Can I fix recurring black bathroom grout myself?« Back to Previous Page

My bathroom’s grout has been getting these black spots for a couple of months now, especially behind the toilet where it’s a bit dark. I tried scrubbing it with bleach, but it just faded a little and came back worse a week later. I’m in an older building in Bur Dubai and I’m worried the humidity is making it a bigger issue. Is this something I can fix myself with a stronger product, or do I need to call a professional cleaning company?
Posted by Minho Matsumoto
Asked on May 6, 2026 1:10 am
Recurring black mold in bathroom grout is common in Dubai due to high humidity and poor ventilation, especially in older buildings. Bleach often fails because it only surface-cleans and doesn't address the root moisture problem or the mold's root structure (hyphae) penetrating the porous grout.

For a DIY attempt, use a dedicated mold-removing product containing hydrogen peroxide or quaternary ammonium compounds, not just bleach. Apply it, let it sit for the recommended time, and scrub thoroughly. Crucially, improve ventilation by running your bathroom exhaust fan for at least 30 minutes after every shower and opening windows if possible. A dehumidifier can also help measurably reduce ambient moisture.

If the mold returns after a proper DIY treatment with improved ventilation, the issue is likely systemic. This indicates persistent high humidity within the wall cavity or behind the tiles, which you cannot address yourself. In such cases, especially in older Bur Dubai buildings, a professional assessment is needed to identify the hidden moisture source and determine if the grout requires sealing or full replacement to prevent regrowth.
Posted by Sani Admin
Answered on May 8, 2026 10:08 pm