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About Flooring Underlayment

Underlayment is the broad term for the variety of materials that roll out onto your subfloor
subfloor, going between it and your flooring proper, laminate flooring, hardwood or carpet. No pad is used with vinyl. The main purposes served are to block moisture, absorb sound from a floating floor (where pad is a necessity), smooth out very minor imperfections in a subfloor, and provide a bit of insulation for the room.

Almost all underlayment comes in the form of a roll, and most roll out with the proper side facing up. Some laminate products come with pad attached to the back of them. Here are the basics on the various types and their uses. Carpet Pad is the only kind of pad carpet uses. The others are all for laminate or hardwood flooring.


Moisture Barriers

Your moisture barrier, or vapor barrier, will be a roll of thin, polyethylene plastic sheeting. It’s usually 6 mil thick (“6 mil”? That means 6 micrometers, or 6 tenths of a millimeter). Its job is in its name, to protect everything above it from moisture rising up through a floor.

It is an absolute must over concrete, because a concrete floor sits right on the ground, so it’s subject to environmental changes. You will also want it to go over any floor that is directly above an unfinished basement or crawlspace. If not over one of these, moisture barriers are generally not needed, and sometimes not even recommended, over a wood subfloor.

It will be the bottom layer of any complement of padding, and is usually recommended to go up the walls a few inches as you install it. Once the floor is in place, you can remove the excess with an exacto knife.

A moisture barrier is never part of the attached pad on a laminate product. You see, when you roll it out, you have this nice, thick section of plastic. You will overlap the next section and tape the two sections together to make a good seal. Now you really want as few seams as possible, and if there was moisture barrier on each plank of a laminate product, there would be as many seams as there are planks – times four, for each side of the plank. And that much tape. It just wouldn’t work.

On the other hand, moisture barrier almost always is included with rolls of padding you buy separately.


Basic Foam Pad

Most underlayment is made from a synthetic, polyethylene foam, and is typically 2mm to 4mm (1/16″ to 1/8″) thick. Often this padding comes with a moisture barrier attached, as well as a taping system. Such padding will usually meet the minimum requirements for installation of a floating floor, and can be used both at and below ground level.

While these combination pads are very convenient, they usually only meet the bare minimum for what can be done with padding. One thing they will not do very much of is sound absorption. Upgrades to thicker, high density underlayments, made of closed cell materials or felt, can be well worth it for the sound killing features they provide for both the room of, and below, the installation. They can also provide a little bit better insulation, and more smoothing of very minor subfloor imperfections.


Rubber Underlayment

It’s usually made of recycled rubber. It usually comes in the same thicknesses as foam, but it has a higher density than the basic foam pads, which means improved sound absorption and moisture resistance. Rubber pad can come in rolls, and is becoming the more frequent style of attached pad.



Vinyl flooring, over which one can often install a new floating floor, is an excellent moisture barrier. You would not need an additional moisture barrier if you were installing under these circumstances. You would still need a regular pad, foam, felt or rubber, between the vinyl and the new floor, but your moisture issues would be taken care of.

Cork Underlayment

Cork underlayment is considered by some to be the best available. It is exceptionally dense and stable, so your floor is not just cushioned, but supported. Your laminate flooring will feel – not uncomfortably solid, but sturdier, and much quieter than a floor with just foam underneath. It is available in both rolls and sheets, and a range of thicknesses. Unlike the padding, cork can be used with non-floating floors as well as floating floors. In those cases it must be glued down first (gluing it down is an option with any floor). Since cork is so replenishable, it’s another good flooring option for the environmentally conscious.


Carpet Padding

This is much softer than padding for other types of flooring. While carpet is already a soft flooring, the proper padding makes it feel that much softer, sound that much quieter and insulate that much better. It tends to be made of felt, rubber, jute*, urethane or synthetic fibers. Carpet padding is never suitable for laying underneath wood or laminate or flooring.
Now many websites will refer to an ability of an underlayment to compensate for subfloor imperfections. You should consider this with caution. At best, a difference of a couple of millimeters of dip or rise over a 10 foot stretch might be handled, but underlayment is not going to even out a subfloor. There are proper methods to take care of larger than minor issues, and we recommend that you consider those, rather than the claims of an underlayment manufacturer or seller.


Related blog post: Do I Need This? on Accessories & Trims


* “Jute?” Jute is a vegetable fiber, like cotton. It’s used in making rope, sacks, carpets, area rugs curtains and other common things.


– – – –
David is a Writer at Floors To Your Home (.com), as well as the PPC Manager, a Marketing Strategy Team member, a Researcher, Videographer, Social Strategist, Photographer and all around Resource Jitō. In my spare time I shoot and edit video, explore film history, mix music (as in ‘play with Beatles multi-tracks’) and write non-fiction for my friends. Connect with me on W. David Lichty’s Google+

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6 comments on “Padding
  1. Amit Shukla says:


    My goal in selecting a flooring are A) Good Insulation, B) Durability , all within a reasonably low price

    Option # 1
    Ceramic Tiles. Durability is assured.
    But to get good insulation, is an underlay which would give good insulation possible ?
    What thickness and specifications , please guide

    Option # 2
    One option is to install floating laminate flooring in my house, and need your guidance
    – is poly-urethane foam a suitable underlay ? what aboout memory foam ?
    – if yes, what is the right thickness for insulation and also sound damping
    – what is the right density of foam ? Please advise.

    the flooring seller is offering Chinese made laminate, and very low density foam (about 2 lb per cu ft) which looks fishy to me. ( In our market, the local manufacturers have been washed out by a flood of inexpensive Chinese laminates claiming AC3 and AC4 abrasion resistance. )


    Amit Shukla
    Delhi NCR, India

    • David says:

      Hello, Mr. Shukla,

      Sorry for the delay, but I wanted to check into some things before replying.

