This invention relates to a magnetic modular coating for floors and walls, even in wet sites and under water, that is composed of a sole fixing element laid between a magnetic adherence decorative plate and a metallic framework structure (3). Such coating also includes a bi-directional magnetic adherence layer (4) of minimum thickness; a decorative surface layer (5), and an upper rigidifying sheet (6) made up of a laminar unit. Adhesives used can be of any kind suitable to join components together. The modules allow for a fast installation, are easily removable and can be re-used.