This post is an overview of interior and exterior door types, what they are made of and the potential offgassing of VOCs of each type. We will look at which types are non-toxic and safe, with zero to little offgassing, and which ones contain toxic substances.

The post will focus on outlining the types of doors you will find at big box stores like Home Depot, specialty stores, and online. We will also cover unusual and creative options (including non-wood options) that will suit the most chemically sensitive or the true purist who wants the healthiest door possible.

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

If you need assistance choosing non-toxic materials for a build or reno, please contact me for a one-on-one consultation. 

Solid Wood Doors

This category of doors are real solid wood through and through. Only really old doors might be one solid piece (a slab).

Modern solid doors are made from a number of solid pieces glued together in a frame and panel construction.

You might also find flush (flat) doors that have solid wood pieces inside and a veneer on the outside. When looking at a door that has solid strips glued together on the interior, you may want to know the size of the pieces of wood. Some companies may call this “engineered” if the solid wood pieces are as small as 1 inch each. This also, of course, means more glue used in the door.

Wood glues:

Wood glues tend to be quite non-toxic and low to 0-VOC once dry, but you should get a sample if you have reactions to chemicals. I have seen epoxy used as well as wood glue and exterior wood glue.

When testing an epoxy be sure to test both parts mixed in a real-life situation to see how it comes out.

Also, look and what paints or stains are used. This door type can be used for interior and exterior doors. With exterior doors usually coming with a stronger stain or paint.

Accoya wood:

Accoya wood doors are a good option for exterior glass and wood doors. Accoya is a type of wood process where the wood is treated with acetylation to be naturally rot-resistant without adding toxins.

They also claim better dimensional stability and less shrinking and warping from moisture than untreated wood. Check their websites to find the companies that work with this wood and their distributors. These doors are pricey.

Solid wood doors are one of the most non-toxic types. You can find solid wood doors on Amazon, you may find a limited selection at big box stores, and many more options at specialty door stores and though custom builders.

Simpler Versions of doors made only with real solid wood:

Louvered doors can be used when not much privacy is needed. The ones I have seen are made out of just solid wood.

You can find them in unfinished and finish them yourself if you like.

Here is my list of non-toxic finishes and paints.

You can find these on Amazon and at big box stores.

Solid wood barn door can be found at big box stores like Home Depot as well as on Amazon.

You could also make your own solid wood door in this style out of the wood of your choice which would give you more control of the process and the wood itself.

Add hardware from Amazon.

Hollow Core Doors 

Typical interior doors in new houses and apartments are hollow core. You can easily tell as they do seem to be hollow inside and are light.

The interior frames of these doors are solid wood or, more likely, composite like MDF.

To stabilize the hollow interior there may be a honeycomb interior (cardboard, plastic or hardboard) and there might be some solid wood in a strip down the middle.

The outer veneer surface can be real wood in non painted options, but usually, it is HDF/hardboard.

They usually come primed.

Hollow doors could have MDF or other pressed wood products along the frame.

These are interior doors.

What do Hollow Core Doors Like Masonite Offgas?

MDF (in the framing) is made with formaldehyde, there is a fair amount of glue here.

Hardboard/HDF/fiberboards (the door skin) could be made with either phenol-formaldehyde (which offgasses fairly quickly), asphalt or no adhesive, depending on type. Paraffin wax and or linseed can be added.

Masonite brand door:

Masonite doors are the most common door brand of interior hollow core doors. Many want to know if Masonite doors are non-toxic.

Masonite fiberboard skins are not made with an adhesive and are formaldehyde-free, but they do have other additives that are undisclosed (according to the SDS they sent me).

Masonite brand hollow core doors can be made with solid wood framing (which would make those ones non-toxic), but it looks like most of them have at least some composite framing of MDF (which offgasses formaldehyde).

Therefore it’s possible for this door type to have very little offgassing and to be formaldehyde-free if they don’t have MDF and if made with a fiberboard that does not use an adhesive.

Are hollow core doors safe for the chemically sensitive:

Some folks who are avoiding toxins or are chemically sensitive do choose to use this door type. Some do seal it with an AFM sealer or shellac before installing them to seal in some of the offgassing.

See the post on sealers for more info on sealing in offgassing.

Hollow core doors are easy to find at any hardware store and are inexpensive.

Solid Core Doors

Solid core doors have an engineered or composite wood inside, usually a fiberboard.

The outer skin is usually HDF/hardboard.

The other type of solid door is a solid MDF (or another composite wood product molded into a shape and painted).

These are usually interior doors.

This is my least favorite category of doors for those avoiding toxins or for chemically sensitive persons.

