My Chemical-Free House

A Guide to Creating a Healthy Home

Non-Toxic Grout and Thin-Set Mortar

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Updated Spring 2020

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Non-Toxic Thin-Set Mortar

Thin-set is the bonding layer that goes down under your tiles. Concrete based thin-sets are the safest type and are also easy to source.

Brands

I used Custom Building Products Standard Thin-Set Mortar which is zero-VOC (and mildewcide-free). It had a light “wet concrete odor” when wet but it is safe once dry.

Unmodified Thin-set (no Additives)

An unmodified concrete based thin-set that is not mixed with acrylic-latex additives.

The unmodified type is recommended for floors and may not be suitable for all applications. Schulter also makes SET, an unmodified thin-set mortar.

These non-toxic thin-sets are more prone to cracking than ones with additives, and you have to check if your application requires polymers.

Modified Thin-set

On walls thinset usually has some acrylic-latex additive. Ceramic tile doesn’t need much acrylic-latex, porcelain tile needs more.

Other Types

Most chemically sensitive folks would want to avoid the toxic epoxy thin-sets and most mastics. Although there are some safe and tolerable tile glues like AFM 3 in 1.

Thin-set mortar is also known as dry set and dry bond.

Non-Toxic Tile Membranes / Underlayments

non toxic no offgassing odourless underlayment
Schluter Kerdi 

Over the first layer of thin-set, I used Schluter DITRA (polyethylene with a fleece backing), an uncoupling membrane that will help prevent cracking when my tiny house moves (it worked well and did not have an odor to me).

Polyethelene is a very safe plastic. In regular-sized houses, you can use this as well to prevent cracking.

If you just need a waterproofing membrane, use Schluter Kerdi (a modified polyethylene (PEVA) core with non-woven polypropylene).

Membranes for the Walls

For a tiled shower, the Kerdi shower system is recommended by architects to create a mold preventative shower.

Be sure to test all parts including Kerdi Fix sealant if you are sensitive to chemicals (though you can use your own thin-set, as long as it’s compatible).

Integrated Membrane Boards

Instead of using the membranes over concrete backer boards (backer boards discussed in this post), you could use Kerdi Boards or Wedi Panels. Test for tolerability before proceeding, they are not odor-free. But they will be behind the thin-set, tiles and grout, which will be safe for most people.

These integrated membrane wallboards help simplify things by replacing concrete backer boards + membrane with just one substrate that is easy to waterproof.

The panels are made of non-toxic 0-VOC polystyrene with a plastic membrane already integrated.

Concrete Based Non-Toxic Grout

Concrete grouts are the safest grouts and are generally non-toxic. You don’t need to go to a green building store here, these grouts can be found at regular building supply stores.

Top Brand

I used Custom Building Products Polyblend grout, the same brand as the thin-set, which like the thin-set is 0-VOC and contains no mildewcides or antimicrobials.

It comes in sanded and unsanded and in different colors. (Unsanded is for marble and certain tiles). You can find this at Home Depot as well as Amazon.

It barely had an odor, though it does have polymers (listed as EVA). Almost everyone does well with this one.

Alternative Brands

Mapai Keracolor (U and S) is another brand that lists the polymer – we know it is EVA.

If those don’t work for you, Hydroment is also recommended for people with sensitivities. However, it has a small amount of latex additive (this usually refers to acrylic) and contains an antimicrobial, which appears to be silver-based.

Laticrete also makes a number of 0-VOC grouts and thin-sets. It’s a matter of finding out which additives work for you and if additives are required for your application.

Many Laticrete products use Microban, which is this case almost certainly refers to Microban’s silver antimicrobials.

Make Your Own Grout

If you need to avoid all additives, you can make your own grout with Portland Cement mixed with sand, lime, and water for a totally chemical-free option. 

Here are the ratios from Craftsman’s Construction Encyclopedia. To mix your own unmodified grout it is a ratio of Portland cement to sand, 1:1 for 1/8th joints, 1:2 for 1/2 inch joints, and 1:3 for over 1/2 inch joints. Adding up to 1/5 lime increases workability.

What are Grout Additives and are They Toxic?

Those who are sensitive to chemicals will probably want a concrete-based grout (like those above) and then see which additives if any can be tolerated.

Since additives are trade secrets and polymer is a word that can mean a variety of chemicals (there are over 10,000 polymers that can be used in cement) you will probably have to test them against your sensitivities.

Common polymers in grout include: latex-based polymers, acrylate copolymers (acrylic eg. PVA), styrene butadiene rubber copolymers (SBR), vinyl acetate-ethylene copolymers (VAE), and ethylene-vinyl acetate (EVA).

They might come mixed in or you might mix them in yourself. Mixing them means you can test the additive against your sensitivities in a more concentrated form, on the other hand, you may not want to test the polymers and the grout until it has cured.

Polymers are added to improve chemical resistance, reduce porosity, improve flexibility, and freeze/thaw stability (source).

You will have to find out when and where you need additives, which will depend on your specific project. I don’t consider most of these polymers to be toxic.

