Composite seals protect substrates from moisture and reduce efflorescence. They can be used in bathrooms, showers, kitchens in both commercial and private settings, on balconies and terraces above unoccupied spaces, as well as in water containers. The most common cause of damage is a lack of expertise in processing. Proper planning and execution of composite seals are among the most demanding tasks in the tiling trade and require appropriate experience and qualifications. This work provides not only the necessary facts in light of the new sealing standards DIN 18534 and DIN 18535 but also critically examines existing regulations and explains, with the help of sketches and photos, why certain implementations are important and where deviations can be found.