The BS EN 1062-3-2008 standard specifies methods for determining the liquid permeability of coatings and coating systems for exterior masonry and concrete coatings and varnishes. This method is used to evaluate the waterproof performance of coatings on exterior building materials, especially in terms of liquid moisture penetration. The standard describes in detail the test conditions, equipment use, sample preparation and data analysis methods. By measuring the water permeability of coatings under the action of liquid moisture, the waterproof ability of coatings can be effectively judged, thus ensuring the long-term durability of buildings. The standard is widely used in the quality control of exterior paintings and Miscellaneous exterior coating systems to help ensure the waterproof effect of architectural coatings.