Loose floor tiles are a trip hazard and allow water to penetrate the subfloor.
Step 1: Find All Loose Tiles
Tap each tile with your knuckle. A solid tile makes a dull thud. A loose tile sounds hollow.
Step 2: Remove the Tile
Remove grout around the tile with a grout saw. Insert a wide flat chisel under the edge and lever up gently.
Step 3: Clean the Subfloor
Remove all old adhesive completely. The surface must be clean and flat.
Step 4: Apply New Adhesive
Apply fresh tile adhesive to the back of the tile with a notched trowel. Also apply to the subfloor. Press the tile firmly into position and twist slightly. Use tile spacers to maintain even joints.
Step 5: Regrout
Allow adhesive to cure 24 hours. Apply fresh grout over the joints. Wipe away excess with a damp sponge.