Boron-based wood preservatives are effective in controlling fungi, termites, and insect activity in wood. The days and weeks following a flood or natural disaster can be an opportune time to apply borate treatments, not only because damp wood will benefit from protection, but because repair work often makes otherwise hard-to-reach wooden components of historic structures more accessible. The article below includes information and tips on using borate wood preservatives in a preservation context.
Jeff Adolphsen, Senior Restoration Specialist
October 8, 2024
Boron-based wood preservatives are effective in controlling decay fungi, termites, and insect activity in wood. Borates are relatively low in toxicity, easy to apply, and available in powdered and liquid forms as well as solid rods. People with skin sensitivities should check the Safety Data Sheet. The most commonly available borate-based preservative is Bora-Care®, a concentrate of borate salts with polyglycol penetrants to aid in its dispersion through wood fiber. Where mold is a known problem, Bora-Care With Mold-Care® can be used to kill and prevent mold.
It is best to apply Bora-Care® when the wood is wet to improve penetration. The polyglycol will help stabilize the wood to prevent or minimize warping, bowing, or twisting, and facilitate penetration. Borates are typically applied by sprayer but can also be brushed on or injected using syringe or sqeeuze bottle. Apply at the recommended rate, as borate salts can corrode nails and metal junction boxes. Application rates may be by the board foot or square foot.
Apply borates to exposed structure, such as the crawlspace, attic, and where possible, open wall cavities. Also apply to unpainted wood and stained finishes and features (floor, wainscot, ceiling, trim, door and window surrounds, mantels, stairs, etc.) that have been inundated with floodwater. Use a 1:5 dilute ratio on wood floors as too much product will take longer to dry and penetrate leaving a sticky surface. See label for floor application rates. Note that the painted finish on wood may fail or can easily be removed after the material has been inundated, thus improving the efficacy of the borate application.
Proper application combined with adequate ventilation after water inundation may reduce or prevent tongue-and-groove boards (flooring, sheathing, wainscot, ceiling, etc) from buckling. When dry wood gets wet, it can expand ¼” per foot in a direction perpendicular to the grain. This can compress the boards and even result in buckling. If inundated boards can be set flat, there may be a gap between the boards from contraction as the floor dries.
Boron-based wood preservatives can be purchased through these on-line resources and others on the web. These sites also offer technical support.
Nisus Corporation: https://nisuscorp.com/homeowners
Preservation Resources Group: https://prginc.com/