My Chemical-Free House

A Guide to Creating a Healthy Home

Healthy Building

Low-VOC Sealers for Log Cabin Homes (Non-Toxic & Natural Options)

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Low-VOC and non-toxic sealers (and stains) for log cabins fall into two categories: natural oil penetrating sealers and low-VOC synthetic sealants.

For the exterior, we want something as durable as possible. There are two main options here. The first is the all-natural tung oil mix made for exteriors and the second is a low-VOC synthetic from Vermont Natural Coatings.

While there are other options in both categories – other brands that make penetrating oil sealers and other brands that make water-based or oil-water hybrid sealers, these are my top brands and the best in each class.

For the interior, you can use something that is not quite as durable. This allows for more options that are lower in odor than the exterior products. We still have the same two categories, natural penetrating oils and synthetic sealers.

I also cover stains, some are a stain and sealer in one and with other options, you need to add the stain first.

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

1. Natural Penetrating Oil

Penetrating oils come in all-natural formulas. These oils naturally polymerize and form durable coatings. Tung oil is the most durable of the oils and is suitable for exterior applications. It is almost always mixed with a pine or citrus solvent when used on wood, which can be too strong for some people, at least at first.

If the log cabin walls are raw wood with no finish on them you can use a penetrating sealer. If you are unsure if the wood is already sealed, you can do a water test – put some water on the surface and see if it absorbs. If it does, then penetrating oils should work well. If it doesn’t absorb, there is some kind of sealer or finish on the logs that would need to be removed prior to using any penetrating finish.

Penetrating Oil Exterior Log finish

Outdoor Defense Oil (ODO), a natural tung oil mix, is a great sealant for the exterior. If the logs are super dry, you might even be able to use Pure Tung Oil for the first coat or two and then follow up with ODO to top off the wood. For the log ends, the Pure Tung Oil would be best since the “end grain” of the log is super absorbent and will take the tung oil without diluting.

Tung oil is a natural choice but it’s still very durable and holds up well. The Outdoor Defense Oil is made from pure tung oil, pine oil, and zinc. The pine and zinc give it natural anti-fungal properties and some UV protection.

One of the benefits of the tung oil on log homes is it is partially vapor permeable which is usually a good thing for moisture management. Also, tung oil is flexible, so as the wood expands and contracts with the weather the tung oil will also flex with the wood rather than being rigid and cracking.

I would expect annual maintenance for the best protection.

Stains for Natural Oil Finishes

Tung oil naturally darkens the wood somewhat. If you want an even darker color there are some more options.

Dark Tung Oil can be used for the first coat or two, then you can apply the ODO overtop. Or, mix the Dark Half into the ODO to create a tinted version.

You can also use a water-based stain on the wood before applying the oil like AFM Duratone, ECOS Stains, or Pure Color.

You can also paint the exterior of the cabin with Milk Paint! The Milk Paint is very colorfast since they use pigments rather than dyes. You do need to seal over the Milk Paint with the tung oil to give it weather/water resistance.

Their pigments can also be used to tint the tung oil, but if you add too much though you’re essentially creating an oil-based paint.

Interior Penetrating Oil Log Finish

For the interior, any of the penetrating drying oils will work well and you don’t need to fully saturate the logs, usually 1-2 coats will do.

The Hemp Oil is nice for the interior because it doesn’t require any solvent so it is low odor compared to tung oil and is lower in odor than linseed as well.

If you do prefer linseed I like a pure linseed oil with no additives like Tried and True.

If you want to paint your interior walls be sure to use a breathable paint, they are listed here.

2. Low-VOC Synthetic Coating

If you don’t want to go with the natural oils, there are low-VOC synthetic formulas. Some are water-based and some are an oil/water hybrid. I really like the company Vermont Natural Coatings as their products have been both low odor and competitive with more toxic sealers in terms of durability.

Low-VOC Exterior Log Finish

On exterior spruce/fir/pine logs that do not already have a stain/sealant on them, you can use SunCare900 Primer (1 coat), followed by Bohme Ligno Exterior Stain, a super low-VOC water/oil hybrid exterior grade stain and topcoat in one (2 coats).

Choose one of the colors to mask/prevent the natural graying of the wood underneath.

Low-VOC Interior Log Finish

For the interior, you have more choices. Really any acrylic or polyurethane low or zero-VOC coating will do. You can choose from a number of brands. I still really like Vermont Natural Coatings but some people do react to this (possibly to the whey). So you may want to test multiple options if you are sensitive to chemicals.

These are my top picks:

Vermont Natural Coatings PolyWhey was my top choice for a durable coating that holds up well on wood and is very low odor. It has the best combo of durable and low odor that I have found.

ECOS varnishes, which are acrylic-based, are super low toxin. In my experience, they are not as durable as the polyurethane alternatives but that’s not usually a problem on walls.

AFM Polyureseal is liked by many. It is a very tolerable formula by a high-quality brand. This brand is a durable low toxin polyurethane finish for wood floors.

Very low odor polyurethane and acrylic options also include BioShield Aqua Resin, Earthpaint Aqualine, Earthpaint Easy Safe 1K, and Vermeister. I compare them all in a dedicated post if you want to consider more options.

Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

Non-Toxic Grout Sealer Options

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Whether you need a grout sealer depends very much on the situation. A grout sealer could actually do more harm than good.

For that reason, I will list out the non-toxic sealer options by application and then by type of sealer.

The densifiers are the most tolerable least toxic option, they are a very benign product. Topcoats of acrylic or polyurethane do have some odor and offgassing at first, but the offgassing comes to completion in a short time.

There is also the possibility of going with a natural product, some natural penetrating oils can be used on concrete grout.

I recommend all of the products here, some products have affiliate programs and some do not. Upon purchase, I earn a small commission through affiliate links at no extra cost to you.

1. To Seal Grout in Tiled Showers

In wet areas, you generally want to use a breathable sealer. Both Mike Holmes and Cheryl Ciecko recommend this approach to keep the grout breathable and allow water to dry out to the inside.

Your waterproofing is done behind the tile.

You can keep the grout unsealed. If you must seal it, use a liquid glass sealer which still allows some breathability.

Densifiers

AFM Grout Sealer is one option, It’s zero-VOC and is one of AFM’s most tolerated products. It has almost no odor at all even when wet. This is a potassium silicate product also known as a liquid glass densifier. It does not change the look of the grout at all.

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.

A densifier makes it easier to clean and less likely for dirt, grime, and mold to get embedded. It’s not intended to be waterproof.

2. To Seal Grout on Tiled Floors

If your tiled floor is on a concrete slab (on grade or below grade) then Cheryl Ciecko also recommends keeping that breathable so that the concrete can dry to the inside.

Densifiers

Use AFM Grout Sealer or Tilelab Grout Sealer – these are no VOC products that do not change the look of concrete-based grout at all.

If your tiled floor is on an upper level of a house or apartment building and the floor below is the same temperature (more or less) as your space then you can use a tile sealer that blocks moisture.

You can still use a densifier but you can also use:

ECOS Stone Sealer

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 how breathable it is exactly. It is zero VOC.

