What is a likely consequence of not including movement joints in large tile installations?

• A. Tiles will never crack.
• B. Cracking of tiles due to substrate movement.
• C. Substrate will not move.
• D. Mortar will double in strength.

Answer: (B)

Movement joints are places where the tile system can accommodate expansion and contraction from temperature changes, moisture fluctuations, and substrate movement. In a large installation, those forces cause the substrate and the tile layer to shift slightly. If there’s no dedicated joint to relieve that movement, the stress concentrates at tile edges and around restraints, causing cracks in the tiles (and often damage to adjacent grout). So the most likely consequence of omitting movement joints is cracking of tiles due to substrate movement. The substrate can and does move under real conditions, mortar strength isn’t the fix for that, and a strong mortar won’t prevent cracking if the system can’t relieve movement.