What is the recommended minimum thickness for cement backer board used as tile underlayment?

The recommended minimum thickness for cement backer board used as tile underlayment is indeed 1/4 inch. This thickness ensures adequate support and stability for the tile surface, preventing flexing that can lead to cracking of both the tiles and grout. Additionally, a 1/4 inch thickness complies with manufacturer guidelines for various tile installations, allowing for compatibility with standard tile sizes and types.

Using this thickness also ensures that the backer board provides sufficient moisture resistance, enhancing the longevity of the flooring. Thicker boards may be recommended for specific applications or heavier tiles, but for general residential tile installations, 1/4 inch is the industry standard, making it the optimal choice for most projects.