By means of a capacitance moisture meter, moisture fluctuations were studied on boards of Norway spruce (Picea abies), mounted as external cladding on a purpose-built experimental wall. Two causes of variation were included in the study: 1) The difference between heartwood- and sapwood boards, and 2) The effect of an overhanging roof, sheltering the boards from rain. Measurements were performed over 12 weeks from February to May. During this period a general drying of the boards occurred, while variations attributable to rainfall appeared clearly. However, no difference between heartwood vs. sapwood boards could be established. Effects of a protruding roof were studied for heartwood boards only. Between zero- and 1-metre overhang a statistically significant difference was found 30 cm below the gutter, but further down from the roof the differences were but small and insignificant.
Keywords: heartwood, sapwood, water absorption
Authors
A. Bergstedt
University of Copenhagen – The Forestry College, Fredensborg, Denmark
I. G. Johansen
Danish Forestry Extension, Randers, Denmark
M. T. Larsen
ThorConsult, Glostrup, Denmark
Login to download the PDF