This post covers all of the materials you need to complete a tiling job without the use of toxic materials that offgas VOCs.
Luckily this is not too difficult to accomplish if we stick to the right kinds of products.
When tiling, first we lay down a mortar which is almost always a thin-set (not thickset anymore). We might need to use membranes or special backer boards depending on the project. After the tiles are laid, the grout is applied between the tiles. A non-toxic grout sealer is the final product needed.
This post contains affiliate links to relevant products that I use and recommend. Upon purchase, I earn a small commission at no extra cost to you.
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.
Thin-set mortar is also known as dry set and dry bond.
I used Custom Building Products CustomBlend 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 is concrete, sand, and lime and 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.
On walls, thin-set usually has some acrylic (called latex) additive. Ceramic tile doesn’t need much acrylic-latex, porcelain tile needs more. Consult first with the tile manufacturer, if you don’t get a clear answer on which type you need then look to the advice from the thin-set manufacturer. You also need to consider requirements from membrane manufacturers. Source, JLC.
Ideally, I like to see full disclosure on what the polymers are in thin-set.
Ardex X 5 declares EVA as the polymer.
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 (mastics) like AFM 3 in 1. This can be used when applying tiles to a backsplash, however, you do need to consult with AFM on whether this will be suitable for your project (dependant on the weight of the tiles).
Non-Toxic Tile Membranes / Underlayment
Over the first layer of thin-set, I used Schluter DITRA (polyethylene with a fleece backing), an uncoupling membrane that will help prevent cracking in my tiny house (it worked well and did not have an odor to me).
Polyethelene is a very safe plastic.
If you just need a waterproofing membrane, use Schluter Kerdi (a modified 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. With the Schulter systems you generally need to use their thin-set and grout.
Schulter All Set and Schulter Set do contain fly ash (fly ash contains some metals).
Integrated Membrane Boards
Instead of using the membranes over concrete backer boards (backer boards are discussed in this post), you could use Kerdi Board (also available through Walmart) or WEDI Panels (you can mention my name at The Tile Shop for 20% off).
Test for tolerability before proceeding. They will be behind the thin-set, tiles, and grout, which will render them safe for most people with sensitivities.
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 zero-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 for this product, these grouts can be found at all regular building supply stores and online.
You do want to look for a basic concrete-based grout in powder form. I never use pre-mixed grout.
I used Custom Building Products Polyblend grout (or the new Polyblend Plus), it’s the same brand as the thin-set, and like the thin-set, it is zero-VOC and contains no mildewcides or antimicrobials.
It comes in sanded and unsanded and in different colors. (Unsanded is for marble and certain tiles types). You can find this at Amazon, Flooring inc, and Walmart.
It barely has an odor, though it does have polymers (listed as EVA). Almost everyone does well with this one.
Custom Building Products Prism is similar to their Polyblend with some additional aggregates and more of the polymers which makes it a little bit less water absorptive (a little bit less breathable but it’s not that big of a difference).
Mapai Keracolor (U and S) is another brand that lists the polymer – we know it is EVA.
If those don’t work for you, Bostik Hydroment is also recommended for people with sensitivities. However, it has a small amount of latex additive (this usually refers to EVA) and contains an antimicrobial, which appears to be silver-based.
Laticrete also makes a number of zero-VOC grouts and thin-sets. 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 latex additive 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).
The main polymer found in concrete-based “modified grout” is EVA.
Polymers can 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-set 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.
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.
Chromium 6 is usually found in Portland Cement (and therefore in grout and thin-set) – that will also trigger a Prop 65 warning. Be sure to take precautions when it’s in dust form.
Some cement has added fly ash (which contains metals) and some don’t. Check the SDS sheet of the grout or thin-set to check for fly ash.
Use an N95 mask (or better) when mixing grout or thin-set until it is fully wet. Avoid getting wet cement products on your skin. It is safe once in solid form. A grout sealer listed below is an extra form of protection against dusting of cured cement products.
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. There are also acrylic-based premixed grouts that have some offgassing.
I personally would not use a premixed grout and I would keep a close eye on contractors to make sure that they use what you specified and don’t swap that out for a premixed option.
This grout is significantly higher in offgassing and it should not be necessary in almost every application.
Your waterproofing needs to be done properly behind the tiles.
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 in my tiny house. Porcelain and ceramic tiles do not offgas VOCs.
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.
If you are looking for safer tiles, this e-book outlines the XRF lead testing results from 64 ties that are available now in late 2021/early 2022.
It shows the test results for each tile, alongside the photo, description, and where to buy it.
If you buy the same tile from a similar time frame, it is reasonable to assume that the test results could be similar or the same.
This can help guide your purchases towards low-lead, or lead-free tiles.
