Wet scrub resistance is measured according to EN ISO 11998 using a standardised scrubbing machine and a defined abrasive paste. The paint layer is stressed in a wet state with a rotating brush. Based on mass loss and film thickness reduction after 200 cycles, the paint is classified into five classes. Class 1 identifies highly scrub-resistant products with less than 5 µm film reduction; Class 5 identifies those with more than 70 µm. For kitchens, bathrooms and heavily used hallways, tradespeople recommend Class 1 and 2 products. Alongside whiteness and opacity, wet scrub resistance is a key comparison criterion when purchasing premium wall paints.