Durability of English oak (Quercus robur L.) – Comparison of decay progress and resistance under various laboratory and field conditions

• Durability of 3 oak assortments tested in laboratory, semi-laboratory, field tests.
• Only little variation in durability of the different oak origins was found.
• Differences were superposed by the effect of different test methods.
• Transferability of lab results to outdoor performance limited.

Various procedures are used for testing the durability of wood and wood based materials for decades. Generally they can be divided in field and laboratory tests, whereby lab tests allow more defined and reproducible conditions and benefit from shorter test durations. However, while laboratory test results are hardly transferable to real life situations, field tests ensure more realistic conditions. For instance natural weathering and detoxification of biocidal compounds through so called “non-target-organisms” is assured only under outdoor field exposure. Due to these dissimilarities a diverse and in some cases also unrealistic classification of wood durability can be obtained when testing a material exclusively under laboratory conditions.This study will exemplarily focus on English oak (Quercus robur L.), which is classified as ‘durable’ according to the European Standard EN 350-2 (1994). Results from several laboratory and field test studies showed an enormously high variation of its durability between ‘very durable’ (Durability class (DC) 1, EN 350-1 (1994)) to ‘not durable’ (DC 5). Therefore this study aimed on a comparative evaluation of the durability of English oak in laboratory and field tests using standard specimens, but also full-size components under in-service conditions.The test results showed only little variation in durability of different oak origins. However it was indicated that a transferability of results determined in laboratory decay tests with pure cultures to the performance of a certain material in outdoor exposure is possible only to a limited extend.