This method is a 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 (i.e. Use Category 3B).
Jointed samples (lap-joints) consisting of two overlapping parts (joint members) held together mechanically are placed horizontally, out of contact with the ground and exposed to the weather. The test unit specified is designed to simulate a deck or similar construction. The lap-joints are dismantled and examined at intervals. The extent of fungal attack on the external surfaces and within the joint areas is rated according to a specified rating system. Data for lap-joints treated with the test product are compared with those generated using a reference preservative and untreated samples to assess relative effectiveness.
Examples of standardized versions of this test method can be found in AWPA Standard E16 and AWPA Standard E27 (available from the AWPA), and as ENV 12037:1996.