Integral Sealer

AFM Safeseal is an acrylic coating that can be mixed into a dry mix concrete grout (with the water) instead of adding a topical grout sealer.

Polyurethane Sealer

For a strong topcoat sealer, you can also use a water-based polyurethane like Earthpaint Nanotech.

All-Natural Sealer

You can also use a natural oil on concrete-based grout. I have been experimenting with 100% natural tung oil and have so far have liked the effect. It certainly darkens the concrete by quite a bit.

3. To Seal Tile on a Backsplash

You don’t necessarily need to seal grout on a backsplash since it doesn’t usually get that damaged. But if you do want to seal it that can provide some stain proofing.

If your tiled wall is on an exterior wall and you use AC inside the wall should be kept breathable. The most that you should use is a densifier.

Densifier

Use AFM Grout Sealer or Tilelab Grout Sealer.

Acrylic and Polyurethane Sealers

If your tiled wall is not on an exterior wall, or you don’t use AC inside you could use a densifier or something that blocks more moisture like ECOS Stone Sealer, Safeseal mixed into the dry powder at the time of application, or Earthpaint Nanotech.

All Natural Sealer

You can also use a natural oil on concrete-based grout. 100% natural tung oil leaves the grout partially breathable (similar to densifiers) but darkens the look quite a bit. It takes some time to fully cure but provides good protection against stains, especially oil stains.

4. To Seal Tiles on a Countertop

In this scenario, I would want the most protection from moisture and stains as possible.

Synthetic Options

If you can, mix an integral sealer like AFM Safeseal into the dry mix grout and follow that with a topical coating like Earthpaint Nanotech. If that is not possible use AFM Grout Sealer first, followed by Nanotech.

The Natural Option

You can also go all natural with pure tung oil. This darkens the look of the concrete-based grout and will certainly give you particularly good protection from oil-based stains. Tung oil is really quite durable for a natural choice. You cannot use a synthetic sealer over this, and it likely won’t work over a synthetic sealer since it needs to soak in to work.

Related Posts:

Choosing non-toxic grout and mortar

Non-toxic waterproofing in bathrooms

Non-toxic countertops

Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

Study of Lead in Tile (12.5% Contain Lead)

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I conducted a study of lead in tile in 2021. I chose 64 tiles from major retailers in the US and had them professionally tested with a handheld XRF down to 0.00 mg/cm2.

The 64 porcelain and ceramic tiles came from 14 brands and 5 major retailers in the US. Many of the tiles will be available in Canada as well.

The tiles were purchased from Flooring Inc, Stone Tile Depot, Build Direct, The Tile Shop, and Home Depot.

While there are no official limits on the limits of lead in tile in the US, I used a couple of benchmarks.

The first is the level of lead in paint that qualifies it as lead-containing paint. That is 1.0 mg/cm2; 3% of the tiles came in well above this level.

The next benchmark I used is 0.1 mg/cm2 (I actually used 0.09 since one tile came in that close to 0.1). This level of lead in mg/cm2 could still indicate a level of 500 (or more) parts per million (ppm) of lead.

How did I choose this level that I consider to be above trace? Soil contains 50-400 ppm lead naturally (so that can be considered to be trace, source here)

12.5 % of the tiles contained 0.09 mg/cm2 or more lead in the glaze.

Why Should We Care about Lead in Tiles?

While lead in tiles is not considered a risk when the tiles are in place (in almost all circumstances), the dust produced when cutting or demolishing the tiles could easily produce a lead risk.

Just as we are concerned about chipping and flaking paint, in my opinion, we should be just as careful with a product that is installed and demolished in a way that produces a lot of dust.

Contractors are rarely careful with this dust.

It is reasonable to choose to take lead remediation level precautions with all tile dust, however, that is impractical in the real world that contractors and homeowners live in. And also, why are we accepting the tiles that will have lead in the glaze when it’s not necessary?

How Does this Compare to Previous Results?

The amount of lead used in tile glaze has certainly been going down over time.

Heavy metal content in US ceramic floor and tile dropped by 93.6% between 2002 and 2012 (Healthy Building Network).

In 2010, the Ecology Center tested 39 ceramic tiles for sale at Home Depot and Lowes. They found that 74 percent of the tiles contained detectable lead, with levels as high as 1,900 parts per million. (However, “detectable” here could mean anything above 0 ppm). (The Ecology Center)

You can find the whole study here.

Is Plywood Toxic? (Non-Toxic Alternatives)

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This post provides an overview of the formaldehyde and formaldehyde-free glues used in plywood.

I look at the offgassing levels and rates of formaldehyde in various types of plywood so that you can choose the lowest VOC option and minimize offgassing in the home.

There are non-toxic plywoods as well as non-toxic alternatives to plywood listed here.

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

What is Plywood?

Plywood is an engineered wood product made up of thin layers of wood called “plies” glued together. Each layer is laid with the grain running in the opposite direction to the previous layer.

Where is Plywood Used in a House?

  • Often used as sheathing on the exterior of the wood framing of a house
  • Often used as roof decking
  • Often used as subflooring
  • Often used as the boxes of cabinets, and as structure inside sofas and other furniture
  • Sometimes used as an underlayment or the structure of countertops
  • Sometimes (rarely) used as interior walls
A stack of plywood of different thicknesses

Myths About Plywood

That it offgasses forever

Plywood made with phenol-formaldehyde rapidly reaches no-detectible levels. Plywood made with urea-formaldehyde offgasses for longer, but it is up to 60% of the way there in 30 days. Plywood made from urea-formaldehyde is generally avoidable.

That it is high in formaldehyde

Plywood made with phenol-formaldehyde is not high in formaldehyde since it rapidly reaches non-detectable levels. Interior furniture grade plywood (which can be made with urea-formaldehyde) needs to come in at 0.05 parts per million formaldehyde.

That it is toxic

Plywood made from phenol-formaldehyde is not toxic. Plywood made from urea-formaldehyde is also technically not considered toxic at 0.05 parts per million formaldehyde. But those with compromised detox systems can find this level to be toxic to them. Whether it’s toxic or not very much depends on how much plywood is in the room, the size of the room, airflow in the room, and the person that is being exposed to it.

Which Chemicals Offgas from Plywood

Overview of the Adhesives Used in Plywood

Phenol-Formaldehyde (PH) (aka phenolic glue) – Most of the plywood I see now is made with phenol-formaldehyde. The offgassing is much lower and in many products comes to a complete cure in a short amount of time.

Urea-Formaldehyde (UF) – This is the type of formaldehyde that offgasses at higher levels and for longer. When you think of furniture or flooring that is offgassing for many years it was likely made of urea-formaldehyde. The offgassing rate of UF plywood varies by the exact formula (also some companies use heat to accelerate the offgassing) – it can vary from 15-60% offgassed in 30 days (source). Remember offgassing is on an exponential curve.

Melamine-Urea Formaldehyde (MUF) – This is a urea-formaldehyde glue modified with melamine and PVA. It gives the plywood more water resistance and is usually only used for exterior door skin, marine plywood, and concrete formwork plywood. Adding melamine reduces the formaldehyde offgassing levels (source).

No added Urea Formaldehyde (NAUF), this almost always means PF is used.

