Dear James: I'm making house repairs and noticed insect damage to the wood. Other than using pressure-treated lumber, can I treat the wood with a safe chemical to deter insects? — Jamie G.
Dear Jamie: Stopping insects before they enter your house is always better than trying to treat an infestation once it is established. Insects can cause direct structural damage or increase the wood's susceptibility to fungal or biological decay, causing many more problems in the future. The key to preventing wood rot is controlling the wood's exposure to moisture and effectively preventing insect problems.
One basic way to protect your house is to treat the lumber with a chemical preservative. The best type of solution to use is a borate solution. This can be applied directly to the lumber. Since you want to be safe with children and pets around, a borate spray is the perfect choice.
When you purchase the borate solution, make sure the EPA has labeled it as a wood preservative. Although borate chemicals are highly toxic to wood-boring insects and fungi, they exhibit low toxicity to humans and other mammals. Some borate solutions are registered as insecticides and can only be applied by a licensed technician.
When using a borate solution on the exterior of your house, you must remember to apply a penetrating water repellant on a regular basis. Borate comes in a powder form and is mixed with water. The water can evaporate and remove the borate from the wood, making the lumber susceptible to insects. So each time it rains, some protection is being washed away.
Many common water repellents are formulated with silicone, so any surface coated with the repellent cannot be painted until the silicone has worn down. One gallon of repellent can cover up to 200 square feet of wood surface. While the water repellent can protect the wood against warping and cracking, it will not help retain the wood's natural color. If you are concerned with keeping the original color of the wood, try selecting a water repellent material that has UV resistance to stop damage and fading caused by sunlight.
The borate can be applied just like a coat of paint, with a sprayer, a brush, a pad, a roller or by dipping. If you are working outside, watch the weather to be sure rain is not expected anytime soon. Try to avoid breathing the vapors. Always wear a mask and be sure there is adequate ventilation.
Another way to actively stop wood rot is by using Impel rods. These are rods made of highly concentrated boron. The water-diffusible boron is placed in a solid tube that looks like glass. Impel rods are inserted through small holes which have been drilled into the wood where there are signs of rot or in high-risk, rot-prone areas. The holes are sealed and can be finished to match the wood's appearance.
Whenever the moisture content of the wood is high enough to sustain rot, the Impel rods begin to dissolve and release the chemical into the wood. This spreads the borate into surrounding areas. When the wood dries, the preservative remains in the wood.
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