Because the core is a solid MDF (or other lower-density fiberboard) this potentially has the highest offgassing of the door types. MDF is made with formaldehyde, they offgas for quite a while.

You can find solid core doors on Amazon, at hardware stores as well as at specialty door stores.

Glass Doors

Glass barn doors, in clear or frosted

Glass barn doors can be found in clear or frosted and can offer some privacy. The benefit is how little there is to offgas.

Glass and metal are inert. In some instances (or for the most sensitive), you may want to wash factory oils off the metal parts. But if you don’t pick up any chemical odors or reactions there, you may just skip that step. Those that need to go the most extreme, would also want to know what kind of finish in on the metal.

Glass and metal barn door. This style might be easier to find than the all-glass at the big box stores. Both types can be found on Amazon.

Frameless all-glass doors are more commonly seen in office buildings, at least in North America, but they can be seen in very modern houses all over the world.

You may find them at high-end residential companies or you may have to look at office supply companies. Frameless glass doors are all glass (other than the door handle, or the base tracks if it’s a sliding door), and are the safest, purist, least toxic door option.

Mirror closet doors can be safe and non-toxic (but check the backing). You can find these at big box hardware stores.

Solid wood and glass doors. I saw these doors pictured left at a B&B. The doors are framed in real solid wood with glass from a local company in Canada, called Wescon that specializes in doors (both custom and premade).

These are “seconds” so they were a good deal. This is a good example of a local specialty door company. They make solid wood exterior and interior doors, some with veneers. Some do have MDF, but you could avoid that style.

Metal doors

Metal doors are usually intended to be exterior doors. Steel doors are made of heavy-gauge galvanized steel over a core of rigid foam or spray foam (usually with wood framing inside).

They might be coated with a polymer or vinyl that could look like wood or have face veneers, or they can be just painted.

Apartment doors are typically steel in a simple slab construction pictured (the one pictured is by Jeld Wen and is simple steel with paint).

Flush exterior doors often have a core of solid foam (I have seen polystyrene and polyiso). I have seen polyurethane as well. Some have a honeycomb pattern inside as well as steel reinforced.

What’s inside a steel door is well sealed up by the metal (especially if the edges are welded) and so the offgassing should not affect the occupant.

You just want to look at the finish on the outside to make sure that is low-VOC and safe for you. The standard paint on a simple metal door is a primed paint that is baked on and is low-VOC. A simple painted metal door is preferable from a health standpoint to anything faced with vinyl or other polymer.

Masonite metal doors are for residential use (not commercial and apartments) – they have wood framing (real, laminated or composite), some doors have steel framing inside, polyurethane or EPS foam inside and galvanized steel on the exterior (painted).

I have seen folks find used metal doors at used building supply stores. Many supersensitive folks do use metal door intended for the exterior as interior doors, such as the Masonite brand. You can find these at hardware stores and specialty door stores.

Fiberglass Doors

Fiberglass doors are also exterior doors. They have a core of rigid insulation, or polyurethane spray foam inside, and are clad with a fiberglass skin, they usually have a wood look.

Inside the door may be wood (real and or composite) and plastic to frame it. The fiberglass skin is rather thin, but fiberglass is not typically a tolerable material for those avoiding toxic chemicals due to the offgassing.

Though you may find some brands preferable to others, or you may do well with a used one. I prefer metal doors to fiberglass in almost every situation in terms of toxicity and offgassing.

Vinyl Doors

Patio door, sliding glass doors and other glass door types have framing in vinyl, fiberglass or aluminum. Similar to my assessment in my post on windows, I prefer metal. You still have to check for the coating or paint on the metal.

Hard vinyl can be quite tolerable for some, and some brands of fiberglass can be as well. Folks who are sensitive to chemical offgassing and toxins should check out both types, in different brands, if you cannot find metal framed patio doors.

Vinyl can also be used as a skin over metal doors which would not be a preference for me for healthy doors.

Pocket Doors

Almost any type of door including, flush, panel, louvered, and glazed, can be mounted as a pocket door. Just make sure the hardware is rated to handle the size and weight.

Corinne Segura is a Building Biologist with 6 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!

This article is a comparison of linseed and tung oils:

• Are they safe and non-toxic
• What types of chemical additives are used in the different oil types what compounds do they naturally offgas
• When do they cure and stop offgassing VOCs
• Are linseed and tung offgassing any toxic compounds

I review the following oils:

• Tried and True polymerized linseed (pure and with a stain)
• 100% Tung Oil
• Rubio Monocoat (plain and a blue color)
• Odies Oil

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

The video compliments the post:

Linseed and Tung Oil – Chemicals and Offgassing 

Linseed and Tung Oil are the traditional natural finishing oils for wood – some forms also work well as stone and concrete sealers.

