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
Myths About Plywood
That it offgasses forever
Plywood made with phenol-formaldehyde rapidly reaches non-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 (and should be avoided in my opinion).
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 technically 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 (PF) (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 with 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 the 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).
Types of Plywood and Their Glues
Structural Plywood
Structural plywood is softwood plywood (SWPW) and it is used for roof sheathing, subfloors, 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
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 (not Gold).
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.
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 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 8 years of experience helping others create healthy homes.
Buy me a kofi to support the research behind this blog.
Sources
https://pharosproject.net/common-products/2078999#contents-panel
Amazing Grace says
Before installing Wineo’s Purline Organic Floor (from a roll), our floor installer wants to use IronPly Premium Underlayment (https://www.patriottimber.com/ironply/) underneath to create a smooth surface over our existing OSB subfloor. Is IronPly a safe option? Is there a better option?
Corinne says
You’d have to ask them what kind of glue is used.
Kate says
Hi Corinne. It looks like you’d suggest drywall instead of plywood for interior walls. Is that right?
Thanks so much for all the great info you post!
Corinne says
No, I don’t think I have said that. But plywood needs an air barrier usually a smart membrane behind it.
Kate says
Thanks for your reply.
As someone chemically sensitive who doesn’t detox well, I’m trying to decide the best materials for wall coverings.
I’ve read both of your sections on drywall/mud and plywood.
I will be using wool insulation and Intelloplus prior to any wall coverings.
Cost is a factor too but with labor for drywall, plywood application might be pretty close cost wise.
Both options will be painted- yup readin your section on paint too!
I think as you often advise, I need to invest in a sheet of plywood and see how I do with it.
Again, thanks for all you do! The info is most helpful!
Corinne says
you’re welcome
May says
Hi Corinne,
A family member is experiencing a difficult situation at home where a chemical pesticide was sprayed and the dilution was not done correctly as the chemical odor has lasted too long and it has made them ill at home for several weeks (months on to now). The pesticide company neither the manufacturer have been helpful in providing solutions, even after several attempts to clean it with a non-toxic alkaline cleaner. They tried steam cleaning our carpet and after this attempt it made it worse and believe that that pesticide spreaded to the subfloor (plywood). They tried replacing the carpet and padding and that did not help either.
The substrates are the subfloor (plywood), subfloor (concrete), baseboards and a few inches of the wall. The problem is that this pesticide has petroleum and we feel ill from the off-gassing. Their home has never had any issues until now. They have done everything from ventilation to air purification, carbon bags, and we in much need to get this situation resolved. We tried calling several agencies, remeditation company but few or none provide services to help to remediate pesticide. We did read that this happened to several persons through the National Pesticide Center (they were not helpful either) but we were told that peple with this situation have had to replace the subfloor.
When they replace the subfloor, and if you advice that too, should we allow it to ventilate a day or two before we place a low voc laminate? The sealing is not necessary as this would save us money? I read your article on plywood so I will be sure to select one you recommended on this article. This way it offgases, however, we would not have more than a few days, if that, because the contractor has a timeline to get the work completed, and place the laminate on top of the plywood. Should we get a vapor barrier to go on top of the plywood floor?
Do you recommend any low VOC baseboards as they will be replacing those too?
They will be sanding the concrete and cleaning before placing the underlayment and plywood on the areas that have concrete.
They also called an HVAC company and they recommended that they seal the HVAC closet walls and return as the pesticide may have made through there. Do you recommend sealing with tape there?
Thankful for any advice.
Rachel says
Hi, Corrine, do you think soy-based plywood would be appropriate in the construction of bathroom vanities in an oceanfront, climate-controlled house? You said it doesn’t do well in high humidity. If it’s a bad idea, what would you suggest instead? The interior of the cabinets will require furniture-grade plywood. Is phenol formaldehyde furniture-grade plywood a better choice than the soy-based? Is it readily available? Thanks
Corinne says
I would ask the companies that make soy glue plywood what the upper limit for humidity is.
Kelly says
Have you possibly looked into Murphy Plywood or do you have any thoughts on what they have to say here about formaldehyde? https://www.murphyplywood.com/questions-and-answers/
Corinne says
Yes that’s accurate, structural plywood is low in formaldehyde and doesn’t need to be CARB. You should look for APA.
Nick says
Hello Corinne,
I have a question for you regarding interior plywood usage. I’ve recently used 18mm shuttering ply for the interior walls of a workshop/studio and have discovered via the internet that there might be an issue with off-gassing (although I have felt no effects). I had to use a couple of different brands of plywood and can’t be sure what the glues used were. In total I used around 20 – 25 sheets (quite a substantial amount). They’ve been in there for about 6 months, from your article am I right to understand there should no longer be an issue? I frequently have the doors and windows open and by the sounds of it that’s the best way to get any possible formaldehyde levels down.
