For siding and decking applications there is no need but please seek expert advice for window and door applications
From a technical performance perspective, in respect of attributes such as durability and dimensional stability, there is no need to finish Accoya wood for siding and decking applications. However, joinery applications are more complex so it is recommended that you seek expert advice before using Accoya for uncoated windows and doors.
Like any natural wood species, Accoya wood is susceptible to weathering in outdoor circumstances. All materials exposed to exterior conditions are degraded by a series of chemical, biological and physical processes. The surface of any wood will be blemished by a combination of UV, molds, algae, mildew, yeasts and pollution. Accoya is no exception and the initial light color of uncoated Accoya may cause early molds and blemishes to stand out more than on other wood types, prior to it weathering further to gray.