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 d uring piling installation, creating avenues for entry of decay agents. This problem is particularly acute in U.S. coastal marinas. American Wood-Prese rvers' Association standards recommend applying a topical preservative trea tment and a water-shedding cap during piling installation to prevent pile t op decay, but this advice is often ignored because the preservatives are co nsidered sloppy and difficult to apply. In an attempt to increase piling se rvice life, piles along the coast are frequently cut at a steep angle. Unfo rtunately this practice exposes more wood to potential fungal attack, leadi ng to a high incidence of top decay. In this report, we describe the result s of field trials of simple capping devices in combination with remedial ch emical treatments at a marina near Newport, Oreg. In general, capping alone had little effect on the incidence of decay fungi already established in p iles. Remedial chemicals, however, were effective in destroying fungal infe stations.