There are three types of construction and two main finishes to consider when choosing a non-toxic engineered wood floor.
The first thing to note is that engineered wood flooring always refers to a floor with a real wood layer on top and an engineered wood layer as the base.
When looking for a zero-VOC, healthy engineered wood floor, the most important part is the construction type, so let’s start there then go on to the finishes.
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Three Types of Engineered Hardwood Flooring
1. Plywood Construction
The most common type of engineered hardwood floor has a plywood base.
The core is made of plywood and a top layer of real wood is glued on. The real wood top layer can range in thickness from 1mm up to 6mm.
The plywood which is made with phenol-formaldehyde adhesive is done offgassing by the time makes it way to the flooring company and then to you.
In general this type of engineered wood flooring is safe for almost everyone including most people with chemical sensitivities.
Some who are extremely sensitive may notice that this type of flooring can have a little bit higher odor than say a solid hardwood floor.
This is mostly due to the odor of the pine/spruce/fir used to make the plywood, but it’s possible there are some slight remnants of the glues that those who are extremely sensitive can pick up (since wood is so porous).
While the vast majority of brands have a pine/spruce/fir plywood core, Cali Bamboo Meritage line uses layers of acacia and eucalyptus woods as the core for the ply. I do think this has a milder odor than spruce/pine/fir myself. I would encourage you to get samples of both types if you are sensitive to the natural odorants of wood.
This is usually the type to choose for those wanting a non-toxic hardwood floor and for most people with sensitivities. Those who are extremely sensitive might want to look at the second construction type which has less glue.
The brands can claim zero-VOC on this type of construction.
- Cali Bamboo Meritage – Oak $9.99 / sqft
- Shaw Castlewood – Hickory $8.65 /sqft
- Shaw Camden Hills – Hickory $6.89 /sqft
- Johnson Hardwood Vineyard – Hickory $6.05 /sqft
- Anderson Imperial – Pecan $5.99 /sqft
- Johnson Hardwood Toscana – Hickory $5.95 /sqft
- Johnson Hardwood Toscana – Walnut $5.95 /sqft
- Western Skies European Oak $5.70 /sqft
- Mannington Park City – Oak $5.55 /sqft
- Smokey Mountain Engineered – Oak $5.29 /sqft
- Pioneer Engineered – Oak $5.29 /sqft
- Western Skies Engineered – Maple $5.09 /sqft
- Shaw Albright – Oak $4.09 /sqft
- Shoreline Engineered – Birch $3.60 /sqft
- Johnson Hardwood Wilderness – Birch $2.65 /sqft
This video shows the different types of engineered wood, and compares them to the other wood look options:
2. SPF Quarter Sawn Construction
A far less common construction type has a core of quarter-sawn spruce, pine and/or fir (SPF) softwood wood species.
The wood is cut and laid in “pickets” (i.e. it’s strips of solid wood) which run perpendicular to the solid hardwood top layer.
While the hardwood top layer is still of course glued on, and there might be a stabilizing layer below the quarter sawn layer, there are no glues within the main core layer.
This core can also be called “solid cross slat core”. Technically this is also a ply of three layers but it’s distinct from the usual plywoods which have thinner layers (and usually more layers).
For those extremely sensitive to the natural odorants of wood or the glues used in plywood, you might prefer this type.
For most people, it’s not necessary to track this type down and I would choose plywood construction in most cases (for availability and price and because it’s zero VOC as well). But for those wanting to go the extra mile, this is definitely one to get a sample of.
These brands should not have any offgassing and this type of construction should be formaldehyde-free (or more accurately no added formaldehyde in any of the components, since wood naturally contains some formaldehyde).
Tesoro uses pine in the middle solid layer, and a thin layer of ash as the stabilizing layer below.
- Mirage Hardwood Trubalance $6 – $8.50 / sq ft for most species
- Tesoro Coastal Lowlands – White Oak, Hickory, Maple, Walnut $8.87 / sq ft
- Tesoro Great Northern Woods starting at around $7 / sq ft
- Tesoro Great Southern Woods starting at around $7 / sq ft
3. HDF Core Construction
The last type of engineered wood flooring has the same top level of real hardwood but in this case, it’s glued to an HDF (high density fiberboard) core.
HDF is wood fiber that is glued and pressed together with formaldehyde. It’s more commonly seen as the core of laminate flooring.
My post on laminate flooring goes much more into detail on the chemicals and offgassing of HDF.
The main adhesive used here is formaldehyde – the odor is very noticeable to me, though it should be able to reach Green Guard Gold levels.
For this reason, this type is my least favorite type of engineered wood flooring and I don’t see any good reason to choose an engineered flooring that has some offgassing when we have better lower VOC options.
(You also see HDF as the core of Marmoleum Click and many cork floors).
The difference between laminate floors and engineered wood with an HDF core is that laminate does not have a top layer of real solid hardwood, just a printed image, and a melamine protective coating.
You can see the difference between the two in this picture:
- Mirage Lock HDF floors from Mirage Hardwood
- Shaw has some lines with an HDF core
- Some Home Depot Malibu Planks have an HDF core
Two Types of Finishes on Engineered Wood Flooring
1. UV-Cured Polyurethane
The vast majority of engineered hardwood floors have a UV-cured polyurethane finish with aluminum oxide.