Oils that don’t go Rancid

Both of these oils are called “drying oils” which means they polymerize in the presence of oxygen forming a durable and elastic finish. They do not go rancid like semi-drying or non-drying oils.

Are Linseed and Tung Oil 0-VOC?

While all of these oils, the pure ones and ones with additives, claim 0-VOC (a legal term), they do give off natural VOCs, whether these are enough to be considered toxic depends on you and your tolerance.

Are Linseed and Tung Oil Toxic?

The term “non-toxic” means that the toxins are not at high enough levels to do harm to the average person.

During oxidation (curing) of tung and linseed oils, aldehydes and hydrocarbons are produced. Peroxides, alcohols, ketones and acids may also offgas during oxidation (1).

I could pick up this chemical odor very acutely.

In low concentrations, these compounds are not toxic for most people or for healthy folks.

For those who are comprised, aldehydes especially, can be harmful or cause symptoms. This can be considered toxic to someone who is compromised or chemically sensitive. It certainly does cause me symptoms.

Are Linseed and Tung Oil Safe for the Chemically Sensitive?

If you are wondering if linseed and tung are suitable for you and your sensitives be sure to test both in the 100% pure versions, as well as Rubio Monocoat and see how you do.

For those who like pure natural finishes and who are not bothered by the natural aromatics of plants and oils, both 100% linseed and 100% tung would be great options.

Which one was Less Toxic, Linseed or Tung Oil?

I wasn’t expecting to like Rubio Monocoat, the modified linseed oil, because of the lack of transparency of ingredients, but I explain why it turned out to be my top choice in many ways.

The finishes produce slightly different looks and you should also check the application procedure for the oils you are considering, as well as the upkeep

I’m going to compare tung and linseed (including Rubio Monocoat and Odies Oil) in terms of the chemicals added as well as what compounds they naturally give off when curing.

100% Pure Tung – Chemicals and Offgassing

When choosing a tung oil you are looking for 100% pure tung oil.

Are Tung Oils from the Hardware Store Pure and Safe?

I wouldn’t use the “danish oil” mixes from the hardware store, or anything premixed with a thinner.

I have not seen a pure tung oil at Home Depot or other large hardware store (yet). The Behr tung oil contains petroleum waxes, petroleum distillate solvents and metallic driers.

Pure, Safe Tung Oil Brands

My top brands for pure 100% tung oil are Real Milk Paint, The Hope Company and Heritage. We want to start with something pure that does not have additional chemicals added. I found the Real Milk Paint Tung to be more mild than the brand I initially tested in this post which later changed my view more favorable towards tung.

Can Tung Oil be Used Straight Without a Thinner Additive?

Tung oil can be applied without a thinner to weathered wood, new wood floors as well as some old wood floors and concrete.

Check to see if your application requires a thinner before starting because the thinners are chemical compounds that may not be tolerable or desirable.

What are the Chemical Thinners in Tung Oil and are they Healthy and Safe?

Common thinners for tung oil are citrus solvent, mineral spirits, or odorless mineral spirits.

The thinners can be very hard to tolerate. I describe the citrus solvent as “brutal” – it wipes me out and makes me very sick, it does not dissipate quickly. Just because it’s natural does not mean it is safe.

If I had to pick one I would use odorless mineral spirits which should dissipate (offgas) quickly, in theory.

However, whenever you are applying something yourself things get more tricky. If a non-sensitive person is applying the oil you may opt to use an additive that will dissipate quickly and wear protective gear.

Is Tung Oil Food Safe?

100% tung oil is food safe on butcher block, cutting boards, wooden countertops, concrete countertops, and wooden toys once cured. (To err on the safe side, wait 30 days for it to be cured).

Where can Tung Oil be Used/What Surfaces can it Seal?

Apart from wood, tung oil can be used on raw slate (slabs or tiles). Although it did work well on all the stones I tested it on – slate, dark honed marble, light honed marble and granite. It provides such a thick and durable layer that it is not usually used on indoor stone countertops.

You might use it on stones in the shower or outdoor stones.

The Real Milk company has a lot of knowledge here. I was happiest with their tung oil which seemed to be lower odor. I am very happy to support this small company with sharing the discount code for 10% off: mychemicalfreehouse.

It can be used on concrete countertops as well as concrete floors, and works well in those applications.

You can use it on metal, in fact, cans for food used to be lined in tung oil. A coat on some types of steel helps prevent rust.

How Long Does Tung Oil Take to Cure & Offgas?

