I found some black mold on shower grout; and some grout may need to be re-grouted. Please refer to three red-circles in the attached photo. Would you like to let me know the right tool, material (like water-proof sealant or grout) and procedure to do this kind work? Thanks a lot.

enter image description here

enter image description here

  • Are you sure that this is grout and not caulk?
    – BMitch
    Nov 25, 2013 at 1:11

1 Answer 1


I have done this many times in the past.

  1. Make a weak solution of bleach and warm water (this works best) or if you don't want to use anything as aggressive then make a paste out of Bi Carbonate of Soda and Vinegar. Apply either solution to the affected areas and leave to soak for half an hour. Take an old toothbrush and scrub until the mould has gone.
  2. Remove the grout (if needed). This can be done manually with a knife or you can buy tools to do this. Here are some Grout Removers. In my experience they don't work as well as they should. If you only have these 2 small areas, then just use a knife but be very carefull not to crack the tiles.
  3. After grout has been removed, the sections can be re-grouted.
  4. The area where the wall meets the floor can be siliconed after you have re-grouted. I am not sure which country you are in but this is the bees knees in the UK - it won't mould over! Dow Corning Silicone

Tips for applying Silicone

  1. Apply the silicone in the form of a thin bead along the required area.
  2. Make a weak solution of washing up liquid and water in a spray bottle and lightly spray the newly siliconed area.
  3. Run your finger along the silicone to smooth it down

Hope this helps!

  • Thanks. Before applying silicon, I still need to re-grout. The operation and applying silicon and re-grout are two different operations. Generally, which kind of grout material I should use?
    – user288609
    Nov 25, 2013 at 3:45
  • @user288609, although I disagree, common consensus says to only use silicone at all changes of plane.
    – Mazura
    Jul 4, 2015 at 0:42
  • 1
    If the tile are glass, be sure to use a grout which doesn't have sand in it as this will scratch the tiles. With regards to silicone, I always use Dow Corning 785+ Bacteria Resistant Sanitary Silicone. it is far superior than many other sanitary silicone sealants.
    – Simon
    Jul 6, 2015 at 22:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.