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.
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.
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 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!