Variation in moisture content in field trials according to use class 3.2 conditions

IRG/WP 16-20580

S Bollmus, A Gellerich, H Militz

Different test methods to determine the durability of wood in use class 3 (EN 335:2013) are available. Fungal degradation of wood requires liquid water. Different Standards (EN 335-1:2006; DIN 68 800:2011) specify the risk for decay with moisture content (mc) of above 20%. EN 335 (2013) does not specify moisture content but rather defined limited wetting conditions (use class 3.1) or prolonged wetting conditions (use class 3.2). However, in literature moisture content of approx. 30% (SCHMIDT 2005; HUCKFELD 2005) is mentioned as minimum requirement for attack. Earlier studies have shown, that moisture measurement based on electrical resistance of wood resulted in satisfying accuracy for MC between 15-50%. (Brischke et al 2008; Gellerich 2012, Meyer et al 2014). This paper reports on moisture measurement based on electrical resistance of native wood species as well as thermally modified and furfurylated pine in different moisture conditions according to use class 3.2 (EN 335:2014). The used test designs were the so named block test, rail test and decking test. For the evaluation of results, the number of days with mc above 20, 25, 30 and 35% was calculated. The results are evaluated with regard to wood species, mc and test design. All test designs resulted in moisture conditions above 25% for a longer period of time of native wood species in a measurement depth of approx. 20mm. Modified samples showed constantly lower moisture content than native species. However, over the test period of 24 months, the wood species displayed higher impact on moisture content than test design.


Keywords: moisture content, moisture measurement, block test, rail test, decking test

Conference: 16-05-15/19 Lisbon, Portugal


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