No Added Formaldehyde (NAF), this means that no formaldehyde is added to the product – the glue used does not contain formaldehyde. They cannot be labeled “formaldehyde-free” because wood naturally contains formaldehyde. No added formaldehyde plywood is made with “soy-based” glue.

Soy-Based Glue – Soy-based glue is not just one formulation. They use soy protein mixed with polyamidoamine-epichlorohydrin (PAE), isocyanates, and aldehydes. (From the co-inventor of the adhesive for Purebond Plywood). This one is called soy-PAE. A similar type of soy-based glue that may be used to replace formaldehyde in MDF and particleboard is an amine-epichlorohydrin adduct/soy protein/isocyanate (source).

a close up of the veneer on a plywood sheet

Types of Plywood and Their Glues

Structural Plywood

Structural plywood is softwood plywood (SWPW) and it is used for roof sheathing, subfloor, and roof decking.

This type of plywood is made with phenol-formaldehyde as the binder/glue (3.5% formaldehyde to be exact). Phenol formaldehyde is the least toxic type as it offgases less than urea-formaldehyde and it off-gases faster.

Formaldehyde Levels

Formaldehyde levels in freshly produced plywood start out below 0.1 parts per million (ppm). But “emissions rapidly approached zero as the panels aged. In fact, the levels were so low and so close to the ‘background’ levels in the test chamber that it was not possible to measure them accurately” according to the American Plywood Association.

While the APA would not say exactly when the PF levels approached zero (or close to it), I do think that a few weeks is more than adequate for most people.

For most people, exterior plywood in a build will be sufficiently offgassed by the time the building is complete.

Testing Your Reactions

If you are extremely sensitive you should test out plywood when new, after a few weeks, and after 2-3 months of airing. You should also compare that to OSB, to see which is better for your health (I certainly prefer plywood to OSB). The extremely sensitive can often pick up the residual odor of the plywood glue even after the point where it’s undetectable by any instrument. It also becomes difficult to tell where the formaldehyde from the glues ends and the natural level of formaldehyde in the wood starts if you are sensitized to it.

Marine-Grade Plywood Glues

In the US, the marine-grade plywood I’ve seen is made with phenol-formaldehyde, but it can also be made with melamine-urea formaldehyde.

This is not a specific type of plywood in Canada.

Pressure-Treated Plywood Additives

Pressure-treated plywood is commonly treated with alkaline copper quaternary (i.e. copper and quaternary ammonia) (ACQ).

Copper Azole (CBA) is another type, which contains copper, tebuconazole, and possibly boric acid.

Though some wood is still treated with chromated copper arsenate (CCA), this is rare nowadays and it’s definitely not often used in residential buildings.

Product Certification Levels for Formaldehyde

A chalkboard looking graphic that says formaldehyde CH20

CARB II – Formaldehyde Levels CARB II is a standard set by California for products sold there, but when it comes to common building materials like plywood, all major manufactures tend to comply with California’s standards.

Products that fall under this standard include hardwood plywood, medium-density fiberboard, and particleboard – these are pressed wood products sold for interior use.

It does not regulate exterior sheathing products like structural plywood (softwood plywood) and OSB.

(The allowable limits for TSCA Title VI are the same as CARB).

CARB II Formaldehyde Limits Are: Hardwood Plywood 0.05 ppm (parts per million)

The CARB II limit is the same as the GreenGuard limit.

Furniture Grade Plywood

Interior grades of plywood can be made with urea-formaldehyde as the adhesive. Urea-formaldehyde (UF) offgasses more and for longer. Now phenol-formaldehyde (PF) is more standard, but I still see some SDS sheets showing urea-formaldehyde.

Interior plywood is often called furniture grade or hardwood plywood. You will want to make sure your furniture is made with PF or NAF glues, not UF.

Formaldehyde-Free Plywood

1. Purebond Plywood by Columbia Forest Products is a no added formaldehyde plywood (NAF). It is made with a soy-based glue.

When folks talk about formaldehyde-free plywood, this is the one they are usually referring to.

Their adhesive is partially proprietary, but they claim it is “soy-based”. The full Declare label is here but this doesn’t tell us much about what it will offgas in the end, only what went into it.

I have seen extremely chemically sensitive folks react to this brand of plywood so I would make sure to test it out yourself before using it. I do think the odor is extremely mild and unoffensive.

Purebond plywood is intended for interior uses like furniture and cabinets (here are some cabinet makers who use Purebond). It is not structural and it is not made to hold up to high humidity or moisture. Some folks are using this as sheathing and roof decking which is a very bad idea.

You can buy it at Home Depot.

2. SoyStrong Hardwood Plywood is another brand of formaldehyde-free plywood made with a soy-based glue.

You can buy it at Lowes.

How to Offgas Plywood & Seal in the Formaldehyde

1. Give it Time to Air Out

Stack your plywood in a garage or covered area in a way that allows each piece to have some airflow.

Time, heat, and air are the main ways to allow any material to offgas.

2. Seal it

Whether you should seal your plywood partially depends on where it will be going.

If it’s on the interior of your home, then no problem, seal away.

Exterior applications, like wall sheathing and roof decking, are trickier. Wood naturally has the ability to absorb and release moisture. Stopping that natural process could cause problems.

To seal plywood there are a few ways you could go, but the two main options are AFM Safeseal which is a clear acrylic-based coating that helps to block and seal in formaldehyde, or shellac which is an alcohol-based natural wax coating. Shellac does a slightly better job at sealing.

someone brushing on a milky-clear sealant on plywood to seal in the formaldehyde

Alternatives to Plywood, Which Are Less Toxic?

1. Formaldehyde-free plywood is a good non-toxic alternative to regular plywood in most interior applications and in furniture.

2. OSB is often used in place of plywood in structural applications. I don’t consider OSB to be less toxic, as it has higher offgassing and takes longer to come to completion but it’s possible that it works better for some people since the glues are different.

3. XPS foam can replace plywood as wall sheathing (but it’s probably not a good idea in most situations).

4. MgO board can sometimes be used as the subfloor and other sheathings (and I even used it for cabinet boxes and countertop underlayment).

5. Solid wood can replace plywood in some applications, like purlins or skip sheathing on a roof, in subflooring and sheathing, and for cabinet boxes and most furniture.

6. Georgia-Pacific DensGlass can replace plywood sheathing in some areas.

7. Cement board is sometimes used as sheathing, especially in tropical areas. Another concrete-based board, USG Structural Panel, is a thick and very strong board, it is sometimes used on foundation walls when the framing is metal.

8. Drywall, drywall is generally zero-VOC so it is technically less toxic than plywood but there are not many instances where they are interchangeable. If plywood is an option for your walls then you may prefer to use drywall.

Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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Sources

https://pharosproject.net/common-products/2078999#contents-panel

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6723320/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6723320/

Hempcrete for Mold-Safe, Healthy Homes

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Hemp can be used in building homes in many ways but building with hemp is very different than building with conventional construction methods.

Hempcrete can be tamped into board-formed walls, used as premade bricks, sprayed into cavities, or formed into precast panels.

It acts as insulation and as an interior and/or exterior surface, though it is not load-bearing – you still need a wood frame.

