Why grout gets dirty so fast
Regular grout is cement-based, and that kind is porous. The Tile Council of North America (TCNA) says cementitious grout can absorb a stain, and under a microscope it has a large surface area to do it with. In a shower, that surface is wet every day.
Add moisture and mould follows. Health Canada says mould will typically grow indoors where moisture is present, and it advises keeping relative humidity between 30% and 50%. Grout lines in a shower, tub surround or kitchen backsplash are small, damp and out of sight, so the dark colour you see can be growth that has worked into the line, not just dirt on top.
Bleach versus heat
Bleach is the usual first move, and it is the one Health Canada tells you to skip: its mould guide says "Do not use bleach to clean up mould." On porous grout, bleach also sits on the surface while mould keeps growing inside the line.
Heat works differently. Steam pushes high-temperature vapour into the grout line, kills mould on contact and lifts the discolouration out. It does not etch stone, and it leaves no detergent residue behind.
If you clean grout yourself, TCNA has useful rules. Use an alkaline cleaner rather than an acid, because grout is cement and acids such as vinegar dissolve it. Avoid oil or wax-based cleaners, which leave a film that attracts dirt. Rinse well, because leftover soap leaves a sticky film too. TCNA says the best method is to apply the cleaner, then vacuum up the dirty water with a shop vac and rinse the same way.
When it is worth it, and when it is not
Cleaning is worth it when:
- The grout is firm and flush with the tile, but dark, stained or patchy.
- Mould keeps coming back after you scrub it.
- You are selling, renting out or moving out, and want the bathroom to look cared for.
It is not the right job when the grout itself has failed. Health Canada advises you to repair or replace open, cracked or damaged tiles, grout and caulking around showers and tubs. Signs it is time to regrout:
- Cracks, gaps or crumbling lines.
- Tiles that move or sound hollow.
- Dark staining that stays after a proper clean, which can mean the problem is deeper than the surface.
- Water marks on the wall or ceiling below.
Regrouting is a tiler's job, and we do not do it. A large area of mould is also not a cleaning job: Health Canada says a single patch larger than 3 square metres calls for a professional.
A careful DIY clean
If the grout is only lightly marked, try this first:
- Apply an alkaline tile and grout cleaner and let it sit, following the label.
- Scrub the lines gently with a soft brush. Wear gloves and keep the room ventilated.
- Vacuum up the dirty water with a wet/dry vacuum.
- Rinse with clean water and vacuum again, so no soap film is left behind.
- Dry the area completely before you judge the result.
If the colour keeps coming back, the staining may run deeper than a brush can reach. That is where heat helps.
Seal it after cleaning
Clean grout re-stains quickly if it is left bare. TCNA notes that many owners seal cementitious grout, and that the better the sealer, the more protection the joint gets. It also says epoxy grout is virtually as stain proof as the tile. Let the grout dry fully, then follow the sealer's label for coats and cure time.
Then keep the room dry. Health Canada recommends running the exhaust fan for at least 30 minutes after a shower or bath and keeping humidity in the 30% to 50% range.
Where Steam Shines fits
Our bathroom and grout cleaning uses high-temperature steam with no harsh chemicals. It kills mould, lifts soap scum and hard-water stains, and the grout lines come back to their original colour. Steam does not etch stone, and on unsealed or cracked stone we use a lower setting and keep moisture to a minimum. The backsplash and tiles in a kitchen are part of our kitchen deep cleaning.
We come to you in places like Burlington, Brampton and Toronto. If you are not sure whether your grout needs cleaning or regrouting, send us a message, and describe what you see.