There are a variety of underlayments used under wood floors, click-together floating floors, as well as carpet and tile.
Underlay can serve various functions like cushioning, sound deadening, leveling, uncoupling, and moisture resistance.
These are the best non-toxic low-VOC options with a focus on the material composition.
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Paper Underlayments Used Under Wood Floors
Silicone Paper
Silicone paper is usually used under real solid hardwood floors, but it can also be used under engineered wood. It is semi-permeable which is good, as you want your upper floors (over wood subfloors) to be breathable in almost all situations.
It meets perm ratings recommended by the National Wood Flooring Association.
Those extremely sensitive to chemicals have liked this product a lot. If you just need something simple that is not providing sound dampening or leveling this will do the job.
Red Rosin Paper
Tried a true, Red Rosin is the old school underlayment paper used under real wood flooring. It’s extremely low in odor and even that dissipates rather quickly. The extremely sensitive almost always do well with this, with only a few people mentioning that the undyed Rosin Paper was preferred.
This is what I would use under wood floors. Keep it simple and breathable.
Foam Underlayments for Click Together Floors
Basic Polyethylene Foam
For laminate, engineered and other click-together floating floors I prefer the most basic polyethylene underlayment. It’s very simple – it’s one of the safest plastics in terms of odors and offgassing (it’s zero-VOC).
This provides some cushioning which is necessary under flooring types like laminate.
It’s not a complete vapor barrier, so it can breathe, which is great for upper-level floors. Plus, it’s very inexpensive.
This is the type of foam that comes pre-attached in some laminate lines. I find that very convenient.
A “2 in 1” will usually have polyethylene foam and a thin layer of plastic. If you are looking for a vapor barrier, make sure it has one attached. The term 2 in 1 is rather confusing in this sense, as some are moisture-resistant and some have vapor barriers, but they are very thin.
Check with the flooring company and your contractor to make sure you have an appropriate vapor barrier, if one is required.
Cali Bamboo brand makes a good polyethylene underlay with foil as the vapor barrier, made for their floating floors. And Kahrs makes a polyethylene foam with 3 mil poly plastic for their engineered floors.
Some are just the foam, which is the type I would use over wood subfloors.
Polypropylene Foam
Polypropylene foam is another very safe plastic. It’s not as breathable as polyethylene and I have only seen it advertised as being a vapor barrier or as having a vapor barrier (another plastic layer) attached to it.
It’s used for laminate and engineered (mostly) when a vapor barrier is required. It can be used under solid hardwood floors to provide cushioning and sound dampening.
If it’s labeled 3 in 1 that usually means it’s cushioning, sound dampening, and a vapor barrier.
Floor Muffler has not tested their products with carpet. Their polypropylene underlayment is free of any added flame retardants.
They have a high acoustical rating, the one below can meet IIC up to (74) dB per ASTM E 492 / ASTM E 989, STC up to (73) dB per ASTM E 90. Mohawk Silent Guard is STC 73, IIC 71.
EVA Foam
EVA foam is another safe foam. Compared to polypropylene and polyethylene it does have slightly more of an odor.
EVA foam underlayment can be used under floating floors like engineered wood, laminate, bamboo, and vinyl as well as carpet.
IIC (Impact Sound Transmission Test) rating is 73, STC (Sound Transmission Class) is 72.
Felt Underlayment For Engineered Floors
Felt + Vapour Barrier
Quietwalk is felt and a vapor barrier made for under laminate and engineered wood as well as other floating floors like bamboo and luxury vinyl plank.
The felt and (polyethylene) plastic layers are quite safe even for the chemically sensitive. It claims to be zero-VOC.
This one does contain Microban (Microban can refer to hundreds of chemicals, so this could be anything from silver to something more synthetic). If you want it without antimicrobials you can get Quietwalk from Green Building Supply.
Because this has a vapor barrier it’s meant for on top of a slab or basement floor. If you do lay down laminate, engineered, or another organic-based click-together floor on a slab or basement you do need a vapor barrier.
Best practice, according to mold preventative architects, is not to apply flooring that requires a vapor barrier over a slab because a concrete floor is always trying to dry to the inside. As a mold-sensitive person, I can smell the mold that festers underneath when a vapor barrier is applied. And it happens in most homes in my experience.
Available on Amazon or Walmart.