The companies say tung oil normally takes 30 days for a full cure.

The time it takes to cure is not the same thing practically or scientifically as the time it takes to finish offgassing.

However, in my results at the end of this post, I compare all the oils at 30 days to see if I can still pick up the offgassing.

Companies claim 95-98% cured within 7-14 days and depending on conditions, it can take up to 90 days for a full cure.

Does Tung Oil Cure/Polymerise Faster than Linseed Oil?

There is a statement on Wikipedia that tung comes to a full cure whereas linseed continues to polymerize for years.

I was not able to confirm that statement about tung after looking through all the scientific literature on tung oil and talking to many companies.

In fact, my results after 30 days does not confirm this (comparison at the end of the post).

Cure Times Did Not Line Up With Offgassing Times

In the literature, I did see lots of reference to the idea that tung oil has a superior ability to polymerize due to its a-elaeostearic acid (77–82%) content.

In theory, this gives it a greater chemical reactivity and excellent ability to polymerize (cure) (2, 3).

However this didn’t line up with the end of the offgassing level/time, my sniff test at 17 and 30 days revealed more offgassing of tung than all of the linseed oils I tested.

Comparing Offgassing of Tung and Linseed Oil

The offgassing odors of tung are a little different from linseed.

In my assessment, tung is not as pungent when in liquid form, but they both offgas similar VOCs while curing.

During oxidation, aldehydes and hydrocarbons offgas. Peroxides, alcohols, ketones and acids may also offgas during curing. (1).

At the end of the experiment, the two had reversed in my assessment: tung was the strongest at 30 days. The end of the post shows the comparison.

How to apply it instructions here.

Linseed Oil – Review of Chemical Additives and Offgassing

Linseed Oil Comes in Three Types

1.  Raw, which is pure, not usually used for wood, as it takes a long time to dry and is often cut with a thinner.

2. “Boiled” which has driers, usually metals like cobalt, or petroleum (which I would want to avoid), this version could be considered toxic if it has toxic metals.

3. Polymerized/stand oil which is pure, food-safe, and faster to dry. This oil does not require a thinner. Polymerised is the type you want to use. I like the brand Tried and True because it’s pure 100% linseed, and because of their total transparency with ingredients and additives.

Odor and VOCs that Offgas from Linseed

The odors of linseed oil (and the citrus solvent) comes from their naturally occurring VOCs (4). For the chemically sensitive, both tung and linseed have odors that are stronger than some other finishes.

The pungent smell of linseed comes mostly from the aldehydes (5).

Do you Need to Add a Thinner to Linseed Oil?

You should see if the pure version works for you first.

I prefer to use linseed oil only on applications that do not require solvents/thinners.

The solvents/thinners should be tested separately, and are not always tolerable (or needed).

How Long Does Linseed Take to Cure?

Linseed will dry within a few days.

But according to the literature, the drying (curing) reaction of linseed oil continues for many years even when the oil film effectively drie in a few days (7).

You can speed up the offgassing odor by increasing temperature and decreasing humidity. Raw linseed might be different in this regard, compared to modified oils with driers.

Comparison of Linseed and Tung Oil Offgassing

Tung oil has milder offgassing compared to polymerized linseed in my assessment at first, but at the end of the 30 days, tung had a stronger odor left.

Rubio Monocoat (modified linseed with driers), was the exception, it was far less pungent than either polymerized linseed or tung.

Surfaces to Seal with Linseed Oil

Linseed Oil is mainly used to seal wood.

It should not be used on marble or granite.

Odies Oil has been used as a concrete sealer which I am quite certain is linseed based, but the ingredients are not disclosed.

(In the video, I discuss why I think Odies Oil is linseed based.)

Here are the instructions for the application of polymerized linseed oil.

Is Linseed Oil Mold-Prone?

Woodworkers having varying opinions on the two oils, each camp preferring one over the other with some noting caution to linseed as being less mold resistant in certain conditions.

Outside in high humidity linseed does not do well. For indoors with regular humidity levels, linseed will work just fine, and I have no trouble recommending it.

Tung oil has the advantage of holding up well to water and mildew outside.

Top Non-Toxic Brands of Linseed Oil

1. Rubio Monocoat Linseed Oil Finish

Rubio Monocoat makes linseed based finishes (natural and modified) that smell like honey or lemony incense.

It contains a wax component (natural and modified) as well.

They claim zero-VOCs but you should test any linseed product before using it.

Chemical Additives in Rubio Monocoat

The accelerator which is a part B drying agent lists hexamethylene diisocyanate as an ingredient (0.5%), but not all ingredients are listed.

