You have four realistic options: deep clean the grout, regrout, overlay the tiles with a finish such as microcement, or hack and redo the bathroom. If the tiles are sound and there is no leak, cleaning or regrouting fixes the grout, while a microcement overlay removes grout lines altogether without hacking. If tiles are hollow or water is leaking, the waterproofing needs repair first and a full redo may be the right call.
First, check what you are dealing with
- Is it surface mould? Black spots that lift with cleaning are on the surface of the grout.
- Is the grout crumbling? If it is cracked or missing, water can get behind tiles.
- Are tiles hollow? Tap them with a coin handle. A dull, hollow sound means they are no longer fully bonded.
- Any leaks? Stains on the ceiling of the flat below, damp skirting outside the bathroom, or a musty smell all point to water getting past the membrane.
Option 1: deep clean
For mild surface mould, a thorough clean with a mould remover and a stiff brush, followed by good ventilation, can bring grout back. It is cheap and quick, but in a humid bathroom the mould tends to return because cement grout is porous.
Option 2: regrout
Raking out old grout and replacing it, sometimes with a more stain-resistant grout, refreshes the lines while keeping your tiles. It does not change the look of the tiles and will not fix a failed membrane.
Option 3: overlay with microcement
If the tiles are firmly bonded and there is no leak, microcement can go straight over them. The grout lines are filled and covered, so there is nothing left for mould to grow in, and walls, floor, kerb and vanity become one continuous surface. It is a thin overlay, so floor height and doors stay as they are, and there is no hacking. It needs the right care afterwards and does not replace the waterproofing membrane underneath.
Read more in can microcement go over tiles without hacking and is microcement worth it for an HDB bathroom.
Option 4: hack and redo
If tiles are hollow across large areas or there is a leak, the old finish usually needs to come off, the waterproofing redone and new finishes laid. For HDB bathroom floor replacement, HDB requires waterproofing screed and a membrane, and a water test is usually part of the process. For new flats, HDB restricts hacking original bathroom finishes in the early years. Check the current rules on the HDB renovation page.
How to choose
- Tiles fine, grout lightly mouldy: deep clean or regrout.
- Tiles sound but dated, grout keeps coming back: consider a microcement overlay.
- Hollow tiles or a leak: fix the waterproofing first. Hack and redo if needed.
Preventing mould whatever you choose
- Run the exhaust fan or keep a window open after showers
- Squeegee walls and floor after use
- Clean regularly so soap scum does not build up
How Jiu Ding Sheng can help
We survey your bathroom first. If the tiles are sound, we lay the Natural Surface M Series over them at 1 to 1.5mm in four layers with no primer, sealed with two top coats, usually in 3 to 4 working days. If the tiles are not sound or there are signs of a leak, we will tell you rather than lay over a problem. See finished bathrooms on our Projects page and learn about the material on the Material page.
Quick answers
Why does my bathroom grout keep turning black?
Cement grout is porous and Singapore bathrooms stay humid, so mould grows in the joints. Ventilation helps, but the grout will keep absorbing moisture.
Can I cover old tiles instead of hacking?
Yes, if the tiles are firmly bonded and there is no leak. A microcement overlay covers both tiles and grout lines with a thin, continuous finish.
Will covering the tiles fix a leak?
No. A leak means the waterproofing membrane has failed. It must be repaired first.
How do I know if my tiles are hollow?
Tap them gently with something hard. A dull, hollow sound means the tile is no longer fully bonded and needs attention before any overlay.
Next step
Send us photos of your tiles and grout, and tell us about any leaks. We will tell you which option makes sense. WhatsApp +65 8049 1188 or use the contact page.