This article will review all the ways that hemp can be used to build a healthy home and is an investigation into whether it’s mold-prone.

Beautiful hempcrete salon, Hemp House Hair Salon, in British Columbia, Canada.

Before we look at the building methods closer, let’s look at what goes into hempcrete. 

What is Hempcrete Made of

1. Hemp hurd

The first ingredient of hempcrete is the aggregate, called the ‘hurd’. Hurd is the woody core of the hemp plant that remains after the plant has been stripped and the fiber sold for rope or textiles. 

The hurd is like the inside of a twig, after the bark has been stripped off, just less dense and with a hollow core. The woody core is dried and then chopped up; it looks a lot like wood mulch. 

Hemp is an organic material – meaning, it is carbon-based, just like wood (and can be mold food, just like wood). In fact, it contains more cellulose than wood does (hemp has 65-70% cellulose and wood has 40%). 

Quality is not consistent from supplier to supplier, so make sure you are buying good quality hurd before committing to a large purchase.

A good place to buy hemp hurd in the US is through Hempitecture in Idaho. 

2. Lime Binder

The lime binder contains calcium carbonate (lime) and compounds which allow it to harden – either soluble silica, alumina oxide or ferric oxide. When a lime binder can harden with the addition of water, this is called hydraulic lime. 

Hydraulic lime is readily available in the UK and France but is difficult to find in North America and often has to be imported. 

There are some binders that are produced in the US. One place to buy lime binder in the US is also through Hempitecture.

Do your research on binders before choosing one. There are binders out there that have caused mold problems where there shouldn’t have been any due to added ingredients in the binder. 

3. Water

When water is added to the hydraulic lime binder, it causes a chemical reaction (hot!) which makes it possible for it to harden once dried. 

4. Air

It feels funny to list air as an ingredient, but it’s one of the most important parts of hempcrete! 

When dried, there are many air pockets in hempcrete – both between the pieces of hemp and inside each piece of hemp. 

Air is what makes hemp a good insulator (air is the most important part of any insulation) and humidity regulator.

Water, lime, and hemp hurd. Photo courtesy of Homeland Hempcrete in North Dakota.

Put them together! 

When hemp hurd is mixed with the lime binder and water, it dries into a hard solid mass. 

Before it dries, you sprinkle it into framed molds that surround the building’s wood framing. It is then tamped down to compress it a bit, and left to dry. 

The drying time is important (between 4-8 weeks). If you don’t allow it to dry enough before removing the form work and plastering, there could be big problems (mold, staining, crumbling).

Mixing hemp and lime together: https://www.instagram.com/p/Bsn2G21hMxn/?utm_source=ig_embed&utm_campaign=loading

Building with Hempcrete: How it is Used

Hempcrete can take the place of insulation, drywall, and siding in a new wall. 

It is not a 1 to 1 replacement, though; Hempcrete can’t just be substituted for fiberglass insulation (or cellulose, etc.). Using hempcrete requires a different plan and approach compared to conventional building. 

Besides being a totally different type of material and insulation, hempcrete has a different insulation value than fiberglass or cellulose, and so it will require thicker walls.

As Insulation

This is a cross-section of a hempcrete wall – the hempcrete encapsulates the wood framing.

Hempcrete’s most important function is as insulation. The amount of insulation you require will determine how thick your wall will have to be. 

The insulation requirement (R-value requirement) depends on your local codes. The colder the climate, the thicker the wall will have to be.

Hempcrete’s R-Value is usually listed as ranging from 2-3 per inch. But some companies have claimed it can be as high as 4.8 per inch.

Photo courtesy of Hempitecture. 

As Siding (Exterior Skin)

This is the exterior wall of a hempcrete tiny house before plastering.

The outside of hempcrete can be plastered, similar to the interior. This can create more moisture risks if not done precisely or maintained properly. 

This might not be advisable in certain climates. Please find a professional to discuss what the best exterior options are for your climate.

Photo courtesy of Hempitecture.

As Interior Wall Face (Interior Skin)

This is an interior hempcrete lime-plastered wall.

Drywall is not needed when building with hempcrete. The typical interior finish is a lime render (plaster) that is applied directly to the dried hempcrete. This allows the wall to stay vapor permeable.

Anything that you add to the wall must be vapor permeable, inside and out. 

Photo courtesy of Hempitecture.

Note! 

Hempcrete is not concrete. Unlike what the name suggests, hempcrete is not made from concrete and it does not contain concrete. Even though hempcrete dries and hardens, hempcrete is not structural or load-bearing – it can’t hold up the weight of the roof. It must always be used in combination with a wood frame (or other framing material). 

Reasons to consider hempcrete

  • Hemp has a unique cellular structure that allows it to absorb and adsorb water better than other plant-based fibers. This gives it an edge in moisture management over other plant-based materials.
  • The use of a lime binder makes glues and other high VOC materials unnecessary for the wall components. 
  • It can help with maintaining healthy indoor air quality.
  • It is a fast-growing crop, so multiple harvests can be grown in one year (it is a weed, after all).
  • Hempcrete generally has very good (but not excellent) insulation value. 
  • It is very fire-resistant.
  • We know all of the ingredients in it.
  • It is vapor permeable, i.e. “breathable”- if moisture gets in, it can get out.
  • It is carbon dioxide sequestering.

Building with Hempcrete, Various Forms

1. Poured, or Formed Hempcrete

With formed (or poured) hempcrete walls, the finished walls are hardened hempcrete usually plastered with a lime render.

How it works

Forms holding hempcrete to make hempcrete walls. Photo courtesy of UK Hempcrete. Copyright UK Hempcrete

The hemp, lime binder, and water are mixed together on-site. 

Temporary wood framing aka form work (similar to when concrete is poured) is placed surrounding the structural wood frame. 

The hempcrete mix is then “poured” into place inside the wood forms and then tamped down to create a thick wall. The wood forms are left there for several weeks until the hempcrete is dried. 

Hempcrete creates a solid wall. There is no need for an interior wallboard, like drywall, just a nice lime plaster. 

The thickness of the wall will depend on how much insulation is required by code in your location, or how much insulation you want. 

Depending on location, the exterior can also just be plastered, but this should be discussed with a building science-literate professional who is familiar with your climate zone. 

Photo of hemp in exterior forms: https://www.instagram.com/p/Bsa_xkVjMMi/?utm_source=ig_embed&utm_campaign=loading

Benefits of a solid hempcrete wall

  • A good amount of thermal mass (heavy, thick walls) makes temperatures and humidity more even.
  • Using a single material means no seams and gaps like in traditional, wood-framed houses.
  • A homogeneous material makes moisture and temp management more consistent.
  • A heavyweight, formable material means less need for taping or specific air-sealing layers.
  • Building with a homogeneous material means there’s no abrupt shift in temperatures (i.e. at the sheathing), minimizing the chance of condensation.
  • Consistent vapor openness due to single material (hempcrete) makes it easier for the wall to “breathe” and dry.
  • Hempcrete works with moisture, humidity, and temperature like an experienced dance partner; conventional construction relies on keeping them away by using increasingly complex layers of barriers, insulation, boards, and tapes.