      Part one of my answer is that no padding or insulation of any sort can go under ceramic flooring. That has to sit directly on the hard subfloor. Coldness underfoot is also one of the common issues people have with tiling made of ceramic, stone, porcelain and the like. It sounds like you want your padding to excel in the temperature benefits (insulation), so perhaps that rules out that option.

      Part two regards the padding. There aren’t many wrong options in terms of the material itself when it comes to a laminate. The main issue is how much padding you can have, and the range is 2mm to 5mm of thickness, depending on the thickness of the laminate planks. On the low end, such as a 7mm thick laminate, you would want to keep down to 2mm of pad. The thickest laminate made is a 12mm plank, and for those you can go as high as 5mm for the padding. Since you are concerned with what kind of padding you use, I would recommend getting a laminate with no padding attached. Attached pads are almost always 2mm thick. That would either be the limit, and then you’re stuck with whatever they’ve used, or it would limit how much of the kind of padding you would like to have that you can add under the 2mm. Attached padding is done mainly to make installation easier, though a moisture barrier is usually still needed, so it really doesn’t even accomplish that – you’re still rolling out material under your planks. You have much more freedom of choice with a pad-free laminate.

      The memory foam thing was what stopped me. Over here (America) we have some of that just coming out for carpeting, and people seem to like it quite a bit. I don’t yet see it for hard surface plank padding, though doubtless someone will get right on that, and you may even already have it in your part of our fine globe. There are rubber pads too, though they’re not the trend over here. What we have offered as a premium pad has almost always been a 5mm thick felt padding, specifically targeting warmth underfoot as its best feature.

      Your best insulation option is a 12mm laminate with a 5mm pad under it, and most of the materials used for 5mm padding are good insulators, with felt possibly topping the list, keeping in mind my lack of experience with memory foam. (Though I can say that when I shop for beds, the biggest complaint against memory foam mattresses is the heat, such that some even design in venting to flow under the foam to cool off the sleeper. That bodes well for the insulation qualities of memory foam!)

      As for laminates, after the stone-ish floors, laminates win against most other floors for surface durability, and they have done for quite a while. You’ve hit on the best choice for what you’re after. Regarding AC ratings, I cannot advise you on how to know if the labeling is lying to you over there. I’ll bet somebody does know, so it’s worth looking into, possibly even on the internet. We have bought flooring made in our country, Switzerland, Germany and China, and we have not had issues with this particular factor being misrepresented. Two years ago we had issues with formaldehyde levels being miscommunicated by some, but the manufacturers have responded to numerous slaps on the hands, and have cut that out. My guess is that since they’re under the microscope in general, all laminate manufacturers are probably watching their steps in general, and hopefully there is no real issue here. But look into it, specifically into how people in India are verifying, because a manufacturer may have different materials going to different lands, since every country has its own regulations to meet. Local wisdom is probably best in this area.

      What I can say is that, assuming they’re accurate, AC ratings are solid, thorough ratings of a floor. It’s an international standard, and the lab performs something like 10 specific tests on the surface of the floor. Each test has levels of 1-5, and for a floor to get a rating of AC3, it must meet the AC3 level for all 10 tests! This was really remarkable to me when I learned about it. It means that an AC3 floor is at least AC3. It could be halfway to AC4, or even closer, but if it passes any single test at only the AC3 level, then AC3 has to be its rating. Also, in my experience, AC3 has become a bare minimum. I haven’t seen an AC2 floor offered in my 7-ish years of selling and writing about them. I’m sure it’s done somewhere, but we haven’t come across it. We also see quite a lot of AC4 floors, which are rated for commercial use, a higher level of durability than the highest level rated for homes. Some of them are even the thinner floors – thickness doesn’t affect those tests, you see.

      If you can find a genuinely AC4, pad-free 12mm floor, and put 5mm of felt, memory, or even cork underlayment under it, you should be very happy with your results.

      Thank you for asking. We tend to get a lot of really well asked, smart questions on our posts, and they’re such a pleasure to answer.

      – David

  2. Lynette says:

    I’d like cork installed in my second floor condo entryway/ library. The gypcrete was partially removed down to the plywood because of a water tank leak. Does “carpet padding is never suitable for laying underneath wood or laminate…” also apply to cork? Carpet padding was suggested by the flooring company & I mentioned that I’d like to have a cork floor.

    • admin says:

      Hi, Lynette,

      There are two factors that matter here.

      1. THICKNESS. This is often the only relevant consideration. Any floating floor will have a limit to how much padding can go underneath it. This is because if it compresses too much, your planks or tiles may unlock, or separate, or just lower enough to make a trip hazard out of the next plank you haven’t stepped on yet. All floating floors will have a limit on how high the underlayment can go, and with cork I’m betting that number would be too low for carpet padding. Carpet pad tends to be 1/2″ thick, or even 3/4″ or higher.

      2. MATERIAL. This usually wouldn’t matter. Generally as long as your padding is under the thickness limit, it can be felt, foam, rubber or whatever, because they all have a decent amount of density. The issue with carpet padding is that it is designed to be really squishy. Thick and squishy, so that it gives your carpeting a nice, soft, warm feel. This means that it is already more likely to compress too much, even before it gets too thick.

      Check out the article I linked above. I took some pictures that illustrate the relevant factor in padding under particular floors.

      Whatever cork floor you get, it will have documentation listing how thick an underlayment can be, and possibly even what materials will work. You should be able to look at that information before you buy anything too. Check into a couple, and you’ll find the directions to be pretty similar between them, because it’s the material, not the manufacturer, that mandates the limitations.

      – David

  3. Marjorie says:

    Looking for 1/8″ dark brown rubber underlayment in 3’or 4′ wide rolls

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