- Q. I know that some framers are using lumber treated with SBX (sodium borate) as a substitute for ACQ because it is less corrosive to fasteners, but I'm concerned about short-term exposure to rain and the longevity of the borate treatment itself, which could leave the mudsill vulnerable to rot. Are there any other alternatives?
A.Paul Fisette, director of Building Materials and Wood Technology at the University of Massachusetts Amherst and a JLC contributing editor, responds: While borate-treated lumber isn't rated for continuous exposure in wet conditions, it is fine to use it for framing that eventually will be closed up and protected from the elements.
Where there is direct long-term contact with the soil or water, borates can leach out over time, but SBX lumber that's on a dry concrete foundation and covered by sheathing and siding should remain stable. It won't be significantly affected by exposure to the elements during the construction process, either.
Researchers are focused on developing target-specific biocides with the goal of removing metals from the preservatives and making them less corrosive, but we will have to wait a while for these new developments to be fully tested and made available.
Meanwhile, borate-treated lumber offers a relatively benign alternative to ACQ-treated wood for many applications, including mudsills. And like the old CCA-treated lumber, it doesn't require stainless steel or hot-dipped galvanized fasteners.
