Silane-based “Zero VOC” wood flooring adhesives and off-gassing
Hello. I’m on the East Coast of Central Florida, about a mile from the beach and a couple hundred yards from a major lagoon. Our installation of about 1,700 sqft of cork and engineered wood flooring from Cali Flooring started in November and was completed in February 2024.
We measured the VOC off-gassing of the all-natural cork (none), the Cali Meritage Syrah Oak flooring (none), and the Silane-based adhesive (up to 38,000 ppb).
We also measured the VOC content of the air in the home prior to the installation (100-250 ppb).
The measurements were done with multiple different Awair Element meters. All showed consistent results.
The cork and a layer of adhesive were laid down on January 16-18, 2024. The Cali flooring and adhesive were laid down on January 31-February 5.
We were told that any smells and associated VOC off-gassing would be done by the time the adhesive cured, 3-7 days, depending upon the humidity (more humidity means faster curing). During the last month, the humidity has been higher than recommended (60-72%).
It’s now over 1 month since the last bit of adhesive was applied. We are still seeing VOC emission levels equal to the installation day (~38,000 ppb) unless we open up a lot of windows and doors in the house. It takes about 6-12 hours (depending on heat, hotter is faster) after closing the windows and doors to reach 22,000 ppb VOCs and after around 48 hours, it reaches 38,000 ppb.
Each morning, the house is filled with an incredibly strong smell of Silane. It makes my family uncomfortable, and we get symptoms after a few minutes of exposure (dizziness, coughing, eyes itching, etc). Until we can open up a lot of doors and windows to clear the air (which takes 1-3 hours depending upon the wind).
We’ve purchased activated carbon filters for all 3 air handlers and for 4 air purifiers. But even on max 24/7, they don’t seem to make a difference.
We’ve spoken with the manufacturer who has said that the batch is fine and that they can’t explain what we’re seeing. They also say that it is likely caused by something other than their product.
In this video (https://youtu.be/t8RWf53deG8), a different manufacturer says that Silane-based flooring adhesives release methanol when curing by being exposed to water (moisture). This is unlike a Urethane-based adhesive that releases CO2. Unfortunately, the manufacturer of our adhesive hasn’t provided us with the details of what VOCs are released by their glue, but I assume that the chemistry here is similar.
We’ve asked the manufacturer for help and for guidance on how long it will take to fully cure and stop off-gassing, but their guidance (max 7 days) has proven to be way off and they don’t have any other guidance after that.
We’re currently evaluating whether we will need to move out for an extended period of time or tear up the floor.
– Is it true that Silane-based wood flooring adhesives release methanol?
– Does anyone have experience with how long it would take for 2 layers of 1,700 sqft of Silane-based “Zero VOC” adhesive to stop off-gassing?
– Are there any effective VOC mitigation techniques for this scenario?
– How can products like this be sold as “Zero VOC” and even be Greenguard Gold certified?
Thank you.
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Replies
https://rusticwoodfloorsupply.com/sundries/adhesive/#:~:text=During%20its%20curing%20process%20by%20polycondensation%2C%20this%20type%20of%20adhesive%20emits%20methanol seems to state that silane adhesives emit methanol.
The risks and issues with Methanol exposure are detailed here:
https://www.dcceew.gov.au/environment/protection/npi/substances/fact-sheets/methanol
The OSHA limits for methanol in the air are 200,000 ppb over an 8-hour shift, but the limits for 24x7 exposure in your home are unclear, but certainly significantly lower than 200,000 ppb.
It's always difficult to accurately diagnose this sort of thing online, but I may be able to offer some useful guidance.
Silane modified adhesives cure through contact with moisture from the air. In FL, having enough moisture in the air is not going to be a problem.... Although I guess that in winter you may still have the heat on and this does dry out the air. If you indoor humidity is pushing 35% or below, that could be part of the problem.
It sounds like your adhesive is just not curing as quickly as it should have. Here are some things that effect curing:
-Humidity: more causes faster curing. Below 35%, curing slows down or even stops.
-Temperature: Higher causes faster curing. High temperatures coupled with high humidity is best. Summer is coming with its humidity and this might be a good thing.
-Thickness of application. These products cure from the outside in, and they cure to a stretchy rubber consistency. The skin is also somewhat impermeable to water vapor. There can be issues in thick applications where moisture cannot get through the thick skin to fully cure the adhesive inside.
My best guess is that either your adhesive was applied too thickly. If your floor has wide planks, the adhesive and construction of the planks may also reduce vapor permeability. If this is true, it is entirely likely that the adhesive will eventually cure but there is no way to predict how long that will take. Your best approach would be to keep the windows open as often as you can until the smell goes away. You could do some destructive testing by tearing out one or two boards to examine the adhesive. If it's still wet and sticky, you know it's not cured. If you smear the still-wet adhesive and it cures when you leave it outside overnight, then you know the problem is moisture transport to the in-place adhesive in the floors, and more time may help.
The bad news is that there are some reports of these adhesives never fully curing because of the outside skin stopping moisture transport to the wet adhesive inside. There are "activators" that can be mixed into the adhesive during installation that promote full-depth curing, but it's going to be too late for that.
Thank you for your response.
We do have very wide planks for our flooring.
The humidity inside has been averaging 60-72% and should have never dropped under 35% in the last 2 months.
The installers likely did apply the adhesive thickly, and we have two layers (cork and engineered wood).
Was it Bona r851 that was used?
First, we used Fortane Zero, but noticed VOC issues after putting down natural cork and before putting down the engineered wood. We tore up the cork and glue, patched to level, and then used Bona r851. We were told that it would fully cure in 3-5 days, later they said maybe 7 days.
It's 5 weeks now and the VOC levels are the same as installation day when using a Metal Oxide sensor.
With an electrostatic sensor, we are seeing 5 mg/m3 TVOC and 2 mg/m3 formaldehyde.
It’s crazy how these companies can market their products as zero voc snd still be that problematic. It also makes me question the Greenguard Gold certification. I’m having engineered wood floors installed soon and was leaning towards Bona but I may need to keep researching. It seems that most of the adhesives claiming to be zero voc with low odor have similar ingredients though. I feel like I’m having to pick my poison.
Just curious, did they use a Mapei leveling/patching compound before the install? I’ve read complaints about a long lasting odor from that product as well. But if you have two layers over it then it seems more likely to be the adhesive.
Mapei patching, but no full room leveling. I did not notice an odor or increase in VoCs from the Mapei. It was applied for about 24 hours before the cork and adhesive went down.
At this point, I don't trust any Zero VOC adhesive. I don't know the problems with nailing, but that seems like the only no VOC option.
Pardon the ignorance but I'm unfamiliar with Silane based adhesives. What made you choose that over Polyurethane like the adhesive Advantech uses or Locktite PL Premium?
The claims of "Zero VOCs" otherwise we would not have used adhesive at all and done nail down.