Many homeowners focus on tile as the most important bathroom finish, but the hidden waterproofing layer is often what truly determines long-term performance.
Why waterproofing usually comes first
Tile and grout are not a complete waterproofing system. The actual water barrier is usually the substrate treatment and waterproofing layer underneath.
What happens when the sequence is wrong
If the visible finish is completed before wet-zone and wall-to-floor details are properly treated, leaks can still develop even when the surface looks fine.
Why older bathrooms especially need the correct order
Older bathrooms often already have aging substrate, failed waterproofing, or long-term moisture issues, which makes the foundation stage even more important than the visible finish stage.