Because part A (without the drier) takes a very long time to dry, it sounds like part raw linseed to me (though it does not smell like raw linseed). This means Part B is unknown driers and hexamethylene diisocyanate.

It does contain non-aromatic hydrocarbons, I could not get the company to claim no metallic driers, but they do claim no solvents.

I will always prefer brands that disclose all their ingredients.

Why Rubio Monocoat Turned Out to be My Top Choice

Sensitive folks reporting that they really like this brand is important data, and caused me to seriously consider it.

It turned out to be my top pick based on odors, offgassing level as well as personal tolerance.

I was surprised by how mild it was from start to finish, though I did still pick up a chemical odor at 30 days in the plain color.

I was very impressed with Sapphire which I found cured to my nose at 30 days. Because it’s easy to apply, easy to touch up and seemed to have the least offgassing, much lower than I expected, I have to say it is my top pick. Though with reservations, since we don’t know everything that is in it.

I would like the company to confirm no metals since metals are a major health problem for many of us.

Performance of Rubio Monocoat

This brand offers unique colors in their stains that few other natural option offers (greys and white).

Be sure to sample both Part A and Part B as well as different colors, which for me tested quite differently. I tested plain and sapphire.

It also is easy to touch up which is a major bonus.

Cure Time and Offgassing Time of Rubio Monocoat

Rubio Monocoat (Part A & B mixed) takes one week to cure, they say. You could use just part A which takes 3 weeks to dry.

Although I say in the video it is approaching offgassed at 48 hours, at one week my sense of smell ramped way up (due to a reaction I had to something else), at this point, I could still smell it very noticeably.

So the time that it cures will very much be dependent on you and your level of sensitivity.

2. Tried and True – Polymerised Linseed

Tried and True is my top recommendation for pure linseed with a stain because it is totally pure and because of their full disclosure of ingredients.

No driers are used.

This company can claim that metals are not a component in their pigments other than what comes naturally from the soil.

Performance of Tried and True – Review

I really liked the look of the Java stain (pictured), it went on beautifully even though I did not sand and prep my wood properly.

That’s going to give you a high-quality stain/finish in one. I was really impressed with how the stain looked after my disaster trying to mix my own pigments with hemp oil.

They offer versions with waxes and resins as well, check out the different formulas to see which suits your project.

3. Odies Oil (Universal Finish)

Odies Oil (the Universal Finish) is another oil I tested in the video.

I suspect this to be a linseed based finish. The ingredients are listed as: lubricating oil, drying oil, natural waxes; essential oil.

They claim solvent-free, that it contains UV inhibitors, and it has the warning for spontaneous combustion (which is seen on almost all drying oils).

My Experiment to Guess What is in Odies Oil

I made the following mix which came very close to the odor of Odies: mineral oil, linseed, beeswax, carnauba wax, lemon and orange oil.

I did not get the exact match but it seemed pretty close, therefore, that is my guess on the basics of what is in Odies Oil.

There is still is another essential oil I think, lavender or similar, something flowery.

And there is a different mix of waxes I think, compared to my test. But I got quite close to their mix, according to my nose.

Odor and Offgassing of Odies Oil

This tested quite strong to me at first, with the essential oils being overpowering for me (I’m extremely sensitive to essential oils) in the first 24 hours, but at 48 hours that had faded significantly, and what smelled to me like linseed was then dominant.

Those who are reactive to essential oils might have trouble with this one, but you can see how fast it fades for you.

As always, I’m not a fan of using products that I don’t know the ingredients of, we don’t know if there are toxins in here, but it did cure faster than some of the others.

They claim 2-3 weeks to cure.

4. Other Brands

Fusion tung oil is a similar oil and stain in one but they don’t reveal all the siccatives (driers). This brand does have other products that I am a fan of, but unknown driers is not one of them.

Oils labeled as teak oil or danish oil from hardware stores are usually a mix of oils like linseed or tung, solvents, and possibly resins, UV inhibitors and mildewcides.

I wouldn’t use those, go with one of these pure brands.

My Test Results

My test results at 24 and 48 hours are in the video.

My testing at 17 days 

• Rubio 1st place 
• Tried and True Java 2nd place
• Odies Oil and Tried and True still quite noticeable odor, 3rd place
• Tung actually the strongest at 17 days, last place (though I like the Milk Paint version better).

