I spent a weekend scrubbing the bathroom in a Malvern rental before handing back the keys. Bleach, a stiff brush, three passes. The tile came up bright. The grout stayed grey.
I assumed I had not worked hard enough. That was the wrong conclusion, and it took a conversation with someone who does this for a living to understand why.
Grout is porous. Tile is not.
Glazed ceramic tile has a sealed surface. Dirt sits on top of it and a cloth takes it off. Cementitious grout is a different material entirely: it is full of tiny interconnected voids, and over years those voids fill with soap residue, body oil and mineral deposit from hard water.
Once dirt is inside a material, surface abrasion cannot reach it. You can scrub until your arm gives out and you are only ever cleaning the top layer of a substance that is dirty all the way through.
That is why the grout looked streaky rather than clean. I had lightened the outermost fraction of a millimetre and left everything underneath.
What actually works is chemistry and time
The fix is not more force. It is the right product left in contact long enough to dissolve what is in there, then a rinse to carry it out.
Three different problems, three different products:
- Soap scum and body oil are alkaline-soluble. An alkaline degreaser, ten to fifteen minutes of dwell.
- Hard water and mineral deposit need acid. A descaler, similar dwell, and never mixed with the above.
- Mildew in the silicone is biological. Bleach gel does work here, but it needs to sit, and it will not fix discolouration that is actually mineral.
Notice that all three involve waiting. That is the part a weekend of scrubbing skips entirely. The brush is the last five percent of the job, not the first ninety.
Why this hits older housing hardest
Anything built in the GTA before roughly the mid-nineties is full of real grout lines. A condo finished in 2015 is mostly large-format tile, quartz and sealed surfaces, where almost everything genuinely does wipe off.
So two tenants can put in identical effort at move-out and get completely different results, and the one in the older unit concludes they are bad at cleaning. They are not. They are fighting a materials problem with a labour solution.
The people doing deep cleaning in Malvern and the surrounding older Scarborough housing stock told me the same thing in plainer words: they budget dwell time into the job, which is exactly the variable a DIY weekend has no way to price.
The practical version
If you are facing grout before a move-out inspection: put the product on first, go do the oven and the fridge for twenty minutes, then come back and brush. One pass with a wait beats four passes without one.
Effort was never the variable. Chemistry and patience were.
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