Ceramic tiles are typically installed on a solid and stable substrate to ensure their durability and longevity. While both plywood and drywall can be used as substrates for ceramic tile installations, there are some considerations to keep in mind.
Plywood: If you're considering installing ceramic tiles on plywood, it's important to use an appropriate underlayment material to create a stable surface. Plywood tends to have more flexibility and can expand and contract with temperature and moisture changes, which can lead to tile cracking over time. Cement backer board or an uncoupling membrane, such as an anti-fracture membrane, is often recommended as an underlayment over plywood to minimize movement and provide a rigid substrate for tile installation.
Drywall: Drywall is not an ideal substrate for ceramic tile installation in areas prone to moisture exposure, such as bathrooms and showers. Drywall is not water-resistant and can deteriorate when exposed to excessive moisture. However, in low-moisture areas such as kitchens or on walls, you can install ceramic tiles directly on properly prepared and primed drywall.
In general, it's advisable to consult with a professional tile installer or follow the manufacturer's recommendations for your specific ceramic tile product. They can assess the condition of the substrate, evaluate the environment, and provide guidance on the most suitable installation method and materials for your project.