Natural Material Underlayment For Many Floor Types
Breathable Cork
Cork underlayment is one of the most expensive underlayments. It provides good cushioning and sound dampening as well as some leveling.
It can be used under engineered hardwood, laminate floors, hardwood flooring, and ceramic tiles.
The small pieces of cork are usually pressed together with a polyurethane glue which I find to be quite strong in offgassing, so I don’t personally use this underlayment. However some brands are made with polyethylene as the binder, which is much much better in terms of odor and offgassing. Eco Cork Foam, says they use polyethylene as the main binder.
They also recommended to glue the underlayment down.
There are many flooring types and brands that come with an already attached cork underlayment, which also always has this polyurethane offgassing odor.
1/2”(12mm) cork underlayment has STC 49 and IIC 48 sound ratings.
Cork with a Vapour Barrier
Eco Cork Foam is not as natural as the pure cork above. This version combines cork with polyethylene foam and a 6 mil poly vapor barrier.
Pressed Wood Underlayment
This Steico product is a lot more unusual than the others. This is different from the old particle board underlayments. They claim it is more water-resistant than particleboard.
It’s a pressed wood product, but they don’t mention what kind of wax, oil, or glue is used to make it. They do claim it is zero-VOC.
It can be used under floating floors like LVT, laminate, and engineered wood, as well as hardwood floors.
It seems to be very good at sound dampening.
Available on Amazon or Walmart.
Vapor Barrier for Over a Slab or Basement Floor
6 Mil Poly
This is the most common vapor barrier for slabs and basements. If I was going to put down a vapor barrier (which I wouldn’t due to the reasons discussed above) I would go with plain 6 mil polyethylene plastic. There is no need for anything fancy here. Though it does not provide cushioning. If cushioning is required it makes sense to buy a foam and vapor barrier in one. I would make sure it’s 6 mil though.
Flooring with Attached Underlayment
Many click-together floors come with an attached underlayment. This really helps in simplifying things.
I like laminate floors with polyethylene foam backing attached, LVP with rubber underlayment attached, and engineered flooring with cork already attached.
Luxury Vinyl Plank (LVP) with a cork backing does not make sense to me in a basement, slab or wet area since one of the main benefits to LVP is that it is waterproof and very mold resistant.
Some LVP comes with a EVA underlayment.
Underlayment for Tile
I like the Schluter system under tile.
If you need zero-VOC acoustical control under tile Schluter DITRA-HEAT-DUO providers a ΔIIC contribution of 20. Cork underlayment can also be used under tile.
Many acoustical underlayments for tiles are rubber-based, and I would personally avoid those as they are one of the highest offgassing products in a home. (Whisper mat is one that is mostly foam with some asphalt adhesive, so that would be an improvement over most rubber underlays).
Laticrete Fracture Ban is not toxin-free but it’s the only one I have seen that is breathable.
They have different membranes that I discuss more in the grout and thinset post.
They are made of a non-toxic very low odor plastic that even chemically sensitive folks do well with.
Photo Schulter membrane from Amazon.
Underlayment for Carpet
The main healthy options are natural wool felt for wool carpet, polyethylene, EVA foam, low-odor synthetic rubber, or built-in synthetic felt.
My carpet post goes into detail on underlayment for carpet.
Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.
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Britney says
Hi there! Do you have experience with Quietwalk Plus being used with nailed down engineered hardwood on a wood subfloor? We purchased it already to use under floating floors and have now decided to nail them down. Green Building Supply said that nail down is fine and so does the product. Just wondering why you mentioned it is best with floating floors. Thank you!
JY says
Same question – Britney, what did you end up putting under the nail down floor? What floor did you pick out?
Michael says
Hello there. There is so much information here. Thank you. I am wondering if you have anything to say about Absorba sound underlayment. It’s recycled rubber and I am a little wary about offgassing but flooring guy said don’t get foam because it compresses so much. Thank you for any thoughts. We are nailing the hardwood down on second floor over plywood.
Corinne says
I would never use recycled rubber. See the post on Gym Flooring for details on rubber flooring.
Michael says
Thanks so much Corrine. That’s awesome. We’ll shift to polypropylene.
