Marine Surveyors Lexicon

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Treating Isolated Decay, Wood


A method which can arrest the progress of incipient decay, at least temporarily, is as follows:

The affected area is scraped clear of all decayed material and for some distance into apparently clear sound wood. A strong preservative solution, for example l:10 pentachlorophenol stock solution, is applied freely. This is allowed to soak in and dry. Repeated applications are made until the wood refuses to take any more preservative. Often a small "cofferdam" can be made to retain a pool of preservative over the area. To be effective the preservative must sink in and sterilize the wood for a considerable distance since decay sends out spores ahead of the damaged area

After the treatment is completed the cavity made by the scraping may be left unfilled but should be painted. Filling it will simply hide any additional rot still working.

This method is a temporary repair only. It will usually slow decay growth, but will seldom eliminate all traces of decay.

Painting of wood structures not only prevents decay, but also prevents rapid short-term changes of moisture content which result in structurally damaging dimensional changes. The proper coating of wood structures can be as important as coating of steel structures in maintaining structural integrity.

Excerpted from Wood Hull Inspection Guidance (NVIC 7-95)