Black shower grout spreading, bleach failing. Professional needed?« Back to Previous Page

That black mould in your shower grout is a very common issue in Dubai, especially in older buildings. The high humidity provides a constant source of moisture, and the porous grout acts like a sponge, allowing the mould to root deep inside, not just on the surface. Bleach only bleaches the visible colour on the surface; it doesn't kill the root structure, which is why it returns stronger.

For a small, contained area, you can try a targeted approach. Use a dedicated, thick mould remover gel, not a spray, and allow it to sit on the grout for the full recommended time—often several hours—to penetrate. Scrub with a stiff brush and ensure the bathroom is extremely well-ventilated during and after. The key is to dry the area completely after every shower; using a squeegee on walls and running the exhaust fan for at least 30 minutes afterwards is critical.

However, since you mention it's spreading to the ceiling, this indicates a more established and possibly widespread issue. This persistent regrowth suggests the mould has penetrated behind the tiles or into the ceiling material itself, which is beyond a surface clean. In this case, a professional assessment is needed to determine the extent. They can use moisture meters to find hidden dampness and recommend if grout replacement or more intensive remediation is required to resolve it permanently.