Heat is the main enemy. A tiled balcony facing south or west can reach surface temperatures above 60 degrees Celsius in summer, then cool sharply overnight. Rigid adhesives and grout crack under that daily movement, and tiles start to lift.
Sand and dust work their way into failed joints, while sprinklers and occasional heavy rain push water under the tiles. Around pools, chlorine slowly breaks down cement grout. Outdoor repairs therefore need flexible, UV-stable materials and proper movement joints.
For loose tiles inside the home, see loose tile reinstallation. For pool areas and wet rooms, epoxy grout for high-moisture areas gives the most durable joints. Once repaired, many surfaces benefit from tile surface polishing and refinishing.