You can grab it HERE!
Non-Toxic Grout Sealers
For a full review of all the grout sealer types (and where to use each kind) see my dedicated post on grout sealers.
In many situations, you don’t need a grout sealer, or you could even do more harm by blocking moisture.
If your situation does call for sealers to be used, the post on grout sealers will walk you through each type.
Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.
Did you find this post helpful? If so you can buy me a coffee to support the research behind this blog. Thank you!
Thank you, Corinne! Your posts on flooring have led us to wood-look tile for our son’s nursery and the two other bedrooms on our one-story concrete slab house in a humid climate. The tile is porcelain, and the custom blend standard grout that you recommended calls for adding Admix to the mortar for porcelain. On the company website. Mapei’s unmodified mortar also calls for adding a polymer additive for porcelain. I’m wondering then if those are then comparable (with the additives added for porcelain) to buying Mapei large floor tile mortar that mixes with only water and is already modified. The safety data sheet on Mapei’s website says the modified large floor tile mortar is 0g VOC per L as an application property and voc content 0 and TVOC range less than 0.5 mg/m3. It also has the Indoor Advantage Gold. It shares the ANSI A118.4 & A118.11 with the custom blend standard when Admix is added. I plan to use the mapai grout you listed on the post as a safe grout option and luckily it’s also recommended by the tile manufacturer for that tile. Is it better to stay consistent with the brands in matching mortar and grout for porcelain (as it seems I need some kind of polymers for porcelain in general)? Is the mapei large floor tile mortar worse than the standard mortar with the Admix polymer or mapai additive added to the standard mortar? Thank you so much for helping us! Kate
Any modified grout or mortar that is 0 VOC is great in my opinion. The usual additives in those are very benign. I have not tested out for myself the admixes that you mix yourself so I don’t know as much about them.
Thank you so much, Corinne, for sharing your time, help, expertise! All of your posts have helped us tremendously in making these decisions for our family and home. Thank you! Thank you! Kate
I am looking to install small marble tiles on a backsplash. Do you know if the AFM almighty adhesive would be suitable?
It’s not a mortar and is not meant for installation of tiles, I’m not sure what would happen if you used it that way. I would use a concrete based mortar or AFM 3in1 if the tile are lightweight enough. You would have to ask the company if that will work with your tile.
Hi, I have the same question as Alex. In a prior post you said you would recommend polished concrete or tiles with breathable grout for basement slabs so the concrete can breath. In this post you mention a waterproof underlayment for tiles which would not allow the slab to breath correct? Trying to choose a flooring for my basement and I’d like if you could let me know the best option.
Yes correct, the most common underlayments are not breathable. In the post on underlayments there are two options that look to be breathable.
Rachel Quigley says
Thank you for your informative articles. I see that Custom brand grout carries a Calif Prop 65 warning for reproductive harm that is not from inhaling silica during installation:
WARNING: This product can expose you to chemicals
including crystalline silica which is known to the State of
California to cause cancer and hexavalent chromium
compounds which are known to the State of California to cause
cancer and birth defects or other reproductive harm.
The Calif Prop 65 website says hexavalent chromium can be inhaled through dust but also ingested by touching it and putting your hands in your mouth, as children often do. I know that lead crystal produces lead dust over time. Might grout produce hexavalent chromium dust over time that could harm people, especially children?
I cannot ask my tilers to make their own grout. Is there any brand that does not have hexavalent chromium?
They are supposed to start grouting tomorrow, but I will try to delay them until I hear back from you! Hoping to hear soon. Thanks much! -Rachel
Thank you, I added that to the section on prop 65 warning. Portland cement itself usually contains chromium 6, so that can’t be avoided in any concrete based grout or thinset. A silicate based grout sealer will stop “dusting” of the finished product.
Thanks for this valuable information. Is white thinset mortar (Custom Building Products Standard CustomBlend) more toxic than grey as it has more additives to achieve white color? Appreciate a response.
No that is fine. Neither one should be breathed in when in dust form. Both are the same once in liquid and curd.
Tammy Wigington says
I have a dilemma. We have just purchased a home that has 2 of the bedrooms in the basement. The house was built in 2010 and all of the flooring in the basement is vinyl. My son is 18 and has autism and extensive food allergies. One of my main concerns is the plasticizers and phthalates. I had considered pulling the vinyl up (about 1300 sq ft) but was wondering if it would emit more phthalates if it was ripped, cut and torn to pull it up. It is glued down vinyl squares. Do you recommend pulling it up or putting something on top of it? I’ve read that hardwood isn’t recommended for basements. I’ve looked at non toxic or low voc engineered hardwood that is approved for basements. The basement is walkout on one side with 2 sets of French doors and 5 windows. I’d be glad to pay for a phone consult. Thank you for your help.