Bri says
For underlayment under a click and lock waterproof system, how much direct exposure would you really have to the antimicrobials in the underlayment? Does it leach through into the air? If you don’t have any known sensitivities to antimicrobials, how big a deal do you think they are? I’m trying to decide if the QuietWalk without the antimicrobials us worth the extra cost. (It would cost almost twice as much for the amount we need!) The regular kind It is still Green Guard Gold. Their blog lists their antimicrobial ingredient.as Polyphase 678 https://www.mpglobalproducts.com/blog/quietwalk-underlayment-includes-antimicrobial-pesticide-to-eliminate-mold-related-worries/
Corinne says
Under a luxury vinyl plank floor I would say the risk is none.
Bri says
Thanks for putting my mind at ease and helping me prioritize in my budget!
Julie Wilde says
I am buying a 2750 s.f. concrete slab 1970s house on the east coast marsh. I am tearing out the original carpet that covers the entire interior and Ideally would like to replace it with wood flooring (or click lock engineered) for aesthetic purposes and comfort on joints as I have hip issues. I have always lived in older homes with gorgeous wood floors and can not stand comfortably on tile or carpet. I also have extreme sensitivities to chemicals and mildew. I believe that you said not to use a flooring that would require a moisture barrier on slab due to potential mold issues? If I insist on a wood (no vinyl) flooring for reasons stated above, could there be a solution for me?
Corinne says
Talk to Cheryl Ciecko about building a sleeper system (which is not the common one you will see if you google it).
Julie Wilde says
Thank you, Corinne. i appreciate your quick reply. I will try to contact Cheryl right away. If I can’t figure out a way to safely install wood over the concrete flooring, I may need to get out of my contract on the house a.s.a.p.! So glad I came across your article regarding moisture/mold problems in concrete flooring before it was too late!
Dianne Fradkin says
Corrine,
I am desperate to find new flooring in my rental unit to replace carpeting that’s probably 20 years old.
I am very chemically sensitive and have tried bamboo and prestained hardwood, a box of each as a test, both of which I have been unable to tolerate.
After reading your article it seems tile would be best.
Which do you think would be least toxic and what underlayer would I use?
I would gladly schedule a 30 minute phone appointment but it seems that none are available for several months so I am asking for your help in this rather long email.
Thank you so much,
Dianne
Corinne says
Hi Diane, I am doing email consultations if you would like to go through the options. I would also need to know what your subfloor is. https://app.acuityscheduling.com/schedule.php?owner=19257501&appointmentType=16364655
Gaye says
When reading your info you recommend using a product that breathes for an underlayment on 2nd floor over wood. We are floating Engineered Hardwood over old vinyl tiles so should it still be a product that breathes? I am not wanting to trap in moisture! So I am wondering if the Robert’s Serenity polyethylene foam would be our best choice as it would provide some cushioning to dampen the clicking from a floating floor and you say it is also breathable.? Open to other suggestions that would also be good to use . Thanks. (I am not wanting anything with antimicrobials as I don’t want to be exposed to those chemicals.) ( Quietwalk from Green Building is not available in Canada right now.)
Thanks.
Corinne says
Vinyl tiles are a complete vapour barrier so it doesn’t matter if your underlayment is breathable or not.
Tamilyn says
I would be so grateful for any help. Im beside myself reading over and over again all of these floorings and your article. I just bought a mobile home w/crawl space lots of humidity at times. Current flooring vinyl top peeled off prob because of humidity. Which is the safer flooring for a lung condition and some water barrier protection LifeCore waterproof is only Floorscore certified best at blocking water, AquaGuard limestone engineered wood is greenguard gold, HydroShield HDW base core a Laminate is Greenguard Gold or Shaw Laminate OptiCore Board GreenGuard Gold buts also a Laminate. My only other options would be Cali Bamboo Geowood again limestone or Anorim Wise Wood. What out of all of these would be the best for lungs and health? Solid wood in humid mobile home I was told not the best, tile living off a train track also not good and I react to linoleum vinyl super bad. Can you please give me your thoughts begging please.
Akua says
Hello Corrine, this post has been so interesting. I want to put LVP down on a tiled floor. No glue! I am in the UK. I want to know what the best thing to put down underneath is. Least off gassing and most resistant to mold. I live on the 8th floor of a high rise apartment block.. Thanks
Corinne says
Hi Akua, I am also born on a wednesday. This post goes over the main options but also check the warranty as many have a preattached underlayment and the warranty can be voided by adding another underlayment.
