The performance criteria of exterior wood coatings in EN 927-2 [2] are based on visual assessments (cracking, blistering, flaking) after one year of natural weathering, an adhesion test and the measurement of coating permeability. Cracking is often the first sign of degradation. It indicates that the mechanical properties of the coatings are not suited to the dimensional variations of wood but does not explain the film fracture. Flaking occurs later and results from severe cracking. Blistering rarely happens and also depends on the mechanical properties, as the mechanism of blister formation requires deformation of the film, which is regulated by ...