Capping and chemical treatment of Douglas-fir piling to prevent pile top decay: A 13-year test

Preservative treatment can be an excellent barrier against fungal, insect, and marine borer attack. Fabricators, however, often disrupt this barrier during piling installation, creating avenues for entry of decay agents. This problem is particularly acute in U.S. coastal marinas. American Wood-Preservers' Association standards recommend applying a topical preservative treatment and a water-shedding cap during piling installation to prevent pile top decay, but this advice is often ignored because the preservatives are considered sloppy and difficult to apply. In an attempt to increase piling service life, piles along the coast are frequently cut at a steep angle. Unfortunately, this practice exposes more wood to potential fungal attack, leading to a high incidence of top decay. In this report, we describe the results of field trials of simple capping devices in combination with remedial chemical treatments at a marina near Newport, Oreg. In general, capping alone had little effect on the incidence of decay fungi already established in piles. Remedial chemicals, however, were effective in destroying fungal infestations