This document describes a method of test for wood preservatives that are intended for use in wood to be exposed to the weather out of contact with the ground without the additional protection of a surface coating. The method is applicable to the testing of commercial or experimental preservatives applied by techniques appropriate to commercial practice. The method is applicable to chemical products used individually or in combination to prevent the development of decay and/or optional the development of disfiguring organisms in wood and, where suitable, in wood-based products. NOTE 1 The method can also be used to test other treated wood species and naturally durable timbers. It can be adapted for testing the field performance of other wood based systems and treatments designed to enhance durability, for example treated or untreated wood based composites, timber treated with non-biocidal systems, chemically modified or heat treated timber. NOTE 2 Altough the test is used to assess decay, it is possible to use the method to additionally assess stain or each separately when relevant.