Fungal and microbial activity in external woodenpanels as determined by finish, exposure, and constructiontechniques

Microbial activity in external wooden panels was estimated using the followingindicators: visual assessment of blue stain attack, isolation of fungi on a selective medium, FDAhydrolytic activity measurements and determination of the amount of ergosterol. Results showedthat a wall exposed to the south with somewhat higher risk for exposure to driving rain and with ahigher UV-light exposure was colonised by fungi to a much higher extent. The ventilated spacebehind the boarding was often attacked by blue-stain fungi which might indicate that theventilation rate had been insufficient. After 8 years external exposure under the prevailing climaticconditions the attack by micro-organisms on parts of the board far from end grain, or with endgrain protected with a metal flashing, was very low and seem to be independent on whether a purewater borne system, a mixed water-borne–solvent-borne system or a pure solvent-borne systemwas used for coating.