Are Thin-Set and Grout Safe – Why do They Have the Prop 65 Warning?

Sanded grout and thin-sets contain silica (the same substance as glass) which is harmful to breathe in when in dust form; you will see a Prop 65 Warning on every product that contains silica dust.

Use an N95 mask (or better) when mixing it until it is fully wet. This is completely safe when it is no longer in dust form.

There may also be other minerals in there that are only a problem in dust form like aluminum oxide, which can result in a high health rating on the SDS and other warnings. Again, these are safe when it’s mixed wet and when it cures.

Some cement contains fly ash and some don’t. Plain Portland Cement does not have any other harmful additives.

Non-Toxic Thick-Set /Thick-Bed Mortar 

Thick-Bed mortar (also called thick-set or mud set) in its most basic form is simply Portland cement and sand. Custom Building Products makes a mix of 1:3 that is unmodified, it contains no chemical additives like polymers.

This is harder to source than thin-set. 

Alternative to Concrete-Based Grout

For something more waterproof check out QuartzLock; this won’t be tolerable for everyone. It is a urethane-based grout, not cement, and provides more waterproofing.

This grout is significantly higher in offgassing and it should not be necessary in most applications to use this over cement-based grouts.

Your waterproofing needs to be done properly behind the tiles.

There are applications that would call for a waterproof grout.

Epoxy grouts are also waterproof, and may be selected when a clear grout is specified.

Non-Toxic Tile Types

I used concrete tiles from Morocco. For more info on choosing non-toxic tile types, my post on bathrooms goes into the most detail.

Tiles don’t generally have any offgassing. Lead is the biggest concern.

Non-Toxic Grout Sealers

If you are just sealing the grout (and not the tiles) you can use AFM Grout Sealer. It’s 0-VOC and is one of AFM’s most tolerated products. This is a potassium silicate product also known as liquid glass. It’s a breathable densifier (which is what you want).

Custom Building Products grout sealer is another one that many people do well with, less than 1 g/l VOCs. This also looks to be a potassium silicate.

ECOS, a well-liked brand, has a stone sealer that is used on grout. They do not disclose any of the ingredients in this product so it’s not possible to know if it is a breathable densifier or topical coating.

Sodium, potassium, and lithium silicates (aka water glass or liquid glass) is a very safe product that also leaves the grout breathable. It is a densifier so it makes it easier to clean and less likely for dirt grime and mold to get embedded. It’s not intended to be waterproof.

On this topic, I take expert advice from contractor Mike Holmes and architect Cheryl Ciecko. Your waterproofing layer is behind the tile (see the section on Schulter). The grout should be breathable.

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Corinne Segura is a Building Biologist with 6 years of experience helping others create healthy homes.

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Reader Interactions

Comments

  1. Suzmiché Morris says

    Hi, I am preparing to tile a kitchen backsplash over freshly hung, textured, and painted drywall. I’ve extensively read your instructions on tiling a countertop to learn the least toxic way to accomplish this project. Your posting on thin set and grout is helpful, and I have the AFM tile sealer. Now I am wondering if you know of a non-toxic primer sealer to put on the dry wall prior to the mortar? An alternative to Prime Grip perhaps? Or do you know if the primer may not be necessary since the wall is textured?

    Reply

    • Corinne says

      Normally it is primed yes. Not sure about the textured element and how it changes things. It’s normally a standard new wallboard primer, so which ever brand you like there will work. I like ECOS, Farrow and Ball and Ben Moore. More in the paint post.

      Reply

  2. Jennifer says

    Hi! Is the afm 3 in 1 what you could use for marble backsplash in the kitchen? My contractor said he uses mastic, so I came here to check. Will try to buy something safe for him to use.

    Reply

  3. Jules says

    Great guide, many thanks!

    Unfortunately we can’t seem to track down these products, or equivalents, in the UK. I wonder, do you know of any, or of anyone who may know of some?

    Reply

    • Corinne says

      The basic formulas will be the same there but I don’t know the brands there. It’s more than a full-time job to keep track of them over here!

      Reply

  4. Lori says

    May I ask what cement tiles you got from Morocco? I didn’t find it specifically mentioned in either of these posts. I’m trying to get my contractor all the information he needs to not blow me off for being so specific about every little thing.

    Thank you SO much for all you do.

    Reply

    • Corinne says

      I had to order those from Morocco because they were not that popular at the time. I don’t remember the brand it was quite a while ago!

      Reply

  6. Heidi says

    I am just realizing that I am chemical sensitive with our most recent remodel. Prior to my realization, we have already purchased our tile, mortar, grout and sealer from the Tile Shop. The products we purchased are the SUPERIOR PRO-GROUT EXCEL and Ardex X5 Flexible Tile & Stone Mortar 40lb Gray. Haven’t found the receipt for the sealer yet. What are your opinions on those products? I am not familiar with chemicals, so based on SDS I am thinking the silica dust is the biggest problem. Not sure on the off-gassing. Please assist.

