My Chemical-Free House

A Guide to Creating a Healthy Home

Non-Toxic Flooring Underlayment

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.

The following underlayments are relatively high in offgassing (too high for me):

  • Polyurethane foam
  • Rubber
  • Vinyl
  • Most cork underlayments, except the ones listed here

This post goes over the best non-toxic low-VOC options.

engineered wood being installed over a green foam underlayment

This post contains affiliate links. Upon purchase, I earn a small commission at no extra cost to you.

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.

a roll of silicone paper underlayment in white

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.

a roll of red rosin paper

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.

a roll of white polyethylene foam underlayment

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.

a roll of more dense polypropylene foam underlayment

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.

a roll of black EVA underlayment with a foil backing

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.

a roll of synthetic fee "quietwalk" underlayment

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.

a roll of cork underlayment

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.

a roll of cork underlayment with a plastic backing

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.

a stack of wooden underlayment sheets in green

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.

a roll of black plastic underlayment

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.

Schulter has 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.

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 one I have seen that the company says is breathable. LL Floors Fiber Fusion Anti-Fracture Crack Isolation Membrane is also breathable according to the company.

Photo Schulter membrane from Amazon.

a roll of orange Schulter underlayment for tile

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.

a cover of a rug pulled up with a wool pad underneath

Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.

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Reader Interactions

Comments

  1. pmfb

    hi!!
    we are nailing down pine boards for our bedroom flooring. the underlayment suggested was tar paper, and the flooring is already halfway down.
    i did not see this option in your blog post; thoughts?

    Reply

  2. Jay

    Hi! I came across this “Natural LVT SG” underlayment. This stuff makes some bold claims. It’s quite nice-feeling too. I got a small roll to check it out. It adds a degree of warmth, is relatively thick, and does not appear to give off any odor. What category do you think this falls under?
    https:// naturalunderlayment.com/underlayments/natural-lvt-sg/

    Reply

  3. Eliza

    Corinne, I’m desperate for help! We put an engineered hardwood on top of a cement subfloor with a QuietWalk barrier. I’m clearly very mold sensitive because the smell is oppressive and my allergies are on fire. I live in a pretty humid climate. What do we do? What floor can I put on cement subfloor that doesn’t require a vapor barrier? Thanks so much!

    Reply

  4. Jose Poloramos

    A question regarding the sleeper system on a concrete slab. Would Rosin paper be placed over the slab, then the sleeper floor or would some other solution be better?

    Reply

  5. Heather

    What are your thoughts on the air gap underlayments? I’d like to put hardwood over an at/below grade concrete slab. Tile is way too cold for my climate and this is a cold room (and heated tile way too expensive), and carpet is a non-starter with my allergies (I just ripped out the carpet that was down there). I don’t do well with linoleums, laminates or LVP. I’ve seen contractors recommend some of the dimpled underlayments like Dampro or Dricore for preventing mold. Do you have any experience with them and the mold issue?

    Reply

  6. Violetta Sur

    My contractor purchased a waxed paper underlay. It doesn’t seem to smell at all but I wonder if it could possibly contain any PFAS or other chemicals, and if so would this even be a problem in a waxed underlay? It is similar to this: https://www.homedepot.ca/product/roberts-750-sq-ft-3-ft-x-250-ft-x-009-inch-waxed-paper-underlayment-for-wood-flooring/1000496301?eid=PS_GOOGLE_D23%20-%20E-Comm_GGL_Shopping_PLA_EN_Flooring_Flooring__PRODUCT_GROUP_pla-341957376360&gclid=CjwKCAjwvJyjBhApEiwAWz2nLYSgrjmjgjM39Vem9mv_QzNIXZ8m65tf2zGgd8HG0c4iLDI7UC8SvRoCUh4QAvD_BwE&gclsrc=aw.ds
    What are your thoughts?

    Reply

  8. Rene

    Hi Corrine, I have a treated timber subfloor and I am trying to prevent any fumes from the subfloor entering inside the home. We are having engineered timber flooring laid over the subfloor. The glue we are using to secure the engineered timber is very good (A+ French interior air certified) European glue. This glue can also achieve a vapour barrier. If I apply it over my treated subfloor as a vapour barrier do you think this would be a good solution to prevent the subfloor offgasing inside the home? or will this cause mold issues if it is not a breathable layer between the subfloor and engineered timber? If so, is there another solution you could suggest? vapour barriers and mold is all new to me. Many thanks

    Reply

  9. Kavitha

    Dear Corrine,

    First of all, thank you so much for your thorough posts!! It is extremely helpful!! We have one question for you – is Aquabar safe as an underlayment? Thank you so much for sharing your advice and wisdom!

    Thank you again,
    Kavitha and Nicolas

    Reply

  10. Emily

    Hi! Any thoughts on COREtec’s new Soft Step underlayment, touted as being made from 100% recycled plastic bottles? I chatted with a rep on the website who said it is free of phtalates ad parabens, and the greenguard gold certification includes the underlayment. I just worry about adding more plastics.

    Reply

  11. Britney

    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!

    Reply

  12. Michael

    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.

    Reply

  13. Bri

    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/

    Reply

  14. Julie Wilde

    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?

    Reply

      • Julie Wilde

        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!

        Reply

  15. Dianne Fradkin

    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

    Reply

  16. Gaye

    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.

    Reply

    • Corinne

      Vinyl tiles are a complete vapour barrier so it doesn’t matter if your underlayment is breathable or not.

      Reply

  17. Tamilyn

    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.

    Reply

  18. Akua

    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

    Reply

    • Corinne

      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.

      Reply

  19. Rachael Bonsignore

    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.

    Reply

  20. Anne Robinson

    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?

    Reply

  21. zuzana

    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

    Reply

    • Corinne

      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.

      Reply

      • Candice

        So you’re recommendation is to remove any existing plywood and use foam only underlayment, is that what I’m reading? I feel like this was vague in the blog but clarified more in comments. Thanks for the info

        Reply

        • Corinne

          You don’t usually put plywood down over concrete before installing your floor. It is done sometimes like if you want to put solid wood down but that other than that is not the norm.

          Reply

  22. Poon

    Thank you so much Corrine for all the information. Would you suggest using Quietwalk plus under solid unfinished hardwood floors? Thanks.

    Reply

  23. Hawnes

    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.

    Reply

  24. Linda

    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

    Reply

    • Corinne

      Hi, polished concrete or tile or yes like you mention a “sleeper system” which is raised up. I would have Cheryl Ciecko detail that.

      Reply

      • Tatum

        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

        Reply

  25. Jonathan

    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!

    Reply

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