You can lay tile directly on a plywood countertop, but if it’s a high-traffic surface in a kitchen, it’s better to add a moisture-resistant base. Plywood is susceptible to moisture, so if dampness seeps through from the surface around the sink or where you prep food, it can cause the plywood to warp, leading to grout damage, cracked tiles, or mold growth under the surface. 

You can technically install tile over tile, but we don’t suggest it. Installing tile over any surface that isn’t a completely flat and prepared subfloor will result in a shoddy overall job, uneven flooring, tiles that don’t adhere, extra weight, gaps, cracks, and room for moisture and dirt to enter. For the best results, only install new tile on a flat, sanded surface like subflooring or concrete that is prepared for tile.

If you have asbestos tile and would rather tile over it than remove it, or if your existing tile is completely flat and bonded tightly to the floor, you may be able to tile over existing tile. But experts recommend thinking twice before you do.

It’s possible to walk on a clay tile roof, but you run the risk of breaking or cracking the tiles if you’re not careful, so it’s best not to walk on it if you can avoid it. If you or a contractor needs roof access, be sure to distribute your weight evenly and step on the portions of tile that are also supported underneath, which depends on your tile design. Walking on any roofing material is inherently dangerous, so wear rubber-soled shoes and use safety equipment if you need to access your roof.

Yes, unfortunately, it is normal for wall and floor tiles to crack, especially when you drop heavy items on tiled floors or place heavy objects on them. Tiles are also more susceptible to cracking when ceramic tiles designed for walls are installed on floors, as these are often not strong enough to handle heavy loads from foot traffic and furniture. Similarly, tiles that are installed incorrectly, lack adequate subflooring, or have other installation problems are prone to cracking. To avoid these problems and the inevitable repair and replacement costs they bring, always hire a professional for tile work and follow best practices for installation.