Drawbacks of a solid hempcrete wall

  • It could give you false reassurance – it still requires extensive planning and precision to avoid mold.
  • If not planned, mixed, and detailed correctly, it can become moldy .
  • The lime dust can be hazardous to breathe in and for the skin.
  • Using a framing material (i.e. wood) is still necessary. 
  • There are many unknowns about how it will perform in US climates.
  • Contractors and laborers may be inexperienced with hempcrete.
  • You will be an “early adopter”.

2. Pre-Cast Hempcrete Blocks

Precast hempcrete block. Photo courtesy of UK Hempcrete. Copyright UK Hempcrete

In order to make hempcrete thick to have enough insulation value, you can use precast hempcrete blocks on one side of the exterior wall.

The opposite side will be framed with temporary forms and be poured with hempcrete to fill the cavities and encapsulate the wood framing.

Hempcrete blocks are not load-bearing, so they will still need to be used with a wood frame. 

There is one company in Canada that is making a load-bearing block. They have not responded to my request for more information about the block. Their block is not approved for load-bearing use in the US. 

Components

Most hempcrete blocks have the same ingredients as poured walls – hemp hurd, lime binder, and water.

However, there are some that have different binders, or use a finer ground hemp, and these can cause problems. 

Always make sure you know what is in the block before committing to anything. 

Like in the picture below, the hempcrete blocks will be placed on one side of the wood-framed wall. 

A build with hemp blocks in progress: https://www.instagram.com/p/B3WirPkntVr/?utm_source=ig_embed&utm_campaign=loading

Benefits of using hempcrete block

Same as benefits for poured hempcrete, plus:

  • They are pre-dried, so you can begin applying interior plaster weeks earlier than with poured hempcrete. 
  • Faster install time.

Drawbacks of hempcrete blocks

Same as poured hempcrete, plus:

  • The cost is higher due to the labor required to cast and dry the blocks off-site.

A layer of hemp blocks complete: https://www.instagram.com/p/B3pkZnKn8uy/?utm_source=ig_embed&utm_campaign=loading

3. Sprayed-In Hempcrete

This type of hempcrete is mixed on-site, like poured hempcrete, but applied by spraying rather pouring into a form. It’s a similar process to wet-applied dense-packed cellulose or spray foam.

There must be a surface to spray against, like a hempcrete block layer or plywood.

This is a video of the whole preparation and spraying process. 

Components

Same as in poured hempcrete: hemp hurd, lime binder, water.

How it works

Mixed on-site, like poured hempcrete, but applied by spraying vertically rather than pouring into a form. 

According to Alex Sparrow, who owns UK Hempcrete and is the author of The Hempcrete Book, in the UK it is common to use sprayed hempcrete when renovating old stone houses. The stones have uneven surfaces and spraying allows the hempcrete to fill in the gaps and valleys. 

Spraying in hempcrete: https://www.instagram.com/p/Bz_LQRRBYW7/?utm_source=ig_embed&utm_campaign=loading

Benefits of sprayed-in hempcrete

Same as poured-in hempcrete.

Drawbacks of using sprayed-in hempcrete

Same as poured concrete, plus the possible compression of the hempcrete, resulting in lower insulation values.

4. Hempcrete Prefab Panels

Some companies are beginning to produce prefab wood frame hempcrete panels. These panels combine structural wood framing with hempcrete.

Components

The ingredients in prefab panels are usually the same as hempcrete. But, like blocks, it could vary from company to company, so make sure to find out what the binder is before committing to anything. 

How it works

The panels are framed with wood. They are sometimes referred to as “cassettes”. When using prefab panels, the wood framing is not encapsulated with hempcrete. 

Panels will require more care for air sealing, etc. due to the wood joints. There is also more potential for thermal bridging and condensation. 

Uses for prefab hempcrete panels would be similar to any prefab panel. Wall sections are made off-site and transported to the lot for installation. They could be used in place of hempcrete blocks, with poured or sprayed hempcrete on the opposite site.

A video showing hemp precast panels: https://www.instagram.com/p/Bz8amlcBfr-/?utm_source=ig_embed&utm_campaign=loading

Benefits of using prefab hempcrete panels

  • Possible faster install time.
  • Faster dry time.
  • Less on-site prep.

Drawbacks of using prefab panels

  • More detailing, similar to a traditional construction wall, because wood frame is not encapsulated in hempcrete.
  • More expensive.
  • Less oversight for how the wall is being made.
  • More potential for problems with the wood.
  • It makes interior finishes more tricky (lime plaster over studs?).

Precast panels: https://www.instagram.com/p/ttjdPmhKt4/?utm_source=ig_embed&utm_campaign=loading

5. Hemp Insulation Batts

Hemp insulation is not hempcrete but I thought I would briefly mention it here. It is not mixed with a lime binder that encapsulates the hemp hurd and hardens it.

It is hemp fibers, usually with some synthetic fibers mixed in, made into batts and used in walls just like fiberglass, mineral wool, and other batt insulation types.

My post on insulation mentions this in more detail.

Is Hempcrete Mold Resistant?

Photo courtesy of UK Hempcrete

Plain hemp can grow mold in the right conditions, but hempcrete is a little different.

Hemp–lime mixes can go moldy if it 1) it absorbs water for prolonged periods of time in moist conditions, 2) does not have adequeate ventilation inside or 3) wrong choice of protective coating.

Hemp is made of cellulose (it has even more than wood!) and mold likes cellulose. If you put plain wet hemp in a plastic bag and seal it, it will get moldy. 

Hempcrete has less risk for mold. This is because the hemp in hempcrete is mixed with a lime binder that makes it possible for the hempcrete to harden. 

Lime is what gives hempcrete its mold-resistant property. Lime is alkaline (high pH). Mold, in general, doesn’t like alkaline environments. When the lime binder is mixed in and coats the hemp pieces, it essentially creates an inorganic, alkaline buffer that mold cannot survive in.

However, one study I read found that mold was still able to grow, even in the presence of lime binder, when the hempcrete wall was exposed to heavy rain. 

A lot depends on using the right binder, mixing it correctly, making sure anything put on the walls is vapor-permeable, and avoiding bulk water (rain, roof-run off, etc.)

When a hempcrete house is properly planned and correctly built, the chances of mold growing are likely less with hempcrete than with traditional building materials. 

Do your research on binders before choosing one. There are binders out there that have caused mold problems.

If you want to avoid mold in your future healthy house, proper planning for moisture management (weather and vapor) are essential. 

Please find a qualified architect or building science professional to create a plan for your new healthy home.

What climates are safe for building with hempcrete?

This study found the most microbial growth in a simulated tropical environment. The Mediterranean climate simulation induced the growth of six species of bacteria and four species of fungi, with moderate diversity. In the arid climate simulation only four species of bacteria and two species of fungi appeared. Hempcrete certainly faired the best in the arid desert climate simulation.

There are many hempcrete houses in the rainy UK, as well as institutional buildings and multi-family complexes. In North America, there are hempcrete buildings in coastal North Carolina to snowy Idaho and cold, wet Canada. If you intend to build in a wet climate you should go visit some of these homes when possible.

