- 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.