I fully intended to replace the original floors in my shipping containers with new plywood, although I was not looking forward to the work involved. I had read of the chemicals used to treat the plywood floors and the potential health risks to humans, so I really didn’t think I had a choice. Everything that I had read though focused on Basileum SI-84 as the chemical of choice for plywood in shipping containers. When my containers arrived, I was surprised to find that they were treated with Radaleum FHP-60 instead of Basileum – not that I knew what Radaleum FHP-60 even was.
To find out what the plywood flooring has been treated with, you need to look at the container data plate. This should be attached to a door of the container, although they could be missing from containers that have been removed from service. The plate will have a section called “timber component treatment” with three parts separated by forward slashes. The first part “IM” stands for immunity, the second is the treatment chemical, and the third is the date of treatment.
The active ingredient in Basileum SI-84 is Phoxim, an organophosphate compound. Phoxim seems to be commonly used against ants and termites, and can be found under the brand name of Baythion produced by the Bayer Corporation. The active ingredient in Radaleum FHP-60 is theta-Cypermethrin, a 2nd generation synthetic pyrethroid. According to Wikipedia, Cypermethrin is found in many household ant and cockroach killers, including Raid and ant chalk.
Both Phoxim and Cypermethrin are considered moderately hazardous (Class II) by the World Health Organization. What differentiates these two chemicals for my purposes is their vapor pressures. Phoxim has a vapor pressure of 2.63 mm Hg at 20° C, while Cypermethrin has a virtually nonexistent vapor pressure of only 0.0013 mm Hg at 20° C – more than 2,000 times lower. Why is the vapor pressure important? It’s easy to encapsulate the contaminated floors of a shipping container to eliminate physical contact, but it’s very difficult to block their vapors, if present, and their subsequent inhalation.
With the walls removed between my containers, I think it’s necessary to install some kind of subfloor on top of the existing container floor. While this would provide an excellent physical barrier from the treated plywood, I wanted an additional chemical resistant barrier between me and the Cypermethrin just to be safe. I just don’t trust that Cypermethrin is the only hazardous ingredient present in the plywood – it is made in China after all.
After a lot of research, I decided to seal the plywood with epoxy. In theory, the epoxy should be both a physical and vapor barrier to the chemicals. The epoxy I chose to use was Low V from Progressive Epoxy Polymers. Progressive is not a big company, but they have a good reputation among the boat building community. They offer a wide range of high quality epoxies for a very reasonable price. Low V is a solvent free, 100% solids epoxy that they recommend for penetrating and sealing wood surfaces. The only reservation they had with me using this, or any other epoxy, is that it might not bond to the wood due to the pesticides or any oil staining. BTW, there is an absolute wealth of information about epoxies on their website – IF you can navigate through the poor design of their site.
Before applying the epoxy, I chose to solvent wash the floors with 91% isopropyl alcohol. I did this to remove any surface chemicals or oils that would prevent the epoxy from penetrating and adhering to the wood. I used about one gallon of isopropyl per container to wash the floors. Be sure to have plenty of ventilation if you attempt this, as the alcohol vapors can be strong. You will also need to choose your mop carefully, as two different mops that I tried came apart in the isopropyl in short order.
I applied two separate coats of epoxy to the plywood using a paint roller on an extension pole. The first/primer coat was thinned with 25% Xylene to aid in penetrating the plywood floor. The second coat was applied full strength a week later. It takes several hours to dry to the touch depending on the temperature, and after the second coat it dries to a very hard, almost wet looking smooth finish. I doubt anything of significance is going to get through that epoxy.