Since hempcrete is an insulation, it should be just as safe as something like blown-in cellulose. The details will change depending on the climate, however – humid, dry, rainy, cold, warm, etc. 

It might be necessary to protect the exterior wall with large overhanging eaves, or sheathing combined with a rain screen (gap) and siding. 

This is where an experienced architect can help you determine the details that are necessary for your location to avoid mold and rot.

Is Hempcrete Cost Effective?

  • The cost appears to be 10-30% more than typical wood construction.
    • Much of it has to be imported (and it can be difficult to source, depending on where you live).
    • It takes a long time to dry which can slow down the build.
  • The cost depends on the method you use.
    • A double stud wall is more expensive (double cost).
  • There are very few experienced architects or builders.
  • Blocks and precast panels tend to be more expensive because they need to be cast individually unlike a whole wall that can be cast as one.

Related post: on more natural building wall systems to consider.

Where to Learn More About Hempcrete

Helpful books:

Helpful videos:

Trainings:

Products:

Design / Build

USA

Europe

Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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Smoothing the Seams in Mobile Home Walls (With Non-Toxic Materials)

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Walls in mobile homes have a vinyl layer on the wallboard and battens covering the seam gaps. It is possible to remove the battens and mud over the seams. It is also a good idea to prime the walls with BIN Shellac primer to stop any offgassing or leaching of plasticizers from the vinyl.

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

That Kilted Guy recommends the following:

  • Remove the strip
  • Sink the existing nails
  • If there is movement in the boards use screws to secure it, that will prevent cracking of the mud
  • Use drywall mesh tape on the seams
  • Use USG Easy Sand 45 or Easy Sand 20 which are zero-VOC drywall muds.
  • Add texture to even out the surface (since the vinyl is not smooth like the mud)

Corners:

Another contractor recommends using paintable caulk at the small seams like in the corners. Regular paintable caulk is an acrylic latex, and in my opinion, this is too high in offgassing.

A healthier option is a polyether caulk there like AFM Caulking Compound. If you don’t do well with polyether caulking you can use a 100% silicone (like the non-toxic brands outlined here) but then you need a shellac primer before you can paint the caulk with regular paint.

Painting:

One contractor recommends painting the vinyl walls first with a Zinsser primer. BIN Shellac is a great block of VOCs or other chemicals that could be leaching from the vinyl. Those who are chemically sensitive do find that BIN Shellac needs some time to offgas itself but it’s usually well worth it to wait for that to offgas so that you can achieve that blocking of what is below.

Texture:

Orange peel texture often works the best over these types of walls. USG Sheetrock Spray Texture is a good one that is zero-VOC. There is more info in my post on drywall texture and drywall mud.

You can watch a video tutorial here:

Choosing a Non-Toxic Plaster

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Plaster usually means a material used to coat interior walls while “render” more often refers to external coatings even if it’s the same material. Stucco is another word for an exterior wall coating.

The most common types of plasters have a base of gypsum, lime, cement, or clay.

Clay plasters are not very common anymore since they lack tensile and compressive strength. They are still used in some buildings, most commonly in natural buildings, like in adobe or cob homes. Clay plaster in conventional wood-framed homes was replaced by lime and then by gypsum plaster.

This article will look at the chemical composition of plasters and where you can use each type. Plaster is generally a healthy material no matter the base mineral, but those who are chemically sensitive will want to know which additives each type contains to choose the non-toxic options.

Early versions of many plasters used to contain asbestos fibers, so we want to avoid another mishap like that.

I will also look at non-toxic backers for plaster. Wood or metal lathe used to be common in old homes, but now moisture-absorbing board known as “blue board” has mostly replaced lathe.

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

Gypsum Plaster

What is Gypsum Plaster Made of

Gypsum plaster is made from 95% gypsum, plus fillers and functional additives.

Fillers can include: quartz sand, limestone, dolomite flour, chalk, ash, and perlite.

Additives can include: cellulose or starch ethers, cellulose fibers, citric acid and its salts (sodium citrates), tartaric acid and its salts (sodium tartrates) and more, surfactants (listed here).

Where You Can and Can’t Use Gypsum Plaster

Gypsum plaster can be applied directly on brick, solid or hollow concrete blocks, AAC blocks, and drywall.

Gypsum plaster cannot be used on outdoor walls or in bathrooms due to high moisture levels in those areas.

What You Need to Know About Gypsum Plaster

It is more finicky and less expensive than slaked lime plaster. It also requires fewer coats. It can be tinted.

Gypsum plaster is more expensive than cement mortar plaster (cement and sand mixes) for the same thickness. Though a final layer of gypsum plaster is often used with cement base layers.

Plaster of Paris is a gypsum plaster that is usually tolerable for the chemically sensitive as it’s a very simple non-toxic product. The USG brand comes recommended by sensitive folks and can be found at hardware stores like Home Depot.

Drywall compound like USG Easy Sand 20, are also gypsum-based and are similar to gypsum plaster. Structalite is a base coat of gypsum-based plaster that is commonly used.

Nowadays it’s usually applied over gypsum board, aka drywall. Usually, the type of backer board that is used is colloquially called “blue board”, which is a more textured version of regular drywall. I haven’t seen any difference between blue board and drywall in terms of toxicity.

Sometimes a bonding agent is used like Plasterweld. You don’t need to use that.

Veneer Plaster – This is blue board, with a very thin 1/8-inch layer of plaster applied on top. I have seen samples of this from USG and it seemed fairly benign to me. USG Veneer plaster is highly tolerable for the chemically sensitive, many other people report.

Clay Plaster

What is Clay Plaster Made of

Clay plaster is a mixture of clay, sand, natural pigments, with plant fibers for tensile strength. You mix it with water.

American Clay Plaster brand is made of clay, aggregates, non-toxic mineral pigments, and boric acid.

Where You Can and Can’t Use Clay Plaster

You usually use clay plaster over wood lath. It can be applied to drywall if it has a sand coating as the first coat (see instructions on American Clay Plaster website). It’s not used in wet areas, such as bathrooms and kitchens.

What you Need to Know about Clay Plaster

The earliest European settlers’ homes used clay plaster or a clay-lime plaster mixes. But now it’s gaining in popularity again. While it’s very popular in earthen homes it’s also gaining popularity in regular homes. I used clay plaster in my tiny home on wheels, over my MgO board walls, but you can use it over regular walls if prepped correctly.

I personally love the totally natural feel of clay plaster. Here is a detailed post on my experiences using clay plaster and lime wash in my tiny house.

It comes in powdered form in a range of earthy tones and has a very matte, rough-looking finish.

It’s quite labor-intensive to apply and you need to have some practice with it. If you are very handy taking a short course first might be enough for you to apply it yourself.

To learn more, get yourself a copy of The Natural Plaster Book.

Where to Buy:

In the US through Green Design Center

In Canada via Amazon.ca

Lime Plaster

What is Lime Plaster Made of

Lime plaster is a mixture of calcium hydroxide and usually sand, though other inert fillers can be used.

The plaster “sets” when carbon dioxide in the atmosphere transforms the calcium hydroxide into calcium carbonate (limestone). 