    Reply

  7. Jamie says

    Hello!
    Our tiler is wanting to use LATICRETE PermaColor for thin-set and grout. I saw you recommend the Laticrete brand, but maybe not all their products. This one that he wants to use, in particular, has antimicrobials. I understand it to help prevent mold–but are there major concerns with this additive? Any suggested alternatives?

    Thank you for the help!

    Reply

  8. Diane says

    I like the idea of Kerri board for bath, and I see you mention the Kerdi fix, And have you gotten any feed back on the Kerdi Fix and the Kerdi thin set? And thoughts on using that, I realize its a personal thing depending on peoples sensitivity but wondering Safety wise ( toxic wise) your thoughts on this

    Did you hire workers to put in the Kerdi board or was it a do it yourself project.?

    Reply

    • Corinne says

      I have used the membranes myself but not the boards. Kerdi Fix and thinset have been well tolerated by most but definitely I would test them.

      Reply

  10. Cheyenne Hanes says

    very glad i came across this page, we have a baby and are looking to redo the vinyl to tile and was wondering what your opinion was on which brands would be less toxic(no vocs and other harmful chemicals to babies)for us to use! need help picking a back board, mortar/thin set, grout and a sealer if we need it. hoping you could help! thank you.

    Reply

  11. lela says

    Does Schluter (same brand as the ditra you used) all set (their thinset) contain vocs? I would like to use it, because if you use both ditra and their brand thinset there is a lifetime warranty. However I haven't been able to find online if it contains voc's.

    Reply

    • Corinne says

      ALL-SET is modified so it contains unspecified polymers. They don't list the VOCs but it would likely pass as 0 even though the super sensitive cannot tolerate many or all polymers.

      Reply

      • Diane says

        Hi Did you yourself use the kerdi board Kerdi fix or have you gotten any feedback on this. I see how you said some people are more sensitive its pretty much testing for yourself to see. Also with the Kerdi Thinset ? Yet just wondering any feed back you have gotten if most do ok with it, it does up that warranty . And your own thoughts on this.

        Did you do the tile work in your bath yourself with the Kerdi board, or did you hire a professional?

        Reply

  12. PJames says

    Corinne.. you suggested avoiding latex and acrylic additives in thonset. I noticed when looking at the MSDS sheet for Benjamin Moore Natura paint that the base is acrylic latex, can you explain the difference. Can all be most confusing.

    Reply

    • Corinne says

      Many people cannot tolerate the acrylic paints at all though I suggest the ones that are 0 VOC and best tolerated. The additives in grout are not disclosed so I can't do a direct comparison between the ingredients. But some very sensitive people would have trouble with acrylic.

      Reply

    • PJames says

      I have a floor I thought was concrete, I planned to paint it with SafeCoat concrete paint, but it turns out the floor is Gyprete. I want to tile using thinset but can't even walk on the surface because the dust coming off, it needs to be sealed. Talked with tech reps at both SafeCoat and Benjamin Moore, neither is sure they have a product that will adhere to it, and the 046 BM primer they think might work has mildewcide. Any suggestions?

      Reply

  13. truth naked says

    Also I read somewhere on this blog that polystyrene is a safe material to use. An article I read on treehugger.com written by a PhD chemist appears to state otherwise… yet the alternatives suggested are also not green.

    Reply

    • Corinne says

      I consider that to be a safe product other than the flame retardants. Discussed in detail in the post on insulation. Not sure which article you are referring to though. In terms of environmental effects it's not considered the greenest product but I look at effect of its use in homes.

      Reply

  14. truth naked says

    This blog is so informative, but the grout recommended above says on the back of the package that I contains chemicals known in state of CA to cause birth defects or something to this effect.

    Reply

    • truth naked says

      I couldn't find it. Can you please direct me to it somehow?
      Also, why doesn't polyblend advertise their grout as non-toxic? Also, I have old tiles in my apartment. They were put there 67 years ago when the building was first built. When I said this to the worker at home depot he said I have to get the non-sanded grout for the area around my bathtub, saying sanded is usually used for floors. I bought sealer from green planet paints. How does this sealer compare with the one you recommended? Thank you.

      Reply

  18. Mboris says

    Very informative post and site. Thank you for sharing.

    One of the issues I have is finding mortar and grout that are low in VOC as well as chemical exposure but at the same time without any ingredients labeled as carcinogens. Every product that I have found contains some carcinogen or toxic ingredient. Are there any alternatives that you have found on this. Silica sand seems to be the primary issue on the most used ingredient across this products. Hope someone has found an alternative product(s) that they can share.

    Reply

    • Corinne says

      Silica is only harmful when you breath in the dust otherwise it does offgas anything at all (i.e. glass). You could use a really good respirator and stay away when the mortar is being mixed

      Reply

    • Melody says

      Find the least toxic mortar and grout possible and then use a sealer like AFM SafeCoat Grout Sealer, or even their Hard Sealer and Safe Sealer products, concieved especially for stopping off-gassing. They seem to be 0 VOC , formaldehyde etc.
      There surely are other eco-sealers available if you check, so it can be an effective solution for the off-gassing as well as mold prevention for grout, since mold is also a carcinogen and super-toxic in many other ways.

      Reply

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