Often the results prove embarrassing when joints open up and fail. The key is recognizing that all suppliers of marine epoxy adhesives expect that the user will also use the resin to encapsulate the bonded wood. Indeed, it is common for an entire boat to be coated with epoxy, or sheathed using fiberglass cloth and epoxy resin. This approach is often impractical and, at times, impossible for certain projects. But an understanding of why encapsulation works so well will help woodworkers produce products that will survive in exterior applications.
Epoxy resins are very effective moisture barriers.
Wood encapsulated with epoxy has a very stable moisture content that hovers around the equilibrium moisture content for the environmental exposure. Encapsulated wood does not experience the dimensional changes that are normally associated with changes in the atmospheric moisture content. When unprotected woodwork is exposed to exterior environments, the glue joints can be stressed to the point of failure. Woodworkers using epoxy resins must recognize this and strive to protect the wood from deep moisture cycling. Various finish oils, water repellents, coatings and varnishes have proven effective in protecting the epoxy glue joints.