Laying tile directly over a plywood subfloor is generally not recommended because plywood is not an ideal surface for tile installation. Plywood has some inherent characteristics that can lead to problems with the tile installation and the floor's long-term durability. Here are some potential issues:
Flexibility: Plywood tends to flex and expand/contract with changes in humidity and temperature. This movement can cause the tiles to crack or the grout lines to separate over time.
Lack of stability: Plywood may not provide a stable enough surface for the tile to adhere properly. Tile requires a solid, level, and even surface to be installed correctly.
Moisture: Plywood can absorb and retain moisture, especially in humid environments or areas prone to water exposure (e.g., bathrooms, kitchens). Excess moisture can lead to tile adhesive failure, mold growth, and damage to the plywood.
Grout cracking: The flexing of the plywood may also cause the grout lines to crack, leading to an unsightly and unstable floor.
To avoid these issues, it's essential to follow the proper tile installation guidelines. Here's the recommended approach:
Use a backer board or cement board: Instead of laying tile directly on plywood, install a suitable backer board or cement board over the plywood subfloor. These materials provide a more stable and moisture-resistant surface for tile installation.
Check subfloor deflection: Before proceeding with the tile installation, ensure the plywood subfloor meets the necessary deflection requirements. Subfloor deflection refers to the amount of vertical movement or bounce the floor has when weight is applied. Tile manufacturers often provide specific guidelines for maximum allowable deflection to prevent tile cracking.
Apply the right adhesive: Choose a suitable adhesive specifically designed for tile installation on backer board or cement board.
Follow proper tile installation guidelines: Make sure to follow the manufacturer's instructions for laying and grouting the tiles. Properly applied adhesive and grout help prevent issues with tile cracking and grout separation.
By taking these precautions and using the right materials, you can ensure a successful and long-lasting tile installation over a plywood subfloor. However, it's always a good idea to consult with a professional tile installer for more specific advice and to ensure the best results for your particular situation.