If you’ve painted over a damp ceiling patch below your bathroom only to see it return within a season, you’re not alone — it’s one of the most common repeat complaints we handle. Painting treats the symptom, not the source, which is almost always a failure at the tile-joint or grout level above.
Bathroom tiles and the substrate beneath them expand and contract with temperature changes from hot showers and cold mornings, and over years this movement opens hairline cracks in grout lines that are invisible to the eye but wide enough for water to travel through, especially around the shower area and floor drain.
The good news is that in most cases the floor does not need to be broken. Injection grouting chemicals, applied through small drilled points, penetrate these micro-cracks and seal them from within, while surface-applied waterproofing coatings around the shower and drain collar provide a second line of defence.
We always recommend a moisture-mapping check before treatment — tracing exactly where water is entering rather than guessing — because a bathroom leak’s damp patch on the ceiling below is not always directly under the crack that’s causing it; water can travel sideways along a beam or slab before dripping down.
For a lasting fix, treat the whole wet area — floor, wall-floor junction and any pipe penetrations — in one visit rather than patching a single crack, since the surrounding grout is usually at a similar age and condition and will likely fail next.