In Large Timbers Fumigants Stop Rot That Good Design Could Have Prevented

Large timbers, treated or untreated, which cannot be dried to the MCs they attain in service are especially vulnerable to checking and decay. Laminated timbers decay where water enters at the ends or in deep checks caused by swelling and shrinking of the wood. Checking of round and sawed timbers exposed to the weather can be prevented by sawing a groove to the center (kerfing) before treatment. Deep (6-cm) incisions of perforations increase preservative penetration. The method used depends on the treatability of the wood. Internal rot can be stopped by placing volatile chemicals in holes drilled in the timbers and plugged. Gases diffuse through the wood, eliminating decay fungi and insects within about 2.5 m of the treating site. Vapors of some chemicals have been detected 8 years after application, so retreating cycles are expected to exceed 10 years. Solid chemicals may replace liquids, and electrical resistance sensors placed in wood may tell when retreatment is needed.

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