This is a shower floor in a nice home in Debary, Florida. The homeowner told me that it was incorrectly repaired by one of the franchise grout whatever companies only three months ago.
It looks like instead of cleaning and sealing the grout properly. They skim-coated it with cheap hardware store grout. The homeowner said they mixed in penetrative sealer in the grout.
Mixing penetrative sealer in the grout doesn't work well in new construction homes, never mind a shower floor that's been having problems. Sanded grout is basically just sand and cement.
The surface is rough, and that roughness is what traps stain causing dirt. It's best to seal the pores with the right sealer to stop the staining from just happening again. The sealer covers up any existing stains and forms a strong topical bond. Skim-coating over it with more grout makes no sense.
You can see here that the grout didn't form a proper bond and is peeling up. We first had to remove the failing grout repair the previous company had done. You can put grout in missing areas and then seal the grout. But two things happened here.
1 using cheap hardware store grout and not a grout repair compound made for repairs. The stuff I use is called Rock Hard, and there's a link to the description. There's no other product like this one on the market.
The second problem is not cleaning the surface properly, which can also cause the sealer's bond to fail. In this shower, we acid-washed the floor and neutralized it before applying the sealer to the grout joints. This sealer is a heavy-duty product; it's about ten times stronger than most penetrative sealers.
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