break the tie:

First, if your laminate has attached pad, hold it to the same standards that you would if you purchased the underlayment separately. In other words, use everything you’ll read in this guide to determine if it’s quality is up to your standards.

Second, the tie breaker is often cost. How much can you get similar laminate and underlayment for compared to the underlayment with attached pad? This may make the decision simple.

Since underlayment is an important part of the installation, I usually like my underlayment separate just because I can be more choosy on the type and specifications. You do get a little more convenience with having attached pad, but underlayment is easy to install.

Decision 3: Underlayment material options

We discussed the purpose of laminate is to give support, smooth over imperfections, absorb sound, and insulate. Now we’re going to dive into the first of a few choices you’ll have to make when buying your laminate.

What material will be best?

There are multiple materials that can do the job. Different materials come at different price points and have different advantages. Let’s start with the most popular option:

Basic foam

Foam is the most popular laminate option for an important reason: it costs the least. The next important question is does it still do the job?

Yes and no. A decent foam laminate does what is asked of it: support the laminate. However, the cheaper foam underlayments don’t have the density to provide solid support for as many years. It may also make steps on your laminate loud and not have a moisture barrier.

Even with basic foam, you can upgrade to get better acoustics and a moisture barrier. Or if you want to go with a more premium foam you can…

Heavy foam or foam mixed with rubber underlayment

Heavy foam is denser 2+lb per 100 square feet foam. You can also get foam mixed with rubber that makes a denser product.

Denser is beneficial because it holds support better over time. This is important if you want your laminate to last a long time, or if you’re installing it in a higher traffic area.

Heavy foam will naturally be more sound resistant. Also, many heavy foams will come with a moisture barrier (but make sure it specifies that it does).

Felt underlayment

A completely different option is felt underlayment. We talked about how density is important earlier, and felt is typically 10+lbs per 100 square feet. That’s roughly 5x denser than the premium foam.

I wouldn’t go as far to say felt is 5x as good, but it is better. You get great support under your laminate and excellent acoustics. It’s unusual for felt not to come with a moisture barrier, so you should have that covered.

Cork underlayment

Cork is a premium underlayment that provides some unique advantages. It is naturally antimicrobial and hypoallergenic, meaning it resists bacteria and mold growth.

It’s also extremely functional. It provides a solid support under the laminate and possibly the best sound dampening. Cork is less common than the other options, and you may pay more for it.

Decision 4: Moisture barrier attached to underlayment or separate?

Laminate’s technology has improved, but it’s still not good to mix it with moisture. The problem with moisture is the worst kind is the moisture you don’t see. It’s the moisture that seeps through the sub-floor

So the first question to ask yourself is: do I have a moisture problem? If the answer is anything but a definite “no” then you need a moisture barrier. Any floor on a cement floor will need one. You can buy moisture tests if you’re unsure.

The second question to ask yourself is: do I want the moisture barrier attached to my underlayment instead of buying it separately? As far as performance, this doesn’t matter. It comes down to cost and convenience. It’s going to be slightly more convenient to find moisture barrier attached. On the other hand, installing a moisture barrier is fairly simple, so I’d go with separate if there’s much of a cost difference.

Decision 5: Underlayment density

In carpet padding, the density is the key feature. This isn’t the case with laminate, but it’s still worth being aware of. My cutoff is 2lbs per 100 sqft. Above 2lbs, I start to consider the laminate heavy foam. This has advantages described above in “material options.” Most standard foams will be lower.

You can ignore the density with felt and cork. Too low of a density is never an issue.

Decision 6: Underlayment thickness

You might see thickness listed when shopping for laminate underlayment, but it’s usually not important. Most underlayments are 2-3mm thick. The advantage of 2mm would be with radiant heating or under thin laminate but 3mm is more common.

Decision 7 (optional): STC and IIC ratings

First off, what are STC and IIC ratings?

STC rating stands for Sound Transmission Class. The rating is a number that stands for the number of decibels that sound is reduced by when using the underlayment. The higher the number, the more the underlayment will prevent echoing and transmission of voices and background noise.

IIC ratings stands for Impact Isolation Class. Similar to STC, the rating stands for the number of decibels that sound is reduced by when using the underlayment. The difference is that IIC measure the decibels for impact to the underlayment. The higher the number, the more the underlayment will prevent noise from footsteps.

If noise reduction is important to you, look for STC and IIC ratings of 50+. You can find 70+ STC and IIC rated floors that will really dampen sound, but keep in mind some laminate floors won’t list these ratings.

Captain’s warning! Live in a condo, apartment, or commercial building? Your association or governing body may require a minimum STC/IIC. The purpose is to keep you from disturbing your neighbors, so while any regulation may annoy you, you may be able to appreciate this one for helping you get a good night’s sleep.

Decision 8 (optional): Thermal ratings

The amount of heat that is blocked by underlayment is measured as an R-value. The higher the R-value, the more insulating the underlayment is. R2 to R3 is typical for foam laminate. So which do you want?

Most homeowners want a high R-value. This insulates their home from the outside. This is more important on first floors where the floors are facing the outside elements.

If you have radiant heating, you want a lower R-value to allow the heat to penetrate into your home.

Underlayment cost

Most common foam underlayments will cost $0.15 to $0.25 per square foot. You can find underlayment cheaper than this range, but you will pay $0.25 to $0.50 for most heavy foam. Premium foams can go as high as $1 per sqft.

Expect to pay around $0.75 sqft. for specialty underlayment like fiber or bamboo, but these prices can range even more than the foam.

Captain’s budgeting tip! Underlayment typically comes in 100 square foot packages. This means you can’t just multiply your square footage by the cost. This can make a big difference, especially in smaller rooms. In example, if you have a 12 x 10 room, you’ll multiply the cost by 200 (two 100sqft packages)—a 67% increase in price over underlayment for the exact square footage.

Captain’s parting words!

There aren’t too many decisions to make with laminate, but the decisions you make can determine how long your laminate lasts and how it performs. Pretty important.

And to be fair, most underlayment will do a good job of maintaining your laminate. The bigger issue is how it performs. If you don’t like how it feels or sounds, you’re going to hate your laminate every day you run into it.

Most of this is solved by choosing the material properties. You can look at the STC/IIC if sound is particularly important. And pay attention to the R-value and possibly thickness if you have radiant heating.

Density matters, but most of it is solved by the material. And if you have any hint of moisture, don’t roll the dice and go without a moisture barrier.

Your final decision is doing you want the moisture barrier separate or with the underlayment? And to take it a step further, do you want the underlayment attached to the laminate or separate
There’s no perfect answer to that, but I think you’ve got it from here.

Where to next? Make sure to the Captain’s laminate buying guide if you haven’t already. It has tips you don’t want to miss.

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Em Lo

Thank you very much for a very informative article. I am about to put down laminate (7mm, affordable and bought before reading that this is not the greatest, but determined to make a good go of it). Since sound reduction is important to me I was thinking of getting felt underlay. However I spotted an article online at that indicated a case where felt underlay had the opposite effect and a 3mm foam underlay was actually better sound-wise. Why would this be I wonder? I find this a bit confusing and am now really uncertain about what I should… Read more »

Em Lo

Thanks very much for the reply. I will be putting the laminate floor on cement in a single story home, so the sound I am concerned about is that of echoing and possible flexing (which I thought after reading the article mentioned in my original post may have been be the issue there??). I have also seen rubber underlay products mentioned but although it sounds good from a support point of view (and may eliminate flexing more than foam – I am not sure?). Do you know what type of rubber may be used in these products? I do worry… Read more »