My testing at 30 days when they should all be “cured”

• Rubio Sapphire – this is the only one that seems totally cured to me at 30 days 1st place.
• Rubio plain – I can pick up the Rubio plain at 30 days though it is very light. My nose is unable to pick up any offgassing from the
• Odies oil – very slight odor in 3rd place for offgassing levels
• Tried and True Java in 4th place very slight odor
• Polymerized linseed – Tried and True plain still offgassing 5th place
• Tung oil – strongest one. I do not agree that tung oil cures in 30 days, at 30 days I can still pick up the odor of one coat. I kept it at 30C and about 50% humidity. I cannot say it is 100% offgassed. Last place. Later when I tested Milk Paint brand I was much happier with this and would likey choose it over linseed.

Other Natural Oil Options for Sealing Wood

If these two don’t work for you, try hemp oil. I was really happy with pure refined hemp oil. If you want a totally natural purist option, hemp is a good choice. It’s not as strong of an odor as the others.

Other finishing oils reviewed in my main post on finishes are coconut, walnut and rosewood. That post is also a comprehensive overview of water-based 0-VOC and non-toxic finishes for wood as well as stone and masonry.

Corinne Segura is a Building Biologist with 6 years of experience helping folks 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!

Sources for this Post

 1. EPA 1991 Impact Of Declaring Soybean Oil Exempt From VOC Regulations On The Coatings Program  

2. Modern Technology of Paints, Varnishes & Lacquers (2nd Edition), NIIR Board February 7, 2007, ASIA PACIFIC BUSINESS PRESS Inc. 

3. Meiorin, C., Aranguren, M. I., & Mosiewicki, M. A. (2015). Polymeric networks based on tung oil: Reaction and modification with green oil monomers. European Polymer Journal, 67, 551–560. 

4. Identification and Quantitation of Volatile Organic Compounds from Oxidation of Linseed Oil
Juita, Bogdan Z. Dlugogorski, Eric M. Kennedy, and John C. Mackie. Industrial & Engineering Chemistry Research 2012 51 (16), 5645-5652  

5, 6, 7 Low temperature oxidation of linseed oil: a review. Juita, Dlugogorski, B.Z., Kennedy, E.M. et al. Fire Sci Rev (2012) 1: 3.  

Updated Spring 2020

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.

For individual help on choosing the best products and materials for you and your home, you can schedule a consultation with me here.

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

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.

Corinne Segura is a Building Biologist with 6 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!

Updated in Spring 2020

Testing wood glues, construction adhesives and silicone caulks was the hardest part of building my house since I did this when I was highly sensitive.

But, you’re going to need glues, caulks and adhesives if you are building so it’s a good idea to start testing them out!

You’re going to need them for repairs and renovations too. I would suggest knowing which ones work for you before that urgent repair is needed.

This post covers low VOC, low odor, non-toxic options that are suitable for the chemically sensitive or health-conscious.

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

Non-Toxic Wood Glues

It’s difficult to extrapolate a small jar of dry glue to a house filled with it. (In retrospect I would have tested a much larger dry sample.) I smelled them wet because I got a clearer sign of their relative effects on me.

There is no ideal way to test materials. I test everything wet and dry unless it’s solvent-based.

It is usually a better idea to sniff something dry/cured since there can be a dramatic difference between how tolerable something is wet and when cured.

Testing when it’s cured is the most important test in most cases.

Top Non-Toxic Wood Glue Brands

1. Elmer’s Wood Glue – Not good for me when wet, but many chemically sensitive prefer this brand.

This is a PVA based glue, with a mild acetic odor until it’s cured.

Carried at hardware stores and on Amazon.

2. ECOS Wood Glue – ECOS makes extremely tolerable products, and while I didn’t get a chance to test this one, I would expect it to be good.

The ingredients are acrylic dispersion, thickeners made of cellulose and polymers (plastics), and unlisted dispersing aids.

3. Roo Glue – White glue and wood glue – Not great when wet, but not terrible. It seemed totally benign when dry. The severely sensitive might want to try this brand even though it’s special order.

This is a PVA glue.

Available in the US and it ships to Canada from their website.

4. Titebond – This is a brand that is often recommended for chemically sensitive folks. I had already picked Roo Glue before I got a chance to test it. My sofa was later made with this and it worked out well for me, though I received it after it had cured.

Out of the Titebonds, Titebond III technically has the lowest VOC level of the 3 main types of this brand’s wood glues. It comes in at 5.6 g/l VOC. But that doesn’t mean it will be best for everyone when cured.

These are PVA glues.

I would start here with the testing, since it’s inexpensive and easy to order from Amazon and find in stores.

5. Hide Glue is the most natural glue option for wood. It’s made from animal protein of the collagen from skins, bones, tendons and other tissue.

It is a strong glue with no VOCs, but it is not waterproof.

You can mix it yourself from beads or flakes for the most natural option, or you can buy it ready-made, but those do contain some additives. The Titebond brand lists ammonium thiocyanate.