Sometimes it’s simply listed as “aluminum oxide” or just as “UV cured finish”.
Almost every brand, far too many to list!
A similar finish is a water-based polyurethane (or polyurethane/acrylic mix) without aluminum oxide. These are not as durable as an aluminum oxide finished floor but they can be more natural-looking.
The aluminum oxide is not a health concern when in solid form embedded in the floor’s finishes. This finish is so durable it won’t usually show wear for decades. Though I do consider this a risk when (or rather if) the floors are re-sanded.
- Kahrs Water-based Finish Engineered Floors
2. Oil Based Finish
A few brands have an oil-based finish on the wood. They often don’t say which brand of oil-based finish they have used.
A few do say that it is WOCA, I have seen some list the finish as UV cured oil-based – which isn’t a specific brand, but the UV curing does speed up offgassing.
Kahrs and a few other brands list their oil finish as natural and/or zero-VOC.
I definitely can pick up the odor off of Kahrs oil-finished floors whereas I cannot pick up any odor essentially off of polyurethane finishes.
Though keep in mind with the natural oil you do also smell more of the natural wood odor coming through (along with the oil itself), since the aluminum oxide blocks some of the wood odor. The Kahrs oil-finished planks have a very natural look and feel to them whereas Cali Bamboo Odyssey oil finish looked and felt like a UV cured polyurethane with aluminum oxide. They say it needs an oil refresher as well.
This is also another way to avoid aluminum oxide, if you wish to avoid that.
Kahrs maintenance oil which looks to be all paraffin (kerosene), may not be tolerated though, so you do need to test out all of the maintenance products.
Rubio Monocoat maintenance oil is linseed based so should be used over linseed oil finishes or to transition to linseed oil.
- Kahrs Oil Finished Line
- Tesoro Brushed Patina Collection
- Cali Bamboo Odyssey Hardwood Flooring
- Pioneer Engineered Oak
Other Additives to Consider in Engineered Flooring – Antimicrobials
At least one brand, Lauzon, uses titanium dioxide as opposed to aluminum oxide in the topcoat finish.
The idea here is that the titanium dioxide reacts with UV light and a PCO process occurs, which creates OH molecules that can break down germs, VOCs, mold ect.
Sometimes this topcoat is labeled as air cleaning and sometimes as an antimicrobial finish.
Possible antimicrobial additives in engineered wood floor coatings:
- Titanium dioxide (nano) (Nano-TiO2)
- Silver nanoparticle-loaded hydroxyl zirconium sodium phosphate (Ag-HZDP)
- Silver nanoparticle-loaded zeolite (Ag-Z)
- Far infrared ceramic nanoparticles (FICN)
- Zinc oxide nanoparticles (Nano-ZnO)
Companies using unspecified antimicrobial agents in the floor finish include:
- Breezewood floors
- Many more, will add to the list when I come across them
Other Types of Engineered Wood Floor to Consider
1. Hybrid Flooring
A hybrid flooring is a relatively new type of click-together wood flooring.
Like all engineered wood, it does have a real hardwood layer on top. In this case, it’s quite thin.
(Here is a quick visual post showing how to identify engineered wood, versus laminates, vinyl, and hybrid planks).
- Opti-Wood from Home Depot – $3.39 – 4.09 / sq ft
- Raintree – $5.50 – 6.50 /sq ft
- Geowood by Cali Bamboo – Starting at $5.79 /sq ft
- Tesoro Lakewood Composite – Starting at $7.60/ sq ft
- Shaw Floorté Waterproof Hardwood – around $9.59 / sq ft
2. Engineered Bamboo Flooring
Solid bamboo or solid strand bamboo flooring is a type of engineered wood. Though bamboo is technically a grass it’s similar enough to wood flooring.
There are various styles in which the bamboo is glued together but a solid bamboo floor has various layers of bamboo glued together. Sometimes it seems like it is a regular wood glue odor (similar to Titebond) and other times it seems like a different type of glue, maybe polyurethane.
- Ecofusion Solid Strand
- Home Decorators Collection Solid Bamboo Flooring
3. Eucalyptus Flooring
Cali Bamboo Eucalyptus is strands of eucalyptus pressed together with a lot of pressure and heat in a wavy pattern. i pick up the regular wood glue smell but nothing that is different from all other engineered wood.
Installation of Engineered Wood
There are four main ways to install engineered wood.
- Floating Floor – in this method the planks are clicked together and installed over an underlayment but not glued or nailed down. Tongue and groove glue is ofen used on the edges (Roberts is zero-VOC). This installation is good in that it is low toxicity, but the downside is that you can’t re-sand your floors.
- Nail Down – in a nail down installation an underlayment is used and the floor is not glued down. This is my preferred installation method over wood subfloors.
- Glue Assist – this installation involves gluing down and nailing the floor. This is often used for wide planks and/or when there are big fluctuations in humidity. If you want to avoid glue, don’t go for wide planks. Glues can be silane modified or polyurethane. Silane modified is lower toxicity, usually.
- Glue Down – in this method, the glue is installed evenly on the floor. Most of the glues are polyuerethane but many are 0 VOC like Bostik Greenforce. This method is often used over concrete. I would not use this method (and never on concrete personally, since concrete is always trying to dry upwards).
Corinne Segura is a Building Biologist Practitioner with 7 years of experience helping others create healthy homes.
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