Acceptance levels of surface disfigurement - tolerance to defects of coated wood
C Brischke, P Kaudewitz
Service life planning (PSL) has become an important issue in performance based building and substantial progress has been made in recent years. The role of predicting the aesthetical service life of wooden building components has been underestimated for quite long time but is recently attracting more and more notice. It is influenced by numerous factors such as discoloration, fading, flaking, cracking, and in extreme deformation due to interior rot. However, still the acceptance of such superficial disfigurement is subjected to the subjective sensation of consumers and end-users.
This study aimed on evaluating different ‘technically defined’ limit states of weathered coated wood surfaces with respect to the acceptance of users. Therefore different groups of users were addressed in the frame of a survey as well as two different commodity groups were looked at separately, i.e. wooden window joinery and claddings.
A remarkably high percentage of respondents ranked color and gloss related deficiencies as high as technical defects of the coating and recommended maintenance measures even when the coating was still fully intact. Technical characteristics such as the formation of cracks and flaking need to be considered separately from optical and aesthetical parameters for the definition of acceptance levels of coating disfigurements and defects. Limit states need to get defined specifically for different building components since acceptance varied significantly as shown exemplarily in this study between windows and cladding boards. For service life planning the overruling role of the subjective sensation of the user necessitates careful consideration.
Keywords: aesthetics, coating, cracks, flake offs, modelling, service life prediction