Thank you for the informative website.
Nick
Nick says
Hello Corinne,
I have a question for you regarding interior plywood usage. I’ve recently used 18mm shuttering ply for the interior walls of a workshop/studio and have discovered via the internet that there might be an issue with off-gassing (although I have felt no effects). I had to use a couple of different brands of plywood and can’t be sure what the glues used were. In total I used around 20 – 25 sheets (quite a substantial amount). They’ve been in there for about 6 months, from your article am I right to understand there should no longer be an issue? I frequently have the doors and windows open and by the sounds of it that’s the best way to get any possible formaldehyde levels down.
Thank you for the informative website.
Nick
A. Owens says
Thanks for this currently considering builtin plywood bed for kids room.
Diana says
Hi dear! What should i use under ward wood flooring? I guess i can put under some natural rubber? Or still plywood, what kind1 . As well about glue, i need for bathroom. I saw your post of glues but still can’t get which one is best and for water resistance
Corinne says
There is a post on underlayment that will help. I wouldn’t glue down wood flooring but there is a glue recommendation in the post on engineered wood.
Dian says
Thx. But wood floor is 7 wide x 25 long, how you will install this option, thank you.
Corinne says
Oh I see, check out the glue options in the post on engineered wood.
Chris says
Hello,
What would you suggest for a bunkie board to go underneath a non-toxic latex mattress for a child? We bought regular plywood and we have to take it back and get something else non-toxic because we could smell it in the room. Thank you
Corinne says
I wouldn’t put a mattress on a flat board because of condensation and mold. If it’s an air mattress or something that can’t mold, use one of the plywoods recommends in the post – the soy ones.
J says
Full Latex mattresses must be placed on a flat surface.
Air mattresses can/do mold
Corinne says
Well anything can mold in the right conditions. If the air mattress is over a concrete floor that is taking on water outside and drying to the inside then you will probably find mold under it.
but it doesn’t transfer body sweat like most mattresses do which can lead to mold under it on any flat surface/on any wooden floor.
the bases for latex mattresses have slats. you shouldn’t put a thin piece of latex on a flat surface. Go with one of the good brands like avocado that go on slats.
Rachel says
Hi Corrine, I thought the phenol resin glues in plywood incorporate BPA, is that correct? It seems it is quite hard to know what exactly is in the glue. Thank you Rachel
Tami says
What about birch plywood, would you say this is safe? ( after the 30 days)
Gillian Whittall says
Fantastic blog, please keep up the good work and the fight to get this awful stuff out of our homes! I recently bought a recliner sofa and in two hours, my nose and eyes were streaming. Even though companies claim ‘Solid Wood Frame’, all the panels of the arms, the backs, were all plywood and composite board. The company that sold it were good enough to take it back but we lost our deposit. I think it’s a disgrace that companies are shoving this stuff into our homes when it should come with a toxic warning label, particularly for those with respitory issues. Urea Formaldeyde is carcinogenic. I’m not sure about the other versions you have listed here. I wish I could find a sofa manufacturer that does not use this stuff and uses only hardwood.
Corinne says
Ya this is a problem – saying solid wood and then it being engineered wood. I guess they are hoping no one looks inside it, though you can often see it from underneath.
Lisa Samalin says
Dear Corinne,
We moved into a house that was built in 2007 a few months ago and i haven’t been feeling well. When we moved in we ripped up carpeting in 3 rooms including the bedroom and painted the plywood subfloors with latex paint. have a long history of being extremely sensitive to substances and I’m wondering if the plywood could be an issue. If so would you have any suggestions how to remedy it? I so appreciate anything you can tell me. Thank you, Lisa
Monika says
Hi Corinne, I was wondering if you know of this brand and what your thoughts are on it. Would you say any shellac sealer would do or there would still be differences in sealing properties?
https://chestnutproducts.co.uk/product/shellac-sanding-sealer/
Thank you!
Corinne says
Any brand will do.
Monika says
Thank you so much!
Monika says
Do you think Osmo hardwax oil would also seal plywood from off gasing?
Corinne says
No, first it’s high in solvent odor itself and two it’s a breathable sealer so it won’t seal in offgassing. We want the opposite, not breathable.
RobertHan says
Nowadays, high-quality plywood or plyboard products are widely used and available in the market to install or replace my floorings. Thank you for your writing page. It helped me a lot