6. Gorilla Glue – I found this to be difficult when wet, but not terrible. It seemed fine to me when dry.

This is a polyurethane glue that will offgas isocyanates until it’s cured. Isocyanates are potential human carcinogens and known to cause cancer in animals. Like many products, if it comes to you cured it may be perfectly safe.

Easy to find at hardware stores and on Amazon.

Non-Toxic, Low-VOC Caulks and Sealants

Which Caulks are Mildewcide Free?

Note that caulks labeled for bathrooms or as mildew resistant contain a mildewcide. Currently GE I is mildewcide free, GE II contains a mildewcide. Any caulk labeled aquarium safe is free of mildewcides, including DAp Aquarium caulk and others listed below. AFM Safecoat and Chemlink Durasil are also mildewcide free.

Top Non-Toxic Caulking/Sealant Brands

All caulks have a chemical odor when wet. I tested them at 24 hours, 48 hours, one week and two weeks.

I would recommend getting a non-sensitive person to put them in jars and only testing them after they have dried.

1. AFM Safecoat Caulk 

AFM Caulk is one of the top choices along with GE. I used this in my bathroom, you can use this around the shower and sink. It can be used around doors and windows.

My testing: Not the best when wet, not the best at 24 hours, but the best at one week.

Where to use AFM Caulk:

It can be used inside and outside. Around windows, cracks, tub and shower enclosures, backsplash, siding, walls and wood (like sealing molding) and general maintenance. It does not hold up as long in the bathroom as silicone with a mildewcide.

It is polyether resin that does not contain solvents (it’s not acrylic, latex, silicone or polyurethane). It is non-shrinking. 0-VOC once cured.

You have to special order this one from Green Design Center.

Mildewcide: none. Elongation: 35%. Color: white. Paintable: yes

Alternative: ChemLink NovaLink 35 is similar but comes in different colors, if that is needed.

2. GE Silicone 2 Clear Caulk 

This may be a better choice for some applications. This is the next one to test alongside AFM.

My testing: It was not as good at one week as AFM or Ecobond (Ecobond is now out of business). I find that after a couple of weeks it is essentially odor-free (to me).

Testing again in 2020, most sensitive people would not pick up any offgassing at one week (it’s there, but extremely subtle). At two weeks I find this odorless, but when I was at my most extreme I could still pick up something very subtle at two weeks. Thicker amounts take longer.

Offgassing: Most of the caulks (at least all the silicone and polyethers) would be suitable for the chemically sensitive at 2 weeks. Only most extremely sensitive may still pick up some offgassing even at that time.

Where to use GE 100% silicone: Windows, doors, siding, trim, molding, baseboards, vents, around wires/pipes, and more.

We used this on the underbelly of my house and on my windows. It is low-VOC.

Mildewcide: GE 1 is mildewcide-free. Elongation: 50%. Color: Clear. Paintable: No.

Alternative: If GE Silicone doesn’t work for you, you may want to try DAP, their aquarium calk is mildewcide free, Dow Corning 100% Silicone, or Durasil below.

3. ChemLink DuraSil

This is a neutral cure silicone that chemically sensitive folks tend to do well with.

This company makes great products that you can find at the Green Design Center.

I have not tested this one myself but I would expect it to be up there with the most tolerable options.

Mildewcide: No. Elongation: 50%. Color: Clear and White.

4. Silicone Aquarium Caulks

I read that aquarium caulk is the least toxic because fish are exposed to it and they can’t handle chemicals (especially biocides). But it turns out fish are a little different than people.

I tested two brands, Aquarium Silicone Caulker and one called Marina from a local pet food store, they were much more expensive than brands for home use (for no apparent reason), and they were both the worst of the worst to me.

So bad I would not recommend testing or using these brands. Though one super sensitive person preferred the Aquarium caulk Aqueon to GE I or II and Ecobond.

Marine caulking is not the same as aquarium caulk (it’s for marine applications, not fish tanks). I tested GE Marine Silicone Sealer. It had that same pungent odor though, like vinegar x a million.

It did, however, offgas quite rapidly. After one week it was at the same point as GE 100% Silicone, and at two weeks it was just as good (virtually odorless), but there is a different chemical that is offgassing.

Since folks with sensitives vary so much in their individual triggers, it’s worth checking out multiple brands.

5. Chemlink Novalink35

Chemlink makes an elastomeric caulk for sealing concrete and masonry called NovaLink35.

I haven’t tested this one, but it’s a great brand and many chemically sensitive folks do well with it.

You can find it at Green Design Center and Amazon.

