Updated Spring 2021
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.
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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.
Thin-set mortar is also known as dry set and dry bond.
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 / Underlayments
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. 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 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.
Integrated Membrane Boards
Instead of using the membranes over concrete backer boards (backer boards are discussed in this post), you could use Kerdi Board or Wedi Panels. 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 used Custom Building Products Polyblend grout, it’s the same brand as the thin-set, and like the thin-set, is zero VOC and contains no mildewcides or antimicrobials.
It barely had an odor, though it does have polymers (listed as EVA). Almost everyone does well with this one.
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 EVA) and contains an antimicrobial, which appears to be silver-based.
Many Laticrete products use Microban, which is this case almost certainly refers to Microban’s silver antimicrobials.
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).
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.
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. My post on lead testing explains the different approaches that you could take.
Non-Toxic Grout Sealers
If you are just sealing the grout (and not the tiles) you can use AFM Grout Sealer. It’s zero-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 Tilelab grout sealer is another one that many people do well with – it has 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.
Corinne Segura is a Building Biologist with 6 years of experience helping others create healthy homes.
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