To stabilize the lime plaster, some Plaster of Paris (gypsum plaster) often is incorporated into the mix

Where You Can and Can’t Use Lime Plaster

Left unpainted, lime plaster can take on moisture and release it, just like clay plaster. But unlike clay plaster, lime plaster can be used in kitchens and baths (but shouldn’t be exposed directly to water unless it’s the Tadelakt variety). A protective layer of beeswax or Marseilles soap can be added to the plaster for water resistance.

What you need to know about lime plaster

Lime plaster was a common building material for wall surfaces in the lathe and plaster system. The lath is the wooden slats that are the backing for plaster pictured above.

The plaster used in most lath and plaster construction in North America was lime-based.

A modern form of lath is expanded metal mesh over wood or metal structures.

Slaked Lime Plaster

This is what the plaster walls in your great grandparents’ house were probably made of.

Starting with wood lath, a coarse coat of plaster was added first. This first coat is called a “scratch coat”. It’s plaster mixed with shrinkage-preventing aggregates, back in the day that was horsehair. Next is the “brown coat”, which is plaster mixed with sand, and finally a fine skim coat that does not have coarse aggregates.

Hydrated, or slake, lime plaster is made of limestone that has been baked at extreme temperatures. It comes in a putty form, not a dry mix.

It’s pure white in its basic form (brighter whites than clay plaster can achieve), it now comes in a huge range of colors.

Venetian plaster is pigmented slaked lime plaster. What makes Venetian plaster unique compared to other lime plaster is that there are no aggregates mixed in.

Marmorino plaster is when marble dust is added.

Tadelakt

Tadelakt is a type of lime plaster from Morocco. Tadelakt is composed of lime plaster, with calcium aggregate (crushed marble), optional pigments, and black soap made from olives. 

When the ingredients are combined, a chemical reaction between the lime and the soap creates a waterproof surface. Tadelakt can be used right in the showers and baths as the walls and on vertical surfaces like countertops and for sinks.

Concrete Plaster

What is Concrete Plaster Made of

The most basic cement plaster (usually called stucco when on the exterior ) is made from Portland Cement, sand, and water.

There are also mixes that are cement, lime aggregates, and water.

Admixtures may be added to it for various purposes including workability.

Where You Can and Can’t use Concrete Plaster

Portland cement plaster is applied either by hand or machine to the exterior and interior walls in two or three coats.

It is applied directly to a masonry or concrete wall (concrete bricks, solid concrete, red bricks) or it could be applied to a metal lath attached to frame construction.

When applied to metal lath, a vapor-permeable, water-resistant building paper is used over the framing.

Concrete plaster is used in much of the world in masonry buildings. It’s applied to all walls of the house, including the bathroom and kitchen walls, and then painted.

What to know about Concrete Plaster

Interior surfaces sometimes are finished with a final layer of gypsum plaster.

Concrete plaster can also be called adamant plaster.

Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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Sources

Non-Toxic Paint Strippers (All Types Compared)

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First, a History of “Whack A Mole” on Toxic Solvent-Based Strippers

Pre-1970s benzene was a popular paint stripper, it was later determined to be carcinogenic. It was replaced by methylene chloride, a very fast and effective paint remover. Methylene chloride/dichloromethane (DCM) is now considered a neurotoxin and a possible carcinogen that has caused many fatalities. It is banned in the US and many countries.

The latest replacement NMP (n-methyl-2-pyrrolidone), which is not as harsh as Methylene chloride, and is actually quite tolerable for many chemically sensitive folks, does have a Prop 65 warning for birth defects or other reproductive harm. I list only one paint remover with this chemical alongside the best alternatives.

In the mainstream realm, new formulas are being sold with acetone, turpentine, toluene, and xylene. I don’t list any paint strippers with these solvents because their higher VOC levels emit the strongest fumes and they are challenging to use.

An Alternative – Safer Solvents?

There are better options now, lower (and even zero-VOC) formulas. Safer more environmentally friendly solvents include dibasic ester, bio-based solvents, and alcohol solvents.

In this article, I look at those options along with “soy-based” and “citrus-based” paint and varnish strippers – though these terms are misleading because they don’t refer to the active majority ingredient. Often the majority ingredient is NMP, but I list brands with safer solvents.

You still need to wear protective gear including safety glasses, gloves, and a mask. Though all of the options here can technically be used indoors.

These safer solvents are effective but they take considerably longer on most coatings than the harsh solvents of the past.

Solvent-Free Options to Remove Paint

Depending on what kind of paint or varnish you are removing and what the substrate is, there may be other (solvent-free) options. In this post I discuss – boiling with baking soda, mechanical options, and eco-friendly lye-based options.

[Read more…] about Non-Toxic Paint Strippers (All Types Compared)

Non-Toxic Deck Cleaners (For Every Deck Type)

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This is a comprehensive list of healthier alternatives to bleach and toxic deck cleaning formulas that still work to get your deck clean even if it’s covered in mold, stains, and debris.

I cover deck and outdoor furniture cleaners that are safe for you, your kids, your pets, and your plants.

Some are simple DIY natural recipes and others are ready to use soaps that are eco-friendly (and biodegradable).

I list which options are appropriate for wood decks, painted decks, composite decks, and vinyl decks.

The same solutions that work on decks also work on fences, siding, and outdoor furniture.

[Read more…] about Non-Toxic Deck Cleaners (For Every Deck Type)

Non-Toxic Deck Stains (A Comparison)

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This article digs into non-toxic and natural options for staining and sealing wood decks as well as most outdoor wood like fences, furniture, windows, doors, play gyms, and planters.

This post covers both water-based sealants and natural oil-based options that are either zero or low-VOC and have been vetted by the chemically sensitive.

Penetrating sealers require that older decks and outdoor wood be sanded all the way down, but the film-forming options can be applied to lightly sanded older wood.

The water-based finishes don’t work over oily dense tropical woods like Ipe, Teak, and Mahogany but the natural oil-based stains and the hybrid work well over these woods.

If you are working with pressure-treated wood, all stains require that the wood has time to dry out first which can take anywhere from 3 months to a year.

If you would like to look at wood types and other decking materials that do not require a finish like composites and even aluminum, see my post on deck materials.

Top picks:

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

Non-Toxic Sealants and Stains for Decks, Fences, Outdoor Furniture, Play Sets & Planters

Staining a wooden deck with a all natural tung oil
Milk Paint Company All Natural Outdoor Defense Oil Sealant

1. Vermont Natural Coatings & Böhme – Terra Plus Exterior Deck Stain

Two cans of Bohme Terra Plus

What is it: This is a natural oil / waterborne hybrid penetrating stain. The colors are semi-transparent. It is a waterproofer with UV protection. It has better UV protection than the other options by this company.

Where to use it: On exterior decks and stairs.

Types of wood: Use on new or properly prepared decks. You can use it on Ipe, Mahogany, and Teak as well as non-tropical deck woods (be sure to talk to the company for direction). You only need a light sanding on a previously coated deck because it’s a film-forming sealant.

Specs: Low VOC. One person who was super sensitive thought this was better than PolyWhey. The company describes the smell as a sunflower or pumpkin odor, not a linseed odor.

