Remove as much rotten wood as possible (and economically feasible) before beginning repairs. In structural wood — columns, beams, girders, and the like — it’s important to cut back to sound wood; if possible, the cut should be made at least one foot beyond the last evidence of rot. You don’t have to be as aggressive on things like window trim, but you still should remove as much rotten wood as you can. If you’re replacing structural wood, keep the new lumber away from the old if at all possible, and be sure to use pressure-treated wood. For repairs in hard-to-maintain areas or in wood that’s constantly exposed to the elements, you’ll want to treat existing wood, too. Borates are the chemical of choice for treating and stopping rots, and have been used for this purpose for many years. They are water-based, low in toxicity, environmentally friendly, and they last a long time. Since they are water-based, they actually use the water in wood as a carrier. When wood is dry, borates stay in place. When wood gets wet, the borates move through the wood. As they do, they both kill fungi and protect the wood from future infections. Borate products are sold under a number of brand names, including Bora-Care, Guardian, Jecta, Tim-bor, Shell-Guard, and IMPEL Rods. All of them both protect and treat wood and wood-foam composite materials against fungi and wood-destroying insects (more about these in The Trouble with Termites). Some are solutions that you spray or brush on. Tim-bor is available as a dust that you inject into cracks and hard-to-reach spaces. IMPEL Rods, as the name suggests, are rod-shaped devices that slip into holes drilled in wood. Choose the product that best suits your needs, and follow the label directions for mixing and application.