I would pull it up but you’ll have to see if it can be peeled up or it’s going to crack. If it’s going into a dust you can put it under basic containment.
Wow, Great info! I am confused about something. You’ve mentioned in other posts that over concrete slab you only recommend tiles or polished concrete. The reason is that it is more breathable and other materials might require a vapor barrier, which can cause mold to fester. In this post you recommend an underlayment under tiles that would also act as a moisture barrier. I might be misunderstanding, can you clarify?
Thank you to Corinne for this valuable information. I have the same question as Alex.
On the bottom behind kitchen cabinets there is an open space that I need to close to prevent roaches from coming from the apartment below. Should I use concrete? If so, what kind should I use? What else might work?
How bad are antimicrobials in grout? My contractor is recommending Bostik Vivid grout because it has the sealer mixed in and lasts forever. It’s zero VOC so from what I can tell the antimicrobial may be the most toxic thing about it.
I mention them in the post, we expect that they are nano silver which isn’t particularly toxic at least not in this application/form.
Mamta Borkar says
Thanks for all the helpful insight into tiling a bathroom. Appreciate your knowledge & help.
We are planning on tiling our bathrooms and using Porcelanosa tiles:
1. AMSTERDAM HEXAGON GREY BPT 19X19X1,4 – wall tile
2. ALEXANDRIA WHITE MATT 33X66(A) – floor tile
The grout they recommend is –
1. COLORSTUK RAPID MANHATTAN N 5 KG
GROUT FOR AMSTERDAM GREY HEXAGON TILE
2. COLORSTUK RAPID BLANCO N 5 KG
GROUT FOR FLOOR TILE ALEXANDRIA WHITE MATT
Can you please provide some guidance into if these grouts are safe to use? This is for my kids bathroom, so wanted to be sure before the purchase.
Also, both these are portland cement based grouts.
Your guidance is greatly appreciated.
If I can help you one on one with reviewing products I offer email consultations that are booked online https://app.acuityscheduling.com/schedule.php?owner=19257501&appointmentType=16364655
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?
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.
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.
It depends on the weight of the tile, you can ask AFM. Otherwise you can use regular thinset and grout.
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?
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!
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.
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!
Hi, which Mapei Kerracolor is safe?
The seem to have Kerracolor in FF, GG, SF, and Flex varients?
I have looked at Keracolor S and U (sanded and unsanded).
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.
I would have to look at that.
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!
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.?
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.
Cheyenne Hanes says
What do you think about forbo marmoleum 885 adhesive, how safe is it compared to the ones you listed!
On paper it looks fine.
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.
Brands are listed here. There is also a post on bathrooms with backerboards and tiles.
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.
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.
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?
Phil Hyland says
I am also considering Schluter ALL-SET, just like another person in this thread (lela above). I am trying to decide between Schluter ALL-SET and Schluter SET (which is the product you recommended in your link above).
I need to make a decision for a person who is currently too sick to test products.
Is Schluter SET a lower risk or are the two products comparable from a chemically sensitive point of view?
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.
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.
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?
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.
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.
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.
Silica. In dust form it is harmful. Don't breath it in in dust form just like any product containing silica. Completely safe once dry. Glass is silica. Think of glass in solid form.
truth naked says
Premixed version of same exact product says the same.
truth naked says
Premixed version of same exact product says the same. Is it just as safe to get the Premixed one then?
I wouldn't use the premixed version because of the VOC levels. The California warning is on Ethylene Glycol/
Diethylene Glycol Monobutyl Ether
What about caulk? Is there a completely nontoxic zero voc one I can use around my bathtub where the water will be touching it every day?
I have a post on that
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.
Here it is https://www.mychemicalfreehouse.net/2013/09/chemical-free-glues-and-silicone-caulk.html
I do not know of a sealer by Green Planet Paints. Send me the link that you have.
A lot of products that were never toxic don't advertise as such. The same thing goes for drywall mud and until recently drywall too. I suspect certain grouts will seek green certifications soon.
truth naked says
Thank you. Your posts are very informative and useful.
I couldn't copy the link here, but if you go to http://www.thefirstgogreenstore.com and once there click on green coatings and toppings you'll see the description.
Greenplanetpaints.com is their sister site.
How have the tiles held up after moving the TH? any cracking of the grout?
Thanks for the informative article!!
No, no cracking after the move!
The Kremers says
I already have QuartzLock urethane grout. Do you think that product would be okay to use to re grout bathroom tiles?
It has a VOC level 35 g/L, so up to you. That is low VOC.
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.
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
I had the same concerns reading the MSDS of the products. Happy to hear once cured …. that is safe.
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.
Pretty tiles! Great post.