Where to buy: Through the Vermont Natural Coatings website; sometimes on Amazon.

2. Penetrating Water Proofer Infused With Juniper

A can of VNC Pentrating Water Proofer

What is it: This is a water-based penetrating sealer. It does not form a film and the wood looks totally bare after applying it. The only purpose of this sealant is to provide waterproofing. It does not provide any UV or abrasion resistance. The wood will gray out naturally.

Where to use it: It is used on decks, railings, shake roofs, siding, fencing, indoor/outdoor play gyms, the exterior of planters/raised garden beds, outdoor furniture, and animal hutches/pens. It is not suitable for subterranean or submerged wood. It can be used indoors as well as outdoors. It cannot go over or under another product.

Types of wood: It can be used on new, or weather wood as well as pressure-treated wood. For pressure-treated wood allow 6-12 months before application. It can work on Teak and other oily woods and it is a good choice for cedar, pine, spruce, and fir.

Specs: It is zero-VOC and contains no solvents, dyes, biocides, or fungicides.

Where to buy: From Walmart and you can sometimes find it via Amazon.

3. PolyWhey Exterior Penetrating Wood Stain

Vermont Natural Coatings Exterior Penetrating Wood Stain

What is it: This is one of the most durable water-based non-toxic deck stain/sealers that I know of. This is a semi-transparent stain and topcoat sealer in one. It is a waterproofer with some UV resistance (more UV resistance the darker you go in stain color).

Where to use it: Wood siding, decks, fences, outdoor furniture, log cabins, exterior wood doors, play gyms, swing sets, beehives (it’s well-known for this application), pet hutches, barns, chicken coops, and other outdoor wood surfaces. This coating is great for the exterior of raised garden beds with AFM Dynoseal for waterproofing on the interior.

Types of wood: It can be used on new, pressure-treated, and weathered wood. Like with all deck stains, pressure-treated wood needs to dry out for 6 months to a year before application. Not for use on exotic super dense woods such as Teak, Ipe, or Garapa/Brazilian Ash.

It can be applied over older oil-based stains or finish, as well as other water-based finishes if it’s been fully sanded first so that it can penetrate into the wood. No product can go over top of this in exterior applications.

Specs: It is non-toxic, low odor, low-VOC, and contains no biocides, fungicides, or anti-microbial agents. The pigments act as natural UV inhibitors.

The folks at Green Building Supply have tested the non-toxic options on fences and found this to be as durable as oil-based stains and more conventional toxic stains/sealers.

Where to buy: You can buy it online at Walmart and sometimes via Amazon.

4. AFM Safecoat EXT Exterior Polyureseal

A can of AFM Safecoat EXT

What is it: A clear acrylic urethane coating for exterior use on wood and concrete. This is a water-resistant coating with good abrasion and UV resistance.

Where to use it: On walkways, decks, fences, floors, patios, doors, and pet cages. It can be applied to raw wood or wood stained with AFM Safecoat wood stains, as well as concrete or previously painted (with water-based paint) surfaces.

For abrasion resistance on outdoor tables, a paint and sealer combo would work well: AFM Safecoat All Purpose Exterior Satin and then AFM Safecoat EXT Exterior Polyureseal. (And if you really wanted a painted deck, this would be the only non-toxic combo to achieve that look).

Types of wood: Use on dry and absorbent wood. It can be applied to raw wood or wood stained with Safecoat DuroTone, concrete, and previously painted surfaces that are properly prepared. This product can not be used over oil-based coatings.

Specs: Low-VOC, it also can function to seal in offgassing of hazardous chemicals.

Where to buy: Through Green Design Center/Building for Health.

5. Milk Paint Outdoor Defense Oil

a bottle of Outdoor Defense Oil

What is it: An all-natural oil sealer made from pure tung oil, pine oil, and zinc. Out of the natural penetrating oils, tung oil is the most durable (and also the most difficult to apply).

Where to use it: On outdoor wood like picnic tables, wooden Adirondack chairs, wood furniture, decks, siding, wood fencing, front porches, concrete patios, park benches, wooden storage sheds, wood doors, and windows. You can use it on beehives with a full 30-day cure. This is the all-natural option for sealing raised garden beds (both inside and out).

You can also use this over Milk Paint to protect it from the elements or you can mix (some) pigments into the tung oil.

Types of wood: You can use this on all wood types. Extremely dense woods such as Teak, Ipe, etc may require thinning with more (natural) solvent. Not for use over new oil-based sealers/stains or other finishes. You can use it over aged penetrating oil finishes (like aged linseed oil).

Specs: No metallic driers. Full ingredient disclosure: pure tung oil, pine oil (which acts as a solvent), and zinc. Some highly chemically sensitive folks have preferred these natural oil coatings to synthetic coatings like PolyWhey (others would find the opposite preferable). Always test for your own tolerance and I would recommend not using or being exposed to these natural solvents when they are wet if you are sensitive. My in-depth look at tung and linseed oils goes into more detail.

Where to buy: Through the Real Milk Company’s website. You can use code mychemicalfreehouse for 10% off.

PS to clean your Tung oiled deck, you can use gentle soaps, but some non-toxic cleaners can damage it – this post goes over the best options.

6. Monocoat Hybrid Exterior Wood Protector

Rubio Monocoat Hybrid Wood Protector

What is it: A modified linseed oil and wax penetrating oil finish that is applied with just one coat. It provides protection from water and UV (except for the color “Pure” which has no UV protection).

Where to use it: Wooden decks, façades, patios, shutters, portals, garden furniture, pontoons, windows, doors, etc.

Types of wood: Works well over almost all wood types including oily exotic woods (Ipe, Teak, etc).

Specs: Solvent-free, technically 0-VOC because it’s a natural product. Though see my in-depth review of Rubio Monocoat and other linseed oils for information on naturally occurring VOCs. Rubio Monocoat is preferred to plain linseed oil in many ways because it’s lower in odor. You need a part B accelerator, be sure to test that out as well.

Where to buy: Directly through their website.

PS To clean your linseed oiled deck, make sure to use specialty products that won’t damage the surface.

Conclusion, Top Picks for Deck Stains:

  • Top water-based option: Vermont Natural Coatings PolyWhey Exterior Penetrating Wood Stain

  • Top oil-based option: Outdoor Defense Oil or Rubio Monocoat Hybrid Exterior

    • Bonus: Cleaning and Reviving Your Wood Deck

    Rubio Monocoat Exterior Wood Cleaner

    To remove green algae, moss, dirt stains, and graying from wood prior to staining and sealing your deck or other outdoor wood you can use Rubio Exterior Wood Cleaner.

    Use this before applying water-based stains like Vermont Natural Coatings PolyWhey Exterior Penetrating Stain or oil-based finishes like Monocoat Hybrid Exterior Protector.

    One sensitive person described the feel as a light soap but with almost no odor.

    Related Posts:

    Looking for non-toxic exterior paints? This post goes over the options.

    For a review of deck materials – alternatives to pressure-treated wood, low odor woods, wood that doesn’t need a sealant, and non-wood alternatives, see this post on decking materials.

    How to clean your non-toxic deck? Here are healthy cleaning products for every decking material.

    Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.

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