There are several ways of bricklaying: back-to-back and back-to-back. The second method of laying is considered the most reliable method of bricklaying, providing a very long time of operation of the room.
In any construction and repair work, the main thing is to know and adhere to the correct technology of work, since by purchasing even the highest quality material, you can spoil everything with incorrectly executed works.
Expanded polystyrene is a lightweight, but at the same time durable material that has minimal water absorption, which is very important for insulation from the inside. Polyurethane foam is characterized by high adhesion to any type of surface and monolithic coating.
Laying ceramic tiles on a painted surface is possible provided that high-quality paint has been applied to the base and it holds very firmly on the surface, without having any hints of peeling, cracking or peeling.
If you have at least the slightest doubt about the strength of the old tile layer, it is better not to risk and remove it. If you are confident in the reliability of the old facing coating, then choose a high-quality adhesive material, for example, Teknofay 200 D2TE and feel free to get to work.