Tile is durable, but it can be damaged. Improper installation, poor adhesive bonds, and falling objects can cause it to crack or chip. Repairs start with removing the grout and tile. Before replacing them, diagnose the problem to see if you need to make structural repairs to prevent subsequent damage.
If the grout is soft and powdery, remove it and regrout. If the cracked grout is hard, remove it and fill the joint with a matching colored caulk. Cracked tiles on a long length of floor are caused by either a faulty adhesive bond or an underlying crack. Before you remove the tiles, tap them lightly with a metal object, such as a wrench. If you hear a hollow sound, the bond is probably at fault. A thorough cleaning and new mortar will fix the problem. If the wrench "rings," the bond is probably solid; you may need to isolate the crack with a membrane.
About 1 1/2 hours to remove and replace grout and tile, at least a day to regrout a large area
Grout saw or utility knife, small sledgehammer and cold chisel, putty knife or margin trowel
Breaking tile with a hammer and cold chisel, driving fasteners, troweling
Replacement tiles, thinset, grout, tape