Honoring expansion joints in a concrete floor is critical to the success of a ceramic tile floor installation. Choosing to ignore them is a bad idea and will eventually come back to haunt the installer for a long time. Actually, they don’t go away; they just get worse.
First, let’s define an expansion joint. The American National Standards Institute (ANSI) A108.01 section 3.7 provides this explanation: “Expansion Joint: (1) A separation provided between adjoining parts of a structure to allow movement where expansion is likely to exceed contraction; (2) a separation between pavement slabs-on-grade, filled with a compressible filler material; (3) an isolation joint intended to allow independent movement between adjoining parts.”