Yes, Marfil Grey Porcelain can be used outdoors as it is a durable and weather-resistant material. However, it is important to ensure that the installation is done properly with the appropriate sealants and grouts to prevent moisture from penetrating the material and causing damage. It is also recommended to choose a porcelain with an anti-slip surface for outdoor areas to prevent accidents and injuries. Consult with a professional installer for the best installation methods and maintenance recommendations for your specific outdoor space.