Caulking Materials – What Caulks are Made of?

Polyurethane caulks – Usually contain isocyanate. Might not be as safe. This type smells strongly like typical fresh paint, and takes a while to offgas. They can be made without solvents. If they do contain solvents it would typically be mineral oil, toluene or xylene. It’s not used as widely as the others. I tried Loctite PL S40.

Acrylic Latex caulk – They have the mildewcide octhilinone or carbendazim in them as well as a benzoate plasticizer (which has largely replaced phthalates) and naphtha (source). They are often water based but still could contain mineral spirits, mineral oil, and propylene glycol (source). Painters caulk are usually acrylic latex and are sandable and paintable.

I tried DAP Dynoflex 230 latex caulk and DAP Alex Plus, an acrylic latex with some silicone. At one week they both had more offgassing than the silicones, though they had different chemicals offgassing. At two weeks Alex was still clearly offgassing (at three weeks I could still pick up the odor, at 5 weeks it was very mild), and Dynoflex was close to done at two weeks.

Silicone – While silicone itself is not toxic, the chemicals added to keep caulking in liquid form are. For silicone caulk, look for 100% silicone. There are different types listed below that offgas different chemicals. Once they are cured, you may find them to be essentially the same.

The chemical additives in “100% silicone” are not usually listed. Silicone doesn’t usually have a solvent but some have traces of benzene and toluene (source). Plasticizers are typically added. The biocide, if it has one, is likely to be phenoxarsine oxide, according to Pharos.

Types of silicone caulk and what chemicals they offgas:

1. Typical silicone caulking is acetoxy silicone and it offgasses acetic acid. On the SDS you will see “odor: acetic acid”.

2. The less common type, labeled “neutral cure silicone”, does not give off acetic acid, but instead offgasses alcohols, methyl ethyl ketoxime or acetone. (source)

3. Aquarium caulk is usually acetoxy silicone without mildewcide. It might be labeled aquarium caulk or you can just get GE 1 if you are avoiding mildewcide, which will be less expensive.

4. Paintable silicone caulk is a mix of silicone and acrylic latex.

Top Choices: GE 1 100% silicone doesn’t contain a mildewcide. GE 2* Advanced 100% silicone is “neutral cure”.

Polyether – specialty silicone replacement caulks are often polyether. My top pick is AFM Caulk.

Acoustical Caulk – this non-hardening sealant prevents sound leakage. They are mostly water-based acrylic. They are about 20% ethenylbenzene. In smaller amounts, they typically contain plasticizers, naphtha (as the solvent), ethylene glycol, and formaldehyde.

Solvents common in caulking (of all types) include acetone, methyl ethyl acetone, toluene, xylene, and naphtha (Source).

Non-Toxic Adhesives

Construction adhesives are used for subfloors, to install doors (glue down threshold), to build stairs, exterior brickwork, under countertops, and more.

Non-Toxic, Low VOC Construction Adhesives

1. AFM Almighty Adhesive

Almighty is the best adhesive I have ever tested. I had absolutely no problem and no reaction to smelling it while it was wet.

This was a pleasant surprise after all the other glues and silicones.

It is a highly tolerable very low odor, multipurpose adhesive (make sure it’s right for your application).

It is a polyether adhesive with 1-3% silanes.

I used Almighty to install my shower, on subfloors, and my countertops. I would use this anywhere and everywhere this can be used since it’s the healthiest adhesive I have found.

Insider tip, this is the same formula as Build Secure by Chemlink.

2. Chemlink Wallsecure

Wall Secure is made for bonding drywall, gypsum, landscape blocks, capstones, stone, foam, fiberglass, FRP panels, and ceiling systems.

I haven’t tested this one but this brand makes great low toxin adhesives.

3. Ecotite ET 5500 and 9500

This is another good brand that is well-liked by the chemically sensitive.

Their ET 5500 is an adhesive that works on multiple surfaces: PVC, concrete, glass, aluminum, painted surfaces, wood plywood, marble, metal, and more.

At about one week most would find this odorless. At two weeks it seemed totally offgassed. I was very happy with this one.

The 9500 is used for windows, doors, trim and some kitchen applications. At three weeks it’s still not odorless/offgassed. I’m not as happy with this one as it did not stop offgassing by three weeks.

The bottles say odorless, but the point in time that it is odorless depends on the conditions (curing rate) and how sensitive your sense of smell is.

Right off the bat, the 5500 is significantly milder, and lower odor than conventional adhesives.

The links to the 5500 and 9500 are to a Canadian store, but you can find this product in the US as well.

Corinne Segura is a Building Biologist Practitioner with 6 years of experience helping folks 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!