Rachael Bonsignore says
Hi Corrine. Have you found out anything about the possible toxicity of Iron Ply that is used under linoleum in the bathroom? It looks like a kind of thin plywood. It looks benign, but I started getting symptoms after it was installed- very loud ear ringing, chest or lung pain…Could be the wood itself I am reacting to, or something else in the house (a little bit of spray foam used recently or vinyl siding stored in house). I didn’t smell anything when I put a piece of it up to my nose, but I did smell a strong chemical smell on it after I soaked it in water for an hour or so.
Corinne says
I haven’t seen that before, could you ask them what is in it?
Rachael Bonsignore says
Thanks. I just called them this morning after having another bad reaction when just smelling the sticker that came off of the Iron-Ply board. It smells so strongly of chemicals. I was told that there is nothing added to the plywood, except the glue used to glue it together. He said the glue is an exterior guy, and it does have formaldehyde in it. But he said it is under the EPA levels. My gut feeling is that the chemicals are very unhealthy and I should rip it out. But I wonder if I could seal it. What would be good to seal it with? It will be used in a bathroom under linoleum.
Anne Robinson says
Hi there-
Thanks so much for all this information.
We are using self-leveling concrete on our basement floor and then buying wool carpet with wool padding. Are there any concerns with self-leveling concrete?
I have looked all over the internet but have not found definitive information. The self leveling was our only option as redoing the floors entirely was beyond our budget and would have lowered the wall height. Should we air out for a long time after using the self-leveling concrete?
Corinne says
Most of them are 0 VOC.
zuzana says
Hi,
I bought recycled hardwood floor which I would like to lay in my basement apartment. What underlay would you recommend for the basement flat? I am confused about the vapour barier! The floor is concrete.
Many thanks,
Zuzana
Corinne says
I personally would not put any type of wood over a concrete basement floor or slab on grade due to moisture. People do this, it’s the norm but mold is also the norm in buildings.
Poon says
Thank you so much Corrine for all the information. Would you suggest using Quietwalk plus under solid unfinished hardwood floors? Thanks.
Corinne says
I would talk to your installer about that, since it’s mainly specified for floating floors.
Hawnes says
Hi Corinne, thanks for the informative post.
I want to install linoleum upstairs. What would you recommend for either linoleum sheet vs. click as an underlayment?
Thanks.
Linda says
Corinne,
Thank you for sharing this valuable healthy living information. You mentioned not to install flooring that requires a vapor barrier over a slab. I am having a concrete slab house built and am trying to be as green and non-toxic as possible. Mold terrifies me.
What type of floor that does not require a vapor barrier can be installed over a concrete slab? Also, is it possible to put a raised sub-floor to eliminate the need for a vapor barrier, if I can get the builder to do it?
Thank you,
Linda
Charlotte, NC
Corinne says
Hi, polished concrete or tile or yes like you mention a “sleeper system” which is raised up. I would have Cheryl Ciecko detail that.
Linda says
Thanks.
Tatum says
Corinne,
Can you clarify doing polished concrete if you are under grade as I thought I read you recommend against sealing the slab (epoxy or other) due to ensuring it dried to the inside?
Wouldn’t polishing it prevent it from drying to the inside?
I appreciate the clarification as I’m trying to figure out our best flooring route for our finished walk-out basement. The north wall is completely under grade, while the west and east are partially under grade and the south wall is fully walk-out.
Blessings,
Tatum
Corinne says
Polishing with (sodium/potassium/lithium) silicates is breathable according to the building science experts I work with.
Jonathan says
Thank you so much Corinne, this is very helpful!
I called MP Global regarding Quietwalk and they said the use Polyphase 678 antimicrobial made by Troy (http://www.troycorp.com/product_view_Preservatives.asp?unitName=Preservatives&cat=products&sub=functions&ID=483) in their Quietwalk underlayment. The product info sheet (which I found doing a search since Troy requires an account) seems concerning. What are your thoughts?
Would something like FloorMuffler be a safer choice? https://www.floormuffler.com/products/floormuffler/
Thanks so much!
Corinne says
Green Building Supply sells quietwalk without the antimicrobial.
Jonathan says
Ahh yes, I forgot you mentioned that! Thanks!