Bathroom mold, explained
When Bathroom Mold Is More Than a Cleaning Problem
Every bathroom mold call falls into one of two buckets. Some of it is surface growth on grout lines and caulk, feeding on body oils and soap scum, and a good cleaning handles it. The harder cases are growing out of sight, in the wall behind the tub surround or in the subfloor, kept damp by a cracked shower pan liner, a dripping valve body or a toilet seal that's been seeping for a long time.
Silicone caulk is a common trap. Once mold roots into the silicone itself, bleach only lightens the color for a few weeks, so the bead has to be cut out, the joint dried and cleaned, and fresh mildew-resistant silicone laid in. Ceilings are the other hot spot: steam from long showers condenses on cold drywall above the tub when the exhaust fan is undersized, isn't run long enough, or vents into the attic instead of outdoors.
In a lot of older baths, the tile was set over standard paper-faced drywall instead of cement board, and that facing feeds mold as soon as moisture reaches it. That's why Bathroom Mold Removal in La Grulla so often